Pulse Shape Discrimination Circuit Research Articles

Analog Pulse Shape Discrimination Circuit for High Event Rates and Fast Scintillators with a Dynamic Deadtime

Analog Pulse Shape Discrimination Circuit for High Event Rates and Fast Scintillators with a Dynamic Deadtime

N/[formula omitted] discrimination of SiPM array-based CLYC detector

Cs2LiYCl6:Ce3+ (CLYC) is one of the most ideal scintillators for n/γ detection. Compact CLYC detectors with SiPM array readout have wide-spreading interests recently. In this study, we evaluated the pulse shape discrimination (PSD) of a 2-inch CLYC crystal coupled with SiPM array and digitized by a dedicated PSD circuit board. Energy resolution and figure of merit (FOM) were obtained and compared in different detector configurations also with PMT and commercial waveform digitizing circuit. The results show that the SiPM array-based CLYC detector combined with the dedicated PSD circuit has a good performance of n/γ discrimination.

Liquid scintillators and composites in fast neutron detection

Helium-3 world crisis requires a development of new methods of neutron detection to replace commonly used 3He proportional counters. One of the option is application of liquid scintillators widely used in detection of fast neutrons, mostly in physics experiments, especially in applications where large volumes are required. Moreover, recently studied 10B loaded liquid scintillators cover detection of neutrons down to thermal energy. The several years' studies of liquid scintillators in our laboratory, brought us a knowledge about their efficiency to neutron detection, gamma sensitivity, etc. We have also tested composite scintillators, which are an alternative to organic single crystals, used in the 70's last century.In the report, we will present the results of the study of several liquid scintillators, also 10B loaded, as well as high flashpoint ones. We also show the neutron detection properties of some samples of composite scintillators. Composites are based on small grains of p-terphenyl or stilbene, introduced into a polymer matrix, which acts as a diffuser. The composite is encapsulated in a housing made of organic glass. P-terphenyl and stilbene are organic scintillators, which were commonly used in the seventies last century. They are characterized by good neutron/gamma discrimination properties. The present studies covers neutron/gamma discrimination by the zero-crossing method, a comparison of detection efficiency of liquid scintillators to 3He detectors and methods to reduce their gamma-ray sensitivity. In conclusion, a detection system, based on several small liquid cells of 2′′ × 2′′, is preferred, with pulse shape discrimination circuit equipped with the pile-up rejection circuit (PUR), as well as lead and tin shielding.

Fast collimated neutron flux measurement using stilbene scintillator and flashy analog-to-digital converter in JT-60U

A line-integrated neutron emission profile is routinely measured using the radial neutron collimator system in JT-60U tokamak. Stilbene neuron detectors (SNDs), which combine a stilbene organic crystal scintillation detector (SD) with an analog neutron-gamma pulse shape discrimination (PSD) circuit, have been used to measure collimated neutron flux. Although the SND has many advantages as a neutron detector, the maximum count rate is limited up to ∼1×105counts∕s due to the analog PSD circuit. To overcome this issue, a digital signal processing system (DSPS) using a flash analog-to-digital converter (Acqiris DC252, 8GHz, 10bits) has been developed at Cyclotron and Radioisotope Center in Tohoku University. In this system anode signals from photomultiplier of the SD are directory stored and digitized. Then, the PSD between neutrons and gamma rays is performed using software. The DSPS has been installed in the vertical neutron collimator system in JT-60U and applied to deuterium experiments. It is confirmed that the PSD is sufficiently performed and collimated neutron flux is successfully measured with count rate up to ∼5×105counts∕s without the effect of pileup of detected pulses. The performance of the DSPS as a neutron detector, which supersedes the SND, is demonstrated.

First measurement of neutron emission profile on JT-60U using Stilbene neutron detector with neutron-gamma discrimination

This article describes a diagnostic for measuring neutron emission profile in JT-60U. The Stilbene neutron detector, developed by TRINITI laboratory in Russia, has been installed on the JT-60U Tokamak to measure the neutron emission profile for the first time. The Stilbene neutron detector is a detector which combines a Stilbene crystal scintillator with a neutron-gamma pulse shape discrimination circuit, with a very compact size. Performance tests were carried out using neutron and gamma-ray source prior to installation on JT-60U. Good gamma suppression of the Stilbene neutron detector was verified. Though the neutron emission profile obtained by Stilbene neutron detectors has error of 30% in innermost channel with a calculation using measured plasma parameters, there is an agreement within 10% error in the other channels.

The gamma-ray burst monitor for the Russian Mars 1996 mission

We describe an innovative detector designed primarily for the study of cosmic gamma-ray bursts aboard interplanetary spacecraft. The experiment is a fully functional, low cost, low mass, low-power instrument, which, when combined with other similar instruments, has the capability of localizing bursts to arcminute precision. The burst monitor is based on a photomultiplier tube and a plastic/CsI(Tl) phoswich detector and records photons in the 20-150-keV energy range with time resolutions up to several milliseconds. In addition, it records photon energy spectra. Events in the plastic scintillator are distinguished by a pulse shape discrimination circuit and are used to count electrons and protons. In a planetary orbiter or fly-by mission, this capability can be used to detect the presence of a magnetosphere. We describe in detail a version of this instrument which was built for the Russian Mars 1996 mission.

