Consistency test of PMT SPE spectrum from dark-noise pulses and LED low-intensity light

Photomultiplier tube(PMT)has been an essential instrument for low background experiments,and the accuracy of single photoelectron(SPE)calibration will directly affect the energy reconstruction of the detector.The SPE spectrum can be acquired from the charge distribution of dark-noise pulses or the low-intensity light signal triggered by LED.However,there are arguments on whether the two methods are consistent.In this paper,the Hamamatsu R5912-20mod PMT and the EMID642KNFL PMT have been tested adopting the two methods with signal waveform recording electronics.As comparison,traditional charge-to-digital conversion system is also used to test SPE spectrum.The results show that they are consistent when the PMTs are working at typical recommended high voltage(HV).

Calibration of liquid argon detector with ^(83m)Kr and ^(22)Na in different drift fields

Introduction Liquid noble gases are widely used as targets in low background search experiments,particularly in direct dark matter search experiments.83mKr is an excellent low-energy internal calibration source for future larger liquid noble gas detectors.Purpose To calibrate liquid argon detector with 83mKr in different drift fields and to study the correlation between light yield and drift fields.Method A dual-phase LAr prototype detector was designed to study the 83mKr responses in liquid argon.83mKr atoms are produced through the decay of 83Rb and introduced into the LAr detector through the circulating purification system.Conclusion We report that the light yield reaches 7.26±0.02 pe/keV for 41.5 keV from 83mKr and 7.66±0.01 pe/keV for 511 keV from 22Na,as a comparison.After stopping the fill,the rate decays of 83mKr are with a fitted half-life of 1.83±0.11 h,which is consistent with the reported value of 1.83±0.02 h.The light yield that varies with the drift electric field from 0 to 200 V/cm has also been reported.

Preliminary measurement of the spherical proportional counter prototype

Introduction A novel large-volume spherical proportional counter(SPC)aims at relatively large target masses with low threshold,low background,and possible particle identification,with an extremely simple and robust operation.Experimental In this paper,we present some progress on the study of such a kind of detector,with a prototype in Beijing for alpha neutron measurement and long-term running stability.Results Preliminary understanding was achieved with a SPC prototype.It can measure alpha and neutron and show the capability of particle identification.Long-term running of the detector shows that it is a good stable detector.Discussion It needs more tests and studies to reach lower energy region,better particle identification,more understanding of efficiency,etc.Conclusions The SPC,in principle,is capable of detecting very low energy nuclear recoils(in the few tens keV energy region)and smaller energy with lower pressure,thus being a very good candidate for rare event searches.

Prospects of detecting the reactor v_(e)-Ar coherent elastic scattering with a low-threshold dual-phase argon time projection chamber at Taishan

Background We propose to measure the coherent elastic neutrino-nucleus scattering(CEvNS)using a dual-phase liquid argon time projection chamber(TPC)with 200 kg fiducial mass.The detector is expected to be adjacent to the JUNOTAO experiment and to be about 35 m from a reactor core with 4.6 GW thermal power at Taishan.The antineutrino flux is approximately 6×10^(12)cm^(−1)s^(−1) at this location,leading to more than 11,000 coherent scattering events per day in the fiducial mass.Motivation The nuclear recoil energies concentrate in the sub-keV region,corresponding to less than ten ionization electrons in the liquid argon.The key question is how to veto and shield the background in the hall where the vertical overburden is about 5 m.w.e.And what is the signal count rate and the background rate.In addition,what physical parameters can be measured what is the sensitivity.Methods We used the Geant4 to simulate the backgrounds from cosmic ray muons and ambient radioactivity decays.And a veto and shielding design is presented.Then a χ^(2) function is constructed and the sensitivity calculate package built to calculate the sensitivity of physical parameters.Results The detection of several ionization electrons can be achieved in the dual-phase TPC due to the large amplification in the gas region.With a feasible detection threshold of four ionization electrons,the signal rate is 955 per day.The detector is designed to be shielded well from cosmogenic backgrounds and ambient radioactivities to reach a 16%background-tosignal ratio in the energy region of interest.With the large CEvNS sample,the expected sensitivity of measuring the weak mixing angle sin^(2)θ_(w),and of limiting the neutrino magnetic moment are discussed.In addition,a synergy between the reactor antineutrino CEvNS experiment and the dark matter experiment is foreseen.