Welcome

• Leszek Ropelewski (CERN)
• Maxim TITOV (CEA Saclay)

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Introduction to ESS

• Richard Hall-Wilton (ESS - European Spallation Source (SE))

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Monte Carlo simulations of neutron interaction with LiF and Boron cathodes

• Lina Quintieri (ENEA)

Room: The Globe This presentation will concern the comparison of the estimated detector efficiency conversion in solid LiF and B cathodes as obtained with some of the major Monte Carlo codes, Fluka and Geant4, extensively used in high energy and health physics domains.

Differences in the transport of ions in the two codes will be highlighted, as well as, several different options in retrieving and storage data of the emitted ions will be discussed, in the frame to couple this information as input of more suitable codes to describe and account of the ionisation of gas detector.

Thin film Boron deposition for GEM-based neutron detectors

• Antonino Pietropaolo (ENEA/INFN)

Room: The Globe He-free neutron Detector based on Gas Electron Multiplier devices are very promising for a series of applications. The activity carried out within a collaboration between INFN and ENEA on thin film boron depositions will be briefly described, as this represents a different strategy as compared to the typical B4C material. This envisages an intensive research and development activity including substrate material analysis, target production and characterization and thorough mechanical and physico-chemical analysis of the deposited films.

A Deposition Facility for Boron Carbide

• Linda Robinson (ESS)

Room: The Globe Due to the urgent need for alternatives to 3He-based neutron detectors at large-scale neutron research facilities, a new generation of detectors uses thin films with a high neutron absorption cross section as the converting material. High quality thin films are essential ingredients in these detectors and are the subject of the research collaboration between the European Spallation Source (ESS) and the Thin Film Physics Division at Linköping University (LiU). The first choice of thin film material is 10B4C, which is deposited onto Al-blades or Si-wafers with the physical vapor deposition (PVD) technique DC magnetron sputtering (DCMS) . One full-scale large area detector at the ESS needs in total ~1000 m2 of two-side coated Al-blades with ~1 um thick 10B4C films. This presentation will discuss the tough demands on film purity and thickness uniformities and the challenge to upscale the process in order to have the first detectors ready for use at the ESS already at the end of this decade. In the context of this challenge, ESS has recently commissioned a deposition facility, adjacent to Linkoping University, based upon industrial techniques to provide the volume of coatings required for this strategic material. A wide variety of coatings have already been provided to the community developing novel neutron detectors; examples are shown. In particular, the ongoing work on expanding and qualifying the list of substrates on which such depositions can be made is shown, with glass taken as an example.

Development of GEM-based thermal neutron detectors

• Gabriele Croci (Universita & INFN, Milano-Bicocca (IT))

Room: The Globe The research of valid alternatives to 3He detectors is fundamental for the detector affordability of new neutron spallation sources like the European Spallation Source (ESS). In the case of ESS it is also essential to develop high-rate detectors that can fully exploit the increase of neutron flux relatively to present neutron sources. One of the technologies fulfilling these requirements is the Gas Electron Multiplier (GEM) coupled to boron converter layers. Some developments and improvements are needed in order to make this detector technology mature to be really competitive. The detector has to be able to sustain a high rate thermal neutron flux, must have a high efficiency (similar to 3He) and the resolution of FWHM of diffraction peaks must comparable to those of 3He systems. This presentation shows recent improvements obtained in the last two years in these directions. The neutron rate capability was tested under a very high flux thermal neutron beam (108 n/cm2*s) showing no decrease of performances up to several MHz/cm2; neutron diffraction experiments with a GEM detector took place (for the first time) on the INES instrument at ISIS, showing results directly comparable to those of 3He tube; a new prototype of higher efficiency boron GEM based detector was realized and recently tested showing an efficiency between 15% and 20% to 25 meV neutrons. This prototype represents a further step towards the realization of high efficiency thermal neutron GEM based detectors.

uTPC analysis for neutron detection

• Filippo Resnati (CERN)

