The trajectory of particle beams can be obtained by using an active gas target, multiple-sampling and tracking proportional chamber (MSTPC), as a proportional counter. Because of intensity of low energy radioactive beam, in the stellar reaction such as (α, p), (p, α),. . . it is necessary to increase the gain for the counter. In this case, a gas electrons multiplier (GEM) foil will be used, so the proportional counter is called GEM-MSTPC. The efficient gas gain of GEM foils which relates to foil thickness and operating pressure was investigated with two type of the foils, 400 um and 200 um, in argon (70%) – carbon dioxide (30%) mixture. | Communications in Physics, Vol. 22, No. 3 (2012), pp. 283-287 INVESTIGATION OF GAS GAIN OF GEM-FOIL USED IN LOW ENERGY RADIOACTIVE BEAM EXPERIMENT NGUYEN NGOC DUY Dong Nai University LE HONG KHIEM Institute Of Physics, VAST Abstract. Nuclear reaction measurement with radioactive beam at low energy plays an important role in nuclear astrophysics and nuclear structure. The trajectory of particle beams can be obtained by using an active gas target, multiple-sampling and tracking proportional chamber (MSTPC), as a proportional counter. Because of intensity of low energy radioactive beam, in the stellar reaction such as (α, p), (p, α),. . . it is necessary to increase the gain for the counter. In this case, a gas electrons multiplier (GEM) foil will be used, so the proportional counter is called GEM-MSTPC. The efficient gas gain of GEM foils which relates to foil thickness and operating pressure was investigated with two type of the foils, 400 um and 200 um, in argon (70%) – carbon dioxide (30%) mixture. I. INTRODUCTION An active gas detector, multiple-sampling and tracking proportional chamber (MSTPC) [1] has advantage for direct measurement of stellar reaction using radioactive ion (RI) beams. The trajectory of particles in three-dimension and energy of particles can be measured with high accuracy. However, it is necessary to get high gain for MSTPC since the RI beam has low intensity. One or more GEM foils [2] are mounted between the drift space and the readout pads to increase the output signal. GEM foils works as an amplifier to amplify the ionization electrons in the drift region of MSTPC so it is very important to know the gain of GEM foils. The gas gain of GEM foil as a function of high voltage (corresponding to operating electrict field) applied for GEM. Here, the operating electric field EGEM is defined as: EGEM = ∆V where ∆V is high voltage applied for GEM-up and GEM-down, d is the thickness of GEM foil and p is the operating gas pressure. In this .
