# The time-focusing neutron spectrometer SHARP

J.-M. Zanotti, S. Rodrigues, P. Lavie, P. Permingeat, B. Homatter, Q. Berrod

► To cite this version:

J.-M. Zanotti, S. Rodrigues, P. Lavie, P. Permingeat, B. Homatter, et al.. The time-focusing neutron spectrometer SHARP. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2026, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1084, pp.171196. 10.1016/j.nima.2025.171196. hal-05406523

HAL Id: hal-05406523

https://cnrs.hal.science/hal-05406523v1

Submitted on 9 Dec 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

# The time-focusing neutron spectrometer SHARP

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

J.-M. Zanotti<sup>a, ID,*</sup>, S. Rodrigues<sup>a, ID</sup>, P. Lavie<sup>a</sup>, P. Permingeat<sup>a</sup>, B. Homatter<sup>a</sup>, Q. Berrod<sup>a,b ID,1</sup>

## ARTICLE INFO

**Keywords:**

Neutron scattering

Spectroscopy

Instrumentation

Spectrometer

Time focusing

## ABSTRACT

SHARP (Spectromètre Hybride Alpes Région Parisienne) is a new-generation time-of-flight neutron spectrometer installed at the Institut Laue-Langevin (ILL). It is designed to investigate dynamical processes in condensed matter with high energy resolution and broad experimental versatility. Developed as a complete upgrade of the former IN6 instrument, SHARP addresses key scientific challenges in soft matter, biology, energy materials, and solid-state physics, where precise measurements of atomic and molecular motions are essential. The main design objective is to achieve a higher counting rate while maintaining the IN6 strong neutron flux, by providing wide angular and energy coverage through multiple take-off angle geometries. Notable features include a fully vacuum-compatible secondary spectrometer, a retractable sample window allowing the detector tank to remain under vacuum while enabling experiments requiring controlled sample environments, and a bank of 240 position-sensitive <sup>3</sup>He detectors operating at 5 bar, ensuring enhanced spectral spatial definition. Compared to IN6, SHARP delivers a twofold increase in counting rate in the elastic region and a lower background. This paper outlines the scientific motivations behind the SHARP project, describes the main instrumental innovations, and demonstrates the instrument's performance through initial scientific results on molecular diffusion in zeolite, determinant of the selectivity of these materials for use in membrane-based gas separations.

## 1. Introduction

This article presents a newly designed and optimized secondary spectrometer of the time-of-flight instrument SHARP, which is operated by the Laboratoire Léon Brillouin (LLB, Saclay, France) as a Cooperative Research Group (CRG) instrument, at the Institut Laur Langevin (ILL, Grenoble, France). The secondary spectrometer encompasses all components from the sample area to the detectors. This development marks the first stage in the construction of SHARPER, a new LLB CRG instrument which is currently being commissioned. For SHARPER, a new primary spectrometer was additionally developed, used in conjunction with the SHARP secondary spectrometer. SHARP replaces the former IN6 instrument at ILL.

Here, we place particular emphasis on the innovations in sample environments and detector configurations developed for SHARP. The descriptions and visualizations present key technical advances aimed at meeting the potential scientific needs of next-generation neutron spectrometers.

### 1.1. Inelastic neutron scattering: a key probe of the dynamical processes of condensed matter

Thermal neutrons have associated wavelengths of a few Å and energies of a few meV (1 meV = 8 cm⁻<fnref n="1" />). These quantities being both in tune with the atomic distances and energies of the dynamical modes at play in condensed matter, inelastic neutron scattering is a perfect spectroscopic probe to reveal simultaneously the structural and dynamical phenomena in a vast variety of complex systems. It is also possible to take advantage of isotopic effects and/or polarization of the incident beam and scattered neutrons to discriminate between collective or individual phenomena.

INS (Inelastic Neutron Scattering) is a major branch of neutron spectroscopy, with QENS (Quasi-Elastic Neutron Scattering) as a particular case involving small energy transfers.

Classically, in inelastic neutron scattering, the sample is set in a collimated beam of monochromatic neutrons with energy *E*ᵢ. They are extracted from the incident white beam delivered by the source (spallation or reactor) by a monochromator system (Bragg reflection

<footnote><sup>a</sup> Université Paris-Saclay, Laboratoire Léon Brillouin (CEA-CNRS), CEA Saclay, France</footnote>

<footnote><sup>b</sup> Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, IRIG, SyMMES, Grenoble, France</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: jean-marc.zanotti@cea.fr (J.-M. Zanotti).</footnote>

<footnote n="1">¹ Present address: Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, IRIG, SyMMES, Grenoble, France.</footnote>
on a monocrystal or a chopper cascade). A detector array centered on the sample records the scattered neutron intensity as a function of energy transfer and scattering angle $2\theta$ i.e. $d^2\sigma(2\theta)/d\omega/d\Omega$, within the solid angle element $d\Omega$. Time-of-Flight (ToF) neutron spectrometers are designed such that each detector measures the neutron ToF, $\tau$, from the sample to the detector, which is then used to determine the energy transfer during the scattering process: the sample to detector distance, $d_{SD}$, being precisely known, $\hbar\omega = E_f - E_i = 1/2.m_n(d_{SD}/\tau)^2 - E_i$, the energy transferred from the neutrons to the sample is measured with high precision. The analysis of this resulting dynamical structure factor $d^2\sigma(2\theta)/d\omega/d\Omega$ is central to gain insights into the excitations and relaxational phenomena in condensed matter. QENS which involves small changes in energy (from neV to a few meV), gives access to both correlation times, transport properties (translational or rotational diffusion coefficients) but also geometry of the movements (jump distance in a jump diffusion process, size of confinement of a molecule trapped in a permanent or transient cage). INS refers to neutrons scattered inelastically at higher energy transfer on the Stokes or anti-Stokes sides of the elastic peak. It gives access to lattice vibrations and other elementary excitations. Time-of-flight spectroscopy must be used in conjunction with neutron spin-echo, backscattering, and triple-axis spectrometers, as each technique probes a distinct energy-time window and only their combined use provides a complete picture of the dynamics.

