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# GANIL Scientific Annual Report 2023

P. Roussel-Chomaz, Fanny Farget

► To cite this version:

P. Roussel-Chomaz, Fanny Farget. GANIL Scientific Annual Report 2023. GANIL. 2024. hal-04780854

HAL Id: hal-04780854

https://hal.science/hal-04780854v1

Submitted on 13 Nov 2024

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CANIL

GRAND ACCÉLÉRATEUR
NATIONAL D'IONS LOURDS

Scientific annual report

2023
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# CONTENTS

<table><thead><tr><th></th><th></th><th></th></tr></thead><tbody><tr><td>01</td><td>INTRODUCTION</td><td>5</td></tr><tr><td>I.</td><td>A FEW WORDS FROM THE GANIL MANAGEMENT</td><td>5</td></tr><tr><td>II.</td><td>KEY NUMBERS</td><td>7</td></tr><tr><td>III.</td><td>COMMUNICATION AND OUTREACH</td><td>9</td></tr><tr><td>IV.</td><td>ENVIRONMENTAL REPORT</td><td>11</td></tr><tr><td>V.</td><td>ACTIVITIES IN TECHNOLOGICAL TRANSFER</td><td>13</td></tr><tr><td>02</td><td>SCIENTIFIC RESEARCH</td><td>15</td></tr><tr><td>I.</td><td>STRUCTURE, ASTROPHYSICS, REACTION AND SPECTROSCOPY</td><td>17</td></tr><tr><td>II.</td><td>PHYSICS OF HEAVY AND SUPERHEAVY NUCLEI</td><td>20</td></tr><tr><td>III.</td><td>FISSION AND REACTIONS</td><td>23</td></tr><tr><td>IV.</td><td>FUNDAMENTAL INTERACTIONS AND DARK SECTORS</td><td>26</td></tr><tr><td>V.</td><td>DOSIMETRY, APPLICATIONS AND NUCLEAR DATA</td><td>28</td></tr><tr><td>VI.</td><td>CIRIL</td><td>30</td></tr><tr><td>03</td><td>OPERATION, TECHNOLOGICAL RESEARCH AND DEVELOPMENT</td><td>31</td></tr><tr><td>I.</td><td>EXECUTIVE SUMMARY OF ACCELERATOR AND EXPERIMENTAL AREAS OPERATION</td><td>33</td></tr><tr><td>II.</td><td>ION BEAM AND RADIOACTIVE ION BEAM DEVELOPMENTS</td><td>37</td></tr><tr><td>III.</td><td>PHYSICS OF ACCELERATORS</td><td>41</td></tr><tr><td>IV.</td><td>EQUIPMENTS FOR BEAM ACCELERATION, TRANSPORT AND DIAGNOSTICS</td><td>45</td></tr><tr><td>V.</td><td>AUTOMATS AND COMMAND CONTROL</td><td>48</td></tr><tr><td>VI.</td><td>ACHIEVEMENTS IN MECHANICS</td><td>51</td></tr><tr><td>VII.</td><td>DETECTION AND LASER FOR PHYSICS</td><td>54</td></tr><tr><td>VIII.</td><td>DATA ACQUISITION</td><td>59</td></tr><tr><td>IX.</td><td>MANAGEMENT AND ORDERING OF INSTALLATIONS</td><td>61</td></tr><tr><td>X.</td><td>STATUS OF SCIENTIFIC AND ACCELERATOR PROJECTS</td><td>63</td></tr><tr><td>04</td><td>EXPERIMENT REPORTS</td><td>73</td></tr><tr><td>I.</td><td>NFS</td><td>75</td></tr><tr><td>II.</td><td>VAMOS</td><td>95</td></tr><tr><td>III.</td><td>LISE</td><td>99</td></tr><tr><td>IV.</td><td>D1-HE</td><td>109</td></tr><tr><td>V.</td><td>D1-SME</td><td>115</td></tr><tr><td>VI.</td><td>IRRSUD</td><td>125</td></tr><tr><td>VII.</td><td>ARIBE</td><td>145</td></tr><tr><td>05</td><td>ANNEXES</td><td>163</td></tr><tr><td>I.</td><td>PUBLICATION LIST</td><td>165</td></tr><tr><td>II.</td><td>CONFERENCE LIST</td><td>171</td></tr><tr><td>III.</td><td>COMMITTEES</td><td>172</td></tr><tr><td>IV.</td><td>ORGANISATION CHART</td><td>181</td></tr></tbody></table>
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40th GANIL anniversary
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## I. A few words from the GANIL management

Forty years after the first experiment, a new dynamic is shaping GANIL.

A large renovation program for the cyclotrons (CYREN) has been proposed in 2022 for a realization in the years to come, strengthening a long-term future of the cyclotron scientific program. In June 2023, the Minister of Research and High Education confirmed the interest in maintaining GANIL installation at the fore-front level, allocating a dedicated significant budget. This long-term commitment supports for a great part the exotic beams of SPIRAL1, which are of the outmost importance for the DESIR hall, of which the construction site was inaugurated in 2023 after the official authorization.

The beam-line for the transport of exotic beams of SPIRAL1 to DESIR has been assembled and tested before its future implementation planned in 2025.

CYREN is already going on with a new prototype validated for the power supplies of the magnets and a refurbishment of the CSS1 vacuum system.

Looking ahead, new beams are under development at GANIL.

On the side of cyclotrons, the newly accelerated $^{232}$Th beam allowed to enlarge the domain of fission studies at VAMOS.

For the first time, $^{8}$Li beam was provided at SPIRAL1, accelerated with CIME and decelerated in a dedicated installation in the G2 experimental hall to meet astrophysical nuclear reaction conditions. Further developments of SPIRAL1 beams are going-on to prepare for the future.

On the side of the LINAC, heavy-ion beams of Argon and Oxygen were accelerated through the 26 cavities of the LINAC and the ion-source has received a large program of optimization for its reliability and for recycling of the rare isotopes in the plasma chamber.

To prepare for a further enlargement of the heavy ion beams accelerated by the LINAC, and increase their intensities, NEWGAIN project entered its construction phase.

Preparing for the parallel operation of the LINAC and the cyclotrons, the LINAC was tuned for the first time in the main control room, and the cryogenic system of EXOGAM detection set-up was doubled.

The LINAC beam diagnostics have followed in 2023 an important upgrade to adapt to the heavy-ion beams of S³. The rotating target station of S3 was tested, as well as SIRIUS, the instrumentation for the study of super-heavy isotope spectroscopy. S3-LEB completed its off-line commissioning and optimization of its performances, and prepared its moving to S3 hall.

In 2023, the GANIL nuclear physics scientific Community applied to more than 3500 hours of beam-time, and only half of these experiments could be approved, showing a strong request on the cyclotron and LINAC beams. The results of the previous experimental campaigns were intensively discussed during the GANIL colloquium in Soustons, in September 2023, where more than 100 participants contributed.

GANIL is proud to contribute to important scientific publications with high impact : more than 120 articles were published in 2023 related to GANIL experiments. GANIL is also contributing to young researchers training, in particular with more than 95 PhD theses presently under preparation based on data obtained at GANIL.
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## II. Key Numbers 2023

### Resources

- State subsidy: 12,8M€

- Normandie Region: 1,2M€

- ANR: 2,8 M€

- Europe: 0,4 M€

- Other: 0,9 M€

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### Staff
300

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### Expenditures

- Operation: 10 M€

- Investment: 8,1 M€

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### Publications
121

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### Visitors
884

(general public)

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### Experimentation

301 Experimenters

103 Scientific visitors

5 Long-term visiting scientists

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### Operating hours

Cyclotrons: 3046 h

LINAC: 1774 h

SPIRAL1: 167 h

Beam on target:
4600 h

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### Internships

38 interns
27 doctoral students
16 post-docs

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### Partners

6 international agreements

6 european contracts

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### Consumption

Electricity: 27 GWh

Gas: 2 GWh

Water: 20 000 m³

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### Accepted experiments

PAC: 241 UTs

IPAC: 416 UTs

(Acceptation rate: 58%)

### Number of experiments

8 nuclear physics

48 interdisciplinary physics

23 industrial applications

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## III.Communication and outreach

### 40th GANIL anniversary

March, 2nd

On March 2, 2023, GANIL celebrated 40 years of the laboratory's first experiment with more than 400 participants. This anniversary was an opportunity to celebrate a rich history of research at the dawn of a new phase in the development of scientific programs thanks to very intense ion and neutron beams.

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### Brochure on the DESIR public inquiry

April, 24th

GANIL produced a communication brochure for the public inquiry concerning the modification of INB 113 in order to include the DESIR project.

### Ministerial visit to GANIL to address the development of future projects

June, 9th

On June 9, 2023, Sylvie Retailleau, Minister for Higher Education and Research, and Agnès Pannier-Runacher, Minister for Energy Transition, visited the GANIL facilities. On this occasion, Sylvie Retailleau announced €40 million for GANIL's projects funding, in particular the renovation of the cyclotrons (CYREN project) and the DESIR project, thanks to an investment made possible by the Research Programming Act. The NEWGAIN project will also benefit from this funding.

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### GANIL thesis prizes awarded to Chloé Fougères and Lukas Madauss

September, 28th

For the first time, two GANIL thesis prizes were awarded this year. The first went to Chloé Fougères for her thesis at GANIL under the supervision of François de Oliveira, entitled « Understanding the cosmic abundance of 22Na: lifetime measurements in 23Mg », and the second to Lukas Madauss for his thesis entitled « Structurally modified two-dimensional materials for membrane applications », at the University of Duisburg-Essen under the supervision of Marika Schleberger.

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### Science festival

October, 13th, 14th, 15th

On the occasion of the three days science festival, organized by the Ministry of Research and Higher Education, several scientific demonstrations, two conferences, games and stands were made by GANIL the Caen science village. The science festival on average attracts a very general public.
### Festival of Normandie's excellence

October, 20th, 21st, 22nd

GANIL participated in the 3 day exhibition displaying excellence of the region of Normandy, organized by the Region of Normandy. Here the researchers, engineers and technicians presented the activities of through scientific demonstrations and games to a very broad public. This exhibition had ~40000 visitors.

### Inauguration of the DESIR construction site

November, 10th

On November 10, 2023, GANIL inaugurated the construction site of the new DESIR experimental room during a ceremony which welcomed nearly 250 people. This experimental hall for very low energy nuclei will link GANIL's two accelerators, the cyclotrons and the linear accelerator, using the ion beams produced by each of them.

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### Exhibition "150 years of particle accelerators"

November, 17th and 18th

On the occasion of the 150th anniversary of the French physics society, GANIL presented the exhibition "150 years of particle accelerators". The public discovered the world of particle accelerators through fun, spectacular and intriguing experiments!

### Master's Day

November, 18th

As every year, GANIL organised the "Master's Day". This event aims at presenting the PhD opportunities offered at GANIL for Masters students from all Universities in France. This is combined with extensive visits to the accelerators and detectors. More than 120 students participated at the master's day.

### GANIL open days

December, 2nd

GANIL welcomed more than 600 visitors and 110 pupils during its open days. Guided by researchers, engineers and technicians, the visitors discovered the installation from the ion sources to the experiment rooms.

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# IV. Environmental report

## 1. Radioactive releases

The nuclear facility GANIL is under supervision of the French Nuclear Safety Authority (ASN), which gave in 2015 the authorisation for atmospheric radioactive emission with limits for cyclotrons and spiral2 facility (see table below). GANIL carries on-going monitoring in both chimneys and each month, GANIL reports on the quantity of radioactivity released to the Authority.

<table><thead><tr><th>GANIL</th><th>Tritium (Bq)</th><th>Noble gas (Bq)</th><th>Iodines (Bq)</th><th>Other β and γ emitters (Bq)</th></tr></thead><tbody><tr><td>Annual limit for GANIL cyclotrons</td><td>2.10E+09</td><td>3.27E+10</td><td>1.94E+08</td><td>9.70E+12</td></tr><tr><td>Release in 2023</td><td>7.32E+07</td><td>8.34E+09</td><td>2.87E+05</td><td>6.85E+11</td></tr><tr><td>% release in percentage of the annual limit in 2023</td><td>3.5%</td><td>25.5%</td><td>0.15%</td><td>7.1%</td></tr></tbody></table>

<table><thead><tr><th>GANIL SPIRAL2</th><th>Tritium (Bq)</th><th>Noble gas (Bq)</th><th>Iodines (Bq)</th><th>Other β and γ emitters (Bq)</th></tr></thead><tbody><tr><td>Annual limit for SPIRAL2</td><td>6.50E+09</td><td>2.20E+12</td><td>5.00E+05</td><td>1.40E+12</td></tr><tr><td>Release in 2023</td><td>1.06E+09</td><td>3.33E+10</td><td>1.09E+05</td><td>4.96E+11</td></tr><tr><td>% release in percentage of the annual limit in 2023</td><td>16.3%</td><td>1.5%</td><td>21.8%</td><td>35.4%</td></tr></tbody></table>

All along the years, the releases were low and complied with the annual authorized limits.

The dosimetry due to those releases in 2023 is estimated up to 2 µSv for a representative population living at 500 m from GANIL.

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## 2. Environmental monitoring

The radiological monitoring of GANIL's environment is defined by the regulation and the ASN. Certified laboratories analyse each month 80 to 90 samples of air, water, plants and milk. Once a year, some soil samples and agricultural products are also analysed. GANIL has two air monitoring stations. On-going irradiation monitoring are carried on with detectors in those stations and dosimeters around the site and in towns near GANIL. All the radiological values are available in the official website for the radiological environmental monitoring in France: https://www.mesure-radioactivite.fr (available in English).

During 2023, the daily global beta radioactivity measured in aerosols are due to the natural environmental radioactivity. All the other results are under the detection limits excepted a few rainwater measurements of global beta emitters staying nevertheless inside natural level standards.

The activity and releases of GANIL's facility do not involved any increase of radioactivity in its environment.

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## 3. Non radioactive releases

The main risk concerns the cooling towers of GANIL's and SPIRAL2's facilities releasing steam. The monthly water analysis showed the absence of legionella bacteria in water.

GANIL's activities do not induce specific conventional pollutant release in the atmosphere. The sole releases are due to the heating system burning gas and the burning of diesel for the periodic tests of electric generators needed for safety. The quality of the effluent are controlled regularly and meet the standard values.

Few years back, GANIL took some measures to restrict the release of perfluorocarbon gas used in detectors. The loss of those gases were of 8 kg in 2023 which represent 52 tons equivalent carbon dioxide and were less than in 2022. GANIL will continue to study how to reduce the release of such gases.

## 4. Liquid effluents

Wastewater are transferred to the public sewerage system (20 525 m³ yearly). Accredited laboratory analyses the quality of wastewater 4 times a year with radiological and chemical tests. All the measured parameters were under the limits required by the Nuclear Safety Authority and the local public department for water.

In 2023, about 8 m³ of effluents containing less than 100 Bq/L of tritium were transferred to the public sewerage system, corresponding to a total of 240 kBq of tritium representing 24% of the authorized limit.

## 5. Wastes

Dangerous wastes were produced in 2023 in smaller amount than during 2022 on GANIL site recovering the usual production excepted for asbestos-containing wastes coming from asbestos removal operation.

Three campaigns occurred for the conditioning of radioactive wastes including one concerning historical electronic wastes containing dangerous compounds. These operations occurred in a new dedicated room equipped for this purpose.
# V. Activities in Technological Transfer

GANIL is participating to Regional, National and European Economic Networks.

## 1. Service to industries

Industrial applications using stable ion beams focus today on microporous membrane production by irradiating polymer films with heavy ions, on the tests of electronic components to study their behavior and resistance under irradiation and biology under irradiation in collaboration with CIMAP.

<figure><img src="image_26.png" /><figcaption>Figure 1: Sales of heavy ion beams</figcaption></figure>

This second type of application is presently undergoing a strong rise of activity due to the development of “new space” activities, as shown in Figure 1. Companies dealing with the aerospace industry have developed programs of component certification with the use of GANIL beams. The beam time dedicated to these various applications is billed to the user at an hourly rate. CNES asked GANIL to propose solutions to improve access to GANIL's beams for the space industry community. This idea led to the launch of the emergence phase of the SAGA (Space Applications at Ganil Accelerators) project.

GANIL is present at european conferences such as RADECS (Radiation and its effect on Systems and Components) and RADNEXT (RADiation facility Network for the EXploration of effects for indusTry and research) and at national meetings (RDV CARNOT) that foster links between academics and industrial partners.
With its scientific and technological expertise, GANIL also acts as a relay enhancing the transfer of its employee skills to industrial companies and their applications.
## 2. Technology transfers in 2023:

* Beam profile monitor with regional company PANTECHNIK

* Patent on mechanical structure for specific aluminium vacuum pipes with national company STIRWELD

* A glove box project for the NFS experiment hall has been built around an industrial collaboration validated in 2023 for development of new types of adaptable gloveboxes for radioactive sample manipulation with national company IDEALEX

This collaboration has been the subject of grant applications for academic/industry R&D collaboration in the Normandy and Occitania regions. These grants cover almost all the investment and the costs of 2.3 FTEs.

Differents various collaboration agreements have been studied in 2023.

They are related to various domains that reflect the variety of techniques and scientific specialties of GANIL:

* BOREALES Energy (Normandy)

Case studies of applications of their innovative energy storage system to save energy

* INSTITUT DE RECHERCHES GEOLOGIQUES ET MINIERES (Cameroun)

Development of environmental radiation protection equipment

In more upstream research, connection to industrial partners exist in the fields of Artificial intelligence for monitoring complex and multi-parameters systems as accelerators.

PANTECHNIK
Boost Your Physics

stirweld

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IDEALEX®
RADIATION PROTECTION

<figure><img src="image_28.png" /></figure>

BOREALES
Energy

Solutions de stockage des énergies renouvelables

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INSTITUT
DE RECHERCHES
GEOLOGIQUES ET MINIERES
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02

SCIENTIFIC RESEARCH:
Internal activities and user experiments
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# I. STRUCTURE, ASTROPHYSICS, REACTION AND SPECTROSCOPY

The STARS group leads experimental research in the fields of nuclear structure and nuclear astrophysics using heavy-ions collisions and high-resolution charged particles and gamma-rays spectroscopy. The group is involved at high level in the development and running of state-of-the-art instruments such as AGATA(γ), EXOGAM(γ), PARIS(γ), MUGAST/GRIT(lcp), ACTAR (active target) and NEDA(n). Members of the group have high responsibilities in the nuclear physics international community (AGATA project Manager, NuPECC chairman, RESANET GDR chairman, GANIL beam coordinator, leader of the European astrophysics schools of the Chetec-Infra project). The publications presented in the following are the result of PhD work supervised or co-supervised by a member of the group.

## 1. Elucidating the nature of the proton radioactivity and branching ratio on the first proton emitter discovered $^{53m}$Co

The observation of a weak proton-emission branch in the decay of the 3174-keV $^{53m}$Co isomeric state marked the discovery of proton radioactivity in atomic nuclei in 1970. Here we show, based on the partial half-lives and the decay energies of the possible proton-emission branches, that the exceptionally high-angular momentum barriers, play a key role in hindering the proton radioactivity from $^{53m}$Co, making them very challenging to observe and calculate. Indeed, experiments had to wait decades for significant advances in accelerator facilities and multi-faceted state-of-the-art decay stations to gain full access to all observables. Combining data taken with the TASISpec decay station at the Accelerator Laboratory of the University of Jyväskylä, Finland, and the ACTAR TPC device on LISE3 at GANIL, an international collaboration measured their branching ratios as $b_{p1} = 1.3(1)%$ and $b_{p2} = 0.025(4)%$. These results were compared to cutting-edge shell-model and barrier penetration calculations. This description reproduces the order of magnitude of the branching ratios and partial half-lives, despite their very small spectroscopic factors.

[Luis G. Sarmiento, Thomas Roger et al Nature Communications volume 14, Article number: 5961 (2023)]

<figure><img src="image_32.png" /><figcaption>Figure 2: 4D decay of very exotic isotopes in ACTAR</figcaption></figure>

## 2. Search for $^{22}$Na in novae supported by a novel method for measuring femtosecond nuclear lifetimes

Classical novae are thermonuclear explosions in stellar binary systems, and important sources of $^{26}$Al and $^{22}$Na. While γ rays from the decay of the former radioisotope have been observed throughout the Galaxy, $^{22}$Na remains untraceable. Its half-life (2.6 yr) would allow the observation of its 1.275 MeV γ-ray from a cosmic source. However, the prediction of such an observation requires good knowledge of its nucleosynthesis. The $^{22}$Na($p, \gamma$)$^{23}$Mg reaction remains the only source of large uncertainty about the amount of $^{22}$Na ejected. Its rate is dominated by a single
resonance on the short-lived state at 7785.0(7) keV in <sup>23</sup>Mg. Here, we performed a combined analysis of particle-particle correlations and velocity-difference profiles to measure femtosecond nuclear lifetimes. The application of this method to the study of the <sup>23</sup>Mg states, places strong limits on the amount of <sup>22</sup>Na produced in novae and constrains its detectability with future space-borne observatories. Chloé Fougère obtained for this work the 2023 GANIL thesis prizes.