Room: The Globe Several instruments at the European Spallation Source (ESS) will require small to medium sized neutron detectors with an unprecedented spatial resolution and superb local rate capabilities. Micro-Pattern Gaseous Detectors (MPGDs), devices widespread in the High Energy Physics community and in the collider experiments, are very good candidates to meet these requirements. The typical range in gas of the secondary charged particles produced by the neutron capture on the converter material is at least of the order of 1cm. This is apparently in contrast with the requirements of an uncertainty of the neutron conversion position of ±200um. A data analysis techniques based on the principle of the Time Projection Chamber (TPC) was developed, and the proof of principle demonstrated with the data from a laboratory setup with 241 AmBe source and a GEM detector. During a neutron test beam at the IFE research reactor in Norway, the so called uTPC analysis was successfully applied to data acquired with a resistive Micromegas. The analysis improves the position resolution from 1mm to better than 200um for 10B as conversion material. This technique is already used by the ATLAS collaboration to improve the reconstructed position of muon interaction in Micromegas detectors.

Neutron detectors for the NMX instrument at ESS

• Dorothea Pfeiffer (CERN)

Room: The Globe The European Spallation Source (ESS) in Lund/Sweden is foreseen to be operational in 2019. It will become the world¹s most powerful thermal neutron source, with a significantly higher brightness than existing reactor sources. Currently 22 neutron scattering instruments are planned as the baseline suite for the facility, one of these instruments is the macromolecular crystallography instrument NMX. Whereas macromolecular crystallography instruments at reactor sources typically use neutron image plates with ca 200 um spatial resolution, spallation source instruments require time resolution that the image plates lack altogether. Scintillation based detectors on the other hand are currently limited to ca 1 mm spatial resolution. The solid neutron converter Gd in combination with Micro Pattern Gaseous Detectors (MPGDs) might be a promising option to achieve the spatial resolution of the neutron image plate combined with time resolution, high-rate capabilities and a good neutron detection efficiency. This talk presents the first results of measurements with MPGD based neutron detectors with Gd cathodes, and summarises the detector development strategy and schedule for the NMX instrument.

A 4-PAD MicroMegas system for monitoring purpose at n_TOF facilities (CERN)

• M. Sabaté-Gilarte (CEA/CERN/Universidad de Sevilla)

Room: The Globe The neutron time-of-flight (n_TOF) is a neutron beam facility at the European Organization for Nuclear Research (CERN), mainly dedicated to measure neutron-induced cross sections for nuclear technology, astrophysics and basic nuclear physics applying the time of flight technique. A proton beam with momentum of 20 GeV/c is produced in the PS at CERN and impinging on a cylindrical lead target. By spallation processes a large number of neutrons are generated. Neutrons fly 185 m in a horizontal direction through an evacuated beam tube until they reach the first experimental area, EAR1, as well as 20 m in the vertical direction, 90 º, to reach EAR2. MicroMegas detector systems are used at n_TOF for monitoring purposes, i.e., to characterize the neutron flux of the facility. In particular the energy dependence of the neutron flux is important for cross section measurements. The absolute level of flux is determined by a reference cross section. While for fission or charge particles neutron induced reaction, a ratio cross section is obtained respect to a standard reference. For the new EAR2 the expected count rate is 100 times higher as compared with EAR1. Therefore, a new design based on microbulk technology was developed to minimize in-beam material that contributes to the background. The Anode electrode was segmented in four pads to reduce the capacitance of the detector and the count rate with respect to the MESH electrode.

A new transparent XY-MicroMegas neutron beam profiler

• M. Diakaki (CEA/CERN/Universidad de Sevilla/JRC-IRMM Geel)

Room: The Globe A MicroMegas detector based on microbulk technology with an embedded XY strip structure was developed, obtained by segmenting both the mesh and the anode. This results in a very lowmass device with good energy resolution capabilities. Such a detector is practically “transparent” to neutrons, being ideal for in-beam neutron measurements. It will be used as a neutron beam monitor and profiler at neutron TOF facilities, as the n_TOF facility (CERN, Geneva), GELINA (IRMM, Geel) and NFS (GANIL, Caen). The development of such a detector offers new possibilities for the measurement of neutron induced charged particle reaction cross sections, as well as the angular distributions of the emitted particles. The amplification area of 60x60 mm2 is separated in 60+60 strips. The detector data acquisition system is based on the AGET - reduced CoBo technology. Appropriate front-end electronics have been developed for the protection of the AGET chips, the voltage distribution and the readout of the strips. The whole system was tested in neutron beam at the GELINA facility, showing good energy resolution and the potential for good spatial resolution, and the first results will be presented.