## 1.2. The SHARP project in perspective

SHARP was developed in the framework of the Franco-Swedish cooperation agreement for the construction of neutron instruments. This bilateral partnership aimed at strengthening collaboration between the French and Swedish scientific communities in the field of neutron scattering, with a particular focus on training and education to ensure the effective use of the European Spallation Source (ESS), which was approved for construction in Lund (Sweden) and is currently under construction. To this end, the Laboratoire Léon Brillouin has undertaken the construction of an inelastic ToF spectrometer at the Orphée research reactor in Saclay. Such an instrument was designed to serve both as a state-of-the-art scientific instrument and as a strategic platform for training users, in particular Swedish scientists, and testing technologies relevant to future neutron instrumentation.

After the announcement of the Orphee reactor shutdown in 2019, the project originally planned at Saclay was transferred to the Institut Laue Langevin. On September 29th 2017, a “A” type CRG contract between the CEA/DRF, the CNRS/INP and the ILL concluded that the ILL instrument IN6 would be operated by a team from the LLB. The secondary spectrometer (components from the monochromator up to the detectors) would be redesigned; this was called the SHARP (Spectrometre Hybride Alpes Region Parisienne) project. The instrument was renamed IN6-SHARP until the full rebuild of the secondary spectrometer ended in April 2021. From then on IN6 has been renamed SHARP. In this paper, we report on the improvements implemented in SHARP with respect to the former IN6 spectrometer.

## 1.3. SHARP vs IN6: performances

IN6 [1–4] was a time focusing ToF spectrometer designed for QENS and INS. Before addressing the technical developments of the SHARP project, we first highlight its performance enhancements compared to IN6. The flight path chamber of IN6 was significantly smaller than that of SHARP, due to the limited available volume between IN6 and the neighboring instruments IN5 and D7 (see Fig. 5(b)). To preserve the possibility of operating with four incident wavelengths — and thus four resolution settings — on SHARP, a key modification to IN6 has been the increase in the monochromator-to-sample distance, from 2.1 m on IN6 to 3.3 m on SHARP.

The vertical focusing of the monochromator was adjusted to adapt to this significant change. McStas [5] simulations indicate a resulting reduction in flux of a factor 1.22. This moderate loss in flux is more than compensated by a substantial improvement in the detection system. Whereas IN6 was equipped with 3.13 m² of detectors operated at 3 bar of $^3$He, SHARP employs 11.42 m² of Position-Sensitive Detectors (PSDs purchased from Reuter-Stokes) filled with $^3$He at 5 bar. Each detector tube is 2.54 cm in diameter, 200.0 cm long and is read out with 256 bins along its length, yielding a position resolution of approximately 7.8 mm.

In addition to the increased detection surface, the higher gas pressure boosts the efficiency for detecting shorter-wavelength neutrons, particularly on the energy gain side of the spectrum. For incident neutrons with a wavelength of 5.1 Å, and an energy transfer of 100 meV, the detection efficiency rises from 0.38 at 3 bar to 0.55 at 5 bar. Integrating the gain in detection efficiency over the 0 to 100 meV energy transfer range gives an overall gain factor of 1.32.

It is also worth noting the new oscillating radial collimator developed for SHARP (see Fig. 15) was used in its most selective configuration, with 240 slits corresponding to a pitch of 0.61° (i.e. one slit per detector). The number of slits and thus the pitch is adjustable, allowing the instrument to optimize the trade-off between background and intensity based on experimental requirements. McStas [5] simulations indicate that this maximum-slit setup results in an intensity loss of approximately 25% compared to measurements without the collimator. This loss decreases with increasing the pitch, estimated at about 13% and 7% for pitches of 1.22° and 2.44°, respectively. A pitch of several degrees is actually commonly used on various ToF instruments.

The substantial upgrades to the instrument result in a twofold increase in detected flux in the elastic region, achieved without compromising energy resolution (70 µeV at 5.1 Å), an unambiguously positive outcome of the redesign.

This improvement stems from several contributing factors, which we summarize and quantify below:

*   **Primary spectrometer transmission:** the new primary spectrometer reduces the neutron flux by a factor of 1.22, due to the longer monochromator-to-sample distance (from 2.1 m to 3.3 m), which increases collimation but slightly lowers flux at the sample.

*   **Detector coverage and related solid angles:** The total active detector area was increased from 3.13 m² on IN6 to 11.42 m² on SHARP. Considering a sample-to-detector distance of $d_{SD} = 250.0$ cm, a detector length of $l_{Det} = 200.0$ cm with a diameter $D_{Det} = 2.54$ cm and a detector angular coverage of $2\theta = 145.2^\circ$, with a spacing of $s_{Det} = 0.1$ cm between two successive detectors, this corresponds to a solid angle of:

$$ \Omega^{SHARP} = \frac{D_{Det}}{D_{Det} + s_{Det}} \cdot 2\theta \cdot 2 \arctan \left( \frac{l_{Det}}{2 d_{SD}} \right) \approx 1.85 \text{ sr} $$

The total gain in detection solid angle of SHARP over IN6 is then:

$$ \frac{\Omega^{SHARP}}{\Omega^{IN6}} = \frac{1.85}{0.50} \approx 3.70 $$

*   **Detector efficiency:** replacing the 3 bar $^3$He tubes with 5 bar position-sensitive detectors (PSDs) leads to an estimated relative efficiency gain of 32%, i.e., a factor of 1.32 when normalized to the original IN6 configuration.

*   **Radial oscillating collimator:** the maximum-slit setup (pitch of 0.61°) we have used on the radial oscillating collimator induces an intensity loss of 25% hence a factor of 0.75.

The cumulative product of these contributions gives the following net gain factor in detected flux:

$$ G_{\text{net}} = \frac{1}{1.22} \times 1.32 \times 3.70 \times 0.75 = 3.0 $$

Correcting the estimated gain by removing the detector 1.32 efficiency factor — non-relevant for elastic scattering we consider in Fig. 2 —
<figure><img src="image_4.png" /><figcaption>Fig. 1. (a) The IN6 spectrometer before its shutdown in October 2020. (b) Schematic of IN6 and conceptual design. (c) SHARP up and running with its first neutrons: March 21 2021. A specificity of the instrument is the easy access to a large sample well by a door at the ground level. Here, the door is open.</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Fig. 2. Structure factor (a) and dynamical structure factor normalized to 1 (b) of an annular vanadium foil, 15 mm in diameter and 0.5 mm thick, measured at room temperature on IN6 (orange) and on SHARP (blue). The incident wavelength was 5.1 Å in both experiments. In (b) the data are integrated over the whole Q-range for IN6 and over [0.2--2.3] for SHARP.</figcaption></figure>

leads to a theoretical gain factor of 2.27, closely matching the measured gain of 2.

