Large Plastic Scintillator Research Articles

The SuperNEMO calorimeter

The SuperNEMO double beta decay project is a modular tracker-calorimeter experiment that will reach a sensitivity to the neutrinoless double beta decay half-life of ∼ 1026 years, corresponding to a Majorana neutrino mass of 50-100 meV. The main calorimeter is based on 440 Optical Modules made of large volume plastic scintillators (10L) coupled with large area photomultipliers (Hamamatsu R5912-Mod). They are assembled in walls surrounding the isotope foil and the tracking volume. One of the main challenges of the SuperNEMO detector development programme was to reach an energy resolution, better than 8%(FWHM) at 1 MeV. The other challenge was to satisfy the radiopurity requirements for all the calorimeter materials. The calorimeter design of the first SuperNEMO module is presented as well as its performances and the status of its construction under way in the Modane underground laboratory.

Development of an optical simulation for the SuperNEMO calorimeter

The SuperNEMO double beta decay project is a modular tracker-calorimeter based experiment. The aim of this project is to reach a sensitivity of the order of 1026 years concerning the neutrinoless double beta decay half-life, corresponding to a Majorana neutrino mass of 50-100 meV. The main calorimeter of the SuperNEMO demonstrator is based on 520 Optical Modules made of large volume plastic scintillators (10L) coupled with large area photomultipliers (Hamamatsu R5912-MOD and R6594). The design of the calorimeter is optimized for the double beta decay detection and allows gamma tagging for background rejection. In large volumes of scintillators, a similar deposited energy by electrons or photons will give different visible energy and signal shapes due to different interactions inside the scintillator. The aim of the optical simulation, developed for SuperNEMO, is to model the Optical Module response on the energy and time performances, regarding the particle type.

Calorimeter development for the SuperNEMO double beta decay experiment

SuperNEMO is a double-β decay experiment, which will employ the successful tracker–calorimeter technique used in the recently completed NEMO-3 experiment. SuperNEMO will implement 100 kg of double-β decay isotope, reaching a sensitivity to the neutrinoless double-β decay (0νββ) half-life of the order of 1026 yr, corresponding to a Majorana neutrino mass of 50–100 meV. One of the main goals and challenges of the SuperNEMO detector development programme has been to reach a calorimeter energy resolution, ΔE∕E, around 3%∕E(MeV)σ, or 7%∕E(MeV) FWHM (full width at half maximum), using a calorimeter composed of large volume plastic scintillator blocks coupled to photomultiplier tubes. We describe the R&D programme and the final design of the SuperNEMO calorimeter that has met this challenging goal.

Ultra-violet light-emitting diode calibration system for timing large area scintillation detectors

Timing large area plastic scintillation detectors are developing for the space gamma-ray telescopes now. For the in-flight calibration of these detectors the use of ultra-violet light-emitting diode, irradiating the 1 m long detector module at the center of its lateral side is suggested. The results of the measurements show the possibility of this calibration system implementation as for amplitude as for timing properties monitoring.

The investigation of timing large area scintillation detectors with SiPM light sensors properties

The timing large area plastic scintillation detectors with silicon photomultipliers as photosensors properties were investigated using a cosmic radiation at the ground level. Different techniques of the amplitude spectra and efficiency measurements were implemented. The measurements results are presented.

A second-generation low-background gamma-ray spectrometer

For the ultimate sensitivity in trace radiochemical analysis, the radiation detector must have high efficiency and low background. A low-background gamma-ray spectrometer in regular use at NIST for over twenty years is being supplemented by a new system, improved in several ways. The new detector is much larger, a shield of iron reduces cosmic neutron background compared with lead, large plastic scintillators reduce the muon continuum background, and a digital data acquisition system gives new opportunities for optimization.

A large area plastic scintillation detector with 4-corner-readout**Supported by National Natural Science Foundation of China (U1332207, 11405242)

A 760 mm × 760 mm × 30 mm plastic scintillation detector viewed by photomultiplier tubes (PMTs) from four corners has been developed, and the detector has been tested with cosmic rays and γ rays. A position-independent effective time Teff has been found, indicating this detector can be used as a TOF detector. The hit position can also be reconstructed by the time from the four corners. A TOF resolution of 236 ps and a position resolution of 48 mm have been achieved, and the detection efficiency has also been investigated.

Geant4-GATE Simulation of a Large Plastic Scintillator for Muon Radiography

Envisaging the possibility of using large-area plastic scintillator slabs as robust detectors for high spatial resolution muon radiography, and prior to prototype development, we study expected basic performance by Monte Carlo simulation. We present preliminary results for a scalable square footprint detector unit of ~ 1 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , defining a representative simulation model volume of 50 cm ×50 cm, with reflective surfaces and a light readout by direct coupling of 4 small PMTs (in a square arrangement) at one face of the scintillator slab. Light detection efficiency is calculated for several light collection configurations, considering different values of surface roughness, reflectivity, optical coupling index and scintillator thickness. Values maximizing photon detection have been identified. The light response function of 2.5-3.5 cm diameter PMTs for the proposed configuration has been determined. A detector intrinsic spatial resolution of the order of 1 cm is estimated for muon interactions at the center region of the detector module, using a simple centroid positioning algorithm (Anger logic).