Thin Film Coatings for Neutron Detector Applications

• Jens Birch (Linköping University)

Room: The Globe The Helium-3 crisis requires development of a new generation of neutron detectors. Several suitable alternatives to gaseous helium-3 are solid materials that can be deposited as thin films. These neutron conversion materials require specific thin film development for very particular properties. In this contribution we present neutron converters that are developed using materials theory, advanced diagnostic techniques, and industrial production processes. Thin films of boron-10 enriched boron carbide are vital ingredients in many of the replacement technologies under investigation. We show that it is possible to produce large areas with excellent adhesion at low cost in a production scale magnetron sputter deposition system. Low and high temperature chemical vapor deposition processes for production of this material are also outlined. Finally, depositions of exotic GdN-based coatings are shown, as predicted from first principles calculations. Theory and experiments have throughout the work been applied in parallel to optimize the coating quality, in particular in terms of adhesion, thickness, composition, and neutron detection performance.

Profiling of the nTOF beam with the GEM detector

• Eleni Aza (CERN)

Room: The Globe The neutron beam of the n_TOF facility was characterized by means of three triple GEM detectors in EAR1 and the beam dump. A side-on detector employing 10B was used for beam imaging inside the EAR1 via a horizontal and vertical scan for the reconstruction of the entire image and the energy spectrum was measured from the neutron time-of-flight with an efficiency of 4.3% for thermal energies via an externally triggered FPGA-based motherboard. Two head-on detectors with an active area of 10x10 cm2 were used for the beam profiling at the beam dump with a spatial resolution of 8 mm; one employing B4C for slow and the other polyethylene for fast neutrons, so that the spectrum was measured from thermal energies to 1 GeV. The beam diffusion was measured by comparing the spot dimensions of the slow component in EAR1 and the beam dump, while spot size differences were also observed between the fast and slow beam components at the dump. The time-of-arrival of the photon flash emitted after the spallation process on the target was measured at the beam dump with 50 ns accuracy, yielding count losses due to saturation effects.

GEM based fast neutron detector for fusion and spallation sources experiments

• Andrea Muraro (CNR)

Room: The Globe Fast neutron detectors with a sub-centimetric space resolution are required in order to qualify neutron beams in applications related to magnetically-controlled nuclear fusion plasmas and to spallation sources such as ISIS. A medium size20 x 35 cm2 active area) nGEM detector has been realized for the CNESM (Close Contact Neutron Emission Surface Mapping) diagnostic system that is being designed for installation behind the beam-dump of the SPIDER experiment (the NBI prototype for ITER) and as a beam monitor for fast neutrons beam lines at spallation sources such as ChipIR at ISIS. The detector is a triple GEM gaseous detector equipped with a 2 mm thick polypropylene layer used to convert fast neutrons into recoil protons through the elastic scattering process. The read out anode is composed by 256 PADs, each with dimensions of 13x22mm2. In this presentation the measurements made on the ROTAX beam-line at ISIS will be presented, with particular attention to the measurement of the uniformity of the detector response along the active area. Moreover, the measurements of the nGEM counting rate as a function of the detector gain and of the time are presented, together with a preliminary data-analysis software able to reconstruct a neutron beam pattern similar to the one expected in the SPIDER experiment.

A portable directional fast neutron detector

• Nadine Sauzet (LPSC-Grenoble)

Room: The Globe The MIMAC projet (MIcro-tpc MAtrix of Chambers) is aiming at performing directional non baryonic Dark Matter detection. In the frame of this project, a micro-pattern detector with a pixelised anode, coupled without wiring to a self-triggering electronic, has been developed. This system is currently being adapted to aim at fast neutron detection in the range [10 keV ; 10 MeV], for applications such as homeland security, radioprotection, physics and medical monitoring. The main features of this system are: - An autonomous portable solution, compatible with industrial environments and on-site activities, - Fast neutron detection, with electron and gamma discrimination, - Energy spectrum construction, - Neutron emitter 3-D location.