[Chloé Fougères, François de Oliveira Santos et al, Nature Communications volume 14, 4536 (2023)]

<figure><img src="image_33.png" /><figcaption>Figure 3: Velocity distribution for different excited states. The profile is used to determine sub-ps nuclear lifetime</figcaption></figure>

### 3. High-Precision Spectroscopy of <sup>20</sup>O Benchmarking ab-initio Calculations in Light Nuclei

The excited states of unstable <sup>20</sup>O were investigated via γ-ray spectroscopy following the <sup>19</sup>O(d,p)<sup>20</sup>O reaction at 8 A.MeV. By exploiting the Doppler shift attenuation method, the lifetimes of the 2<sup>+</sup><sub>2</sub> and 3<sup>+</sup><sub>1</sub> states were firmly established. From the γ-ray branching and E2/M1 mixing ratios for transitions deexciting the 2<sup>+</sup><sub>2</sub> and 3<sup>+</sup><sub>1</sub> states, the (E2) and (M1) were determined. Various chiral effective-field theory Hamiltonians, describing the nuclear properties beyond ground states, along with a standard USDB interaction, were compared with the experimentally obtained data. Such a comparison for a large set of γ-ray transition probabilities with the valence space in medium similarity renormalization group ab initio calculations was performed for the first time in a nucleus far from stability. It was shown that the ab initio approaches using chiral effective field theory forces are challenged by detailed high-precision spectroscopic properties of nuclei. The reduced transition probabilities were found to be a very constraining test of the performance of the ab initio models.

[I. Zanon, E. Clément et al. Phys. Rev. Lett. 131, 262501 – (2023)]

<figure><img src="image_34.png" /><figcaption>Figure 4: Comparison of the transitions probabilities in <sup>20</sup>O between experimental data, Shell model calculations and state-of-the-art ab-initio calculations</figcaption></figure>
4. N=16 Magicity Revealed at the Proton Drip Line through the Study of ³⁵Ca

The last proton bound calcium isotope ³⁵Ca has been studied for the first time, using the ³⁷Ca(*p*,*t*)³⁵Ca two neutron transfer reaction. The radioactive ³⁷Ca nuclei, produced by the LISE spectrometer at GANIL, interacted with the protons of the liquid hydrogen target CRYPTA, to produce tritons *t* that were detected in the MUST2 detector array, in coincidence with the heavy residues Ca or Ar. The atomic mass of ³⁵Ca and the energy of its first 3/2⁺ state are reported. A large *N*=16 gap of 4.61(11) MeV is deduced from the mass measurement, which together with other measured properties, makes ³⁶Ca a doubly magic nucleus. The *N*=16 shell gaps in ³⁶Ca and ²⁴O are of similar amplitude, at both edges of the valley of stability. This feature is discussed in terms of nuclear forces involved, within state-of-the-art shell model calculations. Even though the global agreement with data is quite convincing, the calculations underestimate the size of the *N*=16 gap in ³⁶Ca by 840 keV.

[L. Lalanne, O. Sorlin et al. Phys. Rev. Lett. 131, 092501 (2023)]

<figure><img src="image_35.png" /><figcaption>Figure 5: The MUST2 step up with the liquid hydrogen target CRYPTA</figcaption></figure>

5. The AGATA project

GANIL is an important partner of the AGATA collaboration; The Project Manager is part of the STARS group and the GTA group is in charge of the trigger and clock distribution of the Phase 2 Project. GANIL hosts the Operation Cost of the collaboration and contribute to 50% of the French share. The achievement of phase 1, the review of the performances and the technical design of phas 2 have been published in a dedicated topical issue in EPJA. GANIL physicist have beam part of the guest editorial board and leading authors of several contribution

[The European Physical Journal A, AGATA: Advancements in Science and Technology, Nicolas Alamanos, Maria Jose Garcia Borge, Angela Bracco, Emmanuel Clement, Andres Gadea, Wolfram Korten, Silvia Leoni and John Simpson (2023)]

<figure><img src="image_36.png" /><figcaption>Figure 6: The AGATA array at LNL since 2021</figcaption></figure>
## II. PHYSICS OF HEAVY AND SUPERHEAVY NUCLEI

The main research topics of the PHASE group are the studies of nuclear structure and reaction mechanisms from the proton drip line to the end of the periodic table. These studies are based on laser and decay spectroscopy, and mass spectrometry.

The group is in charge of developing the state of art spectrometer (S³) and the associated new instrumentation (SIRIUS and LEB).

### 1. Commissioning of the S³ Target Station at LISE2000

In order to sustain the very high intense heavy ion beams accelerated by the LINAG, a specific target station for stable material was designed and built few years ago and mainly financed by a CPER (Contrat Plan Etat Région Normandie). This station consists of a vacuum chamber equipped with two large wheels and a set of instrumentation for monitoring the target integrity and the beam characteristics, i.e. beam spot profile, intensity and time structure [1].

Until 2022, all the components of the target station were developed and tested separately, and it was essential to evaluate the whole system under realistic irradiation conditions. In July 2023, few UTs of a ²⁰Ne³⁺ beam at 4.5 MeV/u up to 1.8 µA, was delivered to the LISE2000 beam line where the target station was installed.

Firstly, the intensity on the Faraday cup, used to protect the targets during beam tuning, was measured at low intensities, up to about 30 Watts. The response was found to be proportional to the beam intensity monitor of the cyclotron.

The synchronization of the wheel with the beam time-structure was then checked. To avoid irradiating the target frames and to optimize the irradiation of the material effective surface, a user defined signal controls the cyclotron chopper. The signal time-structure was set using an absolute encoder and a National Instrument compact RIO controller with a LabVIEW interface. The count rate of a barium fluoride scintillator, sensitive to gamma radiation emitted by the interaction of the beam with the frames or target material, was used to adjust the delay and the width of the synchronization signal. In addition, an optical switch and a hall effect sensor were positioned on a small toothed wheel fixed on the rotating arm in order to get a redundant signal for each revolution.

The integrity of 16 different targets mounted on the upstream wheel was checked by three methods: alpha particle energy loss, particle scattering and transmission of an electron beam. The working principle and the systems are described in [2] [3] and illustrated in Figure 7. The S³ target station is equipped with an electron gun from STAIEB industry, whose control and command was developed to remotely configure its energy and intensity, as well as the deflection sequence according to the wheel rotation signal. In addition, a current/voltage converter was designed to measure the electron current output signal from the Faraday cup.

All the signals, i.e. from the silicon detectors, the BaF2 scintillator, the electron Faraday cup and the deflector, the wheel rotation, are processed, digitalized and time-stamped by a dedicated NUMEXO2 module. The data obtained make it possible to display the various observables, either their count rate or their energy, along the target. All tests were performed at a speed between 0 to 1000 rpm. Up to about 2 µAe of incoming beam intensity, the obtained spectra were as expected. In addition, a two-dimensional image of each target was obtained, currently at low resolution with on-line data. This display allows to distinguish thin and thick targets and pinholes of less than 1 mm in diameter.

In conclusion, with these beam conditions, we were able to validate the response of the heavy-ion Faraday cup, the synchronization of the beam with the wheel rotation, the detection systems and the data acquisition. Following the feedback from this test, some feedthroughs have been enlarged and added in order to facilitate the access to connections. The station has been moved to S³ and will be commissioned with a LINAG beam in fall 2024.
<figure><img src="image_37.png" /><figcaption>Figure 7: S³ target station</figcaption></figure>

### Reference

[1] C. Stodel, J.-F. Libin, C. Marry, F. Lutton, M.-G. Saint-Laurent, B. Bastin, J. Piot, E. Clément, S. Le Moal, V. Morel, J.-C. Thomas, O. Kamalou, G. Grémont, C. Spitaels, H. Savajols, R. Hue, P. Gangnant, M. Authier, A. Drouart, A. Van Lauwe, E. Lamour, J. Kallunkathariyil, C.-O. Bacri, V. Petitbon-thévenet, H. Lefort and F. Pellemoine, "High Intensity targets stations for S³," *Journal of Radioanalytical and Nuclear chemistry*, vol. 305, no. 3, pp. 761-767, 2015.

[2] C. Stodel, "Methods of Targets' Characterization," *EPJ Web of conferencs*, vol. 229, p. 02001, 2020.

[3] J. Kallunkathariyil, C. Stodel, C. Marry, G. Frémont, B. Bastin, J. Piot, E. Clément, S. Le Moal, V. Morel, J.-C. Thomas, O. Kamalou, C. Spitaels, H. Savajols, M. Vostinar, F. Pellemoine and W. Mittig, "S³ Target Monitoring with an Electron gun," *AIP Conference Proceedings*, vol. 1962, no. 1, p. 030019, 2018.

## 2. Commissioning of SIRIUS

SIRIUS (Spectroscopy and identification of Rare Isotopes Using S³) is a detection setup at the focal plane of S³ designed for the alpha, gamma, conversion electron and fission spectroscopy of superheavy nuclei. The detector was built in collaboration between GANIL, IRFU, IPHC and IJCLab and assembled in GANIL in March 2021.

In June 2023 we performed an online test of the setup in the IRRSUD beamline in order to validate the system under beam conditions and test the time-of-flight measurement. The test used a 0.28 MeV/u ²³⁸U beam from the C02 injector cyclotron in order to mimic the energy deposition of the recoiling nuclei produced in fusion-evaporation reactions. The acquisition system was able to take data with the implantation detector and the tracker detector up to 1000 Hz.

The time of flight is measured between the emissive foil of the Tracker and the Double-Sided Silicon strip Detector (DSSD) where the ions are implanted. The Tracker consists of a Secondary Electron Detector (SeD) with Mylar emissive foil placed at 45° with respect to the beam axis. The time signal of the SeD and the signals of the DSSD are sent into a NUMEXO digitizer where the signal is recorded at 200 MHz and timestamped with 100 MHz clock. The time of flight was measured between the timestamps of the SeD and DSSD and corrected with the trigger point reconstructed on digitized each signal. This measurement provided a time of flight resolution of 2.06 ns FWHM.
In addition to the timing, the Tracker also has a 1mm FWHM position resolution. This allows tracking individual ions at the focal plane of S³ and enhance the mass resolution of the spectrometer. The trajectories of the ions between the SeD and the DSSD were reconstructed during the test. Figure 8 shows the projection of the trajectories on the horizontal plane.

<figure><img src="image_38.png" /><figcaption>Figure 8: Tracking of individual ions between the Tracker and the DSSD of SIRIUS.</figcaption></figure>
### III. FISSION AND REACTIONS

The FIRE (Fission & REactions) group is principally concerned with the study of nuclear dynamics, its interplay with nuclear structure, and its use to better constrain the underlying effective nuclear interactions and their extrapolation towards an equation of state for dense matter. The members of the group are at the forefront of research into topics ranging from nuclear fission to multifragmentation and beyond. As such, the members of FIRE are also responsible for two major instruments of GANIL used in this field, namely the VAMOS++ spectrometer and the coupled INDRA-FAZIA charged particle arrays.

#### 1. Experimental evidence of the effect of nuclear shells on fission dissipation and time

<figure><img src="image_39.png" /><figcaption>Figure 9: Evolution of local even-odd effect as a function of heavy fragment Z and excitation energy above the barrier (see text)</figcaption></figure>

More than 80 years after its discovery, nuclear fission is still one of the most complex physical processes we can observe in nature due to the interplay of macroscopic and microscopic nuclear properties that decide the result. An example of this coupling is the presence of nuclear dissipation as an important ingredient that contributes to drive the dynamics and has a clear impact on the duration of the process. However, different theoretical interpretations, and scarce experimental data make it poorly understood. Thanks to data obtained from transfer-induced fission reactions between a ²³⁸U beam and a ¹²C target, measured in inverse kinematics with the VAMOS++ large-acceptance magnetic spectrometer, we achieved the first experimental determination of the dissipation energy in fission as a function of the fragment split, for three different fissioning systems. The amount of dissipation was obtained through the measurement of the relative production of fragments with even and odd atomic numbers with respect to different initial fission energies (see Figure 9). The results reveal a clear effect of particular nuclear shells on the dissipation and fission dynamics. The analysis of the relative production of even- and odd-Z fragments shows a clear influence of nuclear structure in the dissipation process and fission dynamics: fission is faster when producing fragments with spherical shell Z = 50, but slower and more dissipative when fragments are near the octupole-deformed shell Z = 52.

→ D. Ramos, M. Caamano, F. Farget, C. Rodriguez-Tajes, A. Lemasson, C. Schmitt et al., Phys. Rev. C 107, L021601 (2023)

#### 2. Experimental study of isospin transport with ⁴⁰,⁴⁸Ca+ ⁴⁰,⁴⁸Ca reactions at 35A MeV

The nuclear equation of state (NEoS) of bulk nuclear matter over a wide range of densities, temperatures and neutron-to-proton asymmetries remains a major issue in modern nuclear physics and astrophysics. Heavy-ion collisions are a unique tool to probe the NeoS at finite temperature under laboratory-controlled conditions, especially to constrain the density dependence of the symmetry energy $E_{sym}(ρ)$ of the NEoS. With this aim, isospin transport in heavy-ion collisions around the Fermi energy has been measured with the coupling of the VAMOS high-acceptance spectrometer and the INDRA charged-particle multidetector. Two main contributions to isospin
transport phenomena are generally distinguished: *isospin diffusion*, taking place whenever an isospin gradient is present and inducing isospin equilibration, and *isospin drift*, driven by density gradients, leading to the neutron enrichment of lower-density regions.

<figure><img src="image_40.png" /><figcaption>Figure 10: Isospin transport ratio for PLF/QP produced in isospin-asymmetric reactions as a function of centrality (c=0 corresponds to head-on collisions). The closer the upper & lower branches, the greater the degree of isospin equilibration.</figcaption></figure>

Using isotopically-identified projectile-like fragments (PLF) measured with VAMOS and selected light-charged particles (LCP: Z = 1,2) measured in coincidence with INDRA, the properties of the initial highly-excited quasiprojectile (QP) have been estimated on an event-by-event basis using a novel reconstruction method. Using the asymmetry $\delta = (N-Z)/A$ of either PLF or QP as isospin-sensitive observable and the total transverse energy of LCP for centrality sorting, the isospin transport ratios demonstrate a clear increase of isospin equilibration with increasing centrality, due to isospin diffusion between projectile and target. Isospin drift has also been evidenced through an enhancement of the mean neutron-to-proton ratio of LCP emitted in the mid-velocity region, for the reactions using same-$\delta$ projectile-target combinations where isospin diffusion is expected to be negligible.
→ Q. Fable, A. Chbihi, J.D. Frankland et al. (INDRA Collaboration), Phys. Rev. C 107, 014604 (2023)

### 3. Quasiprojectile breakup and isospin equilibration at Fermi energies: Potential indication of longer projectile-target contact times

<figure><img src="image_41.png" /><figcaption>Figure 11: Comparison of isospin transport ratio centrality dependence (b=0 corresponds to head-on collisions) between binary exit channels leading to a QP evaporation residue (QP evap) or the QP breakup channel, for 32A and 52A MeV reactions. In each case the distance between the upper and lower branch is related to the distance from isospin equilibration.</figcaption></figure>

In our previous analysis of data from the first INDRA-FAZIA campaign (Ciampi et al., 2022), the topic of isospin equilibration in the reactions $^{58,64}$Ni+$^{58,64}$Ni at 32 and 52 A.MeV was addressed by considering the most dominant reaction channel for semiperipheral and peripheral reactions: a binary exit channel resulting in the production of two main fragments, the quasiprojectile (QP) and the quasitarget (QT), accompanied by lighter ejectiles, such as neutrons, LCPs, and intermediate mass fragments (IMFs). Along with the binary exit channel, a ternary (or quaternary) outcome is also possible: in this case, one (or both) of the heavy products may break up into two smaller fragments, in a fission-like process. When the characteristic timescale of this process is short (around or
below 1 zs) the breakup process has been linked to a dynamical origin. In this new analysis, isospin equilibration has been studied for the QP breakup channel, using the isospin transport ratio for the neutron-to-proton ratio of the QP reconstructed from its daughter fragments. Evidence was found that, for the same reaction centrality, a higher degree of relaxation of the initial isospin imbalance is achieved in the breakup channel with respect to the binary channel, possibly indicating the indirect selection of specific dynamical features. An interpretation based on different average projectile-target contact times related to the two exit channels under investigation was proposed, with a longer interaction for the breakup channel. The time information has been extracted from Antisymmetrized Molecular Dynamics (AMD) simulations of the studied systems coupled to the statistical decay code, GEMINI++: the model calculations appear to support the present hypothesis.

→ C. Ciampi, S. Piantelli, G. Casini, A. Ono, J.D. Frankland et al. (INDRA-FAZIA Collaboration), Phys. Rev. C **108**, 054611 (2023)

## Inverse-Kinematics Fission with PISTA at VAMOS++

The Particle Identification Silicon Telescope Array (PISTA) has been developed and installed at VAMOS as collaboration between FIRE group and CEA/DAM. The array of 8 ΔE-E telescopes composed of highly segmented silicon detectors aim at achieving isotopic identification of light charged particles from He to O. The goal is to obtain a precise characterization of the incoming channel of a fission reaction induced by multi-nucleon transfer reactions in terms of fissioning system identification and event-by-event initial excitation energy measurement. The PISTA detector was operated for the first time in a experiment studying the fission of actinides produced in reaction of $^{238}$U beam at Coulomb energies on $^{12}$C target. Fissioning systems ranging between U and Cm where isotopically identified by detecting in PISTA the target-like recoils from He up to Carbon isotopes as shown in Figure 12. The achieved resolution in excitation energy is better than 1MeV FWHM. In addition, for each fission reaction, one of the fission fragments was fully characterized using the magnetic spectrometer VAMOS++ and associated detection equipment.

<figure><img src="image_42.png" /><figcaption>Figure 12: Light charged ΔE-E particle identification in PISTA from He to Carbon. The good separation between the 3 isotopes of Carbon, 12C, 13C and 14C reflects the high identification capability of the detector. [PhD work of L. Begue-Guillou]</figcaption></figure>
IV. FUNDAMENTAL INTERACTIONS AND DARK SECTORS

The Fundamental Interactions aNd Darks Sectors (FINDS) group is looking for evidence of New Physics thanks to
precision measurements scrutinizing the decay or de-excitation of radioactive nuclei. It presently encompasses the
MORA and New JEDI experiments, precision measurements of branching ratio and half-lives of 0⁺ to 0⁺ β emitters,
and the search for a dark decay channel in the decay of ⁶He [1]. In 2023 a proposal to the PAC was accepted to
evaluate the contribution of isospin symmetry-breaking forces to the 0⁺ to 0⁺ superallowed Fermi β-decay of the
¹⁸Ne nucleus at the SPIRAL facility and should be scheduled in 2025.

1. The Matter's origin from RadioActivity (MORA) experiment

MORA is looking for a possible evidence of charge and parity CP symmetry violation in the nuclear beta decay of ²³Mg⁺ and ²³Ca⁺ laser polarized ions [1]. A large CP violation is required to explain the matter antimatter imbalance observed in the Universe. The MORA experiment is using an innovative polarization technique, which combines the high efficiency of ion trapping with the one of laser orientation. It is currently taking data using ²³Mg⁺ beams delivered by the IGISOL [2] facility, at the Accelerator Laboratory of the University of Jyväskylä. A strong isobaric contamination by ²³Na⁺ ions (²³Na:²³Mg ~ 1000), originating from the IGISOL gas cell components, has so far limited the statistics acquired. Despite this limitation, a polarization proof-of-principle has been attempted at the end of 2022. The analysis of this experiment was undertaken during the first semester of 2023. The results were presented during two PhD defences [3,4]. The analysis showed that a contamination of at least a factor of 10 lower is needed to realize the proof of principle in reasonable time (a few days of data-taking). The defences were also displaying in details the otherwise good performances of the MORA apparatus: 10% trapping efficiency, detection (Figure 13) and laser polarization system working nominally, good overall production of ²³Mg from the IGISOL facility, up to a few 10⁵ pps for 10 µA of 30 MeV protons on the thin Mg target. The experimental efforts of 2023 concentrated on reducing possible traces of Na in the target by producing at GANIL different Mg thin foils or MgO crystals, baked and or coated with BaO to reduce potential surface ionization of this alkali element. One on line test was realized

during summer 2023, showing no real improvement with
these optimized targets, but evidencing the possibility to use
molecular sideband formation to move the ²³Mg⁺ beam away
from its isobar contaminant. A few thousands of pps of
²³MgF⁺ were formed thanks to the injection of SF₆ in the gas
cell and could be separated after the IGISOL separator. The
efficiency of the molecular formation remains to be
optimized. Eventually the efforts to reduce the contamination
should enable a measurement of *D* correlation to the ~10⁻⁴
level at IGISOL, which would competitive with the best limit
obtained so far on a non-zero *D* correlation in neutron decay
[5]. As of 2027, the DESIR facility at GANIL will offer rich
perspectives for MORA, thanks to the intense beams from
SPIRAL 1 and ad-hoc instrumentation for beam cooling,
bunching and purification, so that measurements with a
sensitivity to a ~10⁻⁵ level can be hoped for. At this level, the
measurement of the *D* correlation will be sensitive to Final
State Interaction (FSI) effects, which are radiative
corrections arising largely from weak magnetism, and which
are compliant with the Standard Model.

<figure><img src="image_43.png" /><figcaption>Figure 13 : The MORA detection setup around the trap, in the center. The chamber diameter is about 1m.</figcaption></figure>

References

[1] P. Delahaye et al., «The MORA project,» Hyp. Int., vol. 240, p. 63, 2019.

[2] I. D. Moore et al., "Towards commissioning the new IGISOL-4 facility," Nuclear Instruments and Methods in Physics Research B, vol. 317, p. 208, 2013.

