The CASCADE Project - a perspective for Solid State Detectors

2014

1 H-or 4 He-contained gas mixtures are usually used to detect fast neutrons, which relies on elastic scattering between fast neutrons and light gas molecules. In this research, gas mixtures of 4 He/CO 2 (80:20 and 70:30) and 4 He/CO 2 /C 4 H 10 (70:23:7) were flowed through a 10 cmm10 cm triple-Gas Electron Multiplier (GEM) detector at a constant flow rate of 3.0 L/hr in order to detect fast neutrons. Comparisons of relative efficiencies, relative gains, and detection uniformity for all gas types were investigated by measuring signal counts and signal amplitudes. Results showed that a gas mixture of 4 He/CO 2 (80:20) had the highest relative efficiency and relative gains amongst all gas mixture types. In terms of detection uniformity, detection efficiency at the center of the active area was approximately 20% higher than areas close to the detector edges. Details of basic knowledge of GEM, experimental procedures, results and discussion are included in this article.

Journal of Physics: Conference Series

The gas electron multiplier (GEM) detector is a relatively new gaseous detector that has been utilized for less than 20 years. Since the discovery in 1997 by F. Sauli, the GEM detector has shown excellent properties including high rate capability, excellent resolution, low discharge probability, and excellent radiation hardness. These promising properties have led the GEM detector to gain popularity and attention amongst physicists and researchers. In particular, the GEM detector can also be modified to be used as a neutron detector by adding appropriate neutron converters. With properties stated above and the need to replace the previous expensive 3 He-based neutron detectors, the GEM-based neutron detector could be one of the most powerful and affordable neutron detectors. Applications of the GEM-based neutron detectors vary from researches in nuclear and particle physics, neutron imaging, and national security. Although several promising progresses and results have been shown and published in the past few years, further improvement is still needed in order to improve the low neutron detection efficiency (only a few percent) and to widen the possibilities for other uses.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2010

We are developing a neutron beam monitor with a gas electron multiplier (GEM) for the high-intensity total diffractometer at J-PARC. In order to analyze the basic characteristics of the GEM-based detector, a neutron irradiation test was carried out at J-PARC. The wavelength-spectrum distribution obtained from the test is consistent with the calculations, and the beam profiles agree with the simple Monte Carlo (MC) simulation. The position resolution of the GEM-based detector is estimated to be approximately 1.2 mm. Therefore we found that as a neutron beam monitor, the GEM-based detector has good two-dimensional imaging ability.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2005

One of our two methods for fast-neutron imaging with spectrometric capability is presented here. It is a neutron-counting technique based on a hydrogenous neutron converter coupled to Gaseous Electron Multipliers (GEM). The principles of the detection techniques and the optimization of the converter, electron amplification and the readout are described. Evaluation of the properties are derived from a experiment in a pulsed neutron beam of spectral distribution between 2 and 10 MeV.

IEEE Transactions on Nuclear Science, 2001

The Review of scientific instruments, 2014

We present and discuss the operational principle of a new fast-neutron detector concept suitable for either energy-selective imaging or for imaging spectroscopy. The detector is comprised of a series of energy-selective stacks of converter foils immersed in a noble-gas based mixture, coupled to a position-sensitive charge readout. Each foil in the various stacks is made of two layers of different thicknesses, fastened together: a hydrogen-rich (plastic) layer for neutron-to-proton conversion, and a hydrogen-free coating to selectively stop/absorb the recoil protons below a certain energy cut-off. The neutron-induced recoil protons, that escape the converter foils, release ionization electrons in the gas gaps between consecutive foils. The electrons are then drifted towards and localized by a position-sensitive charge amplification and readout stage. Comparison of the images detected by stacks with different energy cut-offs allows energy-selective imaging. Neutron energy spectrometry...

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2020

The CYlindrical neutron SPectrometer (CYSP) is a polyethylene cylinder with diameter 50 cm and height 65 cm equipped with a collimated aperture and an internal capsule embedding multiple thermal neutron detectors. Analogously to Bonner Spheres, CYSP responds from thermal up to GeV neutrons and the spectrum is obtained via few-channel unfolding methods. Due to the specific design and the use of borated materials, the internal detectors only respond to neutrons coming from the desired direction. By changing the type and sensitivity of the internal detectors, the CYSP was adapted to respond over a variety of fluence rates. This work describes HELIOCYSP, an updated design of CYSP, including Helium-3 proportional counters as internal detectors and a more convenient design of the internal capsule. Due to the increased sensitivity, HELIOCYSP is suited for time-effective measurements in very low fluence rate scenarios, as those encountered in cosmic-ray-induced neutron studies at ground level.

Journal of Instrumentation, 2012

Variety of applications of fast neutron detection utilize thermal neutron detectors and moderators. Examples include homeland security applications such as portal monitors and nuclear safeguards which employ passive systems for detection of fissile materials. These applications mostly rely on gas filled detectors such as 3 He, BF 3 or plastic scintillators and require high voltage for operation. Recently there was considerable progress in the development of solid-state neutron detectors. These operate by detection of charged particles emitted from neutron interactions with a converter material. In order to increase neutron detection efficiency to a usable level, the thickness of the converter material must exceed the range of the charged particles in the converter, which limits the efficiency of planar detectors to several percent. To overcome this limitation three dimensional structured solid-state devices are considered where the converter can be thicker but still allow the charged particles to escape into the semiconductor. In the research described here this was accomplished by a semiconductor device that resembles a honeycomb with hexagonal holes and thin silicon walls filled with the converter material. Such design can theoretically achieve about 45% thermal neutron detection efficiency, experimentally about 21% was observed with a partially filled detector. Such detectors can be fabricated in variety of sizes enabling designs of directional fast neutron detectors. Other converter materials that allow direct detection of fast neutrons were also considered by both simulation and experiments. Because the semiconductor thickness is less than a few hundred microns, the efficiency of these detectors to γ-ray(s) is very low.

Nuclear Science, …, 2001

Abstract—Experiments at the anticipated intense spallation neutron sources require neutron detection with typically mil-limeter position resolution. We are investigating the possibility of applying the gas electron multiplier (GEM) for this purpose. For efficient detection, 3He ...