Radiation Hardness Of Detectors Research Articles

TetraBall: A single-moderator neutron spectrometer for HL-LHC

This contribution presents a novel single-moderator neutron spectrometer, named “TetraBall”, developed at INFN and optimized for characterizing the neutron field in the CMS experimental cavern. The TetraBall condenses the functionality of several Bonner Spheres (BS) in a single moderator and it is equipped with 42 SiC radiation-hard detectors organized in a tetrahedral geometry designed to be insensitive to incident gammas and charged particles. Thanks to lead inserts, it can respond up to GeV energies. It works in single exposure mode, suitable for real-time monitoring. It is designed to be used as neutron monitor during the High-Luminosity LHC data taking.

Development of a sapphire microstrip detector for gamma beam monitoring

Artificial sapphire gained interest as radiation detector in the recent years, as an alternative to diamond. The research and development campaign to design, build and characterize a radiation-hard detector for gamma beam monitoring takes place in the scientific context of the Laser Und XFEL Experiment (LUXE) at DESY. The experiment requirements of beam profile reconstruction with micro-metric precision and radiation hardness led to a proposed sapphire microstrip detector design. This work introduces the scientific context for a sapphire microstrip gamma beam profiler (GBP) and describes the experimental campaign for sapphire characterization from early prototypes to the final development of a 192-strip detector.

Modelling Gd-diamond and Gd-SiC neutron detectors

A custom Monte Carlo (MC) computer model was developed to simulate thermal neutron absorption in, and subsequent photon and electron emission from, natural Gd with a view to using the material as a neutron conversion layer for neutron detectors. The MC code also modelled photon and electron detection with two dissimilar detectors: a thick (500 μm) single crystal diamond detector; and a thin (5.15 μm) commercial off the shelf (COTS) 4H–SiC photodiode detector. The detectors’ quantum detection efficiencies (QE) for hard X-rays and γ-rays were relatively low in comparison to their QE for electrons, thus making it possible to collect electron spectra from the Gd layer neutron conversion products which were not overwhelmed by photon emissions from the Gd. The MC code was utilised to determine the optimal thickness of Gd for the efficient detection of a thermal neutron flux. These radiation hard and spectroscopic detectors paired with natural Gd could find utility as robust and compact thermal neutron detectors for nuclear science and engineering, space science, and other applications.

A high-resolution large-area detector for quality assurance in radiotherapy

Hadron therapy is an advanced radiation modality for treating cancer, which currently uses protons and carbon ions. Hadrons allow for a highly conformal dose distribution to the tumour, minimising the detrimental side-effects due to radiation received by healthy tissues. Treatment with hadrons requires sub-millimetre spatial resolution and high dosimetric accuracy. This paper discusses the design, fabrication and performance tests of a detector based on Gas Electron Multipliers (GEM) coupled to a matrix of thin-film transistors (TFT), with an active area of 60 × 80 mm2 and 200 ppi resolution. The experimental results show that this novel detector is able to detect low-energy (40 kVp X-rays), high-energy (6 MeV) photons used in conventional radiation therapy and protons and carbon ions of clinical energies used in hadron therapy. The GEM-TFT is a compact, fully scalable, radiation-hard detector that measures secondary electrons produced by the GEMs with sub-millimetre spatial resolution and a linear response for proton currents from 18 pA to 0.7 nA. Correcting known detector defects may aid in future studies on dose uniformity, LET dependence, and different gas mixture evaluation, improving the accuracy of QA in radiotherapy.

Optical characteristics and wavefront control of femtosecond laser pulses and their effect on the performance of diamond graphite electrodes

High purity diamond is an excellent material for making radiation hard detectors suitable for high-energy particle detection, cancer treatment and other fields. Electrodes are formed by the localized graphitization of the diamond bulk, where fine control of the manufacturing process is essential to the performance of the detector. The resistivity of the electrode formed by diamond graphitization significantly affects the performance of the detector. Femtosecond laser pulses interact with the material for a very short time (10-13 s), exhibiting a cold processing. In this paper, we utilize Spatial Light Modulators (SLM) to optimize the optical characteristics of the 800 nm femtosecond laser pulse and control the graphitization process. Our research focuses on the analysis of the influence exerted by the pulse characteristics on the diameter and resistivity of inscribed graphite structures. By examining these parameters, the study aims to refine the graphitization process, thereby optimizing the functional characteristics of the diamond-based detectors.

Methods for Improving the Radiation Hardness of Detectors Based on Organic Plastic Scintillators

Methods for Improving the Radiation Hardness of Detectors Based on Organic Plastic Scintillators

Diamond based integrated detection system for dosimetric and microdosimetric characterization of radiotherapy ion beams.