[3] N. Goyal, Detection of beta decay in laser oriented trapped radioactive isotopes for the MORA project, PhD of the university of Caen, 2023

[4] S. Daumas-Tschopp, Recherche de violation de CP avec MORA : mise en service de l'installation et premières expériences, PhD thesis of the university of Caen, 2023

[5] H. P. Mumm et al., «New Limit on Time-Reversal Violation in Beta Decay,» Phys. Rev. Lett., vol. 107, p. 102301, 2011
## 2. New Judicious experiments for Dark sectors Investigations (New JEDI):

In 2023, lecture notes concerning the New JEDI project have been published [1]. The focus was set on the ⁸Be data analysis aiming to study the existence of the hypothetical X17 boson, from the experiment carried out at the ANDROMEDE facility (see Figure 14). In practice, algorithms have been developed to check the proper data synchronization between channels and between digitizers (via the Numexo fusion mode), to identify and to correct the data for dead time. Two soft methods have been developed to reconstruct coincidences between the plastic detectors. Results are compatible with the one recorded using an additional analog electronic chain. We studied

also the lepton-nucleons elastic scattering formalisms: quantum-relativistic (Mott) model versus classical (Rutherford). Finally, we made an independent study of the ⁸Be anomaly spectrum from ATOMKI group. We studied the Internal Pair Creation process formalism (IPC) and the Boson emission formalism (X17). We developed tools based on simulations, to fit and interpret the ⁸Be spectrum including IPC, X17 and other contributions, such as the scattering of leptons on nuclei. This work was done in collaboration with Prof (Hon) Tibor Kibédi from the Australian National University. One PhD student, 2 master students and a bachelor student worked on all these aspects. In addition, in October 2023, we performed a complementary experiment at the iThemba LABS facility. The aim of this experiment is to check the existence and the impact of additional nuclear physics effects in the ⁸Be quantum system and to see to what extent it impacts the result concerning the X boson.

<figure><img src="image_44.png" /><figcaption>Figure 14: New JEDI experimental setup at ANDROMEDE</figcaption></figure>

### References

[1] B. Bastin, J. Kiener, I. Deloncle, A. Coc, M. Pospelov, J. Mrazek, L. Lamia, on the Behalf of the New JEDI collaboration, EPJ Web of Conferences 275, 01012 (2023).

## 3. Search for a neutron dark decay in ⁶He

The 1% discrepancy with a 4.4σ between beam and bottle experiments measuring the neutron lifetime has triggered many interrogations within the physics community. In 2018, Fornal and Grinstein suggested that this difference could be the consequence of a new decay channel involving dark matter particle(s) in the final state. Following this idea, Pfützner and Riisager listed radioactive nuclei whose decay could be sensitive to this channel, among which ⁶He:

<figure><img src="image_45.png" /><figcaption>Figure 15: The TETRA detector used in 2021.</figcaption></figure>

$$ ^6\text{He} \rightarrow ^4\text{He} + n + \chi, $$

where a free neutron and DM particle noted χ are emitted, would be a unique signature to look for a potential dark decay as there are no neutron emissions in a standard ⁶He decay from its ground state. ⁶He probes about 75% of the open mass range for χ to be a DM candidate. In 2021, the high efficiency neutron detector TETRA (Fig. 3) was used to look for this specific dark decay at LIRAT with a 10⁸ ⁶He/s beam. The data analysis, concluded in 2023, allowed us to put a stringent upper limit for the branching ratio, at Brχ ≤ 4×10⁻¹⁰, which is about 5 orders of magnitude lower than previously estimated.

M. Lejoubioux et al., Phys. Rev. Lett. 132, 132501 (2024)
# V. DOSIMETRY, APPLICATIONS AND NUCLEAR DATA

The activity of the research group DOSADO in 2023 was mainly focused on 3 topics related to cancer treatment and neutron-induced reactions.

## 1. Radiotherapy and dosimetry

In 2018, the number of people in France who had cancer in their lifetime was around 3.8 million. Their risk of developing a second cancer is on average 36% higher than the risk of cancer in the general population. In this context, reducing side effects and improving quality of life after treatment have become a major issue in cancer research. DOSADO group works particularly on two treatment modalities to address this challenge: pencil-beam scanning proton therapy (PBS-PT) and targeted alpha therapy (TAT).

PBS-PT consists of irradiating the tumor volume with a large number of thin proton beams, whose position, energy and intensity are adapted to deliver the prescribed dose distribution. The delivery technique combined with the Bragg peak dose deposition allows a better sparing of normal tissues than X-Ray radiotherapy and thus a reduction of the risk of radiation-induced cancer. However, quality assurance of PBS-PT treatments is complex, especially for small target volumes (< 3 × 3 × 3 cm³). A 3D scintillation dosimetrer was finalized in 2023 and an experimental program was completed at the Cyclhad protontherapy center. It provided data currently under analysis to perform 3D dose reconstruction.

TAT consists of injecting the patient with a radiopharmaceutical that specifically targets biomarkers of the cancer cells or their immediate environment. In TAT, it is radiolabelled with alpha-emitting radioisotopes. The short range and the high ionization density of alpha particles allow for high dose deposition in cancer cells while sparing surrounding tissues. In this domain, the DOSADO group has two main contributions. The first one deals with the study of the production of alpha-emitting radioisotopes, and in particular of ²¹At to increase its production

efficiency. This research program was funded by the REPARE ANR program that will end in March 2024. In 2023, the ²¹At contaminant production cross section was measured. It is reported in a collaboration report and will be published in the near future. The principal activity was the design of a high-power solid Bismuth target and the first in-beam tests in September 2023. The second contribution of DOSADO to TAT deals with the study of the treatment biological effects at the cell level. In this context, a new detection system and a deconvolution method were developed by A. Doudard during his PhD, which he defended in September 2023. This work was published in Med. Phys. and presented in two international conferences.

<figure><img src="image_46.png" /><figcaption>Figure 16: High power solid Bismuth target installed in the converter room of NFS.</figcaption></figure>

## 2. FALSTAFF

2023 was a busy year for the FALSTAFF collaboration, with a scientific activity shared equally between:

* FALSTAFF's experimental program;

* The project of building the second arm of the spectrometer.

As for the experimental program, first we analyzed the data of the E814_20 experiment, which was performed at NFS in fall 2022 on the neutron-induced fission of ²³⁵U. The analysis is still going on to achieve publishable results
on the dependence of the fission-fragment mass-yields on the incident-neutron kinetic energy, closely linked to the excitation energy of the fissioning system. The existing GEANT4 FALSTAFF simulations were improved to allow a better detector calibration. The data analysis results will be compared to GEF and FIFRELIN predictions, filtered by the GEANT4 simulation. Second, we have designed and proposed a second experiment for FALSTAFF at NFS on the study of the neutron-induced fission of $^{237}$Np. This proposal was recommended by GANIL-SPIRAL2 PAC and will be run in October 2024.

We consolidated the project of building the second arm of FALSTAFF. This second arm will allow measuring in coincidence both fission fragments and performing, event by event, mass, energy and charge balances. Such balances are key observables for fission and fragment-deexcitation models. In addition, we submitted a proposal for funding to the French ANR (Agence Nationale de la Recherche) for the first five years of the scientific program of FALSTAFF. The construction of FALSTAFF second arm started and will allow us to reach our nominal goal with this detector.

<figure><img src="image_47.png" /><figcaption>**Figure 17:** The two-arm fission-fragment spectrometer FALSTAFF installed on the neutron line of SPIRAL2/NFS. The detectors of both arms have been made feasible by transparency of the vacuum vessels. (Scale: The beam pipe is at 1.5 m from the floor)</figcaption></figure>

### 3. Studies on neutron-induced reaction with Medley at GANIL

The MEDLEY detector (see Figure 18) is designed to measure the doubly differential cross sections of light charged particles (LCP) emitted in neutron-induced reactions. It consists of 8 telescopes, each consisting of 2 silicon junctions and a Cesium iodide crystal. The $\Delta$E-$\Delta$E-E technique is used to identify charged particles (p, d, t, alpha and $^{3}$He), measure their time-of-flight and determine the incident neutron energy. Cross sections up to about 40 MeV can be measured at the NFS facility. These cross sections are fundamental quantities for research in many fields, including neutron dosimetry in aerospace, medical applications, radiation effects in electronics and, most importantly, the development of fusion energy.

In addition to feeding the nuclear databases, the results of these experiments will be used to test and improve the models used in the Talys code. Indeed several models, as optical potential, pre-equilibrium and statistical de-

excitation models, are needed to properly describe these reactions. Since 2021, several experiments have been carried out at NFS: LIONS, GARIC and GARROS to study carbon, chromium and iron respectively. The spokesperson of these experiments is D. Tario from Uppsala University. In 2024 a new experiment will be performed on Copper and the spokesperson is I. Ipatova from UKEA. The analysis and interpretation of the results is the subject of Lucas de Arruda's PhD thesis (jointly supervised by the University of Caen-Normandie and the University of Uppsala). In addition to the LCP production cross section, the neutron spectrum and flux can be determined using a CH$_2$ target and detecting the scattered protons.

<figure><img src="image_48.png" /><figcaption>**Figure 18:** The MEDLEY detector with its 8 telescopes</figcaption></figure>
VI.CIRIL

Interdisciplinary research has been part of the GANIL facility's scientific ambition since its inception. The platform for hosting interdisciplinary researches is the CIRIL platform, which runs the beamlines (D1-HE, D1-ME, IRRSUD and ARIBE) for non-nuclear physics and their equipments, develops new devices requested for experiments, manages the proposal selection process of the local interdisciplinary program advisory committee (IPAC) and schedules the interdisciplinary physics beamtimes accepted through scientific committees. Today, up to 4 simultaneous experiments can be hosted using the 4 beamlines corresponding to each step of the ion acceleration at GANIL (ion source: ARIBE, C0 injector: IRRSUD, CSS1: ME, CSS2: HE). This multi-user configuration enables different interdisciplinary research communities to meet up, leading to the emergence of new projects. Simultaneous use of the lines is only possible thanks to the very specific configuration of the GANIL, with its 3 cyclotrons (C0, CSS1 and CSS2) in cascade (for HE, SME and IRRSUD) and the presence of two C0 injector cyclotrons. Thanks to parallel operation for several users, interdisciplinary research has access to beam times comparable to, or even superior to, nuclear physics.

In addition, in-situ characterization techniques have been developed using state-of-the-art online techniques such as X-ray diffraction, IR/Visible/UV emission/absorption photon spectroscopy, gas analysis, mass spectrometry, time-of-flight measurements or electron spectroscopies. Devices for low-temperature and/or high-temperature irradiation, under ultra-high vacuum or in a controlled atmosphere have also been built, expanding the range of studies using accelerated ions. The construction of the biology sample preparation laboratory, ARIA with the newly IBISA accreditation, has improved the facilities for radiobiology experiments and attracted new experimenters.
We will install in 2024 the new IRRSUD command/control program and we will develop a new MIRRPLA multi-beam chamber that will be open to the community in 2026.

If the topics that interdisciplinary physics covers have continually evolved as a result of expanding possibilities (beamlines and on-line instrumentation) and the emergence of new subjects, to date, GANIL's beams remain highly attractive to the interdisciplinary community for which the main physics themes are: materials science applied to inorganic materials, materials science applied to organic materials, astrochemistry or astrophysics, radiobiology and atomic and molecular collision physics.

The collection of experiment reports (see part 04-VI) summarizes the scientific objectives carried out in 2023.
<figure><img src="image_49.png" /></figure>
<figure><img src="image_50.png" /></figure>
# I. EXECUTIVE SUMMARY OF ACCELERATOR AND EXPERIMENTAL AREAS OPERATION

Since 2019, GANIL operation concerns the LINAC as well as the cyclotrons.

The first beam was ejected from CSS2 forty years ago, while SPIRAL1 first radioactive beam is 23 years old.

The LINAC is still in a commissioning phase for S³ beams, but also, for the second year, in operation for experiments in NFS (Neutrons For Science) for nuclear physics, nuclear data and also for nuclear medicine development. For the first time, the operation teams have tuned the LINAC from the main control room.

Compared with 2022, the shutdown began sooner than usually, in mid-November, due to energetics strains in the world. Therefore, the time available for physics in NFS was decreased.

Fortunately, failure rate of the cyclotrons facility in 2023 has been improving compared to 2022. More than 1900 hours are dedicated for beam time in cyclotrons experimental areas.

## 1. GANIL operation status

Over the almost last 30 years, cyclotrons beam time shows a peak in 2005 and a decrease since 10 years due to the construction and operation of SPIRAL2 (Figure 19).

Since 2019 yet, LINAC operation is to be added to cyclotron operation. Total physics beam time is more than 2500 hours in 2023. Moreover, we have parallel beam-time delivered to SME (600 hours), IRRSUD (1305 hours) and ARIBE (790 hours) operation. This corresponds to a total available beam-time for experiments of more than 4600 hours. During next years, the parallel operation of cyclotrons and LINAC will be considered to increase available time for experiments.

<figure><img src="image_51.png" /><figcaption>Figure 19: Cyclotrons Beam time available for physics since 1996.</figcaption></figure>
<figure><img src="image_52.png" /><figcaption>Figure 20: Beam time available for physics (Cyclotrons + LINAC).</figcaption></figure>

## 2. 2023 cyclotrons operation

The accelerator failure rate is much better, with a notable improvement in 2023 (Figure 21), compared to 2022 when a high failure rate due to water leaks inside the machine was observed.

Nevertheless, the failure rate of the recent last years of an 40 year old machine combined with the high-level of demands at the PAC (Physics Advisory Committee)- still claims the need of the CYREN (Cyclotron Renovation) project, a major renovation plan of the cyclotron facility to operate the facility 20 years more.

<figure><img src="image_53.png" /><figcaption>Figure 21: Cyclotron failure rate since 1996</figcaption></figure>

The accelerator tuning rate is at 14%, to be compared to 10% in 2022 and 16% in 2021. Difficulties of tuning have been analysed to be related not to new beams but to experiments needing high intensity, like SPIRAL1 radioactive beams ($^{19}$O and $^{20}$O).

Because of a dedicated time for improving the beam delivery, the part of the machine studies rose up to 6% (2% in 2022). This time for machine studies is related to developments for radioactive beams at SPIRAL1 (see Radioactive Beam Developments in this report) but also to some tests dedicated for SPIRAL2 (production of radioisotopes for medical use in NFS or high-power target development for S$^3$) in mid-2023.
Significant increase of beam-time for interdisciplinary physics or industrial application follow 2022 technical failures during which these programs had been cancelled to preserve nuclear physics experiments (Figure 22).

<figure><img src="image_54.png" /><figcaption>Figure 22: Main Beam Use (High and Medium Energy)</figcaption></figure>

Concerning nuclear physics, LISE (D3/D4/D6) (fragmentation of CSS2 beams and SPIRAL1) is still the most requested experimental area with the cyclotrons beam, right before G1 (fusion reactions or fission studies with CSS1 beams and SPIRAL1).

### 3. 2023 LINAC Operation

With NFS the only experimental facility in operation, the LINAC schedule is shared between physics, improvement of the tuning methods and tools, and beam development for S³.

D⁺, ⁴He²⁺ have been tuned for NFS in 2023, as well as two beams with ratio q/A=1/3 for S³ : ¹⁸O⁶⁺ and ⁴⁰Ar¹⁴⁺ were both accelerated to 7 MeV/u.

Machine studies are related to tests of new tuning methods, beam diagnostics or RF tests, control-command tests.

On the LINAC the tuning time has decreased, going from 20% (in 2022) to 15% (in 2023), demonstrating better control of the accelerator. However, the failure rate (Figure 23) was quite high, increasing from 8 to 19% (mostly RF failures concerning the RFQ).

<figure><img src="image_55.png" /><figcaption>Figure 23: Failure rate (LINAC and NFS)</figcaption></figure>
Five experiments have been proceeded and a new static converter for neutron production from deuteron beam (1,5 kW) has been commissioned. One of this experiment (REPARE) involved <sup>4</sup>He<sup>2+</sup> beam to produce Astatine 211, an experiment of research and development for nuclear medicine.

However the number of physics hours in NFS compared to 2022 has decreased (about 345 hours less) because of the shutdown of LINAC on mid-November (3 weeks less compared to 2022) having limited the number of experiments. In addition, one experiment had to be cancelled due to technical difficulties of the experiment: E856_22 with 42UT allocated by the PAC.

A machine study dedicated on the tuning method has replaced E856.
## II. ION BEAM AND RADIOACTIVE ION BEAM DEVELOPMENTS

### 1. ECR ion sources production on Cyclotron and SPIRAL2 facilities

**New beam: $^{232}$Th**

In the context of requests for a $^{232}$Th beam (LOI10-20, E849_21), the Target and Ion Source group has developed this new beam.

It is produced from a compound of $^{232}$ThF$_4$, for which the safety, security radioprotection group has been in charge of the supply.

The characterization of the compound and the tests carried out on the ECR4 ion source allow to validate this new beam, in terms of intensity, stability and charge state required for an acceleration to 6.1MeV/u.

<figure><img src="image_56.png" /><figcaption>Figure 24: Thorium beam charge states at the extraction of ion source.</figcaption></figure>

Finally, this new beam was programmed for the start of RUN1 2024 on the cyclotron facility. The intensity delivered by the ion source was around 2µAe (for the 30+ charge state) throughout the 15 days with good stability and without interruption. ThF$_4$ consumption was very low.

**High intensity $^{50}$Cr beam**

The E805_20 experiment required a $^{50}$Cr beam with a high intensity over a long period. This experiment was programmed in April 2023.

To meet this requirement, the Target Ion Source group team worked with the IPHC team to produce the beam.

The best method for obtaining an intense medium charge state for a stable, long-duration beam is to use the MIVOC method. This technique is based on the production of a volatile compound including the atom of interest.

For $^{50}$Cr beam, the molecule is $^{50}$Cr(C$_{10}$H$_{10}$) (or Cp$_2^{50}$Cr).

The IPHC team is specialised in producing syntheses with enriched isotopes. This compound has a high vapour pressure, which makes it easy to inject into the ion source.

The plasma of the ECR ion source breaks down the molecule and ionises the atom of interest.

<figure><img src="image_57.png" /><figcaption>Figure 25: Synthesis of Cp$_2^{50}$Cr produce by IPHC Team</figcaption></figure>

Finally, a sample of 1gr of Cp$_2^{50}$Cr allows to produce 35UT of 15µAe of $^{50}$Cr$^{10+}$
## 2. SPIRAL2 injectors : Upgrade for heavy ion source.

### Heavy-ion source: Phoenix V3

The phoenix V3 ion source is installed since 2020 at the LINAC injection and is dedicated to the production of ions with A/Q < 3. During the commissioning of the ion source at GANIL, it presented reliability problems (high voltage, pollution, metallization of insulators) and temporary technical adjustments were made to meet production requirements. In 2023, new devices were developed to improve the ion source and its reliability.

In the same time, the development of the metal beam continued, in particular with the testing of a recycling technique, with the aim of obtaining a $^{48}$Ca$^{16+}$ beam with optimized consumption. During this test, we observed the appearance of a hole in the tantalum liner inserted into the plasma chamber. This hole is the signature of a radial confinement problem produced by the permanent magnet hexapole. Given this weakness of the magnetic field, the hot electrons of the plasma of the source ECR have an output path other than the extraction of the source. The energy associated with this electron leakage creates a local heating zone that pierces the liner.

Studies have been carried out on the hexapolar permanent magnet to solve this problem. After measurements and simulations, some of the magnets in the hexapole were changed and we finally found a broken magnet at the origin of themagnetic field instability. The hexapole has been repaired and the magnetic field is now uniform.

<figure><img src="image_58.png" /><figcaption>Figure 26 : left : Magnetic structure of hexapole. Right : Broken magnet</figcaption></figure>

During the winter 2023, all modifications of ion source were done, including the installation of the new devices for reliability and the ion source restart in June 2024.

## 3. SPIRAL1 : Radioactive ion beam development

### TULIP project

In July 2023, a $^{20}$Ne beam at 4.5MeV/u beam delivered by the GANIL cyclotrons was used to test a second TULIP Target Ion Source System (TISS) to verify the results obtained in March 2022 on the production rates of $^{74-78}$Rb+ ions and the particularly short atom-to-ion transformation time observed. Additional isotopes were observed. Rates were improved compared to 2022 (see table).

<table><caption>Table 1 : Comparison between yields 2022/2023</caption><thead><tr><th rowspan="2">Rb Mass Number</th><th rowspan="2">Half-life T<sub>1/2</sub></th><th colspan="2">Production Rates</th></tr><tr><th>March 2022 <sup>22</sup>Ne 4.5 MeV/u</th><th>July 2023 <sup>20</sup>Ne 4.5 MeV/u</th></tr></thead><tbody><tr><td>74</td><td>64,8ms</td><td></td><td>1,7E+01</td></tr><tr><td>75</td><td>19 s</td><td></td><td>1,5E+04</td></tr><tr><td>76</td><td>36,8 s</td><td>3,8E+03</td><td>2,5E+04</td></tr><tr><td>77</td><td>3,9 mn</td><td></td><td>1,6E+05</td></tr><tr><td>78*/78</td><td>5,7 /17,7 mn</td><td>5,8E+04</td><td>6,8E+04</td></tr></tbody></table>
The atom-to-ion transformation time showed two components. One of them is long enough to partly explain the low production rate of the <sup>74</sup>Rb (65 ms).

An analysis of the production process highlighted several possible improvements: 1 - an increase of the TISS temperature to speed up the release of the radioactive atoms out of the cavity, 2 - an optimization of the primary beam energy to favor the production of <sup>74</sup>Rb nuclei, and 3 - an improvement of the primary beam intensity.

To insure the ability of the target to sustain the primary beam intensity and power, a rotating target is under development. Mechanical parts are under construction for a first test in fall 2024.

The main objective of the TULIP project is to deliver a TISS able to produce metallic ions in the region of the <sup>100</sup>Sn nucleus. For this purpose, the TULIP cavity developed for alkali ion production has been associated to the GANIL FEBIAD (see Figure) for its high performances. The first off-line tests will be performed by July 2024.

