# Diamond-based detector for high-intensity pulsed beam monitoring: a tool for Flash irradiations and beam diagnostics

Robin Molle, Marie-Laure Gallin-Martel, Charbel Koumeir, Jean-Luc Bouly, Johann Collot, Denis Dauvergne, Teddy Durand, Pierre Everaere, Laurent Gallin-Martel, Arnaud Guertin, et al.

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## ► To cite this version:

Robin Molle, Marie-Laure Gallin-Martel, Charbel Koumeir, Jean-Luc Bouly, Johann Collot, et al. Diamond-based detector for high-intensity pulsed beam monitoring: a tool for Flash irradiations and beam diagnostics. Hasselt Diamond Workshop 2023 SBDD XXVII, Mar 2023, Hasselt, Belgium. [hal-04839761](https://hal.science/hal-04839761v1)

HAL Id: hal-04839761

https://hal.science/hal-04839761v1

Submitted on 16 Dec 2024

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R. Molle<fnref n="1" />*, M-L. Gallin-Martel<fnref n="1" />, C. Koumeir<fnref n="3" />, J.L. Bouly<fnref n="1" />, J. Collot<fnref n="1" />, D. Dauvergne<fnref n="1" />, T. Durand<fnref n="3" />, P. Everaere<fnref n="1" />, L. Gallin-Martel<fnref n="1" />, A. Guertin<fnref n="2" />, F. Haddad<fnref n="2" />,<fnref n="3" />, C. Hoarau<fnref n="1" />, E. Lagorio<fnref n="1" />, S. Marcatili<fnref n="1" />, V. Metivier<fnref n="2" />, Q. Mouchard<fnref n="2" />, J-F Muraz<fnref n="1" />, F. Poirier<fnref n="3" />, N. Ponchant<fnref n="1" />, F. Rarbi<fnref n="1" />, O. Rossetto<fnref n="1" />, M. Reynaud<fnref n="1" />, N. Servagent<fnref n="2" />, J. Waquet<fnref n="1" />, M. Yamouni<fnref n="1" />

molle@lpsc.in2p3.fr

## Beam monitoring and applications

The project is to develop a detector for ion beam facilities, that gives informations about the flux, the time distribution and spatial distribution of the beam. The main innovation is the ability of reaching Flash intensities, and beyond.

Nowadays, innovative radiotherapies are underdevelopment, in particular Flash therapies. They consist of delivering the whole dose in a fraction of a second, thanks to ultra-high dose rate with pulsed beams. This type of therapy spares more healthy tissue and is very effective in targeting and destroying tumor volumes [1].

## The ARRONAX Cyclotron

The ARRONAX cyclotron (Nantes, France) is a 35-70 MeV ion accelerator. Beam intensities can reach 20 µA with proton, and 2 µA with alpha particles. ARRONAX beam is used for radioisotope production, radiolysis and study for a wide-range of flux.

In pulsed beam mode, trains of few µs are constituted of bunches of 4 ns ON and 29 ns OFF. "Train duration"(*dt*) and "inter-train time" (*dit*) are tunable.

ARRONAX is a suitable tool for a beam monitor development satisfying the Flash therapy requirement [2]

<figure><img src="image_3.png" /></figure>

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<figure><img src="image_5.png" /></figure>

## Diamond detectors and ANR-DIAMMONI beam monitors

Diamond is a large bandgap semiconductor that can be used as a solid-state ionizing chamber. Diamond exhibits remarkable properties for particle detection [3][4].

<table><thead><tr><th>Properties</th><th>Diamond</th><th>Silicon</th></tr></thead><tbody><tr><td>Electron mobility (cm<fnref n="2" />/V.s)</td><td>~ 1 800</td><td>1 400</td></tr><tr><td>Hole mobility (cm<fnref n="2" />/V.s)</td><td>~ 2 000</td><td>500</td></tr><tr><td>Bandgap (eV)</td><td>5.47</td><td>1.12</td></tr><tr><td>Displacement energy (eV)</td><td>43</td><td>14</td></tr></tbody></table>

<figure><img src="image_6.png" /></figure>

At high flux, a large number of particles impacts the detector, creating a large number of charge carriers. This carrier density creates an internal electric field. This field opposes the applied external field, inducing a particular dynamic, which can affect the charge collection of the detector.