In addition to this increase in signal, a slight reduction in background level has been achieved by lining the redesigned detector tank with cadmium and the use of boron-loaded shielding. Together, these improvements contribute to an enhanced signal-to-noise ratio, which is particularly beneficial for low-scattering samples and measurements under extreme conditions.

## 2. Inventory at the start of the SHARP project: IN6

The IN6 spectrometer (Fig. 1(a) and 1(b)) [1–4], provides the reference framework for SHARP. An intense neutron beam is extracted from the H15 guide by a vertically focusing monochromator. In order to minimize disturbance of the beam serving the downstream instruments D7 and D11, the monochromator in IN6 was set to deliver only four wavelengths (FWHM resolution is given for each wavelength): 4.1 Å (170 µeV), 4.6 Å (120 µeV), 5.1 Å (70 µeV) and 5.9 Å (50 µeV). The cradle of this monochromator was positioned 30 cm from the neutron guide exit. The monochromator assembly consisted of three identical individual monochromators (Fig. 3(a)) each made of a 20.0 × 5.0 cm² highly oriented pyrolytic graphite (HOPG) crystals with a mosaicity of 0.7°. Each element used the full 20 cm height of the guide to achieve vertical focusing onto the sample position. The three monochromators were aligned with the incident beam from the guide and positioned 3 cm apart from each other. The central monochromator was set to a take-off angle corresponding to the nominal wavelength (4.1, 4.6, 5.1 or 5.9 Å). The upstream and downstream monochromators were tilted by –0.8° and +0.8°, respectively, relative to the central

one. This configuration allowed the system to diffract three adjacent wavelength bands simultaneously. The higher order reflections from the monochromator are removed by a 150 × 70 mm² and 120 mm thick beryllium-filter cooled at liquid nitrogen temperature (Fig. 3(b)). Beryllium is commonly used as a neutron filter due to its unique scattering properties rather than its absorption. Contrary to strong absorbers, beryllium has a low neutron absorption cross section but exhibits a pronounced Bragg scattering with a cut-off at approximately 4 Å. When placed in the neutron beam path, polycrystalline beryllium effectively scatters neutrons with wavelengths shorter than this threshold out of the beam, while allowing longer-wavelength neutrons to pass through with minimal attenuation. This makes beryllium filters particularly useful for suppressing higher-energy neutrons (potential harmonics of the nominal wavelength). This explains why on IN6, the shorter available wavelength delivered was 4.1 Å.

To implement the time-of-flight technique, the continuous monochromatic beam was pulsed by a Fermi chopper (Fig. 3(d)). The direction of rotation of the Fermi chopper (Fig. 3(d)) was configured to transmit the slower neutrons diffracted by the monochromator before the faster ones toward the sample, so that all would reach the detectors within a narrow time window. This so-called “time-focusing” strategy [3] enabled high intensity while maintaining good energy resolution. As a typical reference, the rotation frequency of the Fermi chopper at 5.1 Å is 100 Hz, which is also the case for the “suppressor” (Fig. 3(d)) Fermi chopper. This setting minimizes the energy resolution at zero energy transfer. Increasing the chopper frequency improves the resolution on the neutron energy-gain side, while decreasing it enhances the resolution on the energy-loss side. For chopper frequencies above 125 Hz, to avoid frame overlap, the “suppressor” chopper is operated at half
<figure><img src="image_6.png" /><figcaption>**Fig. 3.** IN6 primary spectrometer. Key components reused on SHARP: (a) The HOPG monochromator made of three blades of 200 mm height and 50 mm width. (b) The Beryllium filter (150 mm height × 70 mm wide, 120 mm thick) and associated liquid nitrogen tank. The liquid nitrogen tank is shown. (c) The so-called “suppressor” Fermi chopper (FC) with a 180° boron large window (98 mm height and 50 mm width) to reduce frame overlap. (d) FC: the slit package made a stack 25 µm thick blades of aluminum and gadolinium of 72 mm height, 42 mm width and 12 mm thick. The collimation is 2.4°. (e) The SHARP tunnel housing the Be filter, the “suppressor” FC and the main FC. The portion from the FC up to the enclosure housing the Be filter slides inside the SHARP chamber (see Fig. 4). To minimize the path of the beam through air, the tunnel is ended by a large protective bellow onto a 0.25 mm thin window is fixed. This window makes it possible to leave the sample chamber under air while the tunnel and Fermi systems can be maintained under vacuum. (a), (b), (c), (d): Credit ILL.</figcaption></figure>

the Fermi chopper frequency. A detailed comparison of the capabilities offered by IN6 in terms of resolution in energy compared to other types of inelastic types of instruments has been detailed elsewhere [6]. A tunnel under a secondary vacuum was housing the beryllium filter and the two Fermi choppers (Fig. 3(e)).

The distance from the monochromator to the sample was 2100 mm, made up of a distance from the monochromator to the “suppressor” chopper of 1520 mm, 200 mm from the “suppressor” to the Fermi Chopper and 380 mm from the Fermi Chopper to the sample.

The secondary spectrometer consisted of two separate chambers: one dedicated to the sample and its environment, which can be either under vacuum or under controlled atmosphere, and another for the neutron flight path, which was flushed with helium to minimize neutron attenuation caused by atmospheric water. The detector bank was equipped with 3 bar ³He 337 individual detectors to cover scattering angles from 15 to 115 °. It should be noted that two structural pillars located within the IN6 TOF chamber caused significant signal attenuation near 0.95 Å⁻¹ and 1.55 Å⁻¹ (Fig. 2(a)).

To adapt to the working wavelength (4.1, 4.6, 5.1 or 5.9 Å), the change in take-off angle (75.5, 86.7, 99.1, 123.4° respectively) of the secondary spectrometer was achieved using a motorized system that reoriented the TOF chamber via wheels running on a rail embedded in the floor.

### 3. The project

The SHARP project involved a complete rebuilding of the IN6 TOF chamber, detection systems and sample environment. The technical design and detailed requirements of the SHARP instrument have been defined in accordance with the scientific case and specifications provided by LLB. They addressed several key engineering limitations of the original instrument.

First, the entire detector chamber was placed under vacuum, and the old detectors were replaced by 240 position-sensitive detectors (PSDs), significantly improving spatial resolution. The design aimed to minimize the number of windows along the neutron beam path in order to reduce scattering and absorption losses.