<figure><img src="image_59.png" /></figure>

A detailed description of this development is given in the PhD thesis of V. Bosquet, defended in June 2024

## TISS MonoNaKe

MonoNaKe is a TISS dedicated to the production of radioactive alkali ions, from Li to Rb. After an on-line test performed in spring 2023, technical improvements and tests have been done off-line to compare the performances of two ionizing materials, i.e. Pt and graphite. Regarding their respective physico-chemical features, Pt should offer better performances. Surprisingly, ionization efficiency was better in graphite. A first on-line test with a primary beam of <sup>13</sup>C at 60 MeV/u has provided intensities of ~1E+7 pps of <sup>8</sup>Li+ and of ~1E+5 pps of <sup>9</sup>Li+. As the primary beam intensity was lower than expected, one can consider a room for progress and a post-accelerated beam of <sup>9</sup>Li+ as realistic.

A MonoNaKe TISS equipped with a graphite ionizer was thus used to deliver post-accelerated ions of <sup>8</sup>Li+ at 1.2 MeV/u to the E864_22 experiment in June 2024. The intensity was higher than demanded (> 1E+4 pps).

<figure><img src="image_60.png" /><figcaption>Figure 27: Photo of Graphite and Platinum ioniser</figcaption></figure>
Li is the most difficult alkali to ionize. The ionization obtained for Li ensures a better ionization efficiency for all the other alkali. Moreover, it suggests the possibility of ionizing other elements like alkaline-earth elements while conserving an ionization selectivity. Such test will be performed by spring 2025.

## TISS FEBIAD

In April 2023, a stable beam of <sup>50</sup>Cr at 72 MeV/u was sent into a FEBIAD TISS in order to produce radioactive chromium isotopes. Due to the unexpected exhaustion of the primary beam sample, the experiment was cut short and the beam power was reduced to about 1/30 of the expected value. Nevertheless, the experiment was a success as it was possible to estimate the rates for the new beams <sup>48,49</sup>Cr and <sup>50</sup>Mn and for other several previously measured beams of Cl, Ar and K. These rates can be reasonably extrapolated to higher primary beam power or other available primary beams with higher production cross sections (see table 2 showing the rates in pps per W of primary beam and the expected rate with the GANIL beam yielding the highest production in the target).

We also observed radioactive molecules of AIF and HCl, which could be used in the future for selective extraction of a given species. A small amount of CF4 was injected into the TISS after irradiation, allowing to create several diatomic or triatomic fluoride ions with Be, C, Al, Mg.

<table><caption>Table 2: Rate/W of primary beam, measured during experiment and rate extrapolated with the best primary beam</caption><thead><tr><td>Isotope</td><td>rate 50Cr/W (pps)</td><td>Extr. best beam (pps)</td></tr></thead><tbody><tr><td>50Mn</td><td>3.5E+02</td><td>2.1E+05</td></tr><tr><td>49Cr</td><td>2.5E+04</td><td>1.5E+07</td></tr><tr><td>48Cr</td><td>1.2E+04</td><td>7.0E+06</td></tr><tr><td>45K</td><td>1.1E+02</td><td>5.8E+06</td></tr><tr><td>44K</td><td>1.3E+03</td><td>2.2E+07</td></tr><tr><td>43K</td><td>1.5E+04</td><td>1.1E+08</td></tr><tr><td>43Ar</td><td>2.5E+01</td><td>6.7E+05</td></tr><tr><td>42K</td><td>1.0E+05</td><td>3.3E+08</td></tr><tr><td>41Ar</td><td>2.7E+03</td><td>1.5E+07</td></tr><tr><td>41Cl</td><td>1.6E+01</td><td>2.8E+05</td></tr><tr><td>40Cl</td><td>1.7E+02</td><td>1.5E+06</td></tr><tr><td>39Cl</td><td>1.9E+03</td><td>1.2E+08</td></tr><tr><td>38K</td><td>2.3E+04</td><td>2.5E+08</td></tr><tr><td>38mCl</td><td>9.4E+01</td><td>2.2E+06</td></tr><tr><td>38Cl</td><td>1.2E+04</td><td>2.7E+08</td></tr><tr><td>37K</td><td>4.8E+02</td><td>5.3E+06</td></tr></tbody></table>
# III. PHYSICS OF ACCELERATORS

This report presents new projects started on cyclotrons in order to improve GANIL capacity to deliver beams, in terms of intensity, energy range, or availability. The nominal energy for heavy ions has been reached this year in the SPIRAL 2 LINAC. Theoretical studies on beam dynamics and machine studies in the linac are also described. Artificial intelligence applications for accelerators are also investigated in the frame of a European effort.

## 1. CYCLOTRONS

### Increase of the energy range available on the IRRSUD beamline

The energy range accessible on the IRRSUD beamline is currently between 0.27 and 0.99 MeV/u. However, potential users at the CIMAP laboratory have expressed their interest in very low energy ions and filling an energy zone not accessible at GANIL, between the energies available on ARIBE and those of IRRSUD.

<figure><img src="image_61.png" /><figcaption>Figure 28: $^{18}$O$^{2+}$ beam turn inside the C02 in harmonic 5 with an HF voltage of 25.05 kV.</figcaption></figure>

The EM133 machine study was carried out with success in guiding approximately 500 nA of an $^{18}$O$^{2+}$ beam at an energy of 0.108 MeV/u at the C02 exit in harmonic 5, with an efficiency of 10.6%. The beam optimized in harmonic 5 appears to be usable (intensity and quality in L1 beamline) by physicists on IRRSUD. This $^{18}$O$^{2+}$ beam at 0.108 MeV/u also represents the lowest energy ever achieved with the GANIL cyclotrons (Figure 28).

### Prospective study of new beamlines in G4 for the SAGA project

Among the various users who come to GANIL, tests of electronic components under heavy ion beam irradiation are carrying out for space industrial applications, and their requests for beam time have recently increased significantly. The objective of the SAGA project (Spatial Applications Ganil Accelerators) is thus to improve accessibility to industrialists to the means of irradiation with heavy ions at GANIL. One solution would be to create new high-energy beamlines.

The idea of carrying out simultaneous experiments to maximize the scientific impact of the GANIL accelerator was successfully deployed at GANIL on the medium energy (SME in 1990) and low energy (IRRSUD in 2003) beamlines. These projects have made it possible to significantly increase the productivity of the laboratory (in terms of number of hours of experience per year) and its scientific impact. This currently allows GANIL to regularly carry out three experiments in parallel on IRRSUD, SME and High Energy.

As part of the emergence of the SAGA project, we studied the possibility of creating new high-energy beamlines, to be allocated mainly for industrial applications, in order to increase their beam time without increasing the operating time of GANIL. One of the solutions considered consists of partially degrading the high energy beam in order to create a distribution of charge states, to separate, and to guide these charge states and the primary beam towards different beam lines.
<figure><img src="image_62.png" /><figcaption>Figure 29: Proposal for the implementation of lines G41, G42 and G43 for the realization of 3 experiments in parallel. The G42 beamline corresponds to the one currently used by industrialists in G4.</figcaption></figure>

The study considers to have 3 beamlines in parallel operation in room G4 (Figure 29). To do so, the two 30° deviation dipoles of the fishbone would be replaced by one of 60° and a removable degrader would be positioned at its entrance. This partial degrader would make it possible to create a distribution of charge states, while maintaining an adjustable proportion of primary beam. At the exit of the dipole, the degraded beams whose Brho will be lower than that of the primary beam, will find themselves deflected towards the inside of the bend with an exit angle directly dependent on their Brho.

Although this proposal is feasible from a beam optics point of view, if retained within the SAGA project it will require extensive feasibility studies from an infrastructure and safety perspective. This particular configuration, although complex to achieve, would nevertheless bring numerous benefits. It would make it possible to carry out three experiments in parallel by having equipment (diagnostics and intensity controls) and independent access from one room to another. These different aspects could thus meet the demands of industrialists, and could also benefit to scientific research more widely (interdisciplinary physics, detector tests, etc.).

## Improving a cyclotron injector with a new ECR Ion Source

Two options have been proposed to Accelerator Advisory Committee in 2024 to improve the cyclotron beam intensity. (1) A new ECRIS PHOENIX-V3 developed at LPSC Grenoble, could be installed at the GANIL cyclotrons. Presently the axial injection of C02 cyclotron is relatively inefficient. This, coupled with the growing needs for high intensity beams at GANIL, adds to the difficulty in the optimization of the beam schedule. (2) Another relatively easier choice, requiring a lower manpower and budget (but with a lower performance) could be envisaged by installing a Grenoble Test Source “GTS” (like the one available at ARIBE). Such a choice would need almost no modification of the beam line (same voltage, same inflector). The intensity gain being lower, it would be more effective to put this GTS source on the HV platform of C01.

## Radioactive Beams around 1 MeV/u in G21

The GANIL-SPIRAL1 facility has delivered Radioactive Ion Beams (RIBs) for 20 years. The post-accelerator, the Cyclotron CIME, delivers purified radioactive beams with a good transmission (15%-30%) from 1.8 MeV/u to 15 MeV/u. Attempts have been made to deliver beams at 1.2-1.8 MeV/u with a very low transmission (~ 1%). Figure 30 shows the new set-up in G21 for nuclear astrophysics with ACTAR in G21. The new set-up has been validated in June 2024 with an intense radioactive beam ⁸Li at 1.2 MeV/u.
<figure><img src="image_63.png" /><figcaption>Figure 30: Principle of the degraded beam. Energy degradation of the beam will increase a lot the energy dispersion (+1-2% sigma E). Therefore, a measurement of the energy of each particle is required (TOF).</figcaption></figure>

## 2. LINAC

### Linac tuning with a missing cavity

In the most recent study without CMA6 cavity, a 900 µA $^4$He$^{2+}$ beam was accelerated to 64 MeV instead of the nominal value of 80 MeV. Nevertheless, a 2 kW total beam power was transported to the beam dump with a transmission of 99% (Figure 31). The beam-loss increase in the HEBT confirms the reduction of the longitudinal acceptance in the studied case. Considering the importance of the study to assess the reliability of the LINAC, the need of a dedicated tool to facilitate the calculation of new parameters in case of a cavity failure, and the advantage of being able to conduct tests for its development, the Accelerator Physics group participates to the REFILL project with LPSC Grenoble and other international laboratories. The goal of the collaboration is to improve the reliability of linacs. The first phase plans to develop models, simulations tools that can be adaptable to different high power linacs such as SPIRAL2, ESS, JPARC, MYRRHA/MINERVA, ADS linacs...

<figure><img src="image_64.png" /><figcaption>Figure 31: Transmission (red) and current (green) evolutions of a 900 µA $^4$He$^{2+}$ beam without CMA6.</figcaption></figure>
## Heavy ions at nominal energy

Figure 32 presents the results of the first heavy ion acceleration to 14.5 MeV/u. A power ramp-up to 2 kW with a ¹⁸O⁶⁺ beam at 14.5 MeV/u was performed to qualify the tuning.

<figure><img src="image_65.png" /><figcaption>Figure 32: Power ramp up of 50 µA 18O⁶⁺ beam: Energy (green), transmission (black), average current (orange) and duty cycle (red).</figcaption></figure>

## Beam physics studies

Two studies were recently done for a better understanding of the longitudinal beam dynamics with high-gradient accelerating fields and to increase the accelerating gradient in the first linac cavities. The first one deals with the excitation of the 4th-order resonance (σl_l = 90°) leading to strong longitudinal emittance growths and acceptance reductions, even at low space-charge. In the second one, a new optimized definition of the synchronous phase allowing improving the linac performances was proposed. Already implemented in TraceWin it was successfully used to optimize the SPIRAL2 linac tuning for heavy ions up to A/Q = 7.

## Artificial intelligence for accelerators

Artificial Intelligence use for particle accelerators is increasing every year, improving reliability of related research infrastructures. GANIL started investigating some applications of these advanced techniques in the SPIRAL2 linac. At the same time, GANIL has taken a central place in structuring and coordinating a national and European effort towards a synergetic approach to develop, deploy and disseminate the use of these techniques and bring optimisation and reliability to the next level. At GANIL, the work on AI applications at the accelerator division started with the study of a virtual heat load observer for SPIRAL2 superconducting cavities. A PhD funding allowed to continue this exploratory work.
# IV. EQUIPMENTS FOR BEAM ACCELERATION, TRANSPORT AND DIAGNOSTICS

## 1. Improvement of the precision of measurement of the SPIRAL2 BPM

The Beam Position Monitors (BPM) are beam diagnostics installed in the quadrupoles of the hot sections of the SPIRAL2 LINAC. Twenty BPMs and their instrumentation chain measure the following characteristics: beam position, ellipticity (a characteristic of the transverse shape), and beam phase.

The four electrodes of a BPM pick up the electric field induced by the bunch of ions from the beam. The generated signal is periodic and can be decomposed in harmonics, mainly at the accelerator frequency ($h_1=88.0525$ MHz) and at its double frequency ($h_2=176.105$ MHz). The level of the signal is mainly due to the beam intensity, its energy and the considered harmonics

<figure><img src="image_66.png" /><figcaption>Figure 33: Left: Error of the measurement of level for the four channel as a function of the input level before and after the modifications of the algorithms. Right: Error of the phase measurement as a function of the phase of the signal equivalent to a $1\mu A$ beam.</figcaption></figure>

Improvement of the instrumentation chain has been previously done (see 2022's report), making possible to measure beam characteristics with an intensity down to $50\mu A$, namely signal power down to -90dBm. Below this intensity, the measurement precisions deteriorate quickly. Future beams of $S^3$, including those of Newgain, could have an intensity below this value. It is thus important to increase the dynamic of measure toward the low levels of signal. This improvement was achieved by modifying the digital signal processing.

The acquisition chain is composed of an analog acquisition followed by a digitization. The digital signals are then processed in a programmable electronic component (FPGA). The data is transmitted to a computer card (CPU) for further digital processing and publication to the network.

We have undertaken modifications to the digital processing code embedded in the FPGA chip and the CPU. The graphic in Figure 33 shows the error of the signal level measurement for different signal levels. One can see the increase of the measure range: the measured error is in the range of $\pm 1$dBm for signals levels down to -110dBm, i.e. a beam intensity less than $1\mu A$.

These modifications have shown similar improvements for the phase measurement. Changes were also done in the CPU to deduce parasitic signals (for example perturbation signals from the voltage of the cavities) from the real signal (see Figure 33).

All these improvements are now to be confirmed in real case during future machine studies. Laboratory studies have also shown that improvements could be achieved by enhancing the regulations that are taking place in the FPGA.
## 2. Safety plan for RFQ1 amplifier operation

The RFQ1 (Radio Frequency Quadrupole) is an essential part of the linear accelerator SPIRAL2, bunching and initially accelerating the ions so that they enter the first superconducting cavity at an energy and phase compatible with the operation of subsequent cavities.

This RFQ operates at room temperature, and requires the injection of an RF wave @88.0525MHZ supplied by four 60kW amplifiers. More precisely, four waves of the same frequency are recombined inside the RFQ.

The RFQ1 requires a maximum accelerating voltage of 114kV for heavy ions (Q/A=1/3), and a lower voltage (of the order of 50 to 85 kV) for deuterons and protons. Maximum voltage can only be reached when all 4 amplifiers are switched on, whereas it is possible to operate with 3 amplifiers to deliver proton and deuteron beams.

Since the first power tests of this equipment, a number of failures have affected its operation. In particular, the tetrode tubes of the amplifiers, 2 out of 4 of which have already been replaced, as well as various power components that were replaced or repaired (preamplifiers, dimmers, HV power supply, cooling circuits, sensors, etc...). Over time, we have been able to deploy a limited plan for upgrading certain elements, and purchasing a large number of spare components. However, this strategy does not guarantee 100% availability of these amplifiers, which could jeopardize SPIRAL2's heavy-ion delivery to the spectrometer S³. In addition, the cost of the main components (Tetrodes) is incredibly rising, since the production of tetrodes tubes is becoming a niche market.

In 2023, the division and the group decided to work on a medium-term plan to secure operations, which mainly involved adding a solid-state amplifier, with the aim of significantly reducing the time needed to return to operation in the event of a major failure. This additional amplifier would then be connected in place of the failed one, using coaxial lines. Furthermore, the modular architecture of a solid-state amplifier makes the occurrence of a major failure less likely, as we observe with LINAC superconducting cavity solid-state power amplifiers.

<figure><img src="image_67.png" /><figcaption>Figure 34: RFQ signal architecture with the spare RF Amplifier</figcaption></figure>

During the year, we were able to define the layout of the future crate within the existing amplifier rooms, and identify the requirements in terms of electrical power and cooling (which must remain compatible with what is available in that room). We also had to imagine the structure and estimate the cost of an RF switching grid (see Figure 35, example of coaxial RF power lines), and define the overall architecture of the system with regard to control and feedback signals (see Figure 34).

We have also considered the various possible configurations with respect to the existing Master-Slave concept, and the consequences on the test plan of this 5th amplifier.

We were able to draw up a provisional schedule to make the validation of the future amplifier compatible with SPIRAL2's operating schedule.

Once the broad outlines have been established, we have been able to work on the specifications for the future 5th amplifier, whose main features will be shared with the RFQ2 solid-state amplifiers (Newgain project). The call for tender has been issued, and bids received.
We should work in 2025-2026 to validate the first solid-state power amplifier 40kW for RFQ2 at GANIL, and then the 60kW 5th amplifier for RFQ1.

Sharing the same technologies between this 5th amplifier and the 4 of RFQ2 (with Q/A=1/7) will result in savings in terms of spare parts costs, ease of implementation, and reactivity in the case of potential failures

<figure><img src="image_68.png" /><figcaption>Figure 35: Exemple of RF power distribution</figcaption></figure>
# V. AUTOMATS AND COMMAND CONTROL

## 1. Realization in the experimental areas

### REPARE project

The REPARE project aims at validating the experimental procedure to produce innovative radio-isotope for medical applications. The important radioactivity induced in the irradiation of materials need a complete automatic hand-off handling of the targets. Creation of an electrical cabinet and a control box equipped with a ET200SP PLC and two SINAMICS CU310 drives to allow the unloading of multiple targets after beam irradiation.

<figure><img src="image_69.png" /><figcaption>Figure 36: REPARE's automation management</figcaption></figure>

### Autofill of Liquid Nitrogen for Germanium detectors

Germanium detectors are an important instrumentation for GANIL users who hunt nuclear structure of rare species. In 2022, we designed a prototype of mobile cabinet able to cool up to 16 germanium detectors. Following the success of this project, in 2023, we duplicated this prototype to have a second one. It allows us to have one on the GANIL original installation and one on LINAC's experiment areas.

<figure><img src="image_70.png" /><figcaption>Figure 37: Left: Picture of the new Programmable Logic Controller. Right: Supervision of the Autofill Cabinet</figcaption></figure>
## Automation and electrotechnical renovation of the D5 experiment room

Previously, automatism of vaccum, insertions and all the equipments around INDRA / FAZIA confines was drive with an APRIL brand PLC. In collaboration with the technical coordinator of D5 experience area, we have renovated the electrical engineering and automatism of D5 by using a S7-1500 PLC.

<figure><img src="image_71.png" /><figcaption>Figure 38: PLC before renovation</figcaption></figure>

<figure><img src="image_72.png" /><figcaption>Figure 39: New electrical cabinet</figcaption></figure>

<figure><img src="image_73.png" /><figcaption>Figure 40: New PLC</figcaption></figure>

## 2. CYREN

### Renovation of the vacuum automation of the L3 line and the CSS2 cyclotron

As part of the CYREN project, the renovation of the original GANIL automation systems continues with the renovation of the vacuum automation systems and the Human-Machine Interface (HMI) of the L3 line, composed of seven vacuum chambers and the CSS2 cyclotron.

Previously controlled by S5-135U PLC (programmable logic controller) which are now obsolete, the vacuum equipment is now managed by S7-1500 PLC. This allows to improve the diagnostic, modernize the communication protocol and improve the drive of vaccum equipments.

<figure><img src="image_74.png" /><figcaption>Figure 41: L3 and CSS2 PLC</figcaption></figure>

<figure><img src="image_75.png" /><figcaption>Figure 42: L3's vaccum supervision</figcaption></figure>

### Renovation of CIME vacuum controller

<figure><img src="image_76.png" /><figcaption>Figure 43: CIME's PLC</figcaption></figure>
The CIME vacuum controller has also been revamped with an S7-1500 CPU. This controller also manages the regulation of the new cryopanel cooling system. This renovation is part of the modification of the cooling system of the CIME northern cryostat. Deployment will continue on the southern cryostat when the tests will be validated.

<figure><img src="image_77.png" /><figcaption>Figure 44: CIME's HMI</figcaption></figure>

### 3. Organization of G2CA activity

#### Open Project

G2CA's activity is cross-functional, the automation and IT teams each handle around 400 tasks per year to provide other technical groups solutions for connecting and controlling their equipment.

Since 2023, the group uses the Open Project tool to organize activity. This tool makes it possible to formalize requests, prioritize them in relation to each other and track them, the tool also makes it possible to keep the history of processing a task and sharing information with team members and needs holders. It is a tool that promotes collaboration and allows to have an AGILE approach and apply some simple LEAN rules such as visualizing and limiting tasks in progress in order to positively impact the flow of deliveries.
# VI. ACHIEVEMENTS IN MECHANICS

This chapter describes some of the achievements of the Mechanics group of GANIL.

## 1. S³ Stable target station modification

A stable target station was manufactured for the S³ project a few years ago, and it was tested with beam for the first time in 2023. These tests permitted to define some necessary improvements on the design of the station, including manufacturing modifications. These modifications were not especially difficult, but considering the dimensions of the station, it was not possible to use the numerical machining center. In this context, the GANIL machine shop used conventional milling machine.

<figure><img src="image_78.png" /><figcaption>Figure 45: Measurements and Manufacturing</figcaption></figure>

## 2. S³ Electrical dipole feedthrough integration

The S³ electrical dipole designed by IJCLAB was mounted and integrated in the S³ room in 2021. This operation did not include the feedthrough that were not manufactured yet. As the feedthrough were supplied at the beginning of 2023, the GANIL mechanical team, with the collaboration of IJCLAB, finalized the global assembly of the electric dipole.

