Thin Plastic Scintillator Research Articles

Parametric optimization for estimating beta detection efficiency in thin plastic scintillation detector

A condenser air removal system plays a crucial role in radiation monitoring within nuclear power plants, specifically for detecting potential leaks of radioactive material from primary-to-secondary systems. This system assesses the leakage rate (LR) by measuring the emission of β particles from noble gases using a thin plastic scintillation (TPS) detector, which is specifically designed for counting purposes. Among the factors used in LR calculation, the detection efficiency (k) must be experimentally determined in advance. However, this is challenging because of the limitations posed by radiation safety regulations. Moreover, simulation-based calculations are difficult to achieve because only a portion of the β-ray energy is transferred in the TPS detectors, resulting in a lack of prior energy information. To overcome these challenges, this study employed a multi-objective parameter optimization technique to simultaneously calculate the parameters required for the β-ray detection response function and energy calibration equation. Subsequently, k values were calculated using the optimization results. The optimization performance was demonstrated by comparing the measured spectra of the TPS detector with the spectra obtained from the Monte Carlo N-particle simulation. Furthermore, we confirmed that the calculated k values agreed with the reference values.

Laser-plasma accelerated proton beam transport system using high-field pulsed solenoid magnet

An energetic proton beam with a high divergence cone angle of ∼10°, generated by the interaction of a 25 fs, 800 nm Ti: Sapphire laser pulse with a thin metal foil target, was transported and focused at a specified distance from the source. A pulsed high-voltage solenoid, which generates a magnetic field of 5.7 T at a current of 8 kA, was developed in-house for this purpose. The profile of the proton beam was monitored online at various positions using a combination of a fast thin plastic scintillator and a CCD camera. The effect of solenoid misalignment on the focused proton beam was also investigated experimentally. In addition, the proton beam was transported out of the vacuum chamber into the ambient air for radiography application. A proton flux of ∼2 × 108 protons (energy >4 MeV) was transported and focused at a distance of 1.27 m from the target with a transmission efficiency of 30 % in a single shot. Detailed simulations incorporating particle tracing and transfer matrix method were performed to highlight the role of beam chromaticity and the impact of spherical harmonics on the focusing characteristics of the solenoid. The simulation results qualitatively reproduce the experimental observations. The solenoid provides energy-selective proton focusing for a broad energy proton beam. The proton beam was used for the radiography of reference meshes and has the potential to be used for radiobiological irradiation studies.

Increase in the count rates of ground-based cosmic-ray detectors caused by the heliomagnetic disturbance on 5 November 2023

This letter presents a rare physical phenomenon associated with solar activity, manifesting in anomalies within neutron, electron, and gamma-ray fluxes in the atmosphere. Conventionally, the Earth's magnetic-field disturbances reduce cosmic-ray intensity reaching the surface. However, a temporary surge in cosmic-ray flux occurs intermittently known as the magnetospheric effect (ME). Our observations reveal that this effect predominantly induces a count rate increase in particle detectors positioned at middle latitudes on mountaintops. On November 5, 2023, a 2–3% increase in neutron monitors at mountain altitudes and up to 5% increase in thin plastic scintillators registering electrons and gamma rays was observed. This flux escalation coincided with a southward orientation of the interplanetary magnetic field. Importantly, we present, for the first time, the energy spectrum of the Magnetospheric Effect observed at two mountaintops: Aragats and Zugspitze. Simulations of low-energy proton interactions in the terrestrial atmosphere affirm the augmentation of low-energy cosmic rays. Protons, typically restricted by the geomagnetic cutoff, reached the Earth's atmosphere, generating detectable particle showers on the Earth's surface. To sum up, 1) we measure an increase in the count rate of magnetospheric origin using particle detectors located at mountain altitudes and middle latitudes; 2) for the first time, we measured the energy spectra of the particle fluxes during the magnetospheric effect with spectrometers located on Mount Aragats and Zugspitze; 3) particle flux enhancement coincides with the depletion of the horizontal component of the geomagnetic field; 4) we explain why the magnetospheric effect was observed at mountain altitudes and not at sea level.