Recoil selection by pulse shape discrimination in elastic recoil detection analysis with α-particles (α-ERDA)

In elastic recoil detection analysis (ERDA) with α-particles, recoils can be separated from scattered projectiles by using detectors with a thin depletion layer and a pulse shape discrimination (PSD) circuit [S.S. Klein and H.A. Rijken, Nucl. Instr. and Meth. B 66 (1992) 393]. Improved performance is obtained with a multi-parameter data acquisition system; recoil events are more easily and accurately selected and sensitivity is improved by a factor of 5 to 1 × 10 14 at/cm 2 for oxygen on amorphous silicon. The typical surface depth resolution is 10 nm. Two alternative PSD circuits are proposed neither of them using fast electronics. Examples are given of profiling carbon and oxygen in thin films of Si, C and SiO x N y .

Initial performance of the EXITE2 imaging phoswich detector/telescope for hard X-ray astronomy

The authors have developed, tested, and flown a large-area imaging phoswich detector/telescope for hard X-ray astronomy. This second-generation Energetic X-ray Imaging Telescope Experiment (EXITE) is designed to detect and image cosmic X-ray sources in the 20-600 keV energy range from a high-altitude balloon. Imaging is accomplished via the coded-aperture technique. Laboratory tests have shown that the detector achieves 14% (FWHM) energy resolution and /spl sim/10 mm (FWHM) spatial resolution at 60 keV, and that the pulse-shape discrimination circuit effectively distinguishes between NaI(Tl) and CsI(Na) events from /spl sim/40-400 keV. The first flight of the instrument was from Palestine, Texas, on 13-14 June 1993. The authors present details of the laboratory performance of the system and some flight results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Development of a pulse shape discrimination circuit

A pulse shape discrimination circuit was designed and used in an experiment measuring double-differential cross sections of (n, charged particle) reaction; to identify p, α and γ. The performance of the circuit was tested. With this circuit, excellent identification of p, α and γ was obtained.

Rapid determination of Sr-89/Sr-90 in radwaste by low-level background beta counting system

A low-level background beta counting system has been designed and tested for the measurement of beta-emitting strontium activities, Sr-89/Sr-90, in the waste effluent in a nuclear power plant. The system consists of a CaF 2(Eu)-NaI(T1) phoswich central detector operated in anticoincidence with a low-level HPGe-NaI(T1) gamma spectrometer. This system, in conjunction with the electronic pulse shape discrimination circuit, is capable of distinguishing the beta-gamma radiation from pure beta activities by the scintillation characteristics of the phoswich detector without chemical separation. The interference from gamma-rays can be minimized by the operation of an anticoincidence mode. In order to distinguish Sr activities from other beta activities in a sample, a special correction technique conjugated with gamma spectrometry and simultaneously measured with the system is further employed. With this technique, the Sr-89/Sr-90 activities can be determined within 5% error even if the background activity is 100 times higher than that of Sr. A minimum detectable level (MDL) of Sr-90 is estimated at 20 pCi/L.

A Radiocarbon Dating Protocol for use with Packard Scintillation Counters Employing Burst-Counting Circuitry

Considerable research has been carried out in this laboratory on the use of Packard scintillation counters employing burst-counting circuitry. The nature of the pulse-shape discrimination circuit has led to redefining our sample vialing philosophy and scintillation cocktail optimization. Results presented here demonstrate: 1) the enhancements in efficiency that are achievable using a two-component cocktail compared with the use of a primary fluor only; 2) the development of a cocktail in which efficiency and quenching are relatively unaffected by moderate variations in fluor concentrations and ratio; 3) the rationale behind the use of screw-cap vials rather than sealable ampules; 4) the advantage of nickel/chromium-plated brass caps over standard plastic caps.

A versatile electronic pulse-shape discriminator

A pulse-shape discrimination circuit designed for use with multidetector arrays has been tested. Each module, containing two channels, occupies a single slot in a standard nuclear instrumentation module (NIM) crate and can be used without alteration, tests have shown, with either NE213 liquid scintillator detectors for neutron-gamma ray discrimination or with NaI(Tl) detectors for charged particle identification. Variations of the circuit which minimize either the power consumption or the complexity are presented. Outputs are provided for either a charge-to-digital converter or a time-to-digital converter.

Low level alpha activity measurements with pulse shape discrimination--application to the determination of alpha-nuclides in environmental samples

Liquid scintillation counting of alpha rays with pulse shape discrimination was applied to the analysis of 226Ra and 239+240Pu in environmental samples and of alpha-emitters in/on a filter paper. The instrument used in this study was either a specially designed detector or a commercial liquid scintillation counter with an automatic sample changer, both of which were connected to the pulse shape discrimination circuit. The background counting rate in alpha energy region of 5-7 MeV was 0.01 or 0.04 cpm/MeV, respectively. The figure of merit indicating the resolving power for alpha- and beta-particles in time spectrum was found to be 5.7 for the commercial liquid scintillation counter.

