Development Of Gaseous Tracking Devices For The Search Of WIMPs

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The Time Projection Chamber (TPC) has been recognized as a potentially powerful detector for the search of WIMPs by measuring the directions of nuclear recoils, by which probably the most convincing signature of WIMPs, caused by the Earth’s movement around the Galaxy, seems. We report on the first results of a performance study of the neutron publicity of our prototype micro TPC with Ar-C2H6 (90:10) and CF4 gasoline at one hundred fifty Torr. These particles could be detected instantly by measuring the nuclear recoils produced by their elastic scattering off nuclei in detectors. Probably the most convincing signature of WIMPs appears in the directions of nuclear recoils. For the reason that vitality deposits of WIMPs to nuclei are only some tens of keV and the range of nuclei is proscribed, the micro-TPC ought to be operated at low pressures. In the present work, with a view to examine the response of the micro-TPC to nuclear recoils at low pressures as a first step, we irradiated a one hundred fifty Torr Ar-C2H6 (90:10 mixture) gas (certainly one of the standard gases for TPCs) and CF4 with neutrons from 252Cf. The monitor lengths and deposited energies of Ar, C, and F recoils were investigated.



The prototype micro-TPC used in this measurements is proven in Fig.1. PIC and GEM. The small print of this GEM are described in Refs. The pre-amplified indicators are summed and digitized by one hundred MHz 8bit flash ADCs so as to find out the deposited power and the observe route as the waveforms hold the Bragg curve shapes. Ar-C2H6 (90:10) or CF4 gasoline to a strain of 150 Torr and sealed all through the measurement. For measuring the gasoline gain and the vitality calibration, the fuel was irradiated with 109Cd 22 keV and 133Ba 31.Zero keV X-rays by way of a 1mm thick aluminum window close to the sensitive volume. We irradiated the micro-TPC with neutrons from a 1 MBq 252Cf source on the top of the vessel. 2 cm3 plastic scintillator had been used because the event trigger. PIC and GEM with a quite low gasoline acquire (below 1000) to be able to observe the nuclear recoils.



PIC and adjusted the voltage between the GEM electrodes. Below a fuel gain of about 2000, our system was not capable of measure the 109Cd 22 keV x-ray correctly attributable to a mismatch of the dynamic vary of the ASD chips and the flash ADC; therefore, the deposited energy in low-gain operations was extrapolated from the calibrations with the high gasoline gain operations. We evaluated the track length as a function of the measured electron equal vitality in the next manner. E/dx𝑑𝐸𝑑𝑥dE/dx threshold can also be indicated for a comparability. Under operation with a gasoline acquire of 3000, electron recoils and proton (of C2H6) recoils were clearly observed in keeping with their dE/dx𝑑𝐸𝑑𝑥dE/dx. Alternatively, in the operation of the gas gain of 900, the C and Ar recoils and some proton recoils have been noticed as a result of excessive dE/dx𝑑𝐸𝑑𝑥dE/dx threshold. The measured track length of events when the GEM voltage was set to 215 V (fuel achieve of 4500) and 95 V (gasoline achieve of 800) are shown in Fig.4. We efficiently showed the nuclear recoils in a hundred and fifty Torr of Ar-C2H6 (90:10) and CF4 gases in accordance with their dE/dx𝑑𝐸𝑑𝑥dE/dx by changing the detector threshold. By way of dE/dx𝑑𝐸𝑑𝑥dE/dx, iTagPro bluetooth tracker the tracks in the micro TPC had been a lot easier to detect for C, F or Ar recoils. Ultimately, our concern is the recoil path of such nuclei under 100 keV to allow us to observe the signals of WIMPs. So as to obtain longer tracks and clear Bragg curves, higher fuel gain operations at lower pressures with low-power neutron beams are wanted. The measurement of the incident neutron power with Time-Of-Flight could even be helpful to examine the quenching factor of nuclear ionization within the micro-TPC.



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