Conceptual design and simulations for the Detector Array for Energy Measurements Of Neutrons (DAEMON): Scintillator geometry for the full array

The use of large-scale neutron detector arrays with high energy resolution, especially those that can be coupled with highly efficient γ-ray spectrometers, is imperative in order to increase the understanding of the decay of β-delayed neutron emitters. The DAEMON array, currently being designed for the GRIFFIN decay station at TRIUMF, will improve the precision on the neutron kinetic energy measurement enhancing the current capabilities to study neutron rich nuclei at TRIUMF. The innovative design for DAEMON uses thin fast plastic scintillators placed directly on the front of the DESCANT liquid scintillator cans. To investigate the viability of this augmentation, Geant4 was used to simulate and optimize the experimental design. Two configurations were considered; a geometry using vertical bars spanning the inner arc of DESCANT, and individual tiles matching the geometry of the DESCANT scintillator cans. The latter was found to be the most optimum design, enabling the project to enter a prototype testing phase.

Measurement of the detection efficiency of a 100 µm thin plastic scintillator for muons with p = 28 MeV/c

In the muEDM experiment, a gate detector is used to trigger the storage mechanism when a muon enters the experimental apparatus. This detector should operate at full efficiency and low thermal noise contamination. Furthermore, it should have a very low material budget to minimize the deflection of the muon trajectory by multiple coulomb scattering. A first prototype of this detector is a 100 µm thick plastic scintillator, connected to eight silicon photomultipliers reading out the scintillation light. In a dedicated beamtime at the πE1 beamline at the Paul Scherrer Institute, we measured the detection efficiency of this scintillator with 28 MeV/c muons.

A diamond double-sided strip detector for alpha-tagging in associated particle imaging

- In associated particle imaging, neutrons from deuterium-tritium fusion are used to interrogate objects of interest. The associated particle imaging technique utilizes an alpha-tagging sensor in the neutron generator to detect the alpha particle that is emitted antiparallel to the neutron, providing neutron birth time and direction. This technique of neutron imaging and induced fission imaging can provide higher contrast image reconstructions and better estimations of fissile material mass than passive measurement techniques. The performance goals of an alpha-tagging sensor in associated particle imaging are a 700-ps timing resolution, a 0.5 mm spatial resolution, high level of radiation hardness, low sensitivity to X-rays, high signal-to-noise ratio, and survivability in the high temperature bake out of the neutron generator. Currently employed YAP scintillators are overwhelmed by the intense X-ray field in the neutron generator, requiring a new alpha tagging sensor design to be developed. We have developed and tested a diamond double-sided strip detector as a proposed sensor for associated particle imaging. Diamond is radiation hard, has a low sensitivity to X-rays, fast timing capabilities, high signal-to-noise ratio, and can withstand the temperatures of bake-out. The spatial resolution can be accomplished with a charge division readout and double-sided strip design. We measured the timing resolution of a single crystal chemical vapor deposition (CVD) diamond with a Cividec C6 charge amplifier readout by measuring the time-of-flight of 241Am alpha particles between a thin plastic scintillator and the diamond. We also fabricated a polycrystalline CVD diamond double-sided strip detector with charge division readout to test the spatial resolution of the design. We found that the detector met both the 700-ps timing resolution and the 0.5 mm spatial resolution goals (both reported as FWHM resolution).

Studies of efficiency of the Kratta detectors in the deuteron breakup experiment.

An experiment focused on studies of relativistic effects in the proton-deuteron breakup reaction has been performed at Cyclotron Center Bronowice in Kraków, Poland with the use of the Kratta detectors. Thirty Kratta modules have been arranged in a planar symmetric around beam axis configuration at few selected polar angles at which significant relativistic effects have been predicted. In front of each Kratta module 4 thin plastic scintillators were installed acting as a fast timing detectors to improve a trigger system. Determination of acceptance and efficiency of the detectors is discussed.