<figure><img src="image_79.png" /><figcaption>Figure 46: Feedthrough</figcaption></figure>

<figure><img src="image_80.png" /><figcaption>Figure 47: Integration tool</figcaption></figure>

<figure><img src="image_81.png" /><figcaption>Figure 48: Feedthrough integrated</figcaption></figure>
### 3. REPARE first beam test

The high power irradiation station designed by GANIL in the context of the REPARE project, with the goal to produce up to 100 GBq of $^{211}$At in 8 hours of He beam irradiation, has been installed at the mid of 2023 in the NFS facility to permit the first tests with beam, and the first production of $^{211}$At. Installation and first tests included all the mechanical skills (design, manufacturing, mounting and alignment), and needed an important global coordination to result to experiment with others professions.

These first tests did not permit the final validation of the irradiation station, but made it possible to understand different problems, and to launch global design and manufacturing improvements before the next tests under beam in 2024.

<figure><img src="image_82.png" /><figcaption>Figure 49: REPARE in NFS facility</figcaption></figure>

### 4. EXOGAM in NFS

To allow the E838_21 experiment in NFS, an EXOGAM structure was designed, calculated to stand seisms, manufactured, installed and aligned in 2023. The design was constrained by the NFS facility, but this equipment was designed to be installed also in the G21 experimental room.

<figure><img src="image_83.png" /><figcaption>Figure 50: Design and seism calculation</figcaption></figure>

<figure><img src="image_84.png" /><figcaption>Figure 51: Manufacturing and assembly</figcaption></figure>
## 5. Building Information Management

Considering the evolution of the Building Information Management (BIM) in terms of conception, digital twin, building manufacturing, maintenance, data retention, life cycle and so on..., the design office started a reflection to integrate this new way of working. Indeed, all building and infrastructure companies are engaged in this direction already, and GANIL could have an interest to do the same. That is why a BIM FORUM was organized at the end of 2023.

Its goal was to well understand what is the BIM, what are the advantages, and what is necessary in terms of organization, manpower, skills and budget.

## 6. Phoenix ion source optimized injection

In the goal to improve the reliability of the polarized disk of the Phoenix ion source injection, a design was launched in 2021 to permit the cooling of this disk, and to optimize its materials and its dimensions.

This equipment was supplied in 2023, and it involved different manufacturing technique as 3D metal printing, bi-material brazing, machining, bending...

<figure><img src="image_85.png" /><figcaption>Figure 52: Design</figcaption></figure>

<figure><img src="image_86.png" /><figcaption>Figure 53: Manufacturing</figcaption></figure>
# VII. DETECTION AND LASER FOR PHYSICS

## 1. First use of PISTA in the VAMOS 2023 campaign

PISTA (Particle Identification Silicon Telescope Array) is a highly integrated telescope array with high granularity. It is used to study transfer-induced fission reactions in inverse kinematics to detect light ejectiles from the target. The first stages of PISTA are 100 µm thick single-sided silicon-strip detectors, while the second stages are 1 mm thick single-sided silicon-strip detectors, both with trapezoidal shape. The PISTA detection system measures the angle and the energy of the target-like recoils, which enable the proper characterization of the fissioning system in mass, atomic number and excitation energy. The detector is placed 10 cm from the target position, which permits to detect emitted nuclei from 30° to 60°.

PISTA is a project financed by CEA/DAM/Bruyère le Chatel and GANIL. Only two years have been necessary to design, integrate and optimize the detector system and all has been ready in time for the 2023 campaign in G1, which was a real challenge.

### 1/ Design of the system:

<figure><img src="image_87.png" /></figure>

### 2/ Routing of specific cables and interface vacuum
Flex kapton circuit of 1200 channels connected to
MMR electronics by specific interface

<figure><img src="image_88.png" /><figcaption>Cables</figcaption></figure>

<figure><img src="image_89.png" /><figcaption>Interface</figcaption></figure>

### 3/ Assembling

<figure><img src="image_90.png" /></figure>

### 4/ Integrate in target point G1

<figure><img src="image_91.png" /></figure>

Credits: G.Frémont

## 2. S³LEB

The S³ Low Energy Branch (S³LEB) has been mounted and intensively commissioned off line at the LPC Caen labory during the last past years and resulted in 3 PhD thesis in 2023 [1,2,3]. High resolution narrow-band in-gas jet laser spectroscopy of stable Erbium isotope was performed, achieving a spectral resolution of 268MHz as well as isotope shift and hyperfine constants measurements. These results were published in [4]. However, the resolution attained at S³-LEB indicates a jet with Mach number 4.5 wereas a Mach number of 8.5 was expected. In order to diagnose jet formation, the technique of Resonance Ionization Spectroscopy flow mapping, where the excitation step laser frequency is scanned along the gas jet, was used (see Figure 54). After implementing several improvements as realignement of the lasers, reduction of the laser power to avoid power broadening, correction of the pressure reading and fine tuning of the background pressure, a resolution of 206MHz could be obtained,
which corresponds to Mach number 6.8, as shown in Figure 55 [5]. Further investigations will be necessary in order
to further improve these results.

<figure><img src="image_92.png" /><figcaption>Figure 54: Scheme of gas cell and gas jet with scanning of the position of the probe laser beam.</figcaption></figure>

<figure><img src="image_93.png" /><figcaption>Figure 55: Deduced Mach number as a function of the horizontal position of the probe laser beam in the gas jet after optimization.</figcaption></figure>

Another result deduced from ref [4] is that the ionization scheme involving the 415.2 nm first step is very efficient for Erbium and reasonably sensitive to hyperfine constants measurements. However it provides very small isotope shifts that prevents to deduce the changes in charge radii with a good precision. Therefore, search for other transitions better suited for laser spectroscopy was performed and the transition 408.8nm was found to have much larger isotope shifts, as shown in the Figure 56 [6]. This new transition will be used for the isotope shift measurement of Erbium during the on-line commissioning at S³.

Finally, the TiSa based laser system for laser spectroscopy purposes at S³LEB is being improved with the development of a new direct diode pumped continuous wave Ti:sapphire cavity as shown in Figure 57 [3]. Such a cavity has a wide wavelength scanning range, and is to be used as a seed for the injection-locked lasers. It will replace the cw external cavity diode lasers with limited tuning range that currently act as the seed source, while being cheaper than commercially available cw Ti:sapphire lasers.
<figure><img src="image_94.png" /></figure>

Figure 56: Isotope shifts and hyperfine splitting of natural Er isotopes obtained with the 408.8nm first step transition in gas jet.

<figure><img src="image_95.png" /></figure>

Figure 57: New direct diode pumped continuous wave Ti:sapphire cavity under development for $S^3$LEB.

[1] PhD thesis of A. Ortiz Cortes, GANIL/JYU (2023) https://theses.hal.science/tel-04508679

[2] PhD thesis of J. Romans, KU Leuven (2023) https://lirias.kuleuven.be/4071124&lang=en

[3] PhD thesis of A. Ajayakumar, GANIL (2023), https://theses.hal.science/tel-04483471

[4] A. Ajayakumar et al., NIMB 539, 102-107 (2023)

[5] Private communication, PhD thesis of F. Ivandikov, KU Leuven

[6] Private communication, PhD thesis of W. Dong, IJCLab

### 3. INDRA-FAZIA

During 2023 the INDRA-FAZIA collaboration has launched some developments in order to improve the experimental set-up.

The full INDRA silicon detectors upgrade has been completed and installed. Combined with the new INDRA electronics it allows better isotopic identification up to Z~9-10. We also completed some maintenance on Caesium Iodide CsI(Tl) crystals where photomultipliers were unglued.

In addition, we also started some new works with the old ionisation chambers of INDRA. We have investigated two solutions. First a renovation of the existing one at GANIL, see Figure 58 and second, some new developments and upgrade at LPC Caen. The goal is at least to benefit from two of them, covering rings 6-7 and rings 8-12 for the next INDRA-FAZIA campaign in 2025.
<figure><img src="image_96.png" /><figcaption>Figure 58: Ionisation chamber of INDRA covering the rings 6 and 7, renovated at GANIL.</figcaption></figure>

The FAZIA collaboration has also launched some R&D on very thin silicon detectors (~25 µm) for low energy experiments (with Spiral 1&2 beams for example), see Figure 59. A thin first layer will reduce considerably the detection thresholds as Pulse Shape Analysis for identification (PSA) is (so far) impossible under ~50 µm, which is the case for standard FAZIA telescopes.

<figure><img src="image_97.png" /><figcaption>Figure 59: Prototype of very thin silicon detectors of FAZIA. The PAD covers the first layer of 4 telescopes.</figcaption></figure>

These developments on new thin silicon detectors will enlarge in the future the capabilities of FAZIA to perform in various range of beam energies and thus additional domain of physics. They use the single PAD technology which consists of using the same silicon matrix for four telescopes all together thus reducing dead zone in between them. This technique could be later reasonably used for the standard thicknesses (300, 500 and 750 µm) of FAZIA silicon detectors.

We have also developed a new device to monitor the beam intensity and to be able to measure cross sections for physics analyses. It is composed of four plastic detectors read by photomultipliers and sent as scalers in the INDRA Data Acquisition system (DAQ). They are mounted in circle downstream of the INDRA-FAZIA apparatus at very low angle (1.6°) around the beam axis, see red arrow on Figure 60.
<figure><img src="image_98.png" /><figcaption>Figure 60: INDRA (left)-FAZIA (right) apparatus in D5 at GANIL, the red arrow indicates the location of the beam detectors monitor downstream the beam line, behind the 12 FAZIA blocks.</figcaption></figure>

Those plastic detectors and the electronic chain behind have been validated in G4 using parasitic Xe and Kr beams devoted to industrial applications in spring 2023. Plastic detectors are fast and sustain large counting rates, so are well adapted for this task.

In parallel of detector developments, we have also updated the whole command and control for vacuum control and target loader.
# VIII.Data Acquisition

## 1. Experiments support

Support to experiments is an important mission of the acquisition technics group. It corresponds to 30% to 50% of the group's activity. The experiments E839, E805, E815, E843, E850, S³ target and Sirius tests, Tulip, E838, E802, E858... have used GANIL Acquisition developped and maintained by the group. The group provides support in the preparation of electronics, the triggering systems, the configuration of digitizers, the implementation of user accounts and associated softwares. On-call duty was carried out for more than 1600 hours.

## 2. SMART

2023 is a key year for the SMART project in terms of results. SMART (Sfp connectivity and Microtca for Advanced Remote Trigger) is a new time-stamping and selective trigger system. The architecture, built according to the MicroTCA standard, uses a tree configuration with a single HUB card and up to 16 ROUTERS to reach 240 digitizers called END POINTS. These modules exchanging data at 4 and 2 Gbit/s are connected by high-performance copper cables, or optical fibers for distances that can exceed 100 meters. This device allows the synchronous distribution of a 100 MHz clock to each END POINT and a timestamping system where each clock of each END POINT is capable of tagging data buffers on 48 bits/10 ns with a temporal error of +/- one LSB. Further testing is still underway and the second step is the validation of trigger processing. At the same time, phase 2 of the SMART project, called SMART_MCH was launched at the end of 2022 and a prototype design started in 2023, it will double the number of controlled END POINTS going from 240 to 480 mainly for the needs of the AGATA detector. It will also permit to upgrade the SMART board toward an independent complete trigger module.

## 3. VTC

By the end of 2023, a new trigger using VME bus standard has been validated and proposed for physics experiments. This VME module from CAEN company is based on an INTEL/ALTERA FPGA. A full firmware has been developed at GANIL in order to propose this board to physicists who want to control a full VME data acquisition system. In particular, a CENTRUM interface has been implemented in the FPGA to allow a synchronization by the GANIL BEAST modules.

## 4. Negma and REActif

The NEGMA project (NEw Generation of Multifunction ADCs) was subject to an audit by external experts (Engineers and researchers). Following this meeting, the concept based on the ZCU216 evaluation KIT (see Figure 61) was validated. We created a Front-End card to adapt our signals to the dynamics of the kit. The first tests are very encouraging. Several parts of the project have been validated. Currently we are working on the transmission of data to JETSON (HACKtif prototype based on JETSON compact computer) in order to allow the visualization and analysis of the data.

<figure><img src="image_99.png" /><figcaption>Figure 61: ZCU216 evaluation kit with a front-end board for input signals</figcaption></figure>
The REActif project (signal processing on embedded GPU) aims at implementing the signal processing algorithms using a computer language (e.g. energy calculation in C++) more flexible and more responsive. The signal can come for instance from a digitizer (eg NEGMA). On the hardware side, the prototype of the HACKtif card (See Figure 62) was produced, integrated into a 1U NIM module, and on the software side, the REAssemble data aggregator permits to collect the processing outputs of several HACKtif cards.

<figure><img src="image_100.png" /><figcaption>Figure 62: HACKtif card</figcaption></figure>

## 5. DAQ up

The year 2023 marks the beginning of developments aimed at renovating the data acquisition system for physics experiments. Preliminary work began with (in collaboration with the G2I) a server package facilitating the simple and rapid installation of tools and software and also with the implementation of development and implementation tools, in continuous integration thanks to the IN2P3 GitLab platform.
# IX.Management and ordering of installations

## 1. NFS

### New Beryllium converter

The first neutron beam produced by irradiation on a static Beryllium target, (Figure 63), cooled by water in Copper support, has been produced in the converter room of NFS.

The converter has been tested with a D⁺ ion beam of maximum intensity 42 µA. The temperature produced by the beam was controlled and compared to the simulation. The flux measured on the MEDLEY detector was close of 5.10⁷ n/cm²/s for the maximum power of 1680W.

<figure><img src="image_101.png" /><figcaption>Figure 63: Target in the ion beam axis</figcaption></figure>

It was shown that the orientation of the incoming beam to the neutron beam axis influences the neutron beam. If the D⁺ beam has a little angle with the theoretical beam axis, then the neutron beam is also with an angle compared to the expected axis. A really good adjustment of the incoming primary beam with profilers is essential. It is also measured that the design of the support with some Cu behind the Be reduces the flux of around 20% compared to the simulation.

### REPARE in NFS

REPARE was installed in the converter room of NFS (Figure 49) to study the Astatine production on Bi plates irradiated by 7 MeV/u He ions. A first session of tests have shown that some adjustments were necessary. To optimize the integration in the irradiation line, some changes have been made. In particular, the Elcom chassis of NFS (Figure 64) was cut as it was on the way to install REPARE with only one movement axis. It induced that the support of the line was shifted and a new mechanical component was added.

<figure><img src="image_102.png" /><figcaption>Figure 64: Modifications of the line NFS</figcaption></figure>
## 2. NEW G21

### Modifications on G21 line

The G21 beam line (Figure 65) has just been completely overhauled to transport low-energy radioactive beams (1MeV/u to 2MeV/u).

The project took place over 5 months with the contribution of many persons supervised by G2 technical coordinator.

The new beam line makes it possible to slow down the beams of the CIME cyclotron while measuring the energy of each particle with a great precision.

With this new device, the SPIRAL1 beams have an energy close to that of nuclei in stars. It is now possible to reproduce as close as possible the stellar nuclear reactions in the laboratory.

<figure><img src="image_103.png" /><figcaption>Figure 65: Beginning of the line, with an energy degrader (thin sheet) and a detector to measure the time of flight of ions hitting the active target of ACTAR TPC 10 meters further. Thereby it is possible to measure the energy of each event.</figcaption></figure>
# X.Status of scientific and accelerator projects

## 1. DESIR

### Presentation

<figure><img src="image_104.png" /><figcaption>Figure 66: Schematic view of the future desir building, between spiral1 and spiral2 budildings</figcaption></figure>

DESIR (Disintegration, Excitation and Storage of Radioactive Ions) will be the new "low-energy" experimental hall for GANIL and SPIRAL2. It will receive radioactive beams produced by SPIRAL1 and S³. The experiments carried out there will enhance our understanding of the fundamental rules governing the structure of atomic nuclei. These experiments will be based on the following three pillars of low energy experiments: the study of radioactive decay modes, laser excitation and storage in traps.

* Radioactive decay studies can be used to determine the lifetime and the structure of nuclei. These parameters are key to understanding the synthesis of chemical elements in stars.

* Laser excitation provides information on the shape, magnetic and quantum properties of nuclei.

* Storage of ions in electromagnetic and optical traps to determine their mass or study their decay with high precision.

### DESIR building and infrastructure

The first half of 2023 was dedicated to preparing the construction site for the DESIR installation (see Figure 67). Clearing operations were carried out to free up space for the future site base and the extension of the Nuclear Base Installation (INB) perimeter necessary for the construction of the installation. These operations were carried out by implementing the recommendations of the Environmental Authority given in March 2023. The fire water, wastewater and rainwater networks circulating in the area of the construction site were diverted, and the area itself stripped and feced to make the construction site closed and independent.

<figure><img src="image_105.png" /><figcaption>Figure 67: Compilation of pictures of the DESIR construction site preparation in 2023</figcaption></figure>
In the second half of the year, general earthwork operations began as soon as the building permit was obtained. They continued with the digging of the construction site to a depth of around ten meters (level -3), so as to allow the future connection of the DESIR installation to the buildings of the SPIRAL2 installation and to those of the original GANIL facility. Once the drainage operations were carried out, the design of the rafts of the junction rooms with the existing installations and the DESIR experimental hall were carried out. The end of the year was marked by the raising of the sails of the premises on levels -3 and -2 of the junction block with the SPIRAL2 installation and the drilling of the first of the common emergency exits with the existing installations at the level of the SPIRAL2 experimental room S³.

The construction site for the DESIR installation on the GANIL site was inaugurated on November 10th, 2023 during an event gathering the supervisory bodies of the laboratories involved in the project, local and territorial authorities, as well as the various stakeholders of the project.

## Safety licensing

The favorable report of the Environmental Authority for the DESIR licensing paved the way for the launch of the required Public Inquiry, the terms of which are set by prefectural decree. The investigation took place between the end of April and the end of May 2023. It concerned the 22 municipalities located within a 5 km distance to the INB and was instructed by an investigating commissioner mandated by the Administrative Court of Caen. Its favorable opinion led to the publication of the building permit for the DESIR installation at the end of June 2023. The decision endorsed by the Prefecture of Calvados marked the end of a long instruction process of administrative authorizations that begun in March 2022 with the submission of the Modification Authorisation Request (DAM) file to the Ministry of Ecological Transition and to the Nuclear Safety Authority. This process will end with the publication of the decree authorizing the modification of the INB 113-GANIL, expected in 2024.

In the meantime, the nuclear safety group of the DESIR project has started compiling the Commissioning Request (DMES) file for the installation, the second of the two major administrative files necessary for operation. Its preparation requires taking into account changes in the GANIL installation since its last safety review and data from the DESIR Preliminary Safety Report in the INB 113-GANIL Safety Report.

## Quality

The GANIL Quality unit is responsible in close collaboration with the Nuclear Safety group of the compliance, by the various stakeholders of the project, of the safety-quality requirements of the project. Following the Project Management Plan issued in 2022, the Quality Safety Management Plan of the project was reviewed and validated in 2023. The unit was heavily involved in 2023 in monitoring the execution of the building construction work and in the installation of the beam process equipment in the premises of GANIL. In order to improve the document management within the framework of the project, "Quality Information" was regularly produced and distributed to the project's technical groups.

## Beam process

Two of the thirty identical sections that will constitute the DESIR transport beam lines were assembled at LP2iB and GANIL (see Figure 68). At LP2iB, two complete vacuum chambers were assembled with the aim of validating the principles of the automated management of the pumping and the online insertion of the beam diagnostic equipment. At GANIL, it is a first complete "head of series" section of transport line that was mechanically assembled in the premises of GANIL at their interface with DESIR in order to test the assembly procedures. Corrections and technical adjustments were validated in order to ease the integration of similar equipment for the entire DESIR transport beam lines. The commissioning of this first definitive beam transport section is planned beginning of 2025. It will be an opportunity to test full-scale and in real operating conditions the equipment of the DESIR transport beam lines as well as the remote control systems and adjustment procedures required for commissioning the entire installation.
<figure><img src="image_106.png" /><figcaption>Figure 68: Picture of the assembly of the transport beam line from the SPIRAL 1 facility towards DESIR.</figcaption></figure>

## Beam preparation and purification devices

Characterizing the performance of the high resolution separator dedicated to the purification of ion beams delivered to DESIR experimental devices requires studying its optical properties at high orders. For this purpose, an upgraded version of an emittance-meter was installed at the exit of the HRS presently commissioned at LP2iB. This allows now a much more sensitive and faster measurement of optical aberrations to characterize the HRS. New magnetic probes including Hall probes have also been installed in the HRS magnets to facilitate and accelerate the measurement of their magnetic field. The developments made in recent years and the performances of the device have been the subject of two publications in Nuclear Instruments and Methods in Physics Research Section B.

The performances of the double Penning trap PIPERADE, dedicated to the purification of ion beams used in DESIR as well as to very precise measurements of the mass of nuclear species, were tested at LP2iB using the Phase-Imaging Ion-Cyclotron Resonance technique. Simulations and programming work has been carried out to facilitate the implementation of this technique, which offers the highest precision in measuring the mass of trapped ions. The diaphragm between the two traps has also been reduced, which made possible to significantly improve the precision of the device: by minimizing the gas leaking from one trap to the other on the one hand and by reducing the anharmonicities of the electric field in the traps on the other hand.

## Experimental process

The MORA device (see section 02|IV.-1.) is currently being tested at the University of Jyväskylä, Finland, pending transfer to the DESIR facility.

