Development of a prototype GEM TPC with a gating grid for an H-dibaryon search experiment at J-PARC.
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| Title: | Development of a prototype GEM TPC with a gating grid for an H-dibaryon search experiment at J-PARC. |
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| Authors: | Sako, H.1 hiroyuki.sako@j-parc.jp, Sugimura, H.1,2, Ahn, J.K.3, Han, Y.4, Hasegawa, S.1, Hwang, S.H.1, Ichikawa, Y.1,2, Imai, K.1, Kiuchi, R.1,5, Ozawa, K.1,6, Sato, S.1, Shirotori, K.7 |
| Source: | Nuclear Instruments & Methods in Physics Research Section A. Nov2014, Vol. 763, p65-81. 17p. |
| Subjects: | Photomultipliers, Time projection chambers (Nuclear physics), Prototypes, Ion flow dynamics, Magnetic fields |
| Abstract: | We have developed a prototype TPC (Time Projection Chamber) based on GEMs (Gas Electron Multipliers) with a gating grid for an H-dibaryon search experiment at J-PARC. To investigate its performance, we conducted laboratory tests and a beam test with two kinds of gases, Ar–CH 4 (90:10) and Ar–CF 4 (95:5), where the former is mainly used for the tests. The hit detection efficiency per pad row was measured to be 98% at the beam rate up to 5×10 5 cps cm 2 (counts per second), and 90% at the rate of 3×10 6 cps/cm 2 . Based on the measured horizontal resolution of 0.19–0.46 mm at the drift length of 5–20 cm, the horizontal position resolution of better than 0.3 mm is estimated in 1 T magnetic field for the final experiment. The ion backflow fraction was measured to be 5% and reduced up to 3% by tuning the GEM voltage configuration, at the gain of 1.6 × 10 4 . The horizontal position distortion due to ion backflow in the gate operation was suppressed within 0.2 mm at the beam rates up to 5 × 10 5 cps / cm 2 , corresponding to the ion backflow up to 2.7 × 10 8 s − 1 cm − 1 . On the other hand, the distortion with the gate open was measured to be 1.3 mm, corresponding to the backflow of 1.3 × 10 9 s − 1 cm − 1 . The distortion in the final experiment is estimated to be 0.3 ± 0.2 mm , within the requirement of 1 mm . The GEMs have been operated continuously for a comparable period of the final experiment, with average energy deposit rates per unit GEM area of 30 times as high as that expected for the experiment. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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