MONDO : A neutron tracker for particle therapy secondary emission fluxes measurements

• Michela Marafini

Room: The Globe Particle therapy (PT) is a novel technique that uses accelerated charged particles for cancer treatment. The PT high irradiation precision and conformity allows the tumor destruction while sparing the surrounding healthy tissues. Monitoring methods using photons and charged particles have already been proposed, but no attempt has been made yet to use the abundant neutron component. The large penetrating power of neutrons produces nearly energy threshold free escape, providing a secondary particle sample that is higher in number with respect to photons and charged particles. Therefore, neutrons allow for a backtracking of the emission point that is not aected by multiple scattering. Since neutrons can release a signicant dose far away from the tumor region, a precise measurement of their ux, production energy and angle distributions is eagerly needed in order to improve the Treatment Planning Systems (TPS) software, so to predict not only the normal tissue toxicity in the target region, but also the risk of late complications in the whole body. Up to now, neutrons secondary emission has been very poorly investigated for monitoring purpose. This underline the importance for an experimental eort devoted to the precise measurement of the neutron production, induced by the beam interaction with body tissues. The technical challenges posed by a neutron detector aiming for high detection eciency and good backtracking precision will be addressed within the MONDO (MOnitor for Neutron Dose in hadrOntherapy) project. The MONDO main goal is to develop a tracking detector capable of a full reconstruction and backtracking of fast and ultrafast secondary neutrons produced by the primary beam interaction with the patient body. The tracker is composed by a scintillating ber matrix ((4 4 8 cm3). The bers is coupled with a triple GEM detector used as an image intensier. The photons produced during the electron multiplication will be read out by a CMOS sensor (thinned until the epitaxial layer). The full reconstruction of protons, produced in elastic interactions, will be used to measure the kinematic of the impinging neutron in the (20-300) MeV kinetic energy range. The neutron tracker will measure the neutron production yields, as a function of production angle and energy, using dierent therapeutic beams at CNAO in Pavia (protons, 12C ions and possibly 4He and 16O ions). A device will reduce signicantly the large uncertainties currently related to the neutrons ux estimate produced in typical PT treatments, as well as in other medical therapies involving the neutrons production.

Neutron beam characterization with silicon micropixelated detector

• George Stuart (CERN)

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Fabrication of large area 10B MultiGrid detectors: conclusion of the CRISP project

• Bruno Guerard (ILL)

Room: The Globe Most of the Neutron Scattering facilities are committed in a continuous program of modernization of their instruments, requiring large area and high performance thermal neutron detectors. Time Of Flight instruments are using 3He PSDs mounted side by side to cover tens of m2. As a result of the so-called “3He shortage crisis”, the volume of 3He needed to build one of these instruments is not accessible anymore. The development of alternative techniques without 3He, has been given high priority to secure the future of neutron scattering instrumentation. One of these alternatives is the Multi-Grid introduced at the ILL in 2009. A Multi-Grid detector is composed of several independent modules mounted side by side in air or in a vacuum TOF chamber. One module is composed of segmented boron-lined proportional counters mounted in a gas vessel; the counters, of square section, are assembled with Aluminium grids electrically insulated and stacked together. Prototypes of different configurations and sizes have been developed and tested. The largest one, with a sensitive area of 0.8 m x 3 m, has been studied during the CRISP project; it contains 1024 grids, and a surface of isotopically enriched B4C film close to 80 m2. Its size represented a challenge in terms of fabrication and mounting of the detection elements. Another challenge was to make the gas chamber mechanically compatible with operation in a vacuum TOF chamber. Optimal working condition of this detector was achieved by flushing Ar-CO2 at a pressure of 50 mbar, and by applying 400 Volts on the anodes. This unusual gas pressure allows to greatly simplifying the mechanics of the gas vessel in vacuum. Experimental results will be presented.

Summary Document

• Bruno Guerard (ILL)

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Opportunities with regard to MPGD-related technologies

• David Mazur (CERN)

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CAEN

• Alessandro Iovene

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ELSE NUCLEAR

• Giacomo Manessi

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SCIENTIFICA INTERNATIONAL

• Lander Gonzalez Larrea

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SITAEL

• Carlo Avanzini

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REUTER-STOKES

• Mathieu Boucher

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Round table Room: The Globe