Ion beam therapy allows for a substantial sparing of normal tissues and higher biological efficacy. Synthetic single crystal diamond is a very good material to produce high-spatial-resolution and highly radiation hard detectors for both dosimetry and microdosimetry in ion beam therapy. The aim of this work is the design, fabrication and test of an integrated waterproof detector based on synthetic single crystal diamond able to simultaneously perform dosimetric and microdosimetric characterization of clinical ion beams. The active elements of the integrated diamond device, that is, dosimeter and microdosimeter, were both realized in a Schottky diode configuration featured by different area, thickness, and shape by means of photolithography technologies for the selective growth of intrinsic and boron-doped CVD diamond. The cross-section of the sensitive volume of the dosimetric element is 4mm2 and 1μm-thick, while the microdosimetric one has an active cross-sectional area of 100×100μm2 and a thickness of about 6.2μm. The dosimetric and microdosimetric performance of the developed device was assessed at different depths in a water phantom at the MedAustron ion beam therapy facility using a monoenergetic uniformly scanned carbon ion beam of 284.7MeV/u and proton beam of 148.7MeV. The particle flux in the region of the microdosimeter was 6·107 cm2 /s for both irradiation fields. At each depth, dose and dose distributions in lineal energy were measured simultaneously and the dose mean lineal energy values were then calculated. Monte Carlo simulations were also carried out by using the GATE-Geant4 code to evaluate the relative dose, dose averaged linear energy transfer (LETd ), and microdosimetric spectra at various depths in water for the radiation fields used, by considering the contribution from the secondary particles generated in the ion interaction processes as well. Dosimetric and microdosimetric quantities were measured by the developed prototype with relatively low noise (∼2keV/μm). A good agreement between the measured and simulated dose profiles was found, with discrepancies in the peak to plateau ratio of about 3% and 4% for proton and carbon ion beams respectively, showing a negligible LET dependence of the dosimetric element of the device. The microdosimetric spectra were validated with Monte Carlo simulations and a good agreement between the spectra shapes and positions was found. Dose mean lineal energy values were found to be in close agreement with those reported in the literature for clinical ion beams, showing a sharp increase along the Bragg curve, being also consistent with the calculated LETd for all depths within the experimental error of 10%. The experimental indicate that the proposed device can allow enhanced dosimetry in particle therapy centers, where the absorbed dose measurement is implemented by the microdosimetric characterization of the radiation field, thus providing complementary results. In addition, the proposed device allows for the reduction of the experimental uncertainties associated with detector positioning and could facilitate the partial overcoming of some drawbacks related to the low sensitivity of diamond microdosimeters to low LET radiation.

Emerging SiC Applications beyond Power Electronic Devices.

In recent years, several new applications of SiC (both 4H and 3C polytypes) have been proposed in different papers. In this review, several of these emerging applications have been reported to show the development status, the main problems to be solved and the outlooks for these new devices. The use of SiC for high temperature applications in space, high temperature CMOS, high radiation hard detectors, new optical devices, high frequency MEMS, new devices with integrated 2D materials and biosensors have been extensively reviewed in this paper. The development of these new applications, at least for the 4H-SiC ones, has been favored by the strong improvement in SiC technology and in the material quality and price, due to the increasing market for power devices. However, at the same time, these new applications need the development of new processes and the improvement of material properties (high temperature packages, channel mobility and threshold voltage instability improvement, thick epitaxial layers, low defects, long carrier lifetime, low epitaxial doping). Instead, in the case of 3C-SiC applications, several new projects have developed material processes to obtain more performing MEMS, photonics and biomedical devices. Despite the good performance of these devices and the potential market, the further development of the material and of the specific processes and the lack of several SiC foundries for these applications are limiting further development in these fields.

TCAD simulation of radiation hard n-MCz and n-Fz Si microstrip detector for the HL-LHC

A radiation hard Si detector is used in the new CMS tracker detector at HL-LHC. It has been observed that n-MCz and n-Fz Si as a material can be used for the Si micro strip detector. The detector design for this material should be simulated and optimized to get high CCE. In order to understand the charge collection behavior of the n-MCz/n-FzSi detector, it is required to simulate and compare the radiation damage effects in the mixed irradiated n-MCz Si and proton irradiated n-Fz Si micro strip detector equipped with metal overhang and multiple guard rings. In this paper, we have done analysis and optimization of the radiation hard n-MCz Si/n-Fz Si strip detector design for the HL-LHC experiment in order to get high CCE.