Identifying key surface parameters for optical photon transport in GEANT4/GATE simulations

For a scintillator used for spectrometry, the generation, transport and detection of optical photons have a great impact on the energy spectrum resolution. A complete Monte Carlo model of a scintillator includes a coupled ionizing particle and optical photon transport, which can be simulated with the GEANT4 code. The GEANT4 surface parameters control the physics processes an optical photon undergoes when reaching the surface of a volume. In this work the impact of each surface parameter on the optical transport was studied by looking at the optical spectrum: the number of detected optical photons per ionizing source particle from a large plastic scintillator, i.e. the output signal. All simulations were performed using GATE v6.2 (GEANT4 Application for Tomographic Emission). The surface parameter finish (polished, ground, front-painted or back-painted) showed the greatest impact on the optical spectrum whereas the surface parameter σα, which controls the surface roughness, had a relatively small impact. It was also shown how the surface parameters reflectivity and reflectivity types (specular spike, specular lobe, Lambertian and backscatter) changed the optical spectrum depending on the probability for reflection and the combination of reflectivity types. A change in the optical spectrum will ultimately have an impact on a simulated energy spectrum. By studying the optical spectra presented in this work, a GEANT4 user can predict the shift in an optical spectrum caused be the alteration of a specific surface parameter.

Time and Amplitude Characteristics of Large Scintillation Detectors with SiPM

A large plastic scintillation detector system with silicon photomultiplier (SiPM) readout has been developed as a prototype for future astroparticle experiments’ detectors. A set of SiPM connected in parallel was used in order to enlarge the light collection effective area and thus enhance the detector's amplitude and timing performance. Here we report on the values of time resolution and scintillation detection efficiency of such a system for different types of SiPM as a function of the distance between the scintillation strip edge with photomultipliers attached to it, and the penetrating particle. Results of a special simulation study of the system's amplitude and timing performance as a function of the SiPM radiation aging are also presented.

Large area position sensitive β-detector

A new conceptual design of a large area electron detector, which is position and energy sensitive, was developed. This detector is designed for beta decay energies up to 4MeV, but in principle can be re-designed for higher energies. The detector incorporates one large plastic scintillator and, in general, a limited number of photomultipliers (7 presently). The current setup was designed and constructed after an extensive Geant4 simulation study. By comparison of a single hit light distribution between the various photomultipliers to a pre-measured accurate position-response map, the anticipated position resolution is around 5mm. The first benchmark experiments have been conducted in order to calibrate and confirm the position resolution of the detector. The new method, results of the first test experiments and comparison to simulations are presented.

A Monte Carlo calibration of a whole body counter using the ICRP computational phantoms.

A fast and versatile calibration of a whole body counter (WBC) is presented. The WBC, consisting of four large plastic scintillators, is to be used for measurements after accident or other incident involving ionising radiation. The WBC was calibrated using Monte Carlo modelling and the ICRP computational phantoms. The Monte Carlo model of the WBC was made in GATE, v6.2 (Geant4 Application for Tomographic Emission) and MATLAB. The Monte Carlo model was verified by comparing simulated energy spectrum and simulated counting efficiency with experimental energy spectrum and experimental counting efficiency for high-energy monoenergetic gamma-emitting point sources. The simulated results were in good agreement with experimental results except when compared with experimental results from high dead-time (DT) measurements. The Monte Carlo calibration was made for a heterogeneous source distribution of (137)Cs and (40)K, respectively, inside the ICRP computational phantoms. The source distribution was based on the biokinetic model for (137)Cs.

POLITRANI, A New Toolkit to Simulate Organic Scintillator Pulses

3He shortage has provoked a renewed interest for organic scintillation detectors (good neutron detection efficiency) with neutron-gamma discrimination capability. Pulse Shape Discrimination (PSD) with plastic scintillators has recently shown important progresses and raises a great interest as plastic detectors are not toxic and not inflammable contrary to liquid scintillation detectors. In this context, the French Alternative Energies and Atomic Energy Commission (CEA), within the FP7 European project SCINTILLA, is studying the possibility to produce large size plastic scintillators as candidates for 3He tube replacements together with the related FPGA electronics. To support the design of plastic scintillators with enhanced neutron-gamma discrimination power, software based on ROOT data analysis software was developed to couple photon-neutron transport with MCNP PoliMi and optical photon tracking in the scintillator with Litrani. This new tool called “POLITRANI” allows to build realistic electronic pulses delivered by radiation detectors, and thus to study PSD sensitivity to various factors such as plastic shape, size, coating, scintillation decay time for neutrons vs. gamma rays, and radiation scattering in the detector. Parameters of the FPGA-based electronics can also be investigated, such as sampling frequency, trigger, and length of the integration gate.