In this spirit, a custom retractable window was developed to connect the sample chamber and the detector tank under vacuum, eliminating the scattering previously caused by the separating wall used in IN6. This window opening or closing is controlled automatically and when closed, the detector volume can be left under vacuum and the sample can be in a controlled atmosphere. The sample chamber itself was enlarged to accommodate the use of bulky equipment such as superconducting magnets, thereby extending the range of experiments possible on SHARP. The vacuum system was designed to support cryogenic

vacuum levels (better than 10⁻⁷ mbar), which would allow, in future upgrades, the removal of the 300 K external screen from the cryostat, a significant source of background scattering in the current configuration. Achieving such vacuum levels would require the installation of two cryopumps, which have not yet been implemented due to budgetary constraints. Furthermore, once the TOF chamber is decoupled from the Beryllium filter and Fermi Chopper tunnel, the entire spectrometer chamber can be moved over the experimental area chamber without being constrained by a rotation around the monochromator axis like IN6 was, greatly simplifying maintenance and improving accessibility to all components.

After 18 months of a phase of detailed design, SHARP construction started at the end of October 2020 and was completed by March 21st 2021, when the brand-new instrument (Fig. 1(c)) saw first neutrons. The secondary spectrometer was therefore reconstructed in a remarkable short time (4.5 months) by the LLB's engineer and technicians team, plus 2 technicians from SDMS (Saint-Romans, France) who won the international call for tender for the work. Key parts of the work included a full refurnishment of the chamber (delivered in November 2020) fully covered inside with Cd, and the installation of 240 ³He Position Sensitive Detectors (PSDs) along with their individual rear collimators (needed to avoid re-scattering from one detector to another one) and the associated electronics. The final scattering angle coverage was from 0 to 145.2°.

### 4. Instrument description

The key elements of the instrument are shown in Fig. 4. Below we describe and give details on them.

#### 4.1. Time of flight chamber and change of take-off angle by an innovating ground link

The chamber is made of 30 mm-thick welded aluminum elements, with a total volume of 23 m³ for the detector chamber and 3 m³ for the sample one. To support this assembly weighing 25 tons, the ground was reinforced with a 70 cm thick concrete base, on top of which a marble floor was installed. To avoid magnetic interference when using the 10 T coil from the Services for Advanced Neutron Environments of ILL, the concrete was not reinforced with magnetic rebar, but with stainless steel.

As seen in Figs. 3 and 4 a key feature of SHARP is that the tunnel housing the beryllium filter and the two Fermi choppers slide into the body of the TOF chamber. The mechanical clearance allowing the adaptation of these two parts is of the order of millimeters and the protective bellow making the connection between this mechanical
<figure><img src="image_7.png" /><figcaption>Fig. 4. (a) Three dimensional drawing of SHARP and (b) sectional view. The chamber is entirely made of aluminum.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>Fig. 5. The four take-off angles of SHARP. For each the wavelength and energy resolution (FWHM) is shown. The position of the Fermi chopper and "suppressor" are shown in blue. The two neighboring instruments IN5 on the left and D7 on the right are shown.</figcaption></figure>

system and the sample environment can operate under extension but
not under torsion.

During configuration changes, such as adapting the take-off angle to the selected working wavelength (Fig. 5), the 25-ton spectrometer chamber could have been supported by a dozen of aerocasters. These systems are generally efficient for moving heavy structures, but in the specific case of SHARP, they present a limitation: in the absence of an active control system, they could induce a rise of the chamber of several centimeters. Such a vertical displacement would place mechanical stress on the fixed tunnel. As this tunnel is rigidly connected to the time-of-flight chamber, any uncontrolled vertical movement may lead to misalignment or deformation of sensitive components. As a consequence, the control system has been developed as follows: a mechanical beam fixed to the bottom of the ToF chamber supports only four aerocasters. This beam is ended by a set of two large preloaded return springs. Then after a fine setting of the springs force, the height of the lifting is controlled and set in such a way that it is in tune with the acceptable deformation of the tunnel end bellow connecting the tunnel to the sample chamber. The remaining 10% of the weight is supported by a system of 10 independent sets of 3 polypropylene balls of 76 mm in diameter (Fig. 6(a), (b)).

The changes in take-off angle is operated using a roller (Fig. 6(c)). This is a geared motor assembly with a 220 Nm stepper motor driving a 250 mm diameter wheel.

## 4.2. Detector system and mechanical integration

The original IN6 detection system consisted of 337 squashed Xeram Nuclear "42NH 30P" detectors ($16 \times 32 \text{ mm}^2$) filled with $^3\text{He}$ at 3 bar and arranged along Debye-Scherrer rings covering angles from 15° to 115° (Fig. 7(a)). In the SHARP upgrade, all of these detectors have been

replaced by 240 Reuter-Stokes PSDs, each 2000 mm long and 25.4 mm in diameter, with stainless steel envelopes and filled with $^3\text{He}$ at 5 bar. Thanks to their high spatial resolution and extended angular coverage, these new detectors significantly enhance the sensitivity and overall performance of the instrument. Since the majority of experiments previously conducted on IN6 focused on measurements of densities of states, the detector pressure for SHARP was set to 5 bar in order to enhance the detection efficiency on the neutron energy-gain side of the spectrum. The angular step in between detectors is 0.605° so that the angular coverage is now from 0 to 145.2°.

The change in detection system from individual cylindrical detectors arranged on a spherical surface following Debye-Scherrer cones to linear PSDs has significantly impacted the data reduction procedures. With the previous setup, signals from detectors corresponding to a given Debye-Scherrer scattering angle could be directly summed to obtain the intensity at each momentum transfer Q. In contrast, linear PSDs require numerical isotropic grouping to reconstruct the signal as a function of Q. Additionally, for ToF analysis, the varying flight path lengths between neutrons scattered within the scattering plane and those scattered out of plane must be taken into account to correctly compute the energy transfer. These corrections and the associated regrouping are handled automatically by the Mantid [7] software suite, which has been adapted to support SHARP's detection system geometry.

To prevent any mechanical stress and a total decoupling from the enclosure, the detector modules developed to hold the PSDs guarantee their isostatic rest (Fig. 7(b), (c)). The bending of the detector tubes is less than 1 mm.

