Fast Scintillation Detectors Research Articles

Data collecting and treatment control system in the «Alpha-Electron» space experiment on board the International Space Station

The fast multilayer scintillation detector of the new telescope-spectrometer for the ALFA-ELECTRON space experiment is in ground testing mode now. Modules of data control system for spectrometer are discussed. The structure of the main data format and functional blocks for data treatment are presented. The device will planned to install on the outer surface of the Russian Segment (RS) of the International Space Station (ISS) in 2018.

Digital Signal Processing for SiPM Timing Resolution

Digital signal processing (DSP) is an emerging trend in experimental studies and applications of various detectors including SiPMs. In particular, the DSP is recognized as a promising approach to improve coincidence timing resolution (CTR) of fast SiPM-based scintillation detectors. Single photon timing resolution (SPTR) is one of the key parameters affecting CTR, especially important in a case when CTR is approaching to its ultimate limits as, for example, highly demanded in Time-of-Flight PET. To study SiPM timing resolution, we developed a special DSP software and applied it to both SPTR and CTR measurements. These measurements were carried out using 3x3 mm2 KETEK SiPM samples of timing optimized and standard designs with 405 nm picosecond laser for SPTR and with 3x3x5 mm3 LYSO crystals and 511 keV Na-22 source for CRT. Results of the study are useful for further improvements of DSP algorithms and SiPM designs for fast timing.

A Noise Spectroscopy Detector Array for Non-Intrusive Cargo Inspection

Noise Spectroscopy is a statistical technique to extract spectral information from x rays transmitted through cargo and is especially effective when used with fast scintillation detectors and waveform digitization electronics to measure both the waveform mean and its fluctuations during each x-ray pulse. Previous work established feasibility in experiments using LYSO crystals using high-speed electronics in a laboratory setting. Here we describe the results of experiments performed on a larger prototype of 80 LYSO detectors, covering a length of about 1 meter, inserted into a radiography test facility. Calibration data was obtained, and various cargoes with hidden objects were imaged using the system. The analysis of this data provides proof that a practical implementation of Noise Spectroscopy in a cargo inspection system is feasible and also effective in detecting small high-Z objects in realistic cargoes.

Evolution of collectivity near mid-shell from excited-state lifetime measurements in rare earth nuclei

The B(E2) excitation strength of the first excited 2(+) state in even-even nuclei should directly correlate with the size of the valence space and maximize at mid-shell. A previously found saturation of B(E2) strengths in well-deformed rotors at mid-shell is tested through high-precision measurements of the lifetimes of the lowest-lying 2(+) states of the Hf-168 and W-174 rare earth isotopes. Measurements were performed using fast LaBr3 scintillation detectors. Combined with the recently remeasured B(E2; 2(1)(+) -> 0(1)(+)) values for Hf and W isotopes the new data remove discrepancies observed in the differentials of B(E2) values for these isotopes.

Designing a new type of neutron detector for neutron and gamma-ray discrimination via GEANT4

Design of a new type of neutron detector, consisting of a fast neutron converter, plastic scintillator, and Cherenkov detector, to discriminate 14-MeV fast neutrons and gamma rays in a pulsed n–γ mixed field and monitor their neutron fluxes is reported in this study. Both neutrons and gamma rays can produce fluorescence in the scintillator when they are incident on the detector. However, only the secondary charged particles of the gamma rays can produce Cherenkov light in the Cherenkov detector. The neutron and gamma-ray fluxes can be calculated by measuring the fluorescence and Cherenkov light. The GEANT4 Monte Carlo simulation toolkit is used to simulate the whole process occurring in the detector, whose optimum parameters are known. Analysis of the simulation results leads to a calculation method of neutron flux. This method is verified by calculating the neutron fluxes using pulsed n–γ mixed fields with different n/γ ratios, and the results show that the relative errors of all calculations are <5%.