A high efficiency electron pair spectrometer

a multi-detector high efficiency spectrometer for the detection of electron-positron pairs in the presence of high intensity gamma radiation has been designed, built and tested. The spectrometer employs six RCA 8850 photomultipliers. A “sandwich” made of a 0.5 mm thick anthracene glued to the front face of a 45 mm thick NE 102A plastic scintillator was mounted on each photomultiplier. A pulse shape discrimination circuit distinguishes electron from gamma signals, making use of the fact that electrons produce a relatively long scintillation pulse (≈ 25 nrmns) in the anthracene, whereas gammas have a negligible probability to interact with the thin anthracene. The six scintillators cover a solid angle of 3.2 π sr around the target and their front surfaces form nine boundary lines. An annular Si(Li) detector (0.081 sr) used to detect particles backscattering from the target may be operated in coincidence with the electron detector.Proper adjustment of the pulse shape discriminators resulted in accepting the electrons from a 207Bi source and in rejecting 98% of 60Co radiation. The spectrometer was tested using the reaction 19F(p, α)16O at 2.47 MeV proton bombarding energy. Approximately 90% of the 7.12 MeV gammas from the 1− level in 16O were rejected. The pairs from the 6.05 MeV O+ level were detected with 28% efficiency and 12% energy resolution (fwhm).

Pulse shape discrimination technique in a NaI(Tl)CsI(Na) X-ray detector

A simple design of a pulse shape discrimination circuit for “Phoswich” scintillation detectors used in X-ray astronomy is presented. The usefulness of the circuit in distinguishing between X-rays and background gamma rays in the detector is described.

(n,x.GAMMA.) and (n,xn) Cross sections of molybdenum, titanium and nickel for 15-MeV neutrons.

Cross section measurements were made for (n, xγ) and (n, xn) reactions of Mo, Ti and Ni at 120° with respect to the incident neutron. The monodirectional source neutrons were obtained by the associated particle method using D-T reaction. The (n, xγ) and (n, xn) data were simultaneously measured by an NE-213 scintillator using a pulse-shape discrimination circuit. The (n, xγ) cross sections obtained in this paper agreed well with other experimental data. The (n, xγ) data for Ti and Ni given by Drake seem too large in the energy range beyond 4–5 MeV. Followings were pointed out for the evaluated data in the ENDF/B-IV file. 1. The (n, xγ) cross section for Ni and the (n, xn) data for Mo are considered to be adequate. 2. The (n, xγ) cross sections for Mo and Ni are not adequate. 3. The (n, xn) cross sections for Ti and Ni seem to have large errors.

Measured neutron and gamma spectra from californium-252 in a tissue-equivalent medium.

A method of experimentally obtaining both neutron and gamma-ray spectra in a scattering medium is described. The method utilizes a liquid-organic scintillator (NE-213) coupled with a pulse-shape discrimination circuit. This allows the separation of the neutron-induced pulse-height data from the gamma-ray pulse-height data. Using mathematical unfolding techniques, the two sets of pulse-height data were transformed to obtain the neutron and gamma-ray energy spectra. A small spherical detector was designed and constructed to reduce the errors incurred by attempting spectral measurements in a scattering medium. Demonstration of the utility of the system to obtain the neutron and gamma-ray spectra in a scattering medium was performed by characterizing the neutron and gamma-ray spectra at various sites about a 3.7-microgram (1.5 cm active length) californium-252 source in a tissue-equivalent medium.

An electronic circuit for pulse shape discrimination in organic scintillators

A constant fraction type electronic circuit is described that performs a pulse shape analysis of organic scintillator pulses. The main features are: stability at high counting rates and energy independent particle identification over a wide energy range. In conjunction with a NE 213 scintillator, n- γ discrimination over a dynamic range of more than 1:100 can be performed at counting rates up to 5 × 10 4 pulses per second.

A scintillation polarimeter for n-p scattering studies

A neutron polarization analyser is described in which the direction dependence of the scintillation pulse shape discrimination (PSD) properties of an anthracene crystal provide the basis for observing the left-right asymmetry of recoil protons associated with the n-p scattering of monoenergetic neutrons within the crystal. The polarimeter consists of a single anthracene crystal mounted on a magnetically shielded photomultiplier tube which is fitted with a PSD circuit. The pulse height and PSD outputs from the photomultiplier are analysed in two parameter mode and a set of observations consisting of a pair of two-parameter spectra leads to a measurement of the recoil proton asymmetry as a function of recoil angle. The polarization in n-p scattering is then deduced as a function of centre-of-mass scattering angle θ cm for values of θ cm in the range 50°–180°.

A fast neutron-gamma discriminator

A fast pulse-shape discrimination circuit is described which provides time and logic information within 300 ns.