High-precision luminosity instrumentation for the CMS detector at the HL-LHC

The high-luminosity upgrade of the LHC (HL-LHC) is foreseen to reach an instantaneous luminosity a factor of five to seven times the nominal LHC design value. This creates the need for new high-precision instrumentation at CMS, using radiation-hard detector technologies. This contribution introduces the instrumentation for bunch-by-bunch online luminosity and beam-induced background measurements in CMS. The Tracker Endcap Pixel Detector (TEPX) will be adapted for precision luminometry by implementing a dedicated trigger type and a real-time data processing system performing clustering on FPGA. The innermost ring of the last TEPX layer (D4R1) will be operated independently from the rest of TEPX, enabling beam monitoring during the LHC ramp and during unqualified beam conditions with a dedicated timing and trigger infrastructure. A new standalone luminometer, the Fast Beam Condition Monitor (FBCM), which will be fully independent from the central trigger and data acquisition services and will be able to operate during all times is also introduced. FBCM is foreseen to utilize silicon-pad sensors with sub-bunch-crossing time resolution enabling also the measurement of beam-induced background. The potential of the exploitation of other CMS subsystems such as the outer tracker, the barrel muon detectors and the 40 MHz L1 trigger scouting system using a common histogramming firmware is also discussed.

Assessment of single crystal diamond detector radiation hardness to 14 MeV neutrons

Single Crystal Diamonds (sCD) have been selected as neutron detectors for the ITER Radial Neutron Camera (RNC). This paper investigates experimentally the hardness of these detectors to 14 MeV neutrons in order to have indications of their limits of applicability in the RNC. The experiment has been performed at the Frascati Neutron Generator (FNG) facility using three sCDs of different thickness (500,300,100μm).The degradation of the sCD Charge Collection Efficiency (CCE) with increasing 14 MeV neutron fluence has been found to be lower with decreasing sCD thickness.Strong polarization effects produced by the trapping of charge carriers in the defects produced by the neutron irradiation are observed already at about 4⋅1014n∕cm2 in the 100μm thick sCD. A software correction of the polarization effect is proposed, which enables to extend the sCD range of operation up to higher fluences. Taking into account such correction, a 50μm thick sCD is expected to reach 1015n∕cm2 with a CCE greater than 0.7.

SILICON CARBIDE NEUTRON DETECTOR PROTOTYPE TESTING AT THE JSI TRIGA REACTOR FOR ENHANCED BORDER AND PORTS SECURITY

In 2016, the “E-SiCure” project (standing for “Engineering Silicon Carbide for Border and Port Security”), funded by the NATO Science for Peace and Security Programme was launched. The main objective is to combine theoretical, experimental and applied research towards the development of radiation-hard SiC-based detectors of special nuclear materials (SNM), with the end goal to enhance border and port security barriers. Prototype neutron detectors, configured as 4H-SiC-based Schottky barrier diodes, were developed for the detection of secondary charged particles (tritons, alphas and lithium atoms) which are the result of thermal neutron reactions on 10B and 6LiF layers above the surface of the 4H-SiC diodes. We designed a stand-alone prototype detection system, consisting of a preamplifier, shaping amplifier and a multichannel analyser operated by a laptop computer, for testing of neutron detector prototypes at the Jožef Stefan Institute (JSI) TRIGA reactor using a broad beam of reactor neutrons. The reverse bias for the detector diode and the power to electronic system were provided by a standalone battery-powered voltage source. The detector functionality was established through measurements using an 241Am alpha particle source. Two dedicated experimental campaigns were performed at the JSI TRIGA reactor. The registered pulse height spectra from the detectors, using both 10B and 6LiF neutron converting layers, clearly demonstrated the neutron detection abilities of the SiC detector prototypes. The computed neutron detection sensitivity of the single prototype detectors demonstrates that scaling SiC detectors into larger arrays, of dimensions relevant for border and port radiation detectors, could enable neutron sensitivity levels matching gas-based detector technology.

Quality assurance test of the STS-XYTERv2 ASIC for the silicon tracking system of the CBM experiment

The Compressed Baryonic Matter (CBM) Experiment will be one of the major scientific endeavors of the future Facility of Antiproton and Ion Research (FAIR) in Darmstadt. Nuclear collisions at an interaction rate of up to 10 MHz will provide the data for numerous observables, including rare probes with necessary statistical significance. Key to achieve this goal is a fast and radiation hard detector subsystem for particle tracking. In the CBM experiment, the Silicon Tracking System (STS) is the main system for particle tracking. Signal read-out from the 2x1024 channel sensors is based on the self-triggering STS-XYTERv2 ASIC specifically developed for this application. Towards final STS-operation, a down-scaled mini-CBM (mCBM) setup was taken into operation at the SIS18 accelerator at GSI. In this paper, the test measurements of the STS-XYTERv2 asıcs and operational tests performed for quality assurance during the assembly of the mSTS detector modules will be presented and discussed in detail. These measurement procedures will constitute fundamental processes for quality assurance (QA) in the assembly of the roughly 900 STS detector modules.