Development of a PMT base used for the new charged veto detector in the J-PARC KOTO experiment

The KOTO experiment searches for the rare decay at J-PARC. The largest background in the data collected in 2016-2018 was caused by decays of K ±. To detect K ±, we are developing an in-beam charged veto detector to be installed upstream of the KOTO detector. It uses a 0.2mm-thick thin plastic scintillator. The escaped light is reflected and collected by a 12-μm-thick aluminized mylar, and read out by an array of PMTs placed outside the beam. We newly developed PMT bases to be used for this detector. Based on an electron beam test, we expect the K ± background to be reduced by more than a factor 100. We plan to install this detector in the KOTO beam line, in December 2022.

FABRICATION OF PLASTIC SCINTILLATOR USING POLYSTYRENE MATRIX BASED

Experiments on making a plastic scintillator with polystyrene as a base material mixed with fluorescent compounds (primary and secondary dopants) have been performed. Primary dopants (PTP) used to produce emission at wavelengths of visible light and secondary dopants (POPOP) to shift the visible wavelengths to wavelengths that could be detected by Photomultiplier Tube (PMT) ) were carried out. Experiments were performed on the melting points condition of these materials, which had previously been subjected to a thermo-mechanical analysis using a Thermogravimetric Analysis-Differential Scanning Calorimetry (TGA-DSC) machine, where the melting point was in the range of 200-240°C. Furthermore, the fabrication was carried out using the extrusion technique, where polystyrene pellets mixed with PTP (1.5% by weight) and POPOP (0.05% by weight) were fed into an extrusion machine which has four hot areas to obtain a thin plate plastic scintillator. The plates were then analyzed with a UV-Vis Spectrophotometer to determine the absorption spectrum and Fluorescence Spectrophotometer to determine the emission spectrum. From the results of the analysis, it was found that the samples that went through scintillation pellets and without the addition of antioxidants had absorption spectrum data of 330 nm and emission spectrum of 421 nm. These values are in accordance with the characteristics of plastic scintillators on the market.

Comparative Study between Fabricated Plastic Scintillator and Existing Product for Gamma Detection

A plastic scintillator with an injection method has been developed for a gamma radiation detector. The scintillator was made from the main matrix of polystyrene (PS) pellets with the addition of primary dopant PTP (para-terphenyl) 1.5% wt and secondary dopant as wavelength shifter (WLS) POPOP (1,4-bis [2- (phenyloxazolyl) )] - benzene) 0.01 - 0.05% wt. The mixture of pellets and dopants was fed to the extruder machine to obtain scintillating pellets and then referred to the machine to obtain a 3 mm thin plate plastic scintillator. The evaluation of absorption using a spectrophotometer UV-Vis showed that PS absorbs photons at a wavelength of 310 – 340 nm and PS containing POPOP produces a maximum emission at a wavelength of 421 nm. The evaluation of cesium 137 (137Cs) and cobalt 60 (60Co) gamma spectrum using the photomultiplier tube (PMT) Hamamatsu R878 showed the results of Compton spectrum characters with a gross counting maximum of 0.78 and 0.89, respectively, compared to the commercial plastic scintillator. The results of this study are expected to be usefully utilized in the development of a large-volume plastic scintillator for the radiation portal monitor (RPM).

PLASTIC SCINTILLATOR BASED 2D DETECTOR FOR PHOTON RADIOTHERAPY: PRELIMINARY RESULTS

A proof-of-concept study of a new detector based on a thin plastic scintillator monitored by a Charge-Coupled Device (CCD) camera designed for monitoring and characterisation of Linac photon beams is presented. The response of the detector is compared with radiochromic film using 6 and 18 MV radiotherapeutic beams. We have observed: (i) all instruments survived the secondary radiation fields during Linac operation, (ii) it was possible to process the measured data using statistical techniques and (iii) the processed data from the CCD camera qualitatively correspond to film dosimetry results. A statistical technique based on the selection of minimal values provides the clearest results. Quantitatively, CCD and film results can only be compared as 6 to 18 MV response rates. We have observed that the rates from the CCD data are systematically higher than the rates from film dosimetry. Differences are not too high, namely 1.9-2.4 times the combined standard deviation.