The MLLTrap device will be operated at the ALTO installation of IJCLab before its use at DESIR. The commissioning of the ion beam transport section from ALTO to MLLTRAP was carried out between May and July 2023. All the electrostatic elements (quadrupoles, steerers, deflectors) were tested with a stable beam produced by the ALTO ion source.

The assembly and wiring of the deceleration electrodes of the radiofrequency quadrupole ensuring the cooling and pulsing of the ion packets injected into the double Penning trap of MLLTrap were carried out during the summer of 2023. The Penning traps were installed in the vacuum tube (aligned with the field lines of the superconducting magnet) and placed under vacuum.

In parallel, the construction of a system for recovering the Helium evaporated while keeping the superconducting magnet cold was started. Such a system will be deployed at the DESIR installation, with the aim of reducing the operating cost of MLLTrap and PIPERADE, both powered by liquid Helium. A technical study was also launched at IJCLab to develop a system for recovering helium evaporated when filling the cryogenic chambers of superconducting equipment.
## 2. S³ Installations and test

### Introduction

Almost every S³ equipment is now in the caves and the main part is installed and completely or partially qualified (Figure 69).

This involves specific skilled and committed Ganil personnel in several fields, with key contributions from collaborating institutes at CEA and CNRS.

However serious issues arose on the testing of the SMTs in 2023: the newly received SMT did not behave nominally and the cold box was out of order the main part of 2023, preventing from properly diagnose the SMTs. The cold box was eventually fixed by Air Liquide at the end of 2023 but too late for meaningful progress on this topic.

At the end of 2023 and beginning of 2024, an important investigation campaign, within Ganil and with committed and effective help from CEA and CNRS, allowed us to decide, organize and schedule effective an action plan.

Future commissioning phases (spectrometer, Low Energy Branch, SIRIUS) have been now defined by the collaboration.

The exhaustive lists of prerequisites for beam commissioning (as well for equipment readiness and for safety requirements) are identified with assigned responsible personnels and due dates.

Three milestones with three bunches of prerequisites for three consecutive commissioning beam configurations have been identified.

### S³ Installation

<figure><img src="image_107.png" /><figcaption>Figure 69: S³ Experimental area</figcaption></figure>

The installation phase of the spectrometer is still in progress, but around 90% of the main operations is completed. In 2023, the program was disturbed by two liquefier breakdowns, which did not permit to progress as foreseen in terms of SMT electric and cryogenic tests, and then in terms of installation.

In parallel, a global installation review, in several meetings, was organized with all the GANIL task responsible persons involved in the project, with the goal to get a detailed picture of all the technical works and tests remaining before beam commissioning. This review has identified more than 800 action items, and a follow-up has been set up to finalize the installation program in time, considering the different S³ milestones.

<figure><img src="image_108.png" /><figcaption>Figure 70: S³ TiS₃ laser room</figcaption></figure>
**Infrastructure:**

- Power and signal cables connection between equipment's and command and control cabinets are finalized,

- TiSa Laser room is finalized (Figure 70),

- Both HEPA filters plates for the future decay circuit of the LEB/REGLIS3 project are manufactured and installed,

- 80% of the concrete wall openings closed,

- The two Cryogenic lines branches have been installed at the beginning of 2023

**Spectrometer and physic equipment:**

- Last SMT (#7) delivered and installed at a test position,

- Dipoles D11 and D41 seismic-proof installed and connected (hydraulically / electrically),

- SMT positions 5, 6 and 7 seismic-proof installed and connected (hydraulically / electrically),

- Electric Dipole installed with its two feedthroughs (GANIL + IJCLAB), and connected

- Diagnostics box (last object of the spectrometer line upstream the detection setups) installed,

- LEB REGLIS3 project line partially installed (LPC Caen + GANIL + IJCLAB),

- Upstream beam line mechanical section finalized, including the stable rotating target station (Figure 71)

**Main Tests:**

- Qualification of the vacuum and the command & control for: upstream beam line vacuum section, beam dump vacuum section and SMT5 to SMT7 vacuum section,

- Validation of the UGA and UGSx systems,

- First tests for the electrical dipole and its power supplies,

- Cryogenic lines tests,

- SMT cryogenics cabinet's connections and validation (IRFU).

- Some SMT cryogenic and electric SMT partial tests,

<figure><img src="image_109.png" /><figcaption>Figure 71: Upstream Beam Line</figcaption></figure>

**Commissioning of S³ superconducting magnets and associated cryogenic plant**

The acceptance and commissioning of S³'s superconducting magnets was marked by numerous difficulties related to cryogenics, but also by the identification of magnet-specific problems that had not been observed on equipment previously tested.
<figure><img src="image_110.png" /><figcaption>Figure 72: CERNOX temperature monitor on HTS current leads.</figcaption></figure>

Since the delivery of the S³ superconducting magnets, the cryogenic installation and, above all, the distribution line had been operating in partial mode, enabling one or two magnets to be electrically qualified simultaneously. However, as the system had been designed for 7-magnet control, it was difficult to regulate, leading to uncertainties about the behaviour of the magnets due to non-constant cryogenics.

In 2023, the cold box turbines experienced several episodes of stoppage and breakage, which could be attributed to maintenance (outsourced to Air Liquide).

In July 2023, the project received the last magnet (SMT#7) from Cryomagnetics (Oak Ridge, USA).

In November 2023, the team was able to carry out tests on the SMT#5 and SMT#6 magnets, with results that unfortunately differed from previous tests. Operating limitations of the order of 300A (out of a nominal 465A) were observed on several quadripolar coils. These limitations seem correlated with temperature increases in the lower part of the current conductors.

It has been possible to validate the operation of the 3D bench to align SMT#5 cold mass inside the cryostat. It should be noted that in 2023, these tests were carried out with the yokes removed from the magnets, a decision taken in view of previous alignment results, which were not fully reproducible in the presence of the yokes.

Unfortunately, the final highlight was the discovery, after SMT warm-up, of a broken power wire inside SMT#6. This will inevitably lead to the need to open the magnet's helium cryostat for repair.

2023 results led the project and the funding agencies (CEA / CNRS) to organize a review of cryogenics and superconducting magnets to be held in 2024, with the aim to validate and consolidate a strategy for cryogenics and magnets.
### 3. NEWGAIN

<figure><img src="image_111.png" /><figcaption>Figure 73: Schematic diagram of the new injector</figcaption></figure>

The NEWGAIN project (NEW GAnil INjector) aims to construct a second injector A/q=7 to produce very intense heavy-ion beams up to uranium, well beyond the performance of the existing injector of the SPIRAL2 linear accelerator. With the addition of this new injector, the SPIRAL2 LINAC will deliver, within its energy range of operation, the most intense beams in the world over a large variety of ions (ranging from protons to uranium). The second injector is designed to be fully compatible with the existing facility and to further enhance its 'multi-user' capabilities. It is composed of the following:

* A high-performance superconducting ion source (1/7 SC Source)

* A first low energy beam transport line (LBE3) connecting the superconducting ion source to the Radio-Frequency Quadrupole (RFQ2).

* A second low energy beam transport line (LBE1.3) connecting the existing ion source PHOENIX V3 (A/q=3) to the RFQ2

* An RFQ2 that will accelerate heavy ions up to the injection energy for the superconducting LINAC

* A medium energy beam line (LME2) connecting the RFQ2 to the LINAC, with a possibility to send the medium energy beam (via LMEI) to a future experimental area (to be defined).

A schematic diagram of the new injector is presented in Figure 73.

The NEWGAIN project preliminary design phase started on May 7th 2020, and the detailed design phase started in June 2021. In April 2023 started the construction phase.
The project is organized through a broad national collaboration, involving a large number of French laboratories from CEA/DRF/IRFU and CNRS/IN2P3.

As a reminder, the production and validation of the consortium agreement for the Equipex (funding of 13,7M€ out of 20M€ for equipment for the Construction phase) was completed in September 2022, and the consortium agreement signed by all partners was submitted to the ANR in December 2022.
<figure><img src="image_112.png" /><figcaption>Figure 74: View of the injector integrated inside the existing cave and with the existing beam lines</figcaption></figure>

In 2023, the technical specifications being well established and the technical configuration consolidated, the technical specifications for numerous equipments could begin allowing the launch of consultations for vacuum equipments, power supplies for magnets, power amplifiers as well as than the first magnets which are the quadrupoles. This is facilitated by the fact that the design of NEWGAIN relies heavily on the one of SPIRAL2. Even if modifications or improvements resulting from feedback from the operation of SPIRAL2 are necessary, the expressions of need concerning previous products are well known. Copper for the RFQ has been procured, so that manufacturing can begin in 2024.

The configuration of the transmission lines is being finalized and should be finalized in early 2024. Any modification made to the design of these lines will be subject to a specific modification and monitoring procedure.
Safety studies concerning modifications to the existing walls of the SPIRAL2 building are in progress and the technical specifications have been drawn up to assist the project owner in the design and construction of works (emergency exits, wall crossings) and infrastructure modifications.

Concerning EIP equipments (Equipment classified as Important for Protection), X emissive equipments (RFQ and combiner cavities) as well as modifications to the existing walls of the SPIRAL2 building, part of the equipment is under the declaration regime. A strategy for submitting safety files to the ASN is currently being studied to enable GANIL to optimize the phasing of the 3 files.

In December 2023, a review of the detailed design of the superconducting magnet of the ASTERICS source (1/7 SC Source) took place.
4. CYREN (CYclotrons RENovation) Project: Refurbishment of the GANIL cyclotron facility

In order to allow the continuation of experimental programs in nuclear and interdisciplinary physics, to provide exotic beams to the new installation DESIR that will be in operation in 2027, refurbishment project has been launched.

The project CYREN (CYclotrons RENovation) consists of refurbishing the GANIL cyclotron facility that are 40 years old. The perimeter integrates:

* the cyclotrons, beam lines and the experimental areas

* the infrastructure and utilities

* the safety, security, radioprotection systems

The objectives are to maintain the facility in operational conditions for at least 20 years and to optimize the manpower for maintenance after refurbishment.

A preliminary project was launched in 2022 to identify different refurbishment scenarios including all the equipment and system in the CYREN perimeter. The main topic for the cyclotrons is the RF cavities for the two separated sector cyclotrons (SSC). The risk analysis defined two different scenarios (baseline and complete), one where a new cavity is produced and the old one stands as a spare, the other where all 4 cavities are changed.

These scenarios were presented to the CEA/DRF and CNRS/IN2P3 Board of Directors and Scientific Council in 2023. Initial recommendations call for a more in-depth study of the renovation of the 4 cavities to find the best technical solution compatible with resources and accelerator scheduling. A specific pre-project for the renovation of RF cavities will be launched in January 2024 to propose and then select the refurbishment strategy.

The study and implementation schedule for this project is based on 5 to 8 years, depending on the scenario.

Furthermore, funding requests have been made and partial but substantial funding has been obtained in 2023 from the State-Region Plan contract 2023-2027 and the French Ministry of Research and Education. Discussions between France and Germany took place in 2023 to complete the CYREN project funding scheme.

Studies and achievements of the CYREN project in 2023:

* It can be noted that, for the power supplies of cyclotrons and experimental caves, a prototype (see Figure 75) of power supplies for magnets is produced and validated at GANIL. This solution is based on commercial power supplies integrated into a cabinet. The prototype was connected to magnets and the electrical performances (in stability and control) were validated.

<figure><img src="image_113.png" /><figcaption>Figure 75: Prototype of power supplies refurbished for magnet</figcaption></figure>

* The CSS1 vacuum system (primary and secondary pumping and automation) is refurbished

* The studies and the call for tenders for the refurbishment of the control system of the 90kV high-voltage station are carried out
<figure><img src="image_114.png" /></figure>

04

EXPERIMENT REPORTS
<figure><img src="image_115.png" /></figure>
<figure><img src="image_116.png" /></figure>

# I. NFS
Beam was delivered to NFS between September and November 2023. The year 2022 was marked by the failure of the rotating converter. It was no longer rotating and the maximum permitted power was 400W. While waiting for the rotating converter to be repaired, a static water-cooled beryllium converter was designed and built by the CEA/IRFU and GANIL design offices. This new converter was successfully used for experiments in 2023. Six experiments and detector tests were run.

The E802 and E858 experiments with the MEDLEY detector, spokesperson D. Tarrio from the University of Uppsala, on which Lucas Dearruda, a PhD student at GANIL, is working. These experiments are a continuation of those carried out in 2021 and 2022.

The E838 experiment, spokesperson E. Clément (Ganil), deal with the study of $^{56}$Ni produced in the $^{58}$Ni(n,3n) reaction. It was possible thanks to the energy spectrum of the NFS, which extends up to 40 MeV. This is the first time that the EXOGAM detector was installed in the NFS experimental area. The smooth running of the experiment shows that the room is suitable for the use of gamma multidetectors.

The E835 experiment, spokesperson V. Blideanu (CEA/DRT), aimed to measure the cross-section of reactions induced by neutrons on the following elements: stainless steal, Pb, Cu, C and Al. The activation method was used. The sample was irradiated near the converter and then sent by the pneumatic sample transfer system to a gamma spectroscopy station. For this measurement, the pneumatic transfer system, previously used only for ion irradiation, was adapted for neutron irradiation by NPI staff from Rez (Czech Republic).

The REPARE experiment was particularly important in 2023, not because of the amount of beam time used, but because of the amount of work required to set up and dismantle the device in the converter room. The aim was to produce $^{211}$At with an alpha beam impinging on a bismuth target in the REPARE device. The first test went perfectly, but the irradiation a week later was a failure. Bad adjustment of the beam power resulted in partial melting of the target and alpha contamination of the REPARE chamber. There is no consequences in terms of contamination of the facility are because the $^{211}$At period (7.4 hours) is short. The feedback will be used to re-run the experiment under optimal conditions in September 2024.

The E856 experiment was scheduled in November 2023. Its objective was to study fission and (n,xn) reactions on Pu-239. An active target consisting of a fission chamber containing 6 mg of Pu-239 was placed in the center of the SCONE detector. A first experiment was performed in 2022 with a U-238 target. A problem at the beginning of the experiment destroyed the windows of the fission chamber and some of the plutonium deposits were spread in the beam pipe in the time-of-flight room. This stopped the experiment and had a significant impact on the availability of the NFS experimental area.

In addition to the experiments mentioned above, detector tests were carried out. The characteristics of NFS, the energy and time structure of the beam and the dimensions of the NFS room make it a unique facility for this type of measurements. A MONSTER detector, already used the previous year during the E833 experiment, was tested by a team of Spanish physicists from CIEMAT. Two teams, one from CEA/DAM and the other from IRSN, used the NFS neutron beam to characterize paraterphenyl and stilbene-based neutron detectors. One team of CEA/Cadarache tested SiC detectors in the converter room of NFS. Physicists from CEA/Cadarache have tested two SiC detectors in the converter room in parallel with experiments running in the time-of-flight room to study these detectors exposed to an intense flux of high-energy neutrons.

A team from CEA/DAM irradiated an electronic board close to the converter during the physics experiments. The flux and energy of the neutrons delivered by NFS are particularly interesting for studies of the behavior of electronic components under neutron irradiation. This activity will be continued and in 2024 a dose monitoring system will be tested.

The NFS facility is operating correctly, and the beam delivered is in line with forecasts. A permanent effort of adaptation is necessary to control the problems of exploitation which are of 2 orders:

1. The NFS operating period is short, but concentrated in just 2 months. Periods without beam, which would allow experiments to be set up and dismantled, are short and very rare, making it difficult to carry out and sequence experiments.

2. Activation levels in the converter room are very high and any manipulation in this room, whether for installation (eg REPARE) or repair, is difficult, further complicating the operation of the facility.
# 1. Measurement of the light output function of crystalline organic scintillators as a function of incident neutron energy

Date: September 13-18, 2023

## Spokesperson and co-authors

David DENIS-PETIT¹, Benoit LAURENT¹, Xavier LEDOUX², Gabrielle LELAIZANT¹, Laurent LOPEZ¹

¹CEA DAM DIF, 91297 ARPAJON, France

²GANIL, 14076 CAEN, France

## Abstract

A new fast neutron detector, designed as an array of crystalline organic scintillators (made of stilbene or para-terphenyl), is being developed in order to avoid some limitations of ³He-based neutron detectors, whose constraints limit to the sole detection of thermal neutrons and then need a moderator to detect fast neutrons. These detectors are often used to characterize unknown radioactive material not only in homeland security applications but also in the fields of radioactive waste characterization, neutron dosimetry or accelerator management. Organic scintillators being sensitive to both neutrons and gamma rays, a major issue arises from the need for distinguishing these events and using this opportunity as a good complement to ³He-based detectors. After addressing this issue thanks to the usual Pulse Shape Discrimination (PSD) method, different performances have been investigated for both types of crystals, in particular their Light Output Functions (LOF). The current setup is composed of an array of organic scintillators (seven detectors of two different sizes) that have been combined to count neutrons emitted by known sources. In order to fully characterize the different scintillators, a wide energy range has been studied thanks to the GANIL-NFS facility. On another hand, the intense flux of the NFS facility has also enabled to test the saturation limits of the experimental setup. Getting access to the facility during its assays was really useful for our experiment which did not need more than few hours of data acquisition and enabled parallel settings.

## Experiment report

All the detectors had previously been calibrated, first by using both neutron and gamma sealed sources, and then, through monoenergetic neutron beams produced at the 4MeV CEA facility. Nevertheless, the energy range was limited at a maximum energy of few MeV - less than 14 MeV (and without any energy point between 6 and 14 MeV). Therefore, only the first part of the continuous energy spectra of usual spontaneous fission sources of interest, such as ²⁵²Cf or different uranium and plutonium isotopes, had been investigated. The NFS facility was the only solution in order to constrain the calibration parameters in the highest part of energy spectra (until 20 MeV). Indeed, the NFS high time resolution enables to address neutron energies ranging from few hundreds of keV and tens of MeV and then to fully characterize our different stilbene and para-terphenyl crystals following a Time-Of-Flight (TOF) data analysis.

## Experimental setup

The beam was pulsed for TOF measurements, with a period of 4543 ns to allow the slowest neutrons to reach the detector (approx. 0.21 MeV) before the gamma photons of the next pulse. The neutron beam itself is produced by the deuteron break-up reaction on a thick beryllium converter, while the deuteron beam is delivered by a linear accelerator. The neutron spectrum extends higher than at the CEA 4MeV accelerator, up to 40 MeV, with a maximum yield at approximately 14 MeV. This experiment was thus implemented to extend the range of neutron energies formerly investigated.

Both stilbene and para-terphenyl crystals have been characterized. Moreover, two different crystal sizes have been investigated: a cylinder of dimensions Ø1" x 0.5" and another cylinder of dimensions Ø75mm x 50mm, each encased in an aluminium housing. A total of seven detectors are presented in TAB. 1. These detectors were obtained fully integrated, and five of them can be seen in FIG. 1.
<table><caption>TAB. 1: Description of the seven detectors. The names are the ones that will appear throughout the paper</caption><thead><tr><th>Crystal type</th><th>Crystal dimensions</th><th>Aluminium housing thickness</th><th>Photomultiplier</th><th>Number of detectors</th><th>Detector name(s)</th></tr></thead><tbody><tr><td>Stilbene</td><td>Ø1" x 0.5"</td><td>1.5 mm</td><td>Hamamatsu R6094</td><td>2</td><td>S1-1 & S1-2</td></tr><tr><td>Stilbene</td><td>Ø75mm x 50mm</td><td>1 mm</td><td>Photonis XP53X2B</td><td>1</td><td>S3-1</td></tr><tr><td>Para-terphenyl</td><td>Ø1" x 0.5"</td><td>1.5 mm</td><td>Hamamatsu R6094</td><td>2</td><td>P1-1 & P1-2</td></tr><tr><td>Para-terphenyl</td><td>Ø75mm x 50mm</td><td>1 mm</td><td>Photonis XP53X2B</td><td>2</td><td>P3-1 & P3-2</td></tr></tbody></table>

<figure><img src="image_117.png" /><figcaption>FIG. 1: Picture of 5 of the 7 detectors (from left to right: P1-2, S1-2, P1-1, S1-1, S3-1)</figcaption></figure>

## Data acquisition

In each setup, data acquisition was performed with a CAEN V1730SB digitizer [2], with 16 data acquisition channels, 14-bit resolution, a 2-V maximum digitization window and a 500 MHz sampling rate. The Digital Pulse Processing – Pulse Shape Discrimination (DDP-PSD) firmware uses the digitized signals to generate other values of interest, with the CoMPASS software [3]. The recorded data are, among others, time of event detection (picosecond timestamp, using Constant Fraction Discrimination for each pulse), long gate integral (integral of the signal over its entire duration) and short gate integral (integral of the beginning of the signal). All data in this work was processed and analyzed using the ROOT [4] framework. The high voltage for the detector photomultipliers (PMTs) was provided by CAEN V6533 [5] boards.

The location of our scintillator and data acquisition device is shown in FIG. 2.

<figure><img src="image_118.png" /><figcaption>FIG. 2: Picture of the GANIL NFS experimental hall</figcaption></figure>
Each detector was placed individually in the beam trajectory, and two digitizer channels were used: one for the detector, and the other for the beam pick-off signal. The Time-Of-Flight (TOF) spectrum in FIG. 3 is built from the time difference between the two signals.

<figure><img src="image_119.png" /><figcaption>FIG. 3: TOF spectrum, with the gamma peak (left) and the following neutrons</figcaption></figure>

<figure><img src="image_120.png" /><figcaption>FIG. 4: TOF spectrum with carbon screen, showing the gamma peak (green) and the two cross-section resonances (red).
Left: 6.295 MeV resonance; right: 2.078 MeV resonance</figcaption></figure>

For TOF experiments, a precise knowledge of the flight path distance for neutrons is necessary. To this end, a carbon screen was placed in the beam, and a TOF spectrum was measured (FIG. 4). The carbon cross-section presents relatively sharp resonances to neutrons, including at 2.078 and 6.295 MeV [6]. Using the time difference $\Delta$T between the gamma peak and the resonance energies ($E_n$) in the TOF spectrum, the distance D can be determined. A time difference of $\Delta$T = 1358.85 ns between the gamma peak and the 2.078 MeV resonance, the distance between source and detector was found to be D = 28.93 m.