The ANR-DIAMMONI beam monitor is designed for particle counting and time stamp on a wide beam intensity range. To satisfy online ARRONAX beam monitoring, two different operating modes are foreseen.

**Bunch counting mode:** (low intensity)

* Single particle counting up to 100 particles per bunch

* Bunch stamp

**Train counting mode:** (high intensity)

* Particle counting in one train

* Train stamp

Dedicated electronic developments are undertests for each mode. Orthogonal strips in x and y will be used as electrode to check the beam profile.

A hodoscope for single protons tagging has been already developed on this model.

A first prototype will be released in 2024.

<figure><img src="image_7.png" /><figcaption>First beam monitor prototype</figcaption></figure>

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<figure><img src="image_9.png" /></figure>

## Charge dynamics simulation in a diamond detector

### Objectives

A simulation tool has been developed at the LPSC within the framework of the ANR-DIAMMONI in order to study the charge drift as a function of several parameters:

<figure><img src="image_10.png" /></figure>

* **Beam:**
  * Flux
  * Fluence

* **Diamond:**
  * Intrinsic properties
  * Trapping
  * Recombination

* **Detector:**
  * Readout electronics

### Principle

<figure><img src="image_11.png" /></figure>

The modeling is based on the drift-diffusion equations, programmed in 1D on Python 3.9.

### Results

<figure><img src="image_12.png" /></figure>

The simulation highlights the deformation of the electric field across the diamond thickness as a function of time, which affects the charge dynamics.

<figure><img src="image_13.png" /></figure>

## Influence of the beam flux and fluence measured in ARRONAX

### Experimental setup

In order to study the impact of fluence and flux, the objective is to use a homogeneous diamond in charge collection, and to irradiate it at different fluxes. Each irradiation accumulates fluence. The diamond was then irradiated on 5 disjoint points at different fluxes, with constant accumulated fluence.

<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /><figcaption>Forecast</figcaption></figure>

<figure><img src="image_16.png" /><figcaption>XBIC mapping at ESRF</figcaption></figure>

<figure><img src="image_17.png" /><figcaption>Back side of the diamond after irradiation</figcaption></figure>

### Charge collection at different fluxes, as a function of fluence, with 64MeV alpha

Experiment done with 64 MeV $\alpha$ particles. The charge could then be measured on the irradiation points. The fluxes studied correspond to dose rates up to 350 kGy/s. The results at point B were not usable in the analysis.

The charge collection per train is linear on the E-D-C portion, but a saturation phenomenon seems to emerge beyond C, at high flux.

<figure><img src="image_18.png" /></figure>

### Current induced in the diamond as a function of flux, with 68MeV protons

<figure><img src="image_19.png" /></figure>

The signal of traversing particle is triangular as expected. As the flux increases, the apparent electric field varies over time as observed in simulation. The drift of the charge is affected. A satellite peak appears, whose amplitude increases with the proton flux.

## Conclusions and perspectives

Thus, diamond is an excellent particle detector for beam monitoring. The fastness of diamond allows to observe the microstructure and the macrostructure of the beams. Diamond has very promising results for very high dose rates up to 350 kGy/s. But the fluence affects the response of the diamond with time. The current induced in the diamond also allows to study the dynamics of the charges in it. The simulation developed then extends the understanding of the phenomena at very high charge density.

<footnote n="1">¹ Univ. Grenoble Alpes, CNRS/IN2P3 Laboratoire de Physique Subatomique et Cosmologie (LPSC), 53 Av. des Martyrs, 38000 Grenoble, France</footnote>

<footnote n="2">² IMT Atlantique, Nantes Univ., CNRS/IN2P3 Laboratoire Subatech, 4 rue Alfred Kastler, 44 307 Nantes Cedex 3</footnote>

<footnote n="3">³ARRONAX, 1 rue Aronnax, 44800 Saint Herblain, France</footnote>

<footnote>[1] : Favaudon et al. "Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice." [2] : Saade et al. "Ultrahigh-Dose-Rate Proton Irradiation Elicits Reduced Toxicity in Zebrafish Embryos"</footnote>

<footnote>[3] : Curtoni et al. "Performance of CVD diamond detectors for single ion beam-tagging applications in hadrontherapy monitoring" [4] : Behnke et al. "The Charge Collection Properties of CVD Diamond"</footnote>