Development of a neutron beam monitor with a thin plastic scintillator for nuclear data measurement using spallation neutron source

ABSTRACT A neutron monitoring detection system was developed for neutron capture cross-section measurement using a spallation neutron source. A combination of a plastic scintillator and a thin 6 LiF foil was adopted for the detector. The detector system was tested to study the feasibility of the system. Neutron irradiation experiments were conducted with the Accurate Neutron-Nucleus Reaction Measurement Instrument in the Materials and Life Science facility of the Japan Proton Accelerator Research Complex. A neutron time-of-flight spectrum was successfully measured without significant count loss or detector paralysis.

β - and γ -spectroscopy study of Pd119 and Ag119

Neutron-rich $^{119}\mathrm{Pd}$ nuclei were produced in fission of natural uranium, induced by 25-MeV protons. Fission fragments swiftly extracted with the Ion Guide Isotope Separation On-Line method were mass separated using a dipole magnet and a Penning trap, providing mono-isotopic samples of $^{119}\mathrm{Pd}$. Their ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay was measured with $\ensuremath{\gamma}\ensuremath{\gamma}$- and $\ensuremath{\beta}\ensuremath{\gamma}$-spectroscopy methods using low-energy germanium detectors and a thin plastic scintillator. Two distinct nuclear-level structures were observed in $^{119}\mathrm{Ag}$, based on the $1/{2}^{\ensuremath{-}}$ and $7/{2}^{+}$ isomers reported previously. The ${\ensuremath{\beta}}^{\ensuremath{-}}$-decay work was complemented by a prompt-$\ensuremath{\gamma}$ study of levels in $^{119}\mathrm{Ag}$ populated in spontaneous fission of $^{252}\mathrm{Cf}$, performed using the Gammasphere array of germanium detectors. Contrary to previous suggestions, our data show that the $1/{2}^{\ensuremath{-}}$ isomer is located below the $7/{2}^{+}$ isomer and is proposed as a new ground state of $^{119}\mathrm{Ag}$ with the $7/{2}^{+}$ isomer excitation energy determined to be 33.4 keV. Our data indicate that there are two $\ensuremath{\beta}$ unstable isomers in $^{119}\mathrm{Pd}$, a proposed ground state of $^{119}\mathrm{Pd}$ with tentative spin $1/{2}^{+}$ or $3/{2}^{+}$ and a half-life of 0.88 s and the other one about 350 keV above, having spin ($11/{2}^{\ensuremath{-}}$) and a half-life of 0.85 s. The higher-energy isomer probably decays to the $1/{2}^{+}$ or $3/{2}^{+}$ ground state via a $\ensuremath{\gamma}$ cascade comprising 18.7-219.8-$\mathrm{X}$-keV transitions. The unobserved isomeric transition with energy $X\ensuremath{\approx}100$ keV probably has an $E3$ multipolarity. Its hindrance factor is significantly lower than for analogous $E3$ isomeric transitions in lighter Pd isotopes, suggesting an oblate deformation of levels in $^{119}\mathrm{Pd}$. Oblate configurations in $^{119}\mathrm{Ag}$ are discussed also.

Effect of high Z materials loading in the performance of polystyrene-based thin-film plastic scintillators

The paper describes the effect of high effective atomic number (Zeff) materials loading in polystyrene based thin-film Plastic Scintillators (PS). Thin plastic scintillator sheets have been loaded with high Z materials such as BaFBr:Eu, Gd2O2S:Tb, Gd2O3, BaF2, CeO2 and Bi2O3. Polystyrene based PS sheets of 250 ± 50 μm thickness have been prepared by dissolving predetermined quantities of polystyrene, 2,5-Diphenyloxazole (PPO) and 1,4-bis(5-phenyl-2-oxazolyl) benzene (POPOP) in the p-xylene solvent. High Zeff material powders of 23μm size are mixed in the plastic scintillator solution and coated over the cellulose acetate-based transparency sheets. The dried films are peeled off, and their photoluminescence, radioluminescence, pulse height spectrum and response to alpha, beta, gamma and neutron radiations are studied by adopting suitable methods. The high Zeff materials for loading in PS are selected based on their physical properties like refractive index, bandgap, Zeff, Photoluminescence (PL) properties. While the composite scintillator loaded with 14.3 wt% of BaFBr:Eu2+ showed significant increase compare to other high Z materials. The loading concentration has been optimized as 14.3 wt% from the BaFBr:Eu2+ studies. Most of the composite scintillators showed improvement in radioluminescence and pulse height spectra for different radiations.

Charge identification of nuclear fragments with the FOOT Time-Of-Flight system

FOOT (FragmentatiOn Of Target) is an applied nuclear physics experiment conceived to conduct high-precision cross section measurements of nuclear fragmentation processes relevant for particle therapy and radiation protection in space. These measurements are important to estimate the physical and biological effects of nuclear fragments, which are produced when energetic particle beams penetrate human tissue.A component of the FOOT experiment is the ΔE-TOF system. It is designed to measure energy loss and time-of-flight of nuclear fragments produced in particle collisions in thin targets in order to extract their charge and velocity. The ΔE-TOF system is composed of a start counter, providing the start time for the time-of-flight, and a 40 × 40 cm2 wall of thin plastic scintillator bars, providing the arrival time and energy loss of the fragments passing through the detector. Particle charge discrimination can be achieved by correlating the energy loss in the scintillator bars with the measured time-of-flight.Recently, we have built a full-size ΔE-TOF detector. In this work, we describe the energy and time-of-flight calibration procedure and assess the performance of this system. We use data acquired during beam tests at CNAO with proton and 12C beams and at GSI with 16O beams in the energy range relevant for particle therapy, i.e., from 60 to 400 MeV/u. For heavy fragments (C and O), we obtain energy and time resolutions ranging from 4.0 to 5.2% and from 54 to 76 ps, respectively. The procedure is also applied to a fragmentation measurement of a 400 MeV/u 16O beam on a 5 mm carbon target, showing that the system is able to discriminate the charges of impinging fragments.

Evaluation of an ultra-thin plastic scintillator to detect alpha and beta particle contamination

To date, alpha and high beta particle emitters have been detected in the reactor buildings of the Fukushima Daiichi Nuclear Power Station (FDNPS). Since the beta radiation levels in the FDNPS buildings are extremely high, a commercial beta survey meter, such as a Geiger–Muller (GM) counter, would no longer have the ability to measure the beta contamination levels. In order to solve this issue, we utilized ultra -thin plastic scintillators to increase the detection rate of alpha and beta contamination. In this study, ultra-thin plastic scintillators with varied thicknesses of 7, 22, 24, 31, 39, and 55μm were prepared. To test their sensitivity, each scintillator was optically coupled to a glass plate and a 2-in square position-sensitive photomultiplier tube, and exposed to either an alpha, beta, or gamma source. Results from alpha spectrometry show that only the 55μm-thick plastic scintillator fully absorbed the alpha particles (5.5 MeV) with a 16.7% Full Width at Half Maximum. For alpha imaging under a high beta background, the 7μm-thick plastic scintillator was found to be the best choice, with an alpha to beta ratio of 652. This plastic scintillator also had the lowest sensitivity to beta particles, measuring only 41.74 ± 0.93 cps when exposed to a 1MBq 90Sr/90Y source in contact. It would therefore be possible to use the 7μm-thick plastic scintillator, to directly measure the surface contamination levels at the FDNPS site in real-time, where previous methods have fallen short Thus, the developed detector would be a useful tool for the detection of alpha and beta contamination in the FDNPS.

Experimental exploration of a mixed helium/carbon beam for online treatment monitoring in carbon ion beam therapy

Recently, it has been proposed that a mixed helium/carbon beam could be used for online monitoring in carbon ion beam therapy. Fully stripped, the two ion species exhibit approximately the same mass/charge ratio and hence could potentially be accelerated simultaneously in a synchrotron to the same energy per nucleon. At the same energy per nucleon, helium ions have about three times the range of carbon ions, which could allow for simultaneous use of the carbon ion beam for treatment and the helium ion beam for imaging. In this work, measurements and simulations of PMMA phantoms as well as anthropomorphic phantoms irradiated sequentially with a helium ion and a carbon ion beam at equal energy per nucleon are presented. The range of the primary helium ion beam and the fragment tail of the carbon ion beam exiting the phantoms were detected using a novel range telescope made of thin plastic scintillator sheets read out by a flat-panel CMOS sensor. A 10:1 carbon to helium mixing ratio is used, generating a helium signal well above the carbon fragment background while adding little to the dose delivered to the patient. The range modulation of a narrow air gap of 1 mm thickness in the PMMA phantom that affects less than a quarter of the particles in a pencil beam were detected, demonstrating the achievable relative sensitivity of the presented method. Using two anthropomorphic pelvis phantoms it is shown that small rotations of the phantom as well as simulated bowel gas movements cause detectable changes in the helium/carbon beam exiting the phantom. The future prospects and limitations of the helium/carbon mixing as well as its technical feasibility are discussed.

Optimisation and performance test of fibre-based large-area surface contamination monitor

A portable large-area radiological contamination surface monitor of advanced design is now under research and development. This monitor, whose detection area is 1200 cm2, is mainly applied for hot-spot searching for nuclear emergency response or facility decommissioning. It consists of a thin plastic scintillation tile and wavelength-shifting fibres coupled to a photomultiplier tube. To improve the detector performance, it is necessary to calculate the collection efficiency of optical photons from the scintillator. The optical photon transportation processes in the plastic scintillator and wavelength-shifting fibres are simulated using the Monte Carlo code Geant4. For further optimisation, experiments with different fibre arrangements are conducted to verify uniformity. In conclusion, an arrangement of ten neighbouring wavelength-shifting fibres, with alternating fibres connected on opposite sides of a organic support for the plastic scintillator presents a better performance for detection.

FOOT: a new experiment to measure nuclear fragmentation at intermediate energies

Abstract Particle therapy uses proton or 12 C beams to treat deep-seated solid tumors. Due to the advantageous characteristics of charged particles energy deposition in matter, the maximum of the dose is released to the tumor at the end of the beam range, in the Bragg peak region. However, the beam nuclear interactions with the patient tissues induces fragmentation both of projectile and target nuclei and needs to be carefully taken into account. In proton treatments, the target fragmentation produces low energy, short range fragments along all the beam range, that may deposit a non negligible dose in the entry channel. In 12 C treatments the main concern is represented by long range fragments due to projectile fragmentation that release their dose in the healthy tissues surrounding the tumor. The FOOT experiment (FragmentatiOn Of Target) of INFN is designed to study these processes, in order to improve the nuclear interactions description in next generation Treatment Planning Systems software, and hence the treatment plans quality. Target ( 16 O and 12 C nuclei) fragmentation induced by 150-250 MeV proton beams will be studied via an inverse kinematic approach, where 16 O and 12 C therapeutic beams collide on graphite and hydrocarbon targets to provide the nuclear fragmentation cross section on hydrogen. The projectile fragmentation of these beams will be explored as well. The FOOT detector includes a magnetic spectrometer for the fragments momentum measurement, a thin plastic scintillator for ΔE and time of flight measurements and a scintillating crystal calorimeter to measure the fragments kinetic energy. These measurements will be combined in order to make an accurate fragment charge and isotopic identification.

A β-delayed neutron detection system working with the continuous beam mode

Abstract To study the β -delayed neutron decay of nuclei far from β stability line, a new β -delayed neutron detection system working with the continuous beam mode has been built at Peking University and tested with radioactive ion beams . To get fast timing signal for neutron Time-of-Flight (ToF) measurement and good spatial correlation between the implanted particles and the subsequent β particles, a double-sided silicon detector is sandwiched between two thin plastic scintillators , which constitute the implantation and β detection array. According to the test measurements with radioactive ion beams, this detection system has a high β coincident detection efficiency of 30 . 7 ( 5 ) % with much less disturbance from other unstable nuclei and the random background. After the time-walk correction and the flight path calibration, good energy resolution based on neutron ToF measurement can be obtained. The properties of this detection system make the study of β -delayed neutron decay of nuclei with very low beam intensity feasible.