### 4.2.1. Detectors electronics

The detection electronics modules are shown in Fig. 8. Low voltage and high voltage power supplies are located outside of the experimental
<figure><img src="image_9.png" /><figcaption>Fig. 6. (a) Three dimensional drawing of the SHARP ground link making it possible to adapt changes in take-off angle. The key elements are 30 polypropylene balls, 4 aerocasters and a large beam for weight compensation. After the change in take-off angle, the instrument rest on the central pawn. (b) The real system as seen from underneath the instrument. (c) Roller used to move the 25 tons chamber during the change in take-off angle.</figcaption></figure>

<figure><img src="image_10.png" /><figcaption>Fig. 7. (a) Back view of the IN6 detector chamber showing the old generation 3 bar $^3$He detectors. (b) Three dimensional drawing of a SHARP detector module. Each of the 15 modules accepts 16 PSD. (c) A module during the set-up phase. (d) Front view of a detection area. The PSD are seen in between the rear collimators. (e) Flight chamber after detection system installation completion and prior to the oscillating radial collimator insertion. Note the full lining with cadmium.</figcaption></figure>

area. The low voltage supply is sent through 4 cables to 4 boxes located on the chamber. These 4 boxes allow the power distribution to 30 preamplifier boards. The high voltage is sent in the same manner. A single cable is sufficient but three more cables are used as spares and offer ability to finely tune the high voltage. Each preamplifier board manages sixteen channels. The analog signals are not shaped but just amplified to be sent over RJ45 cables (4 cables per box) to the Analog-to-Digital Converter (ADC) boards. They filter the signal and generate a neutron event when the sum of the top and bottom signals exceeds a programmable threshold. The event includes amplitudes of both signals and a time stamp. This is sent to the acquisition board that computes the neutron position as $A_{Top}/(A_{Top} + A_{Bottom})$, where $A_{Top}$ and $A_{Bottom}$ are the amplitude of the signal measured at the top and bottom of the tube respectively. The time stamp is compared to the Fermi Chopper pickup time stamp to determine the ToF channel.

## 4.3. Vacuum

### 4.3.1. PSD anode crossing of the chamber wall and differential vacuum

To ensure reliable operation, the neutron detector electronics are placed outside the vacuum chamber, as they require air for cooling. Without airflow, these components risk overheating and sustaining damage in a vacuum environment. For SHARP, it is indeed necessary to route the anode connections (Fig. 9(a)) on either side of the PSDs across the entire ToF chamber, while preserving the vacuum integrity of the system. Each anode then crosses the chamber wall through a circular aperture ($2\pi \times 2 = 480$ apertures). Any minor leaks that may result from these crossings are managed using a differential vacuum strategy.

Differential vacuum is a way to keep different pressure levels in nearby sections of a machine. It is used in devices like electron microscopes, where some parts need to be in a very strong vacuum, while others can have lower pressure or even normal air pressure. To do this, small openings called apertures are placed between these sections. These openings slow down the movement of gas from one part to another, so that vacuum pumps can keep the different pressures steady. This lets the sensitive parts stay in the right vacuum without affecting the rest.

To adapt such a system on SHARP, the ToF chamber is surrounded by an additive enclosure (Fig. 9). This system creates a secondary vacuum space, a so-called “double skin”, between the main spectrometer vacuum and atmospheric pressure. A detailed view of this important system is shown in Fig. 10.

This intermediate space between the chamber wall and the outer enclosure is actively pumped by a dedicated vacuum line. This creates a pressure gradient: from atmospheric pressure outside, to intermediate pressure in the differential vacuum zone, down to high vacuum inside the ToF chamber. This differential pumping scheme ensures that any gas infiltration is first captured and removed before it can reach the sensitive detector volume. It effectively protects the instrument vacuum against cumulative leakage effects from many small feedthroughs, while keeping all electronics safely outside the vacuum zone. This comes to use a dual-wall all around the ToF chamber.

### 4.3.2. Isolating the sample chamber from the vacuum of the detector chamber: a retractable window

The detector and sample volumes of the ToF chamber are 3 m³ and 23 m³ respectively. If both volumes are at atmospheric pressure, a
<figure><img src="image_11.png" /><figcaption>Fig. 8. (a) Three dimensional drawing of the back of the ToF chamber and (b) real view. Note that here, the HDPE shielding (see Section 4.4.1) has been removed. The top and bottom insets shown on the left of the picture are the power distribution and high-voltage with an amplifier board (open box). The Ethernet cable (not shown) are mounted on a drag chain to be able to follow the change in take-off angle. (c) View of the ToF chamber back with the board access hatches closed. (d) Same as (c) but with one of the hatches open.</figcaption></figure>

<figure><img src="image_12.png" /><figcaption>Fig. 9. (a) Anodes (white cables) on one side of several PSDs. (b) A PSD stand module positioned inside the ToF chamber, with a housing (in gray color) welded to the top of each PSD (identical housings are on the PSD bottoms). This housing encloses the anode and routes it from the inside to the outside through circular holes at the top and bottom of the ToF chamber. (c) Anodes as seen from outside the chamber at the top and bottom. (d) The dual-wall of the differential vacuum system is visible at the bottom. This feature enables achieving a vacuum limit of $10^{-3}$ mbar even when the retractable internal window (see Section 4.3.2) is open i.e. so that the detector and sample environment are communicating. (e) Detail of the crossing system. The detector volume is shown in blue color and the atmosphere in violet. An stainless steel head welded to the top or bottom of each PSD holds by screwing a horizontal tube that guides the wire through the chamber's holes. The vacuum integrity is secured by O-rings at each end. A vertical pipe, welded to the outside of the crossing housing, connects to the differential vacuum dual-wall (large area shown in gray), which is maintained by an independent primary pump.</figcaption></figure>

non negligible time is needed to reach a vacuum good enough to start a measurement. This could slow down the pace of an experiment if frequent access to the sample is required.

To address this, SHARP includes an innovative feature: a retractable aluminum window, 2 mm thick (Fig. 11) which allows access to the sample environment without disturbing the vacuum of the entire secondary spectrometer. The thinness of the window, combined with an efficient radial oscillating collimator (see Fig. 15), makes it nearly transparent to neutrons. This feature is also particularly useful when experiments require the sample environment to be maintained under a controlled atmosphere. The window's opening and closing are automated, supporting flexibility across two configurations:

* Common primary vacuum for both the flight chamber and sample (cryostat configuration).

* Primary vacuum in the ToF chamber with atmospheric pressure around the sample (Paris-Edinburgh press configuration).