Measurement of the Fast Neutron Response for &lt;formula&gt; &lt;tex&gt;$^4 {\rm He}$&lt;/tex&gt; &lt;/formula&gt; Scintillation Detectors Using a Coincidence Scattering Method

Time-of-flight (TOF) and coincident scattering measurements were conducted to measure the light response of a pressurized <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> He fast neutron scintillation detector as a function of deposited energy up to 5 MeV. The energy deposited in the detector by a neutron was measured by its angle of scatter and compared to the resulting light output. Whereas previous research has exclusively focussed on the energy information contained in the slow component, this work demonstrates that the fast component is also sensitive to neutron energy, and the entire scintillation signal can therefore be used. The gamma rejection capability of the detector was also measured for a variety of gamma sources. The detector demonstrated a inherent gamma rejection rate of 97.31%, which was increased to 99.89% after the application of pulse shape discrimination (PSD) algorithms. The characterization of gamma rejection and light response parameters will enable implementation of these detectors for neutron spectroscopy in mixed radiation fields.

The software and hardware for the ground testing of ALFA- ELECTRON space spectrometer

The complex for ground testing and space detector system calibration has been designed. The fast multilayer scintillation detector of the new telescope-spectrometer for the ALFA-ELECTRON space experiment is in ground testing mode now. The device will planned to install on the outer surface of the Russian Segment of the International Space Station. The basic scheme for the detector amplitude parameters measurement by use of specially designed hardware and software are described and the first prototype testing results are demonstrated.

Investigation of the dynamic range of calorimeter scintillation detector for space gamma-ray telescope

An arrangement of the GAMMA-400 space gamma-ray telescope that currently is under the ground testing, suggests implementation of fast two-layer calorimeter scintillation detector system S3 with large dynamic range for electromagnetic showers detection in the main operation mode of the device. The S3 constructive features are demonstrated. The experimental method and basic diagram of the ground prototype dynamic range investigation are described.

Neutron response function characterization of 4He scintillation detectors

Time-of-flight measurements were conducted to characterize the neutron energy response of pressurized 4He fast neutron scintillation detectors for the first time, using the Van de Graaff generator at Ohio University. The time-of-flight spectra and pulse height distributions were measured. This data was used to determine the light output response function, which was found to be linear at energies below 3.5MeV. The intrinsic efficiency of the detector as a function of incident energy was also calculated: the average efficiency up to 10MeV was 3.1%, with a maximum efficiency of 6.6% at 1.05MeV. These results will enable development of neutron spectrum unfolding algorithms for neutron spectroscopy applications with these detectors.

ALFA-ELECTRON Experiment Onboard the International Space Station

The fast multilayered scintillation detector (MSD) of the new telescope-spectrometer for the space experiment ALFA-ELECTRON planned to work on the outer surface of the Russian Segment (RS) of the International Space Station (ISS) is presented. The MSD spectrometer can measure an intensive flow (up to 10MHz or higher) of electrons with energies of from 2 up to 20 MeV and their short-term variations (up to 1ms). An apparatus physical characteristics and operation of the MSD are described. The results of the detector investigations in the mode of high intensities are demonstrated also.

Fission signal detection using helium-4 gas fast neutron scintillation detectors

We demonstrate the unambiguous detection of the fission neutron signal produced in natural uranium during active neutron interrogation using a deuterium-deuterium fusion neutron generator and a high pressure 4He gas fast neutron scintillation detector. The energy deposition by individual neutrons is quantified, and energy discrimination is used to differentiate the induced fission neutrons from the mono-energetic interrogation neutrons. The detector can discriminate between different incident neutron energies using pulse height discrimination of the slow scintillation component of the elastic scattering interaction between a neutron and the 4He atom. Energy histograms resulting from this data show the buildup of a detected fission neutron signal at higher energies. The detector is shown here to detect a unique fission neutron signal from a natural uranium sample during active interrogation with a (d, d) neutron generator. This signal path has a direct application to the detection of shielded nuclear material in cargo and air containers. It allows for continuous interrogation and detection while greatly minimizing the potential for false alarms.

Sector-shaped fast organic liquid scintillation detectors based neutron coincidence counter

A simulation based on the Monte Carlo method is described which has been performed using MCNPX 2.6.0, to model the geometry of a sector-shaped liquid scintillation detector in response to coincident neutron events. The detection of neutrons from a mixed-oxide (MOX) fuel pellet has been simulated for different thicknesses of scintillators. A layer of lead has been used to reduce the gamma-ray fluence reaching the scintillator and, the effect of lead for neutron detection has also been estimated by considering different thicknesses of lead layers.

