Position Sensitive Multiwire Proportional Counter Research Articles

Measurement of the Cross Section for the Neutron-Induced Fission of 238U Nuclei in the Energy Range of 0.3–500 MeV

The cross section for the neutron-induced fission of 238U nuclei has been measured using the time-of-flight spectrometer of the GNEIS neutron complex at the Petersburg Nuclear Physics Institute, National Research Center Kurchatov Institute, in the neutron energy range of 0.3–500 MeV. Fission fragments have been detected by low-pressure position-sensitive multiwire proportional counters. The cross section for 238U(n, f) fission has been measured with respect to the cross section for 235U(n, f) fission, which is an accepted international standard. Data on the energy dependence of the anisotropy of the angular distribution of fragments of neutron-induced 238U nuclei are also presented. The data obtained have been compared to previous experiments carried out using both similar and significantly different methods.

Development of THGEM-based Detectors for Nuclear Fission Studies

To optimize the exploration of Super Heavy Elements (SHE), the key challenge is to understand the dynamics of the fusion-fission through the measurements of mass and angular distribution of the fission fragments. For the detection of fission fragments, position sensitive Multi-Wire Proportional Counters are generally used due to their high gain, good temporal and position resolution. However, these detectors use fragile anode wires having a diameter of only 10 μm and therefore they are vulnerable. In the present work, a detector based on robust Thick Gaseous Electron Multiplier (THGEM) has been proposed. A numerical demonstration of THGEM-Multi Wire hybrid detector technology as a possible candidate for the new generation low-energy fission studies and their evaluation as a function of different possible geometric and electric configuration in low-pressure gas is discussed here.

Development of a time of flight spectrometer based on position sensitive multi-wire proportional counters for fission fragment mass distribution studies.

Characteristics and performance of a time of flight (TOF) spectrometer developed for performing fission mass distribution studies are presented. The spectrometer contains two TOF arms based on multi-wire proportional counters (MWPCs). Each arm has two MWPCs to form a start-stop detection system for TOF measurements. The start detector has an active area of 4 × 4cm2. The stop detector is a two-dimensional position sensitive MWPC with an active area of 16 × 11cm2. Salient features of the MWPCs are the use of reduced sub-millimeter wire pitches of 0.635 and 0.317mm in the electrodes along with the use of gold plated tungsten wires of diameters 10 and 20 µm. A delay line for position electrodes is prepared using chip inductors and capacitors. Ten different configurations of MWPC were investigated for the start detector, which involved the use of three and four electrode geometries, use of different wire pitches, and use of aluminized mylar for timing electrodes. Performance results close to micro-channel plate detectors have been observed with some designs of MWPC, displaying rise times better than 2ns with an estimated inherent time resolution of ∼100ps FWHM. A position resolution of ∼1mm (FWHM) has been observed. Design features of the MWPCs and their test performance results are described in this article.

Measurement of fragment-mass distributions from fission of At214 following the Be9+Tl205 reaction

Background: The recent surprising experimental discovery of asymmetric fission in the nucleus $^{180}\mathrm{Hg}$ at low excitation energy has renewed interest concerning our understanding of the role of nuclear shell effects in the dynamics of the fission process. New theoretical models have been developed that claim to successfully explain the observed asymmetric fission of $^{180}\mathrm{Hg}$ and also predict the nature of mass distributions of several other preactinide nuclei for which experimental data are scarce.Purpose: We investigated fragment-mass distributions in the fission of the preactinide nucleus $^{214}\mathrm{At}$ at different excitation energies near the Coulomb barrier. The present results were compared with the predictions from a recent state-of-the-art theoretical calculation, as well as with our previous measurement for the nearby nucleus $^{210}\mathrm{Po}$.Methods: A pulsed heavy-ion beam was used in the experiment. Fission fragments were detected with two large-area position-sensitive multiwire proportional counters placed at the folding angle. Mass distributions were extracted from time-of-flight differences and position information ($\ensuremath{\theta},\ensuremath{\phi}$) for the fission fragments.Results: An asymmetry in fragment-mass distribution in the fission of $^{214}\mathrm{At}$ was observed at an excitation energy of $\ensuremath{\approx}31$ MeV, where a shell effect is found to influence the potential energy surface. At higher excitation energies, mass distributions are predominantly symmetric indicating the absence of shell effects.Conclusion: This finding is consistent with the prediction of a recent macroscopic-microscopic dynamical model. However, for the preactinides, static models with nascent fragment shell structure are likely to produce similar results.