#### 4.3.3. A competitive vacuum system down to $1.4 \times 10^{-3}$ mbar

The choice of the pumping system was driven by two key criteria: achieving a working vacuum of less than 0.1 bar within about 15 min for the sample chamber (with the window to the detector chamber closed), and reaching the same vacuum in less than one hour in case the detector chamber was at atmospheric pressure, typically after a detector maintenance operation.

To meet this requirements, SHARP takes advantage of the combination of two Busch Cobra NC0200B primary pumps with a Pfeiffer 2000 AM Roots pump to boost the efficiency of the vacuum system (Fig. 12(a)). The Busch pumps handle the roughing stage, where they
<figure><img src="image_13.png" /><figcaption>Fig. 10. Detailed view of the ToF chamber differential vacuum system.</figcaption></figure>

<figure><img src="image_14.png" /><figcaption>Fig. 11. Three-dimensional drawing of the internal window is shown in light green. On the left, the window is in the closed position, isolating the sample chamber from the detector chamber. On the right, the window has been lowered, allowing both chambers to share the same vacuum. (b) The actual window, with two visible black seals ensuring a secure closure. (c) The window in the process of opening after setup. A video demonstration is available on the website referenced in [8].</figcaption></figure>

quickly remove most of the air and bring the pressure down to a lower level. Then, the Roots pump can then take over to reach an even deeper vacuum, faster and more efficiently. By working together, this setup allows for quicker vacuum creation and better overall performance, especially when very low pressure is needed for sensitive processes.

The chamber is pumped through a combination of two pipe systems. First, a 16 cm in diameter metal pipe connects the pumping system to the ToF chamber. To provide the flexibility needed for the chamber's rotation during adjustments of the take-off angle, such a large pipe would be at risk. Instead a “clarinet” system (Fig. 12(c)) is used, consisting of nine flexible tombak pipes, each 5 cm in diameter. This setup ensures the necessary flexibility while minimizing pressure losses.

As this has been described in Section 4.3.2, when the retractable window between the detector and sample volumes is open, both the 3 m³ sample chamber and the 23 m³ ToF chamber share the same vacuum system. When the window is closed, the two volumes are isolated and evacuated independently. This retractable window setup along with the powerful pumping system allows a vacuum down to 0.1 mbar to be reached in 10 minutes in the 3 m³ sample chamber. It reaches 1.4 10⁻³ mbar within 24 h. As required, 0.1 mbar is reached in 45 min in the 23 m³ of the detector chamber.

### 4.3.4. Monitor

Historically, monitors for neutron spectrometers have been based on fission chambers. However, their use on ToF spectrometers was

suffering by the generation of fast neutrons emitted during neutron captures in ²³⁵U and by neutrons scattered by the material of the fission chamber. IN6 was equipped with a commercial monitor that was not designed to work under vacuum. As described before, our goal in designing SHARP was to keep as much as the instrument volumes under vacuum and to limit the numbers of windows on the beam path.

We have implemented a new generation of monitors developed by the ILL detector group, offering enhanced accuracy and reliability [9] (Fig. 13). Operating under vacuum, these advanced monitors minimize air interference and reduce neutron dispersion, supporting stable and precise flux measurements. They use an aluminum common detection volume filled with specific gas mixtures to detect neutrons, with thin, electro-eroded walls that permit neutron passage while minimizing scattering. The monitors are engineered with materials and structures optimized to withstand high pressures and maintain stability even in high gamma environments. In addition to beam intensity monitoring, they can also provide 1D and 2D neutron localization, helping in beam alignment. The ³He pressure is set at 40 mbar, with an additional 620 mbar of ArCO₂ serving as a stopping and stabilizing gas mixture. This mixture decelerates and captures the charged particles produced during neutron capture, creating a detectable signal. The carbon dioxide component plays a crucial role in stabilizing this signal by preventing excessive electrical discharges, thus enhancing measurement reliability.
<figure><img src="image_15.png" /><figcaption>Fig. 12. The SHARP pumping system. (a) Two Roots pumps and a primary pump. (b) Vacuum distribution manifold ('clarinet') designed to accommodate the movement of the ToF chamber during the changes of take-off angle.</figcaption></figure>

<figure><img src="image_16.png" /><figcaption>Fig. 13. A new class of monitor adapted to vacuum. (a) Internal view of the SHARP monitor. (b) The detection area is 70 mm length and 90 mm height, and (c) 8.5 mm thick. Credit ILL.</figcaption></figure>

### 4.4. Shielding

#### 4.4.1. External shielding: High density polyethylene

On a neutron instrument, the presence of neutrons coming from the surrounding neighborhood (including cosmic neutrons) induces a significant detection background. To minimize it, the ToF chamber is entirely covered with 100 mm thick of borated (5% in weight) High Density Polyethylene (HDPE, its density is 1.035 g/cm³), with a total weight of 7.3 tons (Figs. 1(c), 8(c)). The high hydrogen content of HDPE makes it an effective material to moderate high energy neutrons to low energy neutrons that can then be absorbed by the added boron moiety.

#### 4.4.2. Internal shielding: Cadmium

A cadmium coating with a thickness of 0.8 –1.2 mm is placed on all the internal faces of the enclosure (Fig. 7). To avoid long delay of capture of air trapped in between the chamber and the cadmium skin during pumping an aluminum support guarantees a free space of 10 mm with these faces.

### 4.5. Port holes

The door portholes (Fig. 14) are custom-made with a passage diameter of 225 mm and are made from 25 mm-thick borosilicate glass. An additional DN100ISOK window is integrated into the door of the sample enclosure, allowing direct observation of the sample environment to monitor alignment of the sample and any ancillary equipment (e.g., cryostat, furnace, or press). For laser optical excitation of a sample under vacuum, a monocrystalline sapphire window with a 63 mm diameter and 2 mm thickness is used.

### 4.6. Radial oscillating collimator

A radial collimator is installed to reduce background scattering originating from the sample environment, such as cryostats, sample holders, or support structures. This effect is illustrated in Fig. 15(c) where a LED lamp measuring 20 cm in length set horizontally at the sample position appears as just 5 cm long when viewed from the detector side. By limiting the angular acceptance to neutrons directly scattered from the sample, the collimator significantly improves the signal-to-noise ratio, which is particularly important for weakly scattering samples or measurements requiring high sensitivity.

SHARP is equipped with a Radial Oscillating Collimator (ROC) (Fig. 15) composed of an array of blades oriented toward the sample's center. To prevent shadows cast by the blades on the detectors, the ROC oscillates gently around the sample position at a frequency of a few tens of Hz.