Large plastic scintillator panels with WLS fiber readout: Optimization of components

Results are presented on R&D efforts to design and build large size veto panels, optimized for underground low background experiments, in the most efficient and economical way using commercially available components. A variety of plastic scintillators, photomultiplier tubes, wavelength shifting fibers, and light reflector combinations were tested. Results of these studies and performance of a 2.2m long panel are presented.

A Photo-Multiplier Testing Device

The paper reports the design of a photo-multiplier testing device constructed to assess long term stability and suitability of 53 AVP photo-multipliers for use with singles counting, scintillation counter arrays and large plastic scintillation counter arrays (in coincidence) in high energy physics experiments (with muons). The device can be used for routine checking of such phototubes in laboratory.

The design of a low activity laboratory housing a whole body counter consisting of large plastic scintillators and the work towards a flexible Monte Carlo calibration

137 Cs point source. The measured spectra were compared to Monte Carlo simulated spectra. The Monte Carlo code GATE v6.1 was used to simulate the energy deposition with the following optical transport in the scintillator material and detection of optical photons at the photocathode. MATLAB R2012a was used to calculate the multiplication in the photomultiplier tube. The results show the benefits of incorporating optical transport in the Monte Carlo simulations; the resolution in the simulated spectra changed drastically between energy deposition spectra and spectra of detected optical photons at the photocathode and; the measured spectra showed a source position dependence which was not noticed in the energy deposition spectra but first after the optical transport. A detailed description is given of the detector system and surrounding facilities because of their rather unique design.

A comparison between Monte Carlo-calculated and -measured total efficiencies and energy resolution for large plastic scintillators used in whole-body counting

The measured total efficiency for several source positions has been determined for a large, plastic scintillation detector (NE 102A, 91.5 × 76.0 × 24.5 cm(3)) used for whole-body counting gamma spectrometry. The results have been compared with Monte Carlo-calculated total efficiencies; the code used was MCNPX 2.60. For (137)Cs, there was a good agreement between the measured and calculated total efficiencies. MXNPX was also used to calculate the electron light yield for (137)Cs; for the detector material NE 102A, Birks' constant kB was found to be 9.6 mg cm(-2) MeV(-1). The effect of light losses on spectrum resolution has been investigated for (65)Zn.

Monte Carlo investigation and optimization of coincidence prompt gamma-ray neutron activation analysis

Normal Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) suffers from a large inherent noise or background. The coincidence PGNAA approach is being investigated for eliminating almost all of the interfering backgrounds and thereby significantly improving the signal-to-noise ratio (SNR). This can be done since almost all of the prompt gamma rays from elements of interest are emitted in coincidence except hydrogen. However, it has been found previously that while the use of two normal NaI detectors greatly reduces the background, the signal is also greatly reduced so that very little improvement in standard deviation is obtained. With the help of MCNP5, the general-purpose Monte Carlo N-Particle code, and CEARCPG, the specific purpose Monte Carlo code for Coincidence PGNAA, further optimization of the proposed coincidence system is being accomplished. The idea pursued here is the use of a large area plastic scintillation detector as the trigger for coincidence events together with a normal large NaI detector. In this approach the detection solid angle is increased greatly, which directly increases the probability of coincidence detection. The 2D-coincidence spectrum obtained can then be projected to the axis representing the NaI detector to overcome the drawback of low energy resolution and photopeak intensity of the plastic scintillation detector and utilize the overall higher coincidence counting rate. To reach the best coincidence detection, the placement of detectors, sample, and the moderator of the neutron source have been optimized through Monte Carlo simulation.

A large area plastic scintillator detector array for fast neutron measurements

A large area plastic scintillator detector array ( ∼ 1 × 1 m 2 ) has been set up for fast neutron spectroscopy at the BARC-TIFR Pelletron laboratory, Mumbai. The energy, time and position response has been measured for electrons using radioactive sources and for monoenergetic neutrons using the 7Li ( p , n 1 ) 7 Be * ( 0.429 MeV ) reaction at proton energies between 6.3 and 19 MeV. A Monte Carlo simulation of the energy dependent efficiency of the array for neutron detection is in agreement with the 7Li ( p , n 1 ) measurements. The array has been used to measure the neutron spectrum, in the energy range of 4–12 MeV, in the reaction C 12 + Nb 93 at E ( C 12 ) = 40 MeV . This is in reasonable agreement with a statistical model calculation.

Development of MRG10 Mobile Roadway Gamma Monitor

The MRG10 mobile roadway gamma monitor is described in this paper. This system is developed to meet requirements to survey roadways for gamma contamination in nuclear power plants and other nuclear facilities. The system consists of a four wheel electric utility vehicle, two detector modules and a MCU based controller. The detector module consists of a lead shielded large area plastic scintillator(1000×500×50 mm), a PMT and amplifier unit, a MCU based counting unit, and a semiconductor cooler. The detector module and controller unit are connected with RS-485 bus. When a survey starts, the controller unit takes control of the vehicle speed, displays the measurement data, and will switch on the semiconductor cooler when the temperature of detector module is higher than a set point.