Research On Front-End Electronics For PandaX-? Experiment

In high energy physics,low background experiments have attracted the attention of physicists in recent years,which are usually carried out in the underground laboratory.In general,the low background experiment is to research rare events,in which the Dark Matter and the Neutrinoless Double Beta Decay are regarded as the topmost topics to explore the nature of the cosmos and particles.According to astronomers,the visible matter in the universe is only 4.9%,while the rest in inferred as dark matter and dark energy.In order to find the evidence that dark matter exists,some experiments have been carried out in the world,such as LUX,AMS and so on.The neutrinoless double beta decay is a conjecture based on the double beta decay.The double beta decay is also a kind of rare events,which can be happened in some even-even nucleus.During the double beta decay process,two neutrinos will be produced,which has already been observed in the experiment.On this basis,an assumption has been proposed that no neutrinos could be observed during the decay.If the neutroniless double beta decay really exists,the lepton number conservation can be broken and the antiparticle of the neutrino can be confirmed as itself,which is of great significance to the development of high energy physics.Currently,EXO,NEXT and other experiments have been carried out in the world.To search for the above-mentioned rare events,the PandaX series experiments have been developed in China JinPing Underground Laboratory,which is the deepest underground laboratory in the word,providing the most natural barrier for the detection of rare events.As the earliest experiment in PandaX,PandaX-I aims to find the evidence that dark matter exists.PandaX-II is the upgrade of PandaX-I.However,PandaX-III is put forward with a new objective,which is intends to search for the neutrinoless double beta decay.In the first phase of the experiment,a high pressure gas Time Projection Chamber(TPC)will contain 200 kg,90%136Xe enriched gas operated at 10 bar.Fine pitch micro-pattern gas detector(Microbulk Micromegas)will be used at both ends of the TPC for the charge readout with a cathode in the middle.So when a neutrinoless double beta decay occurs,the total charge is?10 pC,and the readout time windows of 95%events are less than 100 ?s.In addition,the total readout channels in the experiment is as high as 10496.To readout all of the 10496 channels and realize the energy resolution of 3%in the first phase,the front-end electronics of high integration,high performance,and low noise have been developed in the paper.In this paper,combined with the readout electronics of related experiments in the world,the readout system following a modular architecture has been put forward at first,which can be divided into the front-end electronics and the back-end electronics with the former as the focus of this paper.The front-end electronics consist of the front end card(FEC)and the mesh readout card(MRC),reading out the strip signals and the mesh signals of the Micromegas detector,respectively.And the data transmission between the front-end electronics and back-end electronics is through optical links.In the FEC,the cornerstone is a 64-channel application specific integrated circuit,namely AGET which is based on a switched capacitor array.Each FEC integrates 256 readout channels,and a total of 42 FECs are needed in the experiment.In the MRC,the analog signal processing is based on discrete components with 42 channels in a board,so 2 MRCs are needed in the experiment.Currently,5 FECs and 1 MRCs have been designed and implemented in the laboratory.In order to study the performance of the front-end electronics,a series of tests have been developed in the laboratory.The test results show that the integral nonlinearity is better than 2%,and the noise is less than 1.7 fC when the equivalent capacitance of the detector is less than 100 pF,meeting the design requirements of the PandaX-?experiment.Then,a joint-test of the FEC and a resistive Micromegas with four corners readout has been carried out in University of Science and Technology of China(USTC)and the testing energy resolution of 55Fe is?18.7%@5.9 keV.In addition,to test various design features of the TPC,a small-scale TPC equipped with 7 Microbulk Micromegas detectors has been built as the prototype detector in Shanghai JiaoTong University(SJTU).At present,just one Micromegas detector has been installed in the TPC,and the joint-test of the FEC and the prototype TPC is being undertaken and further data are still accumulating now