A Neutron Testing Facility to Study the Radiation Hardness of the Electronic Components at the SC-1000 Synchrocyclotron of National Research Center Kurchatov Institute—Petersburg Nuclear Physics Institute

The article presents a description of the ISNP/GNEIS testing facility with a neutron spectrum that reproduces the spectrum of atmospheric neutron radiation. The facility was developed at the Petersburg Nuclear Physics Institute (PNPI) of the National Research Center Kurchatov Institute in collaboration with the Institute of Space Device Engineering, a branch of JSC (Joint Stock Company) United Rocket and Space Corporation. The spallation neutron source of the facility is based on the 1-GeV SC-1000 proton synchrocyclotron at the PNPI. The internal neutron-production lead target produces 10-ns pulses of neutrons with a repetition rate of 45–50 Hz and an average neutron intensity of 3 × 1014 n/s (in the 4σ solid angle). In the irradiation area located at a distance of 36 m from the neutron source, a high-quality collimated neutron beam with a broad energy spectrum of 1–1000 MeV and a neutron flux of 4 × 105 n/(cm2 s) allows conducting accelerated single-event soft error testing of electronic components. In the course of the irradiation, the neutron energy spectrum and intensity and the spatial profile of the beam are controlled using a fission ionization chamber (beam monitor) and a position-sensitive multiwire proportional counter (beam profile meter). The data acquisition system of the ISNP/GNEIS facility utilizes 250 MS/s 12 bit CAEN waveform digitizers for the processing of signals from the monitor and profile meter by the neutron time-of-flight technique. In the report, parameters of the ISNP/GNEIS testing facility are discussed in comparison with analogous world-class facilities, as well as requirements and recommendations of the standards used in this field.

Angular Distributions and Anisotropy of the Fragments from Neutron-Induced Fission of 239Pu and natPb in the Energy Range of 1–200 MeV

The angular distributions of fragments from the neutron-induced fission of natPb and 239Pu nuclei have been measured in the energy of range 1–200 MeV using the neutron time-of-flight spectrometer GNEIS. Fission fragments have been detected by position sensitive multiwire proportional counters. The results for the anisotropy of fission fragments deduced from the measured angular distributions have been presented. The results have been compared with the experimental data of other authors.

Angular distributions and anisotropy of the fragments from neutron-induced fission of 233U and 209Bi in the intermediate energy range of 1–200 MeV

New results of the neutron-induced fission experiments carried out at the neutron time-of-flight spectrometer GNEIS of the PNPI are given. Angular distributions of fission fragments from the neutron-induced fission of 233U and 209Bi nuclei have been measured in the energy range 1–200 MeV using position sensitive multiwire proportional counters as fission fragment detector. The recent improvements of the measurement and data processing procedures are described. The data on anisotropy of fission fragments deduced from the measured angular distributions are presented in comparison with the experimental data of other authors.

Dual Position Sensitive MWPC for tracking reaction products at VAMOS++

The characteristics and performance of a Dual Position Sensitive Multi-Wire Proportional Counter (DPS-MWPC) used to measure the scattering angle, the interaction position on the target and the velocity of reaction products detected in the VAMOS++ magnetic spectrometer, are reported. The detector consists of a pair of position sensitive low pressure MWPCs and provides both fast timing signals, along with the two-dimensional position coordinates required to define the trajectory of the reaction products. A time-of-flight resolution of 305(11)ps (FWHM) was measured. The measured resolutions (FWHM) were 2.5(3)mrad and 560(70)μm for the scattering angle and the interaction point at the target respectively. The subsequent improvement of the Doppler correction of the energy of the γ-rays, detected in the γ-ray tracking array AGATA in coincidence with isotopically identified ions in VAMOS++, is also discussed.