Traditional ROCs rely on robust metal frames on either end to maintain blade tension. However, due to limited space between the neighboring IN5 and D7 instruments (Fig. 15), this setup was not feasible. Instead, the SHARP ROC comprises 244 Mylar sheets, each 50 µm thick, coated with a 25 µm gadolinium layer on both sides. A motorized cam-driven oscillation mechanism, positioned at the top of the enclosure, supports the entire structure. The ROC can be extracted by crane for maintenance.

An innovative aspect of the SHARP ROC is the use of counterweights, which apply tension to each suspended sheet, affixed at the top. These counterweights also serve a dual purpose by ensuring mechanical balance of the oscillating system. A mass equivalent to that of the collimator is symmetrically mounted on the opposite side of the rotation axis, reducing vibrations during high-frequency motion and
<figure><img src="image_17.png" /><figcaption>Fig. 14. (a) Position of the portholes on the flight chamber (highlighted in red). (b) View of the detector chamber through the detector-side porthole. (c) View of the sample area through the sample environment porthole.</figcaption></figure>

<figure><img src="image_18.png" /><figcaption>Fig. 15. The radial oscillating collimator. (a) Three dimensional drawing. (b) The real system awaiting for set-up. (c) after set-up as seen from the sample chamber. (d) View from the detector chamber. The radial exclusion zone is clearly visible.</figcaption></figure>

allowing smooth, stable operation of the motor. Aluminum combs at both the top and bottom keep the sheets precisely positioned, reducing overall weight and minimizing lateral space requirements. Each blade measures 363 mm in length, beginning 620 mm from the sample center, and extends in height from 521 mm near the sample to 797 mm on the detector side. The 0.605° blade pitch aligns with the PSD angular spacing, accounting for rear collimators thickness.

While the foil material is absorbent, it can still scatter neutrons. Therefore, the first 13 blades (angular range is 8°) are removed so they do not intercept the direct beam path (Fig. 15(e)) and eliminate any unintended scattering.

### 4.7. Up-down bellow system to optimize the position of the sample cell in the beam

Classically, the sample height is adjusted based on known distances, which is usually precise enough. Nevertheless, to optimize this crucial step, SHARP is equipped with a motorized up-down lift system (Fig. 16) that allows precise adjustment of the sample height relative to the neutron beam and the center of the detector coverage. Its purpose is to ensure that the sample is correctly positioned within the up to 30 mm wide and 50 mm high beam and aligned with the optimal detection

geometry. The lift enables vertical scans of up to 15 cm, significantly simplifying the alignment procedure.

This system is fully compatible with standard sample environments, including cryostats, even with the sample already installed inside. The height adjustment can be performed regardless of the vacuum configuration — whether the vacuum is limited to the sample chamber only, or extended to include both the sample and detector chambers (i.e., when the retractable window is open).

## 5. First scientific result

Zeolite membranes, composed of porous aluminosilicates, act as permeable barriers that separate gases based on size, diffusivity, and concentration. However, the mechanisms of separation and transport, especially at the interfaces between gaseous and confined phases, are not yet fully understood. In particular, macroscopic separation cannot be reliably predicted from molecular-level coefficients (selectivity, individual or collective diffusion). This topic was the focus of an experiment during the first user cycle. In this study, Kellouai et al. [10,11] investigated the complex interactions between gas molecules and a zeolite membrane $M_{x/n}^{n+}Al_x(SiO_2)_{1-x}$ with Si/Al=0.3. They have specifically focused on a timely issue: the discrimination of small molecules like
<figure><img src="image_19.png" /><figcaption>**Fig. 16.** Sample environment support system including a up-down bellow system (total external diameter is 980 mm): (a) all the pieces taken apart for clarity: fixed tray assembly (1), mobile tray assembly (2), bellows assembly (3), motorization for up-down bellows (4), Tank interface for up-down bellows (5). 3D model of the system. (c) Real system awaiting on the top of SHARP before final set-up.</figcaption></figure>

<figure><img src="image_20.png" /><figcaption>**Fig. 17.** (a) Quasi Elastic signal of the zeolite loaded with (CH₄). (b) Quasi Elastic signal of the zeolite loaded with 28 mg of CD₄. (c) Diffraction signal as measured on the PSD array. (d) Diffraction signal after isotropic grouping.</figcaption></figure>

methane (CH₄) and carbon dioxide (CO₂). This separation remains challenging because these molecules interact only weakly, if at all, with industrially relevant zeolite-based membranes.

Both hydrogenated (CH₄) and deuterated (CD₄) forms of methane have been measured with an incident wavelength of 5.1 Å and a resolution of 70 µeV [12]. The incoherent QENS data measured on the (CH₄) loaded sample (Fig. 17(a)) have been fitted with two independent Lorentzian lines. The rotational and translational diffusion coefficients

of the confined molecules have been inferred from the *Q* dependence of both their intensities and broadening.

All together, these experimental results, also supported by molecular dynamics simulations, suggest that steric repulsion significantly affects diffusion. Kellouai et al. [10] derive a free volume theory to estimate diffusion parameters in the zeolite porous network.

This experiment serves to highlight two important achievements of the new instrument. First is the low background achieved on SHARP,
evidenced by the data collected after 3 h on a zeolite loaded with a very small amount (28 mg) of CD₄ — a primarily coherent scatterer (Fig. 17(b)). As previously mentioned the low background results from the evacuated and cadmium lined detector chamber, combined with the boron enriched high density polyethylene shielding. Note that a more detailed analysis of the coherent signal which takes into account cross-correlations is complex, and is currently underway. Second, this study exemplifies the advantage of an extended angular coverage with PSDs.

Fig. 17(c) shows the diffraction pattern of the neat zeolite. The Debye-Scherrer rings are clearly seen with a high definition. Fig. 17(d) shows the diffraction pattern of several samples after isotropic grouping. As seen on the CD₄ loaded sample, the scattering intensity is very sensitive on the applied pressure. This is particularly seen on the diffracted signal intensity difference in the 10 to 20° range.

An additive isotopic effect can also be clearly detected. In neutron scattering, the intensity of a Bragg peak is expressed as:

$$I(hkl) \propto \left| \sum_j b_j e^{2i\pi(hx_j+k y_j+l z_j)} \right|^2 \quad (1)$$

where:

* $I(hkl)$: Intensity of the Bragg reflection for the Miller indices $h, k, l$.

