Study On Readout Electronics System For LAr-based Direct Dark Matter Detection Experiments

The existence of dark matter has been confirmed by cosmological studies and astronomical observations.In recent years,the research of dark matter is a hot topic in the fundamental Physics community.Many experiments has been carried out,such as AMS02,SuperCDMS and DarkSide experiments.Though more than 80 years have passed since the concept of "dark matter" was proposed,human have not detected dark matter particles and we still know nothing about its nature characteristics.Methods for dark matter detection are generally classified into collider generation,direct detection,and indirect detection.Dark matter particles interact with fundamental particle with very low cross-sections.Direct dark matter detection needs to discriminate the rare dark matter cases from a large number of background cases.The research of detector signals for particle discrimination can distinguish electronic recoil signals from nuclear-like recoil signals,and is the most effective way to reduce background cases.At present,direct dark matter detection is gradually reducing the cross section of dark matter and fundamental particle,and it is expected to find dark matter in lower areas.Direct detection requires higher detector sensitivity to search for areas that are already close to the neutrino background.Therefore,the upgrade experiments have increased the detector volume to tons.The work of this thesis is to design a readout electronics system for the ton-level liquid argon detector.The proposed readout system is composed of pre-amplify module(PAM),front-end digital module(FDM)and trigger clock module(TCM).The PAM amplifies the signal from the PMT in the detector and increases the DC offset to condition the bipolar signal.The FDM exploits a high-speed analog-to-digital converter(1-Gsps,14-bit)to acquire signals from the photomultiplier tube(PMT).The TCM fans the trigger and synchronous clock to each FDM via backplane buses.In this paper,the performance of this electronic system is tested.Firstly,we test the amplification and offset function of the signal conditioning module,and the analog bandwidth.The static performance index test(INL,DNL)and dynamic performance index test(Enob)of the front-end digital module have been tested.In addition,synchronous testing between the channels of the front-end digitization module have been implemented.The results of the electronic performance test were in line with expectations.Furthermore,this paper also carried out joint testing with prototype detectors.Single-photoelectron calibration and radioactive source test are implemented using a liquid-Argon detector.Due to the gain being in the range of 5.89 x 105 to 5.32 x 106,the peak of single-photoelectron spectrum can be clearly distinguished from the baseline.Lifetimes of the fast and slow components of the gamma and neutron events'waveforms are 15.9 ns and 1.312 ?s,respectively.In addition,the nuclear recoil events from a PuC neutron source can be accurately discriminated from gamma events by pulse shape discrimination method.