Anisotropy of the fission fragments from neutron-induced fission in the intermediate energy range of 1–200 MeV

Angular distributions of fission fragments from the neutron-induced fission of 232Th, 235U, and 238U have been measured in the energy range 1–200 MeV at the neutron time-of-flight (TOF) spectrometer GNEIS using position sensitive multiwire proportional counters as fission fragment detector. A short description of the experimental equipment and measurement procedure is given. The anisotropy of fission fragments deduced from the data on measured angular distributions is presented in comparison with experimental data of other authors.

Spectral accuracy of multiwire proportional counter neutron detectors in time-of-flight regime

An experiment is proposed to study the neutron detection depth profile—resulting from the cumulative effect of the gas absorption depth profile and signal detection efficiency—of position-sensitive multiwire proportional counter detectors. The effect of the drift voltage level on the detection efficiency is investigated and a method is proposed to adjust the drift voltage of new detectors to ensure appropriate spectral accuracy.

Direct measurement of cold neutron moderator spectra

The neutron flux distribution with respect to energy/wavelength of the cold source of the Budapest Neutron Centre has been measured using the energy resolved pinhole imaging method. A 2D position sensitive multiwire proportional counter has been used in time of flight regime together with a chopper placed at the position of the pinhole. Gas absorption efficiency and detector dead time corrections have been applied and the accuracy of the results analyzed. Three Maxwell–Boltzmann distributions required for a proper fit to the resulted spectrum yield the multispectral characteristic of the cold source due to incomplete moderation in the finite-sized liquid hydrogen volume. The measurement has been performed during the reconstruction of the out-of-pile guide system of a beamline, offering direct view of the cold source.

Development of advanced x-ray imaging crystal spectrometer utilizing a large area segmented proportional counter for KSTAR

An advanced x-ray imaging crystal spectrometer (XICS) for KSTAR tokamak has been developed by utilizing a segmented two dimensional (2D) position-sensitive multiwire proportional counter. The XICS for the KSTAR tokamak provides time-resolved measurements of the radial ion and electron temperature profiles, toroidal plasma rotation velocity, and ionization equilibrium. The segmented 2D detector with delay-line readout and supporting electronics has been adopted to improve the photon count rate capability. The current fabrication status of the XICS for the KSTAR tokamak and the first performance test results of the prototype segmented 2D detector are presented.

Time of flight (TOF) spectrometer for accurate measurement of mass and angular distribution of fission fragments in heavy ion induced fission reactions

The performance of a dual time of flight (TOF) spectrometer using two 24 cm×10 cm area X – Y position sensitive Multi-Wire Proportional Counters (MWPC) is reported. Good separation of compound nuclear fission channel from elastic, quasi-elastic and non-compound fission channels have been achieved. Time calibration of the spectrometer using a technique, dependent on the detector independence of the mass or kinetic energy distributions gave a three times better mass resolutions compared to the conventional calibration technique using elastically scattered projectiles in a heavy ion induced fission reaction. Detail experimental methods in determining fission fragment mass and angular distribution have been presented and discussed.

Research and development of x-ray imaging crystal spectrometers for KSTAR

The engineering design for two high-resolution x-ray imaging crystal spectrometers for KSTAR tokamak has been completed. A spherically bent quartz crystal and a large area two-dimensional (2D) position-sensitive multiwire proportional counter have been selected for the imaging spectrometers. A prototype 10 cm by 30 cm 2D detector was fabricated and pilot measurement on Alcator C-Mod tokamak was carried out. The final engineering design of the spectrometers and experimental results from the 2D detector are presented.

