p/π + response of single layer THGEM detector in Ar/3%iso *

Transcription

1 p/π + response of single layer THGEM detector in Ar/3%iso * Hong Daojin( 洪道金 ) 1,2,3;1 Yu Boxiang( 俞伯祥 ) 3,4 Liu Hongbang( 刘宏邦 ) 1,2;2 He Xiaorong( 何小荣 ) 1 An Guangpeng( 安广朋 ) 3,4 Chen Haitao( 陈海涛 ) 3,4 Chen Shi( 陈石 ) 2 Hu tao( 胡涛 ) 3,4 Li Jiacai( 李家才 ) 3,4 Liu Qian( 刘倩 ) 2 Niu Shunli( 牛顺利 ) 3,4 Ruan Xiangdong( 阮向东 ) 1 Xie Yigang( 谢一冈 ) 2,4 Zhang Xuan( 张烜 ) 3,4 Zheng Yangheng( 郑阳恒 ) 2 1 Department of Physics, Guangxi University, Nanning , China 2 University of Chinese Academy of Sciences, Beijing , China 3 State Key Laboratory of Particle Detection and Electronics, Beijing , China 4 Institute of High Energy Physics, Chinese Academy of Sciences, Beijing , China Abstract: In this work, we study the response of single layer Thick GEM (THGEM) detector to p/π + at E3 line of Beijing Test Beam Facility. In our experiment, the drift gap of THGEM Detector is 4mm, and the working gas is Ar+3%iso. Result shows at the momentum 500MeV/c to 1000MeV/c, detection efficiencies for p are from 93% to 99% in a relatively lower gain ( 2000), while the detection efficiencies for π + are slightly lower than that for p, which are from 82% to 88%. Meanwhile, simple Geant4 simulations have been done, and results of beam test are almost consistent with it. We preliminarily study the feasibility of THGEM detectors as sampling elements for Digital Hadronic Calorimeter (DHCAL), which may provide related reference for THGEM possibly applied in Circular Electron Positron Collider (CEPC) HCAL. Key words: CEPC; DHCAL; THGEM; p; π + ; detection efficiency. PACS: Cs 1 Introduction In recent years, THGEM has been studied extensively. It is a simplicity, cheap and robust element, and it also offers a few ns rise time and sub mm spatial resolution. Due to its good performance, THGEM has many meaningful applications. It is not only used in X-ray diffraction [1] or X-ray imaging [2], but also used as cosmic-ray muon hodoscope [3] and UV-photon detector for RICH [4]. Currently, CEPC-Higgs factory has been come up for purpose of precision measurement of higgs particle, and DHCAL play a crucial role in this research. As one of the candidates[5], THGEM/GEM must be attractive due to its above mentioned properties. A large area THGEM could be considered as the sampling element for DHCAL. Meanwhile, DHCAL based on THGEM detector has begun studied internationally [6, 7]. However, the related research is rarely domestically [8]. This paper reports the preliminary results of beam test at E3 line of Beijing Test Beam Facility, aimed at studying the response of single layer THGEM detector to p/π + at the momentum 500MeV/c to 1000MeV/c. THGEM detector with 4 mm drift gap and 2 mm induction gap is operated in Ar+3%iso, which has been studied extensively [9], and gain of THGEM detector is about Meanwhile, Experiment and Geant4 simulation results are shown, which is consistent with each other. Based on the whole results, applicability of THGEM detector as DHCAL sampling element may be expected. 2 Experimental setup 2.1 Experimental setup Beam test is conducted at E3 line of Beijing Test Beam Facility which is generated by shooting a target with 2.5GeV/c electron beam. It provide a mixed beam including e, π + and p, and the maximum particle counting rate is about 3 Hz. e is identified by Cherenkov detector, and p or π + is distinguished by the difference of flight time with a TOF system. In our experiment, mainly p and π + are measured. Supported by National Natural Science Foundation of China ( , U , ), State Key Laboratory of Particle Detection and Electronics. 1) hongdj@ihep.ac.cn 2) liuhb@gxu.edu.cn 1

