Properties of thick GEM in low-pressure deuterium

Abstract

Deuteron inelastic scattering (d, d') provides a promising spectroscopic tool to study nuclear incompressibility. In studies of deuteron inelastic scattering of unstable nuclei, measurements of low-energy recoiled particles is very important. In order to perform these measurements, we are developing a GEM-TPC based gaseous active target, called CAT (Center for nuclear study Active Target), operated with pure deuterium gas. The CAT has been tested with deuterium gas at 1 atm and 100-μm-thick GEMs. The low-pressure operation of CAT is planned in order to improve the detection capability for lower-energy recoil particles. A 400 μm-thick gas electron multiplier (THGEM) was chosen for the low-pressure operation of CAT. However, the properties of THGEM in low-pressure deuterium are currently undocumented. In this work, the performance of THGEM with low-pressure pure deuterium gas has been investigated. The effective gas gain of THGEM has been measured in various conditions using a 5.5-MeV 241Am alpha source. The effective gas gain was measured for 0.2-, 0.3- and 0.4-atm deuterium gas and a gas gain of about 103 was achieved by a double THGEM structure at 0.2 atm. The maximum achieved gain decreased with increasing gas pressure. The dependences of the effective gas gain on the electric field strengths of the drift, transfer and induction regions were investigated. The gain stability as a function of time in hydrogen gas was also tested and a relaxation time of THGEM of about 60 hours was observed with a continuous irradiation of alpha particles, which is significantly longer than previous studies have reported. We have tried to evaluate the gas gain of THGEM in deuterium gas by considering only the Townsend ionization process; however, it turned out that more phenomenological aspects, such as transfer efficiency, should be included in the evaluation. The basic properties of THGEM in low-pressure deuterium have been investigated for the first time.

Isoscalar response ofNi68toα-particle and deuteron probes

“…The pad plane will be connected to a new generation electronics, that will allow to connect a large number of channels and have a more selective trigger. Several active targets encompassing such developments are being constructed worldwide [28,[37][38][39], which promise a bright future for ISGR studies of nuclei far from stability.…”

Active targets for the study of nuclei far from stability

“…For example for the (d, d ′ ) reaction with a 100 MeV/u beam of 132 Sn, the scattered d energy is 500 keV at a center-of-mass scattering angle of 1°. The CAT detector was developed to have an angular resolution of 1°(7.5 mrad in lab) and a total kinetic energy resolution of 10% (1 MeV in center of mass) for use with high-energy radioactive beams with light-ion targets [82,80].…”

Property of THGEM in Low-Pressure Deuterium for a Low-Pressure Gaseous Active Target

“…However, some changes of gas pressure P and temperature T were observed and the P/T correction was applied by using the P/T correlation of G eff as f (P/T) = α exp(β P/T), where α and β are the fitting parameters. After the P/T correction, it turned out that the gas gain of THGEM has 2 hours or less of the relaxation time which is significantly shorter than our previous study [4], and the deviation after the relaxation was about 5% (FWHM) (See Figure 4).…”

“…In order to measure such recoiling particles, an effective gas gain of more than 10 4 is required for TPC. The properties of a double THGEM configuration in low-pressure deuterium at 0.2-, 0.3-and 0.4-atm pressure were investigated for the first time by corresponding authors [4]. To have a gas gain of more than 10 4 at 0.4-atm D 2 , a triple 400 µm-thick THGEM configuration was chosen as a amplification device for the low-pressure operation of CAT.…”

“…Figure 1 provides a schematic view of the experimental setup. A 400 µm-thick THGEM and the readout pad in this work have the same features as our previous work [4]. A single readout pad (1.5×1.5 cm 2 ) was used to collect the multiplied electrons.…”