Results from the National Spherical Torus Experiment x-ray crystal spectrometer

A high-resolution x-ray crystal spectrometer has recently been installed at the National Spherical Torus Experiment to record the satellite spectra of helium-like argon, Ar XVII, in the wavelength range from 3.94 to 4.00 A for measurements of ion and electron temperatures, and measurements of the ionization equilibrium of argon, which is of interest for studies of ion transport. The instrument presently consists of a spherically bent quartz crystal and a conventional one-dimensional position-sensitive multiwire proportional counter, but it will soon be upgraded to a new type of x-ray imaging crystal spectrometer by the installation of a large size (10 cm×30 cm) two-dimensional position-sensitive detector that will allow us to obtain temporally and spatially resolved spectra from a 80 cm high cross-section of the plasma. In its present configuration, the spectrometer has been optimized for high throughput so that it is possible to record spectra with small statistical errors with a time resolution of 10 ms by adding only small, nonperturbing amounts of argon to the plasma. The spectrometer is most valuable for measurements of the ion temperature in the absence of a neutral beam in ohmically heated and rf heated discharges, when charge exchange recombination spectroscopy does not function. Electron temperature measurements from the satellite-to-resonance line ratios have been important for a quantitative comparison with (and verification of) the Thomson scattering data. The article will describe the instrumental details of the present and future spectrometer configurations and present recent experimental results.

Imaging x-ray crystal spectrometers for KSTAR

Two x-ray imaging crystal spectrometers are presently designed for the KSTAR tokamak. The instruments will provide temporally and spatially resolved spectra of heliumlike argon (or krypton) from a large cross section of the plasma. The spectral data will be used for profile measurements—both within and perpendicular to the horizontal midplane of KSTAR—of the ion and electron temperatures, the rotation velocity, and the ionization equilibrium. Each spectrometer will consist of a spherically bent quartz crystal and large area two-dimensional position-sensitive multiwire proportional counter. The article presents the design for the KSTAR x-ray imaging crystal spectrometers, and the fabrication and initial test results from the large area two-dimensional multiwire proportional counter.

A fast low noise charge preamplifier for position sensitive detectors

We present the design and the results of the evaluation of a fast, low noise, charge preamplifier. This device uses commercial circuits; the advantages over classical circuits based on transistors are presented. These include short development time, high reliability and reproducibility, and easy maintenance. The amplifier has been tested with a position sensitive multiwire proportional counter with a readout system based on delay lines. With an input impedance of 50 Ω, we have obtained a signal to noise ratio better than 40 dB, a gain of 0.42 μV per electron, a pulse rise time of 9.4 ns, and a total pulse duration lower than 120 ns. These values allow detector data acquisition rates in excess of 1 MHz, and a spatial resolution better than 300 μm.

二つの異なる検出方法による二次元放射能分布測定装置の比較検討

The relationship amang radioluminography (BAS-2000), two-dimentional position sensitive multiwire proportional counter (AMBIS-4000) and autoradiography using X-ray film were examined for their efficiencies for 14C-labelled compounds. Detection efficiencies of BAS-2000 and AMBIS4000 were 0.093% and 1.35%, respectively. There was a good relationship between the two methods. On the other hand, the autoradiography was not sensitive enough to detect labelled materials of 0.018 kBq. However, distances between two shadow spaces of the labelled materials were 3.35 mm by autoradiography, 2.61 mm by BAS-2000 and 1.62 mm by AMBIS-4000.

Capture reactions in the 40,48Ca+197Au and 40,48Ca+208Pb systems.

Capture-fission cross sections for $^{40,48}\mathrm{Ca}$${+}^{197}$Au and $^{40,48}\mathrm{Ca}$${+}^{208}$Pb have been measured at beam energies ranging from 195 to 416 MeV. The fissionlike fragments were detected in a pair of position-sensitive multiwire proportional counters and were identified from measurements of position and time using two-body kinematics. The data taken at energies above the barrier (up to 2.4 times the Coulomb barrier) were analyzed in terms of the extra push model showing a strong dependence on the Ca isotope. This dependence was also observed at energies below the barrier, where the results have been interpreted using a schematic coupled-channel code.

A cylindrical surface MWPC for all-round X-ray vision

We describe the design, construction and performance of a novel type of position sensitive multiwire proportional counter intended for use in a proposed coded mask all-sky X-ray monitor. The sensitive volume is in the form of a cylindrical shell inside a tubular carbon fibre window. The electronic system uses multichannel preamplifier chips developed at CERN, and includes logic and digitising circuits for direct readout to a computer.