Radiation hardness of GaAs:Cr and Si sensors irradiated by 21 MeV electron beam

Silicon detectors generally satisfy the requirements of the modern physics experiments, however, experimental physics develops in the direction of increasing radiation loads, wich leads to increase in the requirements for radiation hardness of detectors. For other applications, such as registration of high energy X-rays, using detectors with high atomic number is important. The interest in using high resistive chromium-compensated GaAs (GaAs:Cr) in high-energy physics and other applied fields is steadily growing. This article presents a comparative study of the radiation resistance of sensors based on GaAs:Cr and Si, irradiated by 21 MeV electrons generated by the LINAC-200 accelerator. The target sensors were irradiated with the dose up to 1.5 MGy. I-V characteristics, resistivity, charge collection efficiency (CCE) and their dependences on the bias voltage and temperature were measured at different absorbed doses.

Diamond-Like Carbon for the Fast Timing MPGD

The present generation of Micro-Pattern Gaseous Detectors (MPGDs) are radiation hard detectors, capable of detecting effciently particle rates of several MHz/cm2, while exhibiting good spatial resolution (≤ 50 µm) and modest time resolution of 5-10 ns, which satisfies the current generation of experiments (High Luminosity LHC upgrades of CMS and ATLAS) but it is not sufficient for bunch crossing identification of fast timing systems at FCC-hh. Thanks to the application of thin resistive films such as Diamond-Like Carbon (DLC) a new detector concept was conceived: Fast Timing MPGD (FTM). In the FTM the drift volume of the detector has been divided in several layers each with their own amplification structure. The use of resistive electrodes makes the entire structure transparent for electrical signals. After some first initial encouraging results, progress has been slowed down due to problems with the wet-etching of DLC-coated polyimide foils. To solve these problems a more in-depth knowledge of the internal stress of the DLC together with the DLC-polyimide adhesion is required. We will report on the production of DLC films produced in Italy with Ion Beam Sputtering and Pulsed Laser Deposition, where we are searching to improve the adhesion of the thin DLC films, combined with a very high uniformity of the resistivity values.

Status of the Compressed Baryonic Matter experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment will investigate high-energy heavy-ion collisions at the international Facility for Antiproton and Ion Research (FAIR), which is under construction in Darmstadt, Germany. The CBM research program is focused on the exploration of QCD matter at neutron star core densities, such as study of the equation-of-state and the search for phase transitions. Key experimental observables include (multi-) strange (anti-) particles, electron-positron pairs and dimuons, particle correlations and fluctuations, and hyper-nuclei. In order to measure these diagnostic probes multi-differentially with unprecedented precision, the CBM detector and data acquisition systems are designed to run at reaction rates up to 10 MHz. This requires the development of fast and radiation hard detectors and readout electronics for track reconstruction, electron and muon identification, time-of-flight (TOF) determination and event characterization. The data are read-out by ultra-fast, radiation-tolerant, and free-streaming front-end electronics, and then transferred via radiation-hard data aggregation units and high-speed optical connections to a high-performance computing center. A fast and highly parallelized software will perform online track reconstruction, particle identification and event analysis. The components of the CBM experimental setup will be discussed and results of physics performance studies will be presented.

Polysiloxane-based scintillators for shashlik calorimeters

We present the first application of polysiloxane-based scintillators as active medium in a shashlik sampling calorimeter. These results were obtained from a testbeam campaign of a ∼6×6×45 cm3 (13 X0 depth) prototype. A Wavelength Shifting fiber array of 36 elements runs perpendicularly to the stack of iron (15 mm) and polysiloxane scintillator (15 mm) tiles with a density of about one over cm2. Unlike shashlik calorimeters based on plastic organic scintillators, here fibers are optically matched with the scintillator without any intermediate air gap. The prototype features a compact light readout based on Silicon Photo-Multipliers embedded in the bulk of the detector. The detector was tested with electrons, pions and muons with energies ranging from 1 to 7 GeV at the CERN-PS. This solution offers a highly radiation hard detector to instrument the decay region of a neutrino beam, providing an event-by-event measurement of high-angle decay products associated with neutrino production (ENUBET, Enhanced NeUtrino BEams from kaon Tagging, ERC project). The results in terms of light yield, uniformity and energy resolution, are compared to a similar calorimeter built with ordinary plastic scintillators.