2 Simple setup of beam test is shown in Fig. 1, from which experiment setup could be observed clearly. There are three plastic scintillator detectors on the beam line, and THGEM detector is located between TOF2 (5x5 cm 2 ) and TOF3 (3x3 cm 2 ). TOF2 is set in front of THGEM detector for purpose of adding to coincidence. Fig. 1 Experiment setup Fig. 2 shows electronics system of this experiment. In this work, TOF1 (5x5 cm 2 ) and TOF3 are used to provide a trigger for CAEN DT5751 which is a 4 channel desktop waveform digitizer. Once DT5751 is triggered by the coincidence signal, the waveforms of 4 channels including THGEM signal are recorded by the data acquisition program of DT5751 named wavedump. Meanwhile, the flight time of p or π + is set as the difference between TOF1 and TOF3, from which p and π + could be distinguished obviously. Fig. 2 Electronics system In this experiment, distance between TOF1 and TOF3 is about 3.85m. According to the relativity theory, the flight time of p and π + could be calculated as shown in Table The THGEM detector Table 1 Flight time of p/π + at the distance of 3.85m Momentum π + ( MeV/c 2 ) p( mev/c 2 ) MeV/c E(MeV) t(ns) E(MeV) t(ns) The single layer THGEM used in this study is 5x5cm 2 in size, with 0.2mm thick, 0.5mm pitch, 0.2mm hole diameter and 10um rim. The THGEM detector with 4mm drift gap and 2mm induction gap is operated in Ar+3%iso. Meanwhile, the drift field is 640V/cm and the induction field is 2kV/cm, and VT HGEM is set to be 545 V under beam condition, thus gain of THGEM detector is approximately 2000 [10]. The induced signal are recorded with a charge sensitive preamplifier(ortec 142AH), then is connected to a linear shaping amplifier(caen N968) with 0.5 us shaping time, 50 coarse gain and 1 fine gain. Finally, signals from THGEM detector and TOF detectors are fed into CAEN DT Measurement of baseline and detector stability To test the response of detector without beam condition, baseline of THGEM has been measured with a random trigger, and result is shown in Fig. 3. The offset value of DT5751 is 160mV, and mean of gauss distribution as shown in Fig. 3 is 180mV, sigma is about 5mV. A cut value could be set at mean plus 3 fold of sigma. Consequently, if signal from THGEM is higher than 195mV, it is considered as a valid event. 2

3 Fig. 3 Baseline measurement with a random trigger Stability of detector is also measured which is calibrated by 55 Fe. Signal of 55 Fe has gone through 3db attenuation before fed into DT5751, and result is shown in Fig. 4. The relative error derived from Fig. 4 is calculated less than 3%, which indicates THGEM detector working in a stable state during the experiment. Fig. 4 Measurement of detector stability calibrated by 55 Fe 3 Results 3.1 Gant4 simulation results A 4mm drift gap with Ar+3%iso has been simulated with Geant4. Fig. 5 shows the simulation results, deposition energy of p is between 0.6keV and 1.8keV, which is 1-4 times higher than that for π +. One thing should be noted that π + is almost MIP at the measured momentum [11], and simulation results also show this conclusion. Meanwhile, with the increasing of momentum, deposition energy of p decreases. Fig. 5. Geant4 simulation of p/π + deposition energy in 4mm Ar+3%iso 3.2 Amplitude spectrum of p/π + 3