Based on the knowledge of the neutron flight distance and of the TOF spectrum, it is possible to determine the energy of each neutron event.
## Results

It is then possible to subdivide the resulting neutron energy spectrum for each detector (example in FIG. 5 for one of them: P3-2) into smaller bins, and extract the Pulse Height Distributions (PHDs) of neutrons corresponding to the selected energies. FIG. 6 shows these PHDs, with the uncertainty showing the width of each selected energy bin.

<figure><img src="image_121.png" /><figcaption>FIG. 5: P3-2 detector neutron energy spectrum at GANIL NFS</figcaption></figure>

<figure><img src="image_122.png" /><figcaption>FIG. 6: P3-2 neutron PHDs for energies ranging 1.1 - 9.0 MeV</figcaption></figure>

The light output functions are ultimately extracted from the mean of each Gaussian fit of the PHDs' derivative, and shown in FIG. 6. A possible empirical formula to fit the LOFs is [7]:

$$L(E_p) = AE_p - B(1 - e^{-CE_p})$$

Where A, B and C are fit parameters, L(Ep) is the light output in MeVee and Ep is the recoil proton energy. Such an expression takes into account the exponential rise at the beginning of each LOF, and becomes linear for higher energies, those reachable only thanks to the NFS facility. Fit parameters for the seven detectors have been assessed from these measurement. FIG. 7 shows these LOF, compared to other works concerning similar detectors [8-11].

<figure><img src="image_123.png" /><figcaption>FIG. 7: LOF of the detectors determined at GANIL NFS</figcaption></figure>
These response functions are in good agreement with each other and with the works of Baramsai [10] for stilbene, Sardet [9] for para-terphenyl and Frégeau [8] for another organic scintillator (liquid EJ309), at least concerning the thicker detectors. Between the data for the 50mm-thick detectors and other works for organic scintillators, the difference is less than 0.2 MeVee in the entire energy range, but there is a higher discrepancy for the 0.5"-thick detectors. As expected, for the 0.5"-thick detectors, a higher light output was measured, due to a lesser self-attenuation in the crystal [11].

We would like to sincerely thank the NFS facility team for having enabled us to get access to the beam in order to complete our study over the whole energy range of interest.

Legend

LEDOUX, X. et al., First beams at Neutrons For Science, EPJA (2021), vol. 57, no. 8

CAEN – Tools for Discovery, CAEN V1730SB digitizer (2019), www.caen.it/products/v1730/

CAEN – Tools for Discovery, COMPASS software (2020), www.caen.it/products/compass/

CERN, ROOT – Data Analysis Framework (2021), root.cern

CAEN – Tools for Discovery, CAEN V6533 board (2019), www.caen.it/products/v6533/

NEA, JEFF-3.3, Incident neutron cross-section for carbon, 2017

KORNILOV, N. V. et al., Total characterization of neutron detectors with a 252Cf source and a new light output determination, NIM A (2009), vol. 599, no. 2-3, pp. 226-233

BARAMSAI, B. et al., Fast Neutron Spectroscopy with Organic Scintillation Detectors in a High-Radiation Environment, NASA, Glenn Research Center (2020)

FREGEAU, M. O. et al., Light response and efficiency calibration of EJ309 liquid scintillator between 3 and 45 MeV, NIM A (2019), vol. 941

SARDET, A., Spectres en énergie des neutrons prompts de fission : optimisation du dispositif expérimental et application à l'238U, Université Paris-Saclay, Saclay (2015)

ENQVIST, A. et al., Neutron light output response and resolution functions in EJ-309 liquid scintillation detectors, NIM A (2013), vol. 715, pp. 79-86
## 2. GARIC – GAs pRoduction In Chromium by neutrons and GARROS – GA pRoduction in iROn by neutronS

Experiment number: E802 and E858

Date: October 2023

### Spokeperson and co-authors

Diego Tarrío¹ (spokeperson), Lucas de Arruda Serra Filho¹,², Xavier Ledoux², Stephan Pomp¹, Diego Ramos², Ali Al-Adili¹, Mattias Lantz¹, Ivan Kodeli³, Iuliia Ipatova³, Udomrat Tippawan⁴, and the Medley Team.

¹Uppsala University, Sweden; ²GANIL, France; ³United Kingdom Atomic Energy Agency, UK; ⁴Chiang Mai University, Thailand.

### Abstract

Two experiments have been recently done to study the light-ion production in neutron-induced reactions in natural chromium and in natural iron, using the white neutron beam of NFS and the Medley setup. Those reactions are relevant for applications in materials for fusion devices and for fission reactors. The data analysis is ongoing, and the goal is to get double-differential cross-sections on the production of light-ions, as a function of neutron energy. The identification of light ions (p, d, t, ³He, and α) is based on energy losses in three-element telescopes.

### Experiment report

These two experiments deal with studies on emission of light-ions in reactions induced by neutrons in chromium and in iron. The goal is to provide with double differential cross-sections for the production of light-ions, with respect to emission angle and to energy of the emitted ion, as a function of neutron energy.

The motivation for these measurements stands on the use of those elements as components in structural materials in fission and fusion reactors. Exposure to highly intense neutron fluxes produces the formation of light ions (protons, deuterons, tritons, ³He, α-particles...). These ions, which are isotopes of hydrogen and helium, represent defect impurities in the lattice. With high temperatures, these impurities migrate through the lattice, creating gas bubbles of hydrogen and helium that can cause swelling and embrittlement in the material, thus degrading its mechanical properties. As a consequence, and in order to calculate the lifetime of structural components, it is required to have a good knowledge on the production cross-sections for light-ions. The lack of a comprehensive set of experimental data on light-ion production cross-sections for these elements, which also covers a continuous and wide neutron energy range, motivates the need for these experiments.

The experiments have been done in October 2023 at NFS using the so-called Medley setup (see Figure 1), designed for detection of charged particles over a wide dynamic range. It consists of eight three-element telescopes mounted inside a 240-mm high cylindrical evacuated chamber with inner diameter of 800 mm. Each telescope consists of two fully depleted ΔE silicon surface barrier detectors (SSBD) and a CsI(Tl) crystal. The back-end part of each crystal is connected to a read-out diode. The setup had been used at quasi-monoenergetic neutrons beams at the currently dismantled TSL facility in Uppsala. In order to be able to use it at a white neutron beam, as the one provided at NFS, the original setup has been upgraded to incorporate time-of-flight capabilities in the detectors. For that, new readout preamplifiers have been developed by GANIL.

<figure><img src="image_124.png" /><figcaption>Figure 1: Inner view of the Medley chamber. The eight telescopes are pointing to the central part of the chamber. A circular target can be seen in the upper side, attached to the lid.</figcaption></figure>
Different targets have been used in these experiments and, being exposed to the beam one at a time. The targets are samples of natural Cr and Fe. For each of them, two different samples have been used: In the case of Fe, the circular samples were 25 mm in diameter, and with thicknesses of 5 µm and 15 µm. For Cr, the samples were squared, with 18 mm in side length, and thicknesses of 15 µm and 75 µm. Moreover, and because of their fragility, the Cr samples were attached to a 150-µm thick polyester backing. Therefore, another target consisting on an empty polyester backing has also been used to account for the effect of the backing in the Cr measurements. Moreover, a good knowledge on the neutron flux is also required to provide to deduce absolute values of the production cross-sections. Therefore, circular targets of CH₂ and C have been also used to measure the neutron flux using neutron-proton elastic scattering on H.

By measuring the energy deposited by each light-ion in the different detectors of a telescope, it is possible to detect it and to identify it, in an event-by-event basis. Moreover, its detection in the second silicon of a telescope produces a time signal which is used as a "start" for the time-of-flight, and the next pulse produced by the LINAC is used as a "stop" signal. The time difference between these two signals corresponds to the time-of-flight of the neutron which produced the reaction and, therefore, its kinetic energy is determined. A correction taking into account the time required by the ion to travel from the target to the telescope is also applied, since its velocity is deduced from the kinetic energy (measured as the energy deposited in the telescope) and the mass of the ion, which is known because of the identification achieved with the ΔE-ΔE-E technique.

The identification of the light-ions is based on the different energy deposition of different particles in the detectors of the telescope, following what is called the ΔE-ΔE-E technique. Figure 2 shows a subset of data on the correlation between the energy deposited in the first silicon ΔE1, in the second silicon ΔE2 (left figure) and between ΔE2 and the energy deposited in the scintillator ΔE3 (right figure) for the telescope placed at 20°. The good energy resolution of the setup allows to distinguish between the different light-ions (p, d, t, 3He, α) produced in the C target. By plotting the energy loss in each of the three elements of the telescope, it is possible to identify the different light-ions produced. Figure 2 shows, using a fraction of the collected statistics of statistics, the correlation between the energy deposited in the first silicon ΔE1, in the second silicon ΔE2 (left figure) and between ΔE2 and the energy deposited in the scintillator ΔE3 (right figure) for the telescope placed at 20°. The good energy resolution of the setup allows to distinguish between the different light-ions (p, d, t, 3He, α). This figure corresponds to the C target, but similar plots have been obtained with all the targets.

<figure><img src="image_125.png" /></figure>

Figure 2: Energy deposited by light-ions in the telescope placed at 20°. Left: Energy deposited in the first silicon (ΔE₁) vs. energy in the second silicon (ΔE₂). Right: Energy deposited in the second silicon (ΔE₂) vs. energy deposited in the CsI (ΔE₃) by those ions with enough energy to pass through the second silicon. The continuous lines represent simulation results from KaliVeda.

As a consequence, it is possible to identify the light-ion produced in each event, and to associate it with the energy of the neutron which has produced it. The analysis of the data is currently ongoing and is expected that double-differential cross-sections for the production of light-ions in Cr and Fe will be obtained.

This work has received funding from the European Union's research and training programme under grant agreements with numbers 847552 (SANDA), 847594 (ARIEL) and 101057511 (EURO-LABS). Part of this work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion). It has also received funding from the European Union's 2020 research and innovation programme under grant agreement No 101008126, corresponding to the RADNEXT project. Funding from the Swedish Centre for Nuclear Technology (SKC) has been also received.
## 3. Measurement of the neutron induced activation in materials: improvement of nuclear reaction models and decay data libraries for the specific case of radiotherapy accelerators

**Experiment number: E835 21**

**Date: November 1-2, 2023**

**Spokeperson and co-authors**

Valentin Blideanu (CEA)

Clément Besnard-Vauterin (CEA)

Xavier Ledoux (GANIL)

Jaromir Mrazek (Nuclear Physics Institute of the Czech Academy of Sciences)

Benjamin Rapp (CEA)

**Abstract**

The aspect of induced radioactivity and waste management for the particle accelerators is currently not properly addressed. There is an increasing demand by accelerator operators to waste management agencies and regulatory authorities to provide the appropriate solutions to this problem. This is particularly true for electron linear accelerators used in radiotherapy for which the activation level is expected to be relatively low when compared to other facilities from the nuclear industry, due to the activation occurring via secondary neutrons created in photo-nuclear reactions. These reactions are usually characterized by a high energy threshold, around 10 MeV for most of the elements, creating neutrons which can further activate the materials only for some operating regimes of these accelerators involving high electron energies. However, without a rigorous methodology able to accurately determine the activation level and the contributions from particular radio-isotopes, no well-grounded decision can be taken on the management of the generated waste.

Methodologies based on Monte-Carlo simulations coupled with activation calculation codes are often used to address this issue since they are able to provide the complete radioactive inventory in each part of the accelerator whose geometry can be modeled with a high level of details. Calculation tools capabilities in terms of accuracy in simulating nuclear reactions at the origin of the materials activation must be however tested against experimental data. The present work focusses on this aspect by producing new macroscopic data in terms of activity induced by neutrons in the materials commonly present in medical electron LINACs allowing to estimate the precision than can be achieved by a fully calculation-based methodology.

**Experiment report**

Samples of six materials in their natural isotopic compositions, (carbon, aluminum, steel, copper, tungsten and lead), selected for being abundantly present in the components of medical electron accelerators, were irradiated under the neutron flux produced at NFS in a particular configuration. The angle of 90 degrees has been selected as the best compromise allowing an enough decrease of the contribution from fast neutrons from the deuteron break-up while preserving a reasonably high neutron flux which would have been much lower at higher backward angles.

After being exposed in the converter room to neutrons with energy distribution as discussed above and at an average flux of the order $10^9$ neutrons/cm$^2$/sec (for deuteron beam intensities of around 20 µA) for a duration of 15 minutes, the samples were quickly transferred through a pneumatic system to the TOF area in front of a Canberra coaxial n-type liquid nitrogen cooled hyper pure germanium (HPGe) detector for the measurements of the $\gamma$ spectra. Data acquisition began approximately 15 seconds after the irradiation ended, allowing the measurement of contributions from short-lived radio-isotopes. This is illustrated by the identification in the $\gamma$ spectra of the radio-isotope $^{16}$N (half-life of 7.13 seconds), produced by the $^{16}$O(n,p)$^{16}$N reaction in the air trapped inside the sample containers.

For the carbon sample no data above the background has been recorded suggesting that no radioactive isotope is created in significant amount in this material when exposed to a neutron energy distribution typical for a medical electron LINAC. The identification of the radio-isotopes from the energies of the peaks in the spectra for the activated samples has been performed based on state-of-the-art nuclear data library developed in the frame of the DDEP project (Decay Data Evaluation Project) and maintained and continuously updated by LNHB.
The experimental set-up has been simulated using the MCNP6.2 code with a detailed geometry model taking into account all the elements present in the converter room strongly influencing the flux and the energy distribution of neutrons: the concrete shielding with walls, roof and ceiling, the magnets of the deuteron beam line, the neutron collimator separating the converter cave from the TOF hall. The simulations result in terms of 2D neutron flux map allow the neutron flux and its energy distribution at the exact location where the samples were irradiated to be determined. The neutron energy distribution has been calculated with MCNP6.2 using the specific CCFE scheme with 709 energy groups, allowing further activation calculations to be performed with the FISPACT-II code using the option of neutron-induced reactions cross-sections from the TENDL library.

FISPACT-II allows to accurately reproduce the irradiation and decay sequences as they were recorded during the experiments. Based on the neutron flux value and the energy distribution previously calculated by the simulations with the MCNP6.2 code at the sample location and considering the known irradiation duration, it uses the energy-dependent cross-section values from the TENDL library to calculate the yields of radio-isotopes produced in each sample by the neutron-induced nuclear reactions on the stable nuclei present in its initial composition. Decay data libraries are further used to calculate the weight of these radio-isotopes at the time after the sample irradiation corresponding to the γ spectrometry measurements. The calculations predictions, thus simulating as accurately as possible the real experimental conditions, can then be directly compared to the data obtained by the experiments performed in this work.

The analysis of the results has been done for each sample individually. The example we are discussing in detail here concerns the case of copper, as it is a material which can generally be always found in particle accelerators. Several radio-isotopes were identified in the γ spectrum acquired after neutron irradiation of the copper sample, created from both ⁶³Cu and ⁶⁵Cu natural isotopes through various neutron-nucleus reaction channels as discussed below. In order to test the accuracy of the calculation by the code FISPACT-II of the radio-isotopes production probability, we further analyzed the corresponding neutron-induced reactions cross-sections behavior and compared the values from the TENDL library used by FISPACT-II with the data available in the literature.

Among the three neutron-induced reactions on the ⁶³Cu natural isotope producing measurable radio-isotopes given our irradiation times, the available experimental cross-sections found in EXFOR database for the reactions ⁶³Cu(n,γ)⁶⁴Cu and ⁶³Cu(n,2n)⁶²Cu are relatively abundant and the evaluated cross-sections from TENDL library show globally a good agreement despite discrepancies being identified in some neutron energy domains. In the case of the other possible reaction ⁶³Cu(n,2p)⁶²Co no data was found in the literature which doesn't allow to test the accuracy of the cross-section values from TENDL library in this particular case.

Concerning the reactions on ⁶⁵Cu, experimental cross-sections are available for all of them and the evaluated values from the TENDL library are in some cases in significant disagreement, namely for the reaction ⁶⁵Cu(n,α)⁶²Co, for the reaction ⁶⁵Cu(n,p)⁶⁵Ni at neutron energies below 10 MeV and for the reaction ⁶⁵Cu(n,γ)⁶⁶Cu in the thermal neutrons region. A very good agreement was found on the other hand for the reaction ⁶⁵Cu(n,2n)⁶⁴Cu.

Provided the good knowledge of the neutron flux and its energy distribution as well as the sample composition and the irradiation-decay sequences when calculating the radioactivity induced by neutrons in the samples with the FISPACT-II code, the main source of uncertainty affecting the calculations results is related to the reaction cross-sections used to determine the probability of production of each radio-isotope. The experimental conditions in which the samples were irradiated at NFS and subsequently analyzed by γ spectrometry are well known and faithfully reproduced in the simulations performed in this work as discussed in the beginning of this section. The next step was the estimation of the calculation accuracy based on the comparisons related to the neutron-induced reactions cross-sections, between the values from the TENDL library used by FISPACT-II and the experimental data.

An article bringing together all the results of this first experiment at NFS will be submitted very soon to Nuclear Instruments and Methods in Physics Research B.

The first measurements performed using neutrons produced at the NFS facility presented in this work are related to the case of medical electron LINACs, but they must be seen as the first stage of a broader scientific program to be continued in the future. Other specific needs can be considered, related to the deep study of neutron-induced activation for other extensively used accelerator-based applications such as cyclotrons for the production of isotopes for nuclear medicine. Large-scale research facilities using particle accelerators such as synchrotrons and spallation sources also have specific needs in terms of neutron-induced activation, especially when considering the large quantities of materials used. On this aspect, we demonstrated that the neutron beams available at NFS offer enough flexibility in terms of energy distribution, considering the kinematics of the reactions used for their production, to cover a wide range of application related needs in terms of neutron-induced radioactivity.
Legend

<figure><img src="image_126.png" /><figcaption>Picture of the inside of the converter cave showing the experimental configuration</figcaption></figure>

<figure><img src="image_127.png" /></figure>

<figure><img src="image_128.png" /></figure>

<figure><img src="image_129.png" /></figure>

<figure><img src="image_130.png" /><figcaption>The γ spectrum measured for the copper sample after neutron irradiation at NFS (right)</figcaption></figure>
# 4. Detector response characterization at a wide energy neutron range

Experiment number: Test MONSTER

Date: September 17-18, 2023

## Spokesperson and co-authors

T. Martínez<fnref n="1" />, D. Cano-Ott<fnref n="1" />, A. Pérez de Rada Fiol<fnref n="1" />, V. Alcayne<fnref n="1" />, E. Mendoza<fnref n="1" />, J. Plaza<fnref n="1" />, A. Sánchez-Caballero<fnref n="1" />, D. Villamarín<fnref n="1" />, D. Doré<fnref n="2" />, P. Miriot-Jaubert<fnref n="2" />, M. Vandebruck<fnref n="2" /> and I. Matea<fnref n="3" />

## Abstract

The characterization of the neutron response of detectors in the energy range from a few 100 keV up to tens of MeV is needed to provide accurate results in many applications where the detection of fast neutrons plays an important role. This is the case of β-delayed neutron spectroscopy of exotic nuclei, nuclear reaction studies, the inspection and characterization of nuclear materials, homeland security applications, and neutron dosimetry in hadron therapy treatments.

## Experiment report

### Introduction

Organic liquid scintillation detectors have been traditionally used for fast neutron spectroscopy due to their high intrinsic efficiency, fast response, and the ability to distinguish between detected neutrons and γ-rays by pulse shape analysis. The characterization of the neutron response in the energy range from a few hundredths of keV up to tens of MeV is needed to provide accurate results in nuclear technology applications as well as in nuclear structure phenomena.

The determination of the neutron light output of the scintillators as a function of the incident neutron energy is required for obtaining the efficiency of the detectors over a broad neutron energy range. This is achieved by including the light output functions in detailed Monte Carlo simulation codes [Sch02] and through the validation of the simulations with accurate measurements.

The MOdular Neutron time-of-flight Spectrometer (MONSTER) [Gar12, Mar14], based on BC501A and EJ301 liquid scintillators, has been designed for β-delayed neutron spectroscopy and other applications like (α,n) and neutron-induced reactions. A first characterization of the light output response in MONSTER detectors for neutron energies up to 14 MeV was performed at PTB and CEA/DAM facilities. The contribution to the light output response due to n-p recoil cross section and ¹²C(n,α) and ¹²C(n,n')3α reactions channels were validated with NRESP and GEANT4 codes [Gar17].

At higher neutron energies (E>20 MeV), other break-up reactions, such as ¹²C(n,p) and ¹²C(n,d), also contribute to the response. These reactions are not accurately implemented in state-of-the-art codes, and therefore specific light output calibration measurements are needed when small uncertainties are required for neutron energies above 20 MeV. In this context, a characterization measurement of the neutron response in the range of 1 MeV up to 40 MeV has been performed at the NFS facility [Led21] of GANIL.

### Experimental methods

At NFS, a neutron beam with a wide energy range was generated through the ⁹Be(d,n) reaction. A primary deuteron beam at 40 MeV impinging on a thick beryllium target provided neutrons with a continuous spectrum thanks to the deuteron break-up reactions. According to the estimated reaction yield, neutron energy range, flight distance, and detector count rate it was necessary to work at a repetition rate below 88 kHz, both to avoid overlap of neutrons from successive bunches and to keep a reasonable neutron count rate. For that, the LINAC frequency (88 MHz) was reduced by a factor of 1000 to 1500 using the bunch selector at the RFQ element. The LINAC RF signal was used to provide the start signal for the determination of the neutrons' time-of-flight (TOF). The beam current was

<footnote n="1">¹CIEMAT, Madrid, Spain</footnote>

<footnote n="2">²CEA DRF/Irfu/DPhN, Saclay, France</footnote>

<footnote n="3">³IJCLab, Orsay, France</footnote>
measured with a faraday cup placed close to the target. The signal provided by a current integrator module was also registered, to be used for normalization.