Event Reconstruction in the Tracking System of the CBM Experiment

The Compressed Baryonic Matter experiment (CBM) will investigate strongly interacting matter at high net-baryon densities by measuring nucleus-nucleus collisions at the FAIR research centre in Darmstadt, Germany. Its ambitious aim is to measure at very high interaction rates, unprecedented in the field of experimental heavy-ion physics so far. This goal will be reached with fast and radiation-hard detectors, self-triggered read-out electronics and streaming data acquisition without any hardware trigger. Collision events will be reconstructed and selected in real-time exclusively in software. This puts severe requirements to the algorithms for event reconstruction and their implementation. We will discuss some facets of our approaches to event reconstruction in the main tracking device of CBM, the Silicon Tracking System, covering local reconstruction (cluster and hit finding) as well as track finding and event definition.

Design and development of radiation hard p+n Si pixel detector for the next generation photon science experiment

Science, at next generation photon science experiment requires radiation hard p+n Si pixel detector for the X-ray imaging. The choice of an appropriate surface radiation hard X-ray thick Si detector design is a challenging task for the long-term operation of the experiment for the different application that involves up to 25 KeV X-ray energy especially in the material science. The test structure for e.g. prototype p+n Si microstrip detector was fabricated at BEL, Bengaluru, India. The current–voltage and capacitance–voltage characteristic of the detector was measured. The experimental macroscopic parameters are used for the designing of the p+n Si pixel detector. The Visual TCAD semiconductor device simulator from Cogenda was used to compare the simulated and experimental results of the prototype detector to see the electric field distribution in the detector. The breakdown performance of the detector has been discussed using simulation result. The experimentally observed microscopic parameters Nfixox (fixed oxide charge) and Nit (interface trapped charge) can be used in the simulation in order to understand the surface radiation damage performance of the detector. The influences of various device and process parameters on the macroscopic parameters of the detector are shown.In this paper, the influence of the X-ray radiation damage on the electrical performance of the p+n Si pixel detector is shown. On the basis of TCAD simulation and experimental measurement, a radiation-hard p+n silicon pixel sensor design, process, device parameter, and specification is proposed for the next generation photon science experiment like Eu-XFEL.

E-SiCure Collaboration Project: Silicon Carbide Material Studies and Detector Prototype Testing at the JSI TRIGA Reactor

In 2016, the ”E-SiCure” project (standing for Engineering Silicon Carbide for Border and Port Security), funded by the NATO Science for Peace and Security Programme, was launched. The main objective is to combine theoretical, experimental and applied research towards the development of radiation-hard SiC-based detectors of special nuclear materials (SNM), and by that way, to enhance border and port security barriers. Along the plan, material modification processes are employed firstly to study, and secondly to manipulate the most severe electrically active defects (which trap or annihilate free charge carriers), by specific ion implantation and defect engineering. This paper gives an overview of the experimental activities performed at the JSI TRIGA reactor in the framework of the E-SiCure project. Initial activities were aimed at obtaining information on the radiation hardness of SiC and at the study of the energy levels of the defects induced by neutron irradiation. Several Schottky barrier diodes were fabricated out of nitrogen-doped epitaxial grown 4H-SiC, and irradiated under Cd filters in the PT irradiation channel in the JSI TRIGA reactor with varying neutron fluence levels. Neutron-induced defects in the material were studied using temperature dependent current-voltage (I-V), capacitance-voltage (C-V) and Deep-Level Transient Spectroscopy (DLTS) measurements. Our prototype neutron detectors are configured as 4H-SiC-based Schottky barrier diodes for detection of secondary charged particles (tritons, alphas and lithium atoms) which are result of thermal neutron conversion process in 10B and 6LiF layers above the surface of the 4H-SiC diodes. For field testing of neutron detectors using a broad beam of reactor neutrons we designed a standalone prototype detection system consisting of a preamplifier, shaping amplifier and a multichannel analyser operated by a laptop computer. The reverse bias for the detector diode and the power to electronic system are provided by a standalone battery-powered voltage source. The detector functionality was established through measurements using an 241Am alpha particle source. Two dedicated experimental campaigns were performed at the JSI TRIGA reactor. The registered pulse height spectra from the detectors, using both 10B and 6LiF neutron converting layers, clearly demonstrated the neutron detection abilities of the SiC detector prototypes.