4 Fig. 6 shows flight time of p/π + at different momentum, from which p/π + could be distinguished obviously. Flight time of π + is between 11 ns and 14 ns at the measured momentum, but flight time of p gradually decreases with the increasing of momentum, which is almost consistent with what Table 1 shows, thus we can select p or π + events. Fig.6 Flight time of p/π + at different momentum. Flight time of p is much more than that for π +. (a) 500MeV/c, (b) 600MeV/c, (c) 700MeV/c, (d) 800MeV/c, (e) 900MeV/c, (f) 1000MeV/c. Fig. 7 shows the amplitude spectrum of p/π + at 500MeV/c, which is fitted with a landau function. MPV of p/π + as shown in Fig. 7 is mv and mv. Fig. 8 shows MPV of p/π + at the momentum 500MeV/c to 1000MeV/c. With the increasing of momentum, amplitude of p decreases, and amplitude of π + is almost a constant value, which also shows π + is almost MIP at the momentum 500MeV/c to 1000MeV/c. After subtracting the baseline(180mv), the amplitude of p is about 1-4 times higher than that for π +. Fig. 7 Amplitude spectrum of p/π + at the momentum 500MeV/c. (a) p, MPV is mv, (b) π +, MPV is mv. Fig. 8 Amplitude distribution of p/π + at the momentum 500MeV/c to 1000MeV/c 3.3 Detection efficiency The detection efficiency of THGEM detector to p or π + is defined as the ratio of valid events to total events. On the basis of cut value(195mv) set above, detection efficiencies of THGEM detector for p or π + are calculated as shown in Fig. 9 Detection efficiencies for p are between 93% and 99%, and detection efficiencies for π + are slightly lower than that for p, which are from 4

5 82% to 88%. Submitted to Chinese Physics C 4 Conclusion Fig. 9 Detection efficiencies of p/π + at different momentum In the future high energy experiment, DHCAL must be an important research, especially for hardron jets etc. High spacial resolution, high counting rate and high detection efficiency could improve HCAL energy resolution. HCAL based on THGEM should be competitive due to its above mentioned properties. In this paper, we preliminary study the response of THGEM to proton and π +. A 4mm drift gap and 2mm induction gap THGEM detector is selected as the research object. THGEM detector works rather stably in Ar+3%iso during the experiment, and gain is about Results show detection efficiencies for p are 93% and 99%, which are a little larger than that for π +. A good explanation may be given by Geant4 simulation results, from Fig. 5 we could see that the deposition energy of p is 1-4 times higher than that for π +. Based on the above results, the better detection efficiency for π + at other momentum should be expected. However, for the sake of possibility using as DHCAL sampling element, THGEM detector should be as compact as possible. Meanwhile, for the purpose of high gas gain and detection efficiency, working condition of THGEM detector should be optimized, including working gas, configuration etc. Far more study is going on. References 1 H.B. Liu, et al., A study of thinner-thgem, with some applications,2012 JINST 7 C Chechik R, et al., Thick GEM-like (THGEM) Detectors and Their Possible Applications, SNIC Symposium, Stanford, California, 3-6 April PANG Hong-Chao, LIU Hong-Bang et al., A Cosmic-Ray Muon Hodoscope Based on Up-down THGEM Detectors, CHIN. PHYS. LETT. Vol. 29, No. 1 (2012) V. Peskov, et al., Further evaluation of a THGEM UV-photon detector for RICH - comparison with MWPC, JINST 5:P11004, The International Linear Collider technical design report, L. Arazi, et al., Beam Studies of the Segmented Resistive WELL: a Potential Thin Sampling Element for Digital Hadron Calorimetry, arxiv: S. Bressler, et al., Beam studies of novel THGEM-based potential sampling elements for Digital Hadron Calorimetry, arxiv: Zhang Ai-wu, et al., Nuclear Instruments and Methods in Physics Research A 722(2013) H.B. Liu, et al., Nuclear Instruments and Methods in Physics Research A 659(2011) ZHOU Xiao-Kang, LIU Qian et al., Study of Thick Gaseous Electron Multipliers Gain Stability and Some Influencing Factors, CHIN. PHYS. LETT. Vol.31, No.3(2014) Xie Y G et al., Particle Detectors and Data Acquisition. Beijing: Science Press, , 33. 5