Several detectors have been irradiated to study their response to neutrons of such energies. Four MONSTER detectors, which combine two types of module design and two kinds of PMT models, and a small EJ315 (deuterated benzene) detector, which is used in neutron capture cross section measurements at the n_TOF facility of CERN. The detectors were placed at the end of the TOF Hall at a flight path distance of ~30 m from the target and at 0 degrees (Figure 1).

<figure><img src="image_131.png" /><figcaption>Figure 1. (Left) Four MONSTER cells used in this test. (Right) Detector placed at the irradiation position.</figcaption></figure>

The detector signals, as well as the RF and current signals, were registered with the Digital data Acquisition System (DAISY), a custom digital DAQ system developed at CIEMAT. It is based on ADQ14DC digitizers from Teledyne SP Devices with 14 bits vertical resolution, 1 GHz sampling rate, and 4 channels [Vil23]. The system integrates custom pulse shape analysis software to perform an online analysis of the signals.

## Results and discussion

A preliminary analysis of the measurement performed with the MONSTER detectors is presented in this section. Linearity and light calibration

The light calibration of the detectors was performed with $^{22}$Na and $^{88}$Y gamma-ray sources that only covered a small energy range. Thus, the linearity of the detectors over the whole range of interest was checked with data from (d,n) reaction runs. As can be seen in Figure 2, the area of the signals is proportional to their amplitude over the whole energy range of interest, confirming the linearity of the detector response.

<figure><img src="image_132.png" /><figcaption>Figure 2. Amplitude of the signals registered during (d,n) reaction runs with MONSTER M3 detector as a function of their area.</figcaption></figure>

Confirming the linearity of the detectors allowed to extend the calibration performed with γ-ray sources to the whole energy range of interest.
## Time-of-flight spectrum

To obtain the TOF spectrum of the neutrons, a selection of the neutron events on the PSD vs light spectrum was performed. In the left part of Figure 3, the selected events are shown. Events corresponding to the detection of γ-rays are filtered out with the excellent discrimination capabilities of MONSTER detectors. In this figure, lower values of PSD correspond to events where the scintillation light has been produced by reactions of the neutrons with the hydrogen in the liquid, while higher values of PSD correspond to light emitted after reactions with heavier ions. On the right side of the figure, the corresponding clean neutron TOF spectrum is shown.

<figure><img src="image_133.png" /><figcaption>Figure 3. (Left) PSD vs light spectrum of the selected neutron events. (Right) Neutron TOF spectrum.</figcaption></figure>

To determine the real flight path of each detector, necessary for the TOF calibration, a measurement with a carbon sample placed between the target and the detector was performed. The resonances of the carbon observed in the TOF spectrum were used to perform a fit and obtain the distance of each detector from the target.

## Detector response function

With a clean and calibrated neutron TOF spectrum, the TOF technique can be applied to obtain the detector response to neutrons of different energies. Cuts at different TOF values have been applied in the neutron TOF spectrum to obtain the detector response function to neutrons of different energies. Some of the response functions obtained can be seen in Figure 4. In this figure, it can be observed that different structures appear on the response functions as the neutron energy increases.

<figure><img src="image_134.png" /><figcaption>Figure 4. Response functions of MONSTER for neutrons of different energies.</figcaption></figure>

The structures that appear at higher neutron energies correspond to the different reaction channels that open as the energy of the neutrons increases. The evolution of these structures can be seen more clearly by checking the
PSD vs light spectrum with a selection of the neutron TOF (i.e. energy). Figure 5 shows this spectrum for neutrons of 20 and 30 MeV, where the different structures can be clearly differentiated as banana-like shapes.

<figure><img src="image_135.png" /><figcaption>Figure 5. PSD vs light spectrum for neutrons of 20 (left) and 30 (right) MeV.</figcaption></figure>

In the figure, three main different structures can be observed. The lower banana-like structure corresponds to events where the light has been produced by protons. The structure immediately above to the protons one corresponds to the light produced by deuteron and protons emitted in the reaction with carbon. In the figure, this contribution is clear for the case of neutrons of 30 MeV (right panel), but not for lower energy ones (left panel). Finally, at higher values of PSD, from 0.38 to 0.45, the contribution of α-particles can be observed as a third banana structure.

## Efficiency

To obtain the efficiency curve of MONSTER detectors, the response function corresponding to each neutron energy considered will be integrated. The obtained values need to be corrected by the total current integrated during the measurement. After the experimental values of the efficiency are obtained, they will be compared to Monte Carlo simulations performed both with Geant4 and PHITS. Some preliminary results of the simulations performed are shown in Figure 6.

<figure><img src="image_136.png" /><figcaption>Figure 6. Simulated efficiency curves of a MONSTER module with Geant4 and PHITS.</figcaption></figure>

As can be seen in the figure, both simulation codes produce results that are in agreement below 20 MeV, within the 5% of uncertainty that has been assigned to each curve. In this energy range, the small differences observed are due to differences in the simulated geometries. In the case of the simulation with PHITS, more geometrical
details need to be included. Above 20 MeV, the differences are mainly due to the fact that Geant4 uses models instead of data.

## Conclusions

The analysis is still ongoing. A successful preliminary analysis of the data taken has been performed. There are still some difficulties to be addressed, such as the lack of a reliable current integration signal in some runs and the pileup caused by the high neutron yield and the difficulty of placing the second collimator on the beam line. Nonetheless, the results obtained so far look promising.

## References

[Sch02] D. Schmidt et al., Nucl. Instrum. Methods A, 476 (2002) 186-189.

[Gar12] A. Garcia et al., J. Instrumentation, 7 (2023) C05012.

[Mar14] T. Martinez et al., Nucl. Data Sheets, 120 (2014) 78

[Gar17] A. Garcia et al., Nucl. Instrum. Methods A, 868 (2017) 73

[Led21] X. Ledoux et al., Eur. Phys. J. A (2021) 57: 257

[Vil23] D. Villamarin et al., Nucl. Instrum. Methods A, 1055 (2023) 168526.
## 5. Neutrons response determination of four LNE-IRSN (LMDN) scintillators in their operating energy range (i.e. between 100 keV-22 MeV)

**Experiment number: LNE-IRSN scintillators test**

**Date: September 15-20, 2023**

### Spokesperson and co-authors

Michaël PETIT/IRSN (michael.petit@irsn.fr), Diane QUEVAUVILLERS (IRSN), Laurent OTTAVIANI (Aix-Marseille Université), Christelle REYNARD-CARETTE (Aix-Marseille Université)

### Abstract

Between September 15th and 20th 2023, the Laboratory for micro-irradiation, neutron metrology and dosimetry (LMDN) of IRSN carried out an experiment on the neutron beam line NFS at GANIL. The aim of the experiment was to determine the neutron response functions for 4 scintillators between 100 keV and 22 MeV. The characteristics of the NFS beam - frequency, energy resolution and count rate - were perfectly compatible with the scientific and technical goal and the technical resources from NFS teams were excellent. Finally, it was possible to obtain completed data for the four detectors within 16 hours. The data are currently being analyzed, and an initial assessment suggests that the objectives have been achieved. NFS is a high-profile facility for this type of calibration, which is essential in neutrons metrology field. The LMDN would like to thank the NFS teams for their welcome, their availability and the quality of the neutrons beam. These scintillators will set LMDN's metrological references for years to come.

This work is supported by LNE, the French National Metrological Institute and is a part of Diane QUEVAUVILLERS' PhD (Characterization and use of stilbene scintillators at AMANDE and CEZANE for neutron metrology and spectrometry between 100 keV and 22 MeV)

### Experiment report

The four scintillators calibrated are two-inch orthocylindrical and are coupled to a DT5730 digital acquisition system driven by the commercial software COMPASS. The operating points of the scintillators had previously been determined by dedicated studies carried out on the AMANDE facility of the LMDN located on the Cadarache site. Neutron calibration of the 4 scintillators was carried out using a neutron beam from the reaction of 40 MeV deuteron pulsed beam on a thick ⁹Be target. This beam provides a neutron spectrum ranging from few keV up to 44 MeV, although the neutron spectrum below 1 MeV is not well known yet. The beam frequency was around 88 kHz, giving a period of 11 µs between two pulses. This delay means that the detector can be considered to have returned to its baseline between two pulses. The intensity of the beam resulted in a count rate of about 8,000 events per second for a background of about 200 events per second. Each detector was calibrated within 4 hours, so with about 100 million events per detector.

Neutron energy is determined by the time-of-flight method. The time resolution of the measurement is less than 1 ns for a flight distance of 29 m. More, the neutron energy was checked with a carbon filter which led to observe by transmission the resonances in the total effective cross-section of ¹²C. The uncertainty on the neutron energy is at most 30 keV for the highest energies, which is less than the intrinsic resolution of the detector. Photon calibration of the detectors was carried out on site using the NFS calibration sources (¹³⁷Cs, ²²Na, ⁸⁸Y, ²⁰⁷Bi). All of this data is currently being analyzed at LMDN.

This type of experiment, which is extremely simple to design and carry out, is nonetheless essential to the LNE-IRSN neutron metrology activities. Technical resources proposed were well suited to the task and the current lack of an equivalent alternative in Europe means that NFS is essential.
<figure><img src="image_137.png" /><figcaption>One of the four scintillators being calibrated on the NFS line.</figcaption></figure>

<figure><img src="image_138.png" /><figcaption>Extract from the raw data for one of the scintillators.</figcaption></figure>
# 6. Shedding new light on the structure of 56Ni using (n,3n) reaction at NFS

**Experiment number: E838_21**

**Date: September 26-October 7, 2023**

**Spokesperson and co-authors**

Emmanuel CLEMENT (GANIL) Maelle Kerveno (IPHC)

**Abstract**

We proposed to re-investigate the nuclear structure of the doubly magic nuclei 56Ni using the (n,3n) reaction from 58Ni. The nuclei near 56Ni are of particular interest as they are amenable to different microscopic theoretical treatments while studying the competition between single-particle and collective excitations. The collective states in 56Ni involve multiparticle multihole excitations across the N=Z=28 shell gap. At high excitation energies, reaction studies have revealed evidence for hyperdeformed resonances in the 56Ni compound. While the structure of 56Ni has been intensively investigated using charge particle or heavy ions collision, the pure neutron probe was never used. The (n,xn) reactions are a long standing reaction mechanism used in the nuclear data evaluation but never used in the framework of nuclear structure. For the first time, using the unprecedented NFS neutron flux at ~30MeV, 56Ni can be populated from 58Ni in a (n,3n) reaction with a cross section of 2 mb opening a new probe and possibly new aspect of the nuclear structure of this doubly magic nuclei. We propose to perform a prompt spectroscopy of 56Ni using the EXOGAM array at NFS using the (n,3n) reaction. Such new spectroscopic informations are also relevant for nuclear reaction mechanism formalism (like TALYS) and nuclear data evaluation. For nuclear structure, the main motivation is the search for low spin (J=2 or 4) states from 3 to 10 MeV excitation energy possibly populating the 0+ states at 3956 keV, 6654 keV and 7903 keV observed only in 58Ni(p,t)56Ni reactions

**Experiment report**

EXOGAM was used for the first time to perform the in-beam spectroscopy of exotic nuclei using the (n,xn) reaction using fast neutron up to 40 MeV. The experiment was very successful and the analysis is led by a PhD student in the STARS group. Reaction products of (n,2n), (n,3n), (n,p), (n,t) and (n,a) have been observed in prompt gamma gamma spectroscopy in coincidence with the fastest neutron. The in-depth analysis of the 58Ni(n,2n)57Ni channel led to the following first observations: the overall picture of the populated states is comparable to the heavy-ions fusion limited to low angular momentum, new states have been observed, the reaction is orienting the initial states, and excitation function can be measured. The analysis will be continued on the (n,3n) and (n, charged particles channel)

<figure><img src="image_139.png" /></figure>
<figure><img src="image_140.png" /></figure>

## II. VAMOS
# 1. Damping of shell effects in nuclear fission

Experiment number: E850_21

Date: June 13-26, 2023

## Spokesperson and co-authors (affiliation)

Julien Taieb (CEA), Pierre Morfouace (CEA), Diego Ramos (GANIL), Antoine Lemasson (GANIL), Audrey Chatillon (CEA), Benoit Mauss (CEA), Laurent Audouin (IJCLab), Lucas Bégué-Guillou (GANIL), Jose Luis Rodriguez (University of Coruna), Alex Cobo Zarzuelo (GANIL), Neeraj Kumar (IPHC), Christelle Schmitt (IPHC), Cyril Lenain (CEA), Théodore Efremov (CEA), Alexis Francheteau (GANIL), Indu Jangid (GANIL), Taiki Tanaka (GANIL), Manuel Caamano (Santiago), Bea Errandonea (Santiago), Owenn Syrett (CEA), Ron Malone (Livermore), Anton Tonchev (Livermore), Anthony Ramirez (Livermore), Charlène Surrault (CEA), Marius Godio (IJCLab), Alicia Munoz (USC-IGFAE), Deby Treasa (LP2IB), Igor Tsekhanovich (LP2IB), Emmanuel Clément (GANIL)

## Abstract

The experiment aim at measuring isotopic fission-fragment yields as a function of excitation energy of the fissioning systems produced by transfer reaction. Using the newly-developped highly-segmented PISTA silicon array (Particle Identification Silicon Telescope Array), we aim at obtaining isotopic fission yields with high statistics per bin of about 1 MeV in excitation energy from 6 up to 20 MeV. Several fissioning systems of interest are populated such as ²³⁶U, ²⁴⁰Pu or ²⁴²Pu. These data will bring new insights on the disappearance of shell effects with the excitation energy of the fissioning system and are of high relevance for the nuclear physics applications, in particular for Gen-IV reactors operating with fast neutrons.

## Experiment report

The experiment took place in June 2023 with a planned beam time of 12 days to measure fission fragments at two angles of the VAMOS spectrometer: 14 and 20 degrees, for 6 days each. However, various issues in the production of the ²³⁸U beam did not allow for 12 days of beam time, but only an effective time of about 6 days. For this reason, the measurement focused on a single VAMOS angle to obtain the necessary statistics. Consequently, the GANIL management agreed to grant us an additional 6 days to perform the measurement at 14 degrees. This additional beam time took place in April 2024. This experiment is part of Lucas Bégué-Guillou's thesis and will be the subject of further theses.

Despite the non-optimal performance of the accelerator, this was the first use of the new silicon detector array, PISTA. Very quickly, we were able to recognize the excellent performance of PISTA in terms of ejectile identification. Indeed, PISTA allows for a much better separation between ⁹Be and ¹⁰Be, as well as between different carbon isotopes, as shown in Figure 1. The quality of this particle identification spectrum clearly demonstrates the added value of PISTA for this experiment. Finally, the better granularity of PISTA, after fine calibration and alignment, will enable a resolution 2.9 times better than that obtained with SPIDER.

In this identification spectrum, we can also see that ¹⁴C is produced ten times less frequently than ¹⁰Be, which will make the study of the ²³⁶U system less relevant compared to ²⁴⁰Pu, where we have ten times more events.

In any case, it is clear that PISTA allows for better identification of the ejectile and will thus enable a much better characterization of the fissioning system in terms of mass, charge, and excitation energy. Its resolution in excitation energy will allow for a much finer probing of the evolution of shell effects with E*.
<figure><img src="image_141.png" /><figcaption>Figure 1: PISTA particle identification</figcaption></figure>

Moreover, the VAMOS spectrometer is dedicated to the mass and charge identification of one of the fission fragments through its various multi-wire detectors and ionization chambers. This spectrometer enables the measurement of both charge and mass with adequate resolution across the entire distribution of fission fragments. The measurement of the mass of the fragments is provided through a time-of-flight measurement combined with a position measurement, thus giving the magnetic rigidity Bp. A current preliminary analysis shows the mass distribution obtained for all excitation energies in the case of $^{240}$Pu, where $^{10}$Be has been selected in PISTA. This distribution is presented in Figure 2. This preliminary distribution shows a mass separation up to mass 150, that is, across the entire distribution of fission fragments as well.

<figure><img src="image_142.png" /><figcaption>Figure 2: Fission fragment mass distribution for $^{240}$Pu</figcaption></figure>
III. LISE

<figure><img src="image_143.png" /></figure>
# 1. How does deformation influence neutron-proton pairing? Study of the two-nucleon transfer reaction $^{48}\text{Cr}(p,^3\text{He})^{46}\text{V}$

Experiment number: E805 20

Date: April 7-20, 2023

## Spokesperson and co-authors

M. Assié<fnref n="1" />, H. Jacob<fnref n="1" />, V. Alcindor<fnref n="1" />, Y. Blumenfeld<fnref n="1" />, Ö. Aktas<fnref n="2" />, D. Beaumel<fnref n="1" />, J. Béquet<fnref n="1" />, S. Bottoni<fnref n="3" />, E. Clément<fnref n="2" />, G. De France<fnref n="2" />, Q. Delignac<fnref n="4" />, F. De Oliveira<fnref n="2" />, N. De Séréville<fnref n="1" />, L. Dienis<fnref n="2" />, S. Franchoo<fnref n="1" />, F. Galtaross<fnref n="5" />, A. Gottardo<fnref n="6" />, F. Hammache<fnref n="1" />, M. Kaci<fnref n="1" />, S. Koyama<fnref n="2" />, A. Lemasson<fnref n="2" />, M. Lozano González<fnref n="7" />, A.O. Macchivelli<fnref n="2" />, I. Matea<fnref n="1" />, O. Nasr<fnref n="1" />, C. Paxman<fnref n="9" />, S. Pigliapoco<fnref n="6" />, J. Piot<fnref n="2" />, T. Roger<fnref n="2" />, F. Rotaru<fnref n="10" />, O. Sorlin<fnref n="2" />, M. Stanoiu<fnref n="10" />, I. Stephan<fnref n="1" />, Ch. Stodel<fnref n="2" />, J.C. Thomas<fnref n="2" />, L. Zago<fnref n="6" />.

## Abstract

Neutron-proton pairing manifests itself predominantly in nuclei with N=Z and is expected to be maximum for open shell nuclei with high-j orbitals. Pair-transfer is one of the experimental signatures for pairing. The experiment aimed at studying the unstable $^{48}\text{Cr}$ nucleus that is the middle of the f-shell, the largest shell accessible experimentally for two-nucleon transfer and also a good rotor. By measuring the neutron-proton transfer reaction $^{48}\text{Cr}(p,^3\text{He})^{46}\text{V}$, the interplay between pairing and deformation will be investigated. The goal was to determine the cross-sections to the ground state (0+,T=1) and to the first 1+,T=0 state in order to: (i) determine the ratio of these cross-sections and put it in perspective with previous measurements in the f-shell; (ii) study the effect of deformation on each pairing channel by comparing with theoretical predictions. The experiment was run as part of the LISE2023 campaign, making use of CATS beam trackers, the MUST2 array, EXOGAM and the 0° degrees detection chamber (ZDD, see Fig. 1).

## Experiment report

$^{48}\text{Cr}$ was produced at 33.9 MeV/u in the fragmentation of a ~50 pnA $^{50}\text{Cr}$ stable beam at 72 MeV/u in a 1mm thick Be target. The secondary beam was purified using a 700 µm thick Be wedge shaped degrader and the LISE Wien Filter set to 1500 kV/m. Up to 2.5 10⁵ pps of an almost pure beam (see Fig. 2) was sent to a 5 mg/cm<fnref n="2" /> CH₂ secondary target.

First, the online analysis focused on the one-nucleon transfer reaction $^{48}\text{Cr}(p,d)^{47}\text{Cr}$ because of its larger cross-section than the (p,³He) reaction. Fig. 3 shows preliminary results for the (p,d) reaction with the kinematic lines and the gamma spectrum obtained by gating on a $^{47}\text{Cr}$ isotope in the ZDD.

Second, after proper calibration of the MUST2 and the CATS detectors, the excitation energy spectrum for the two-nucleon transfer reaction $^{48}\text{Cr}(p,^3\text{He})$ have been extracted in coincidence with the detection of Vanadium ions in the ZDD (see insert on Fig. 4). The angular distribution for the ground state has also been determined and corresponds to an L=0 transfer as expected (see. Fig. 5). The extraction of the gamma-rays in coincidence is still on going.

## Copyright

© IJCLab, GANIL

<footnote n="1">¹ Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France</footnote>

<footnote n="2">² GANIL, CEA/DRF-CNRS/IN2P3, Boulevard Henri Becquerel, Caen, France</footnote>

<footnote n="3">³ INFN Sezione di Milano, Italy</footnote>

<footnote n="4">⁴ University of Bordeaux, CNRS, LP2I Bordeaux, UMR 5797, Gradignan, France</footnote>

<footnote n="5">⁵ INFN Sezione di Padova, Padova, Italy</footnote>

<footnote n="6">⁶ LNL, Legnaro, Italy</footnote>

<footnote n="7">⁷ IGFAE and Dpt. de Fisica de Partículas, Univ. of Santiago de Compostela, E-15758, Santiago de Compostela, Spain</footnote>

<footnote n="8">⁸ Oak Ridge National Laboratory, USA</footnote>

<footnote n="9">⁹ School of Maths and Physics, University of Surrey, Guildford, United Kingdom</footnote>

<footnote n="10">¹⁰ IFIN-HH, Bucharest-Magurele, Romania</footnote>