* $b_j$: Neutron scattering length of the $j^{th}$ atom.

* $(x_j, y_j, z_j)$: Atomic coordinates of the $j^{th}$ atom in the unit cell.

* $h, k, l$: Miller indices corresponding to the crystallographic plane contributing to the Bragg reflection.

* $e^{2i\pi(hx_j+k y_j+l z_j)}$: Phase factor accounting for the position of each atom in the crystal lattice.

The coherent scattering lengths of hydrogen and deuterium are $b_{coh}(H) = -3.74$ fm and $b_{coh}(D) = 6.67$ fm. According to equation (1), this isotopic difference results in a substantial change in the scattered intensity. Its modulation in the region of the first two diffraction peaks clearly illustrates this isotopic effect and can be directly used to identify binding sites as well as to determine methane density.

## 6. Conclusion

In addition to a counting rate that is twice as high as that of IN6, the main advancement lies in the ToF configuration, which now operates under vacuum, significantly reducing background noise. The position-sensitive detectors (PSDs) greatly enhance the definition of diffraction patterns. A removable window between the sample and the detector chambers provides flexibility for experiments, enabling operation with the sample either under vacuum or in a controlled atmosphere. In the full vacuum configuration, the chamber vacuum also serves as the cryostat's isolation vacuum, optimizing performance for low-temperature studies. In the controlled atmosphere configuration, the setup is ideal for experiments requiring specific environmental conditions around the sample, such as levitation studies or complex setups involving laser or electrical excitation. These intricate experiments are further facilitated by convenient access to the sample from the ground side of the sample well (Fig. 1).

### CRediT authorship contribution statement

J.-M. Zanotti: Writing – original draft, Validation, Supervision, Conceptualization. S. Rodrigues: Project administration, Conceptualization. P. Lavie: Conceptualization. P. Permingeat: Conceptualization. B. Homatter: Validation. Q. Berrod: Writing – review & editing, Validation.

### Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Acknowledgments

The SHARP project has been supported by the French-Swedish protocol and agreement (CEA - CNRS - Swedish Research Council) for the design and construction of neutron spectrometers, initiated as part of the European Spallation Source (ESS). The operation of SHARP is funded through Program 172 of the French Ministry of Research. We are deeply grateful to the Fédération Française de la Diffusion Neutronique (2FDN) for funding the sample well lift. We extend our thanks to the ILL technical SCI teams, who collaborated with the LLB workforce on cabling, testing, and integrating the system within the Data Acquisition System. Special thanks go to the ILL vacuum group for designing and installing a vacuum system that ensured a stable vacuum (10⁻³ mbar) in the detector box, and to the ILL detector group for producing the Monitor. We are equally grateful to the ILL safety team and beam distribution service for their efficient management of health physics regulations and associated procedures. We are also grateful to Emmanuel Farhi for his expert and repeated support with the McStas simulations. We thank Wanda Kellouai, Patrick Judeinstein, Benoit Coasne and Marie Plazanet for kindly allowing us to use their SHARP zeolite related data in the present work. Our sincere appreciation also goes to the LLB and CEA administrative teams for their invaluable support throughout the project. Their dedication, professionalism, and meticulous attention to detail played a key role in ensuring the smooth operation and coordination of the various project components. Last but not least, we warmly acknowledge Frédéric Legendre, Sébastien Gautrot, and Thomas Robillard from the LLB technical team for their commitment, traveling from Saclay to Grenoble to contribute to the construction of the instrument.

## Data availability

Data will be made available on request.

## References

[1] R. Scherm, A High-Resolution Spectrometer, Tech. Rep. Jul-295-NP, Kern-forschungsanlage Julich, 1965.

[2] R. Scherm, T. Springer, Proposal of a Multiple Chopper for the Investigation of Very Small Energy Transfer, Tech. Rep., IFF Jülich, 1967.

[3] R. Scherm, C. Carlile, J. Dianoux, J. Suck, J. White, Another Time-of-Flight Spectrometer, Tech. Rep. 76S235, Institut Laue-Langevin (ILL), 1976.

[4] Y. Blanc, Le spectromètre à temps de vol IN6, Tech. Rep. 83BL21G, Institut Laue-Langevin (ILL), 1983.

[5] K. Lefmann, K. Nielsen, Mcstas, a general software package for neutron ray-tracing simulations, Neutron News 10 (3) (1999) 20–23.

[6] J. Ollivier, J. Zanotti, Diffusion inélastique de neutrons par temps de vol, EDP Sciences, 2010, pp. 379–423.

[7] O. Arnold, J.-C. Bilheux, J. Borreguero, A. Buts, S.I. Campbell, L. Chapon, M. Doucet, N. Draper, R. Ferraz Leal, M.A. Gigg, V.E. Lynch, P. Maddison, D. Mikkelson, R. Mikkelson, R. Miller, K. Palmen, P. Parker, G. Passos, T.G. Perring, P.F. Peterson, S. Ren, M.A. Reuter, A.T. Savici, J. Taylor, R.J. Taylor, R. Tolchenov, W. Zhou, J. Zikovsky, Mantid—Data analysis and visualization package for neutron scattering and µSR experiments, Nucl. Instruments Methods Phys. Res. Sect. A: Accel. Spectrometers, Detect. Assoc. Equip. 764 (2014) 156–166.

[8] Retractable window video: https://iramis.cea.fr/wp-content/uploads/2017/07/Rideau_Sharp.mp4.

[9] F. Lafont, et al., Multitube monitors: a new-generation of neutron beam monitors, J. Instrum. P05043 (2022).

[10] W. Kellouai, et al., Free volume theory of self-diffusion in zeolites: Molecular simulation and experiment, Microporous Mesoporous Mater. 113305 (2024).

[11] W. Kellouai, Adsorption et Transport dans des Zéolithes: Simulation Moléculaire et Expériences de Diffusion Neutronique (Ph.D. thesis), 2022, Thèse de doctorat dirigée par Coasne, Benoît et Judeinstein, Patrick Nanophysique Université Grenoble Alpes 2022.

[12] P. Judeinstein, Q. Berrod, B. Coasne, W. Kellouai, M. Plazanet, J.-M. Zanotti, Elementary mechanisms in gas separation using zeolite membranes: Experiment and molecular modeling, 2021, http://dx.doi.org/10.5291/ILL-DATA.CRG-2891.