Study of the effect of pyrex and quartz insulators on X-ray intensity in a 4 kJ plasma focus device

In this paper we study the soft X-ray (SXR) and hard X-ray (HXR) intensity produced in different insulator sleeves by a 4 kJ plasma focus device (APF) using filtered PIN-diodes and a fast scintillation detector. The experiments were performed for a great number of neon filling gas pressures at voltages of 11, 12 and 13 kV. Lengths of 40 and 50 mm look optimal to yield the most SXR intensity for the Pyrex and Quartz insulators respectively. The device appears to optimize much better for Pyrex insulator than the Quartz. For Pyrex and Quartz insulators, the lengths of 40 mm and 50 mm seem optimal to yield maximum HXR intensity, respectively.

Implementation of Noise Spectroscopy Using Biased Large-Area Photodiodes

The bremsstrahlung X-ray spectrum produced by X-ray sources used in cargo inspection systems is attenuated and modified by materials in the cargo in a Z-dependent way and then detected in a radiographic detector array. We have previously shown that it is possible to obtain spectral information indirectly by analyzing statistical fluctuations (the “noise”) in radiographic data, in a technique we call Noise Spectroscopy (NS) or Z-SCAN (Z-determination by Statistical Count-rate ANalysis). The technique is especially effective when the detector array consists of fast scintillation detectors and waveform digitization electronics, measuring both the waveform mean and variance during each X-ray pulse. This previous work, however, used photo-multiplier tubes, which are not especially suitable for a practical implementation. Here we describe the results of R&D performed to produce an effective version of the technique that lends itself to implementation in a single detector array that can be used both for radiography and for NS, with the same imaging spatial resolution as in conventional systems. We characterize the performance of biased photodiodes in combination with trans-impedance preamplifiers, read out with commercially available waveform digitizers. We report on experiments performed with a 16-channel detector array in a test beam, with test samples of different atomic number Z. We also report the implementation of an NS algorithm in an FPGA. In combination, we show that a practical implementation of Noise Spectroscopy in cargo inspection systems is feasible.

Investigation of three-dimensional localisation of radioactive sources using a fast organic liquid scintillator detector

In this paper we discuss the possibility of locating radioactive sources in space using a scanning-based method, relative to the three-dimensional location of the detector. The scanning system comprises an organic liquid scintillator detector, a tungsten collimator and an adjustable equatorial mount. The detector output is connected to a bespoke fast digitiser (Hybrid Instruments Ltd., UK) which streams digital samples to a personal computer. A radioactive source has been attached to a vertical wall and the data have been collected in two stages. In the first case, the scanning system was placed a couple of metres away from the wall and in the second case it moved few centimetres from the previous location, parallel to the wall. In each case data were collected from a grid of measurement points (set of azimuth angles for set of elevation angles) which covered the source on the wall. The discrimination of fast neutrons and gamma rays, detected by the organic liquid scintillator detector, is carried out on the basis of pulse gradient analysis. Images are then produced in terms of the angular distribution of events for total counts, gamma rays and neutrons for both cases. The three-dimensional location of the neutron source can be obtained by considering the relative separation of the centres of the corresponding images of angular distribution of events. The measurements have been made at the National Physical Laboratory, Teddington, Middlesex, UK.

SIDRA instrument for measurements of particle fluxes at satellite altitudes. Laboratory prototype

The design concept and first set of results are presented for electronic modules of a laboratory prototype of the small-size satellite instrument SIDRA intended for measurements of charged particle fluxes in outer space. The working prototype consists of a detector assembly based on high-purity silicon and fast scintillation detectors, modules of analogue and digital processing, and a secondary power supply module. The first results are discussed of a Monte-Carlo simulation of the instrument with the use of the GEANT4 toolkit and of measurements of the main parameters of charge-sensitive pre-amplifiers, shapers, and peak detectors. Results of calibration measurements with the use of radioactive sources and beams of accelerated charged particles are presented.

Detection of MeV particles from ultra-dense protium p(−1): Laser-initiated self-compression from p(1)

Ultra-dense protium p(−1) is a condensed phase of hydrogen which has a shortest H–H bond distance of 3.7pm. It is not identical in form to ultra-dense deuterium named d(−1) or D(−1). The MeV particles released from p(−1) under impact of a ns pulsed laser are studied with time-of-flight energy measurements using a fast plastic scintillator detector. A movable metal plate or foil is used to distinguish fast particles from energetic photons. The fast particles, mainly protons, are delayed by transmission through the plate or foil from the MeV range to 200–700keV. Fast protons are ejected only after a 5–10s induction period after the laser start, and only at high pulse rates, approaching 10Hz. Particles with keV energies are ejected as late as several μs after the laser pulse. Nuclear processes are excluded in the p(−1) case and the laser intensity is quite low. It is concluded that laser-triggered self-compression from p(1) to p(−1) gives the high-energy particles.

Fast scintillation detectors for high-energy X-ray region

We have developed fast scintillation detectors for nuclear resonant scattering experiments using synchrotron radiation and a nuclear excited level existing in >30 keV. A fast x-ray detector using an organic-inorganic perovskite scintillator of phenethylamine lead bromide (PhE-PbBr4) had a dominant light emission with a fast decay time of 9.9 ns. An x-ray detector equipped with a 0.9-mm-thick PhE-PbBr4 crystal (size: ∼8 × 7 mm2) was used to detect nuclear resonant scattering in 61Ni (the first excited level: 67.41 keV; half-life: 5.3 ns). We could successfully record the decaying gamma rays emitted from 61Ni with a relatively high detection efficiency of 24%. A lead-doped plastic scintillator (NE142, Pb ∼5 wt% doped) had been known to have a faster decay time of 1.7 ns. Following a test of a single NE142 detector, a four-channel NE142 detector was fabricated and successfully applied to the synchrotron-radiation based Mossbauer spectroscopy experiment on 61Ni.

Organic scintillators response function modeling for Monte Carlo simulation of Time-of-Flight measurements

In neutron Time-of-Flight (TOF) measurements performed with fast organic scintillation detectors, both pulse arrival time and amplitude are relevant. Monte Carlo simulation can be used to calculate the time–energy dependant neutron flux at the detector position. To convert the flux into a pulse height spectrum, one must calculate the detector response function for mono-energetic neutrons. MCNP can be used to design TOF systems, but standard MCNP versions cannot reliably calculate the energy deposited by fast neutrons in the detector since multiple scattering effects must be taken into account in an analog way, the individual recoil particles energy deposit being summed with the appropriate scintillation efficiency. In this paper, the energy response function of 2″×2″ and 5″×5″ liquid scintillation BC-501A (Bicron) detectors to fast neutrons ranging from 20keV to 5.0MeV is computed with GEANT4 to be coupled with MCNPX through the “MCNP Output Data Analysis” software developed under ROOT (Carasco, 2010).

X-Ray Measurement and Enhancement of SBUPF1 Plasma Focus Device in Different Ar Pressures and Operating Voltages

In this paper, best condition of filling gas pressure and operating voltage for SBUPF1 plasma focus device to have maximum intensity of hard and soft X-ray emission has been reported. For time resolved X-ray detection, PIN detector and fast plastic Scintillator detector with appropriate filters have been used and for time integrated X-ray emission measurement, radiography films with appropriate filter masks have been used. Rogowski coil has been used for pinch detection. The highest hard X-ray emission has been observed at the pressure of 0.45 mbar of Argon and discharge voltage about 23.5 kV. The highest Soft X-ray emission has been observed at the pressure of 0.35 mbar of Argon and discharge voltage about 23.5 kV. For enhancement of hard X-ray emission intensity, lead disk was placed in copper anode tip and measurements were repeated. Results have shown that hard X-ray emission has been enhanced about 23% and soft X-ray emission has been enhanced about 33% with inserting a high atomic number metal disk like lead. Results from integral X-ray measurement have shown presence of dominant peaks in ranges 13.2–15, 21–21.9 and 23.4–24.3 keV with significant spectral components in the range of 0–50 keV. Pinch size has measured with pin hole camera and it is about 0.6 mm × 2.12 mm. Captured images with SBUPF1 have confirmed that it is a suitable source for introspective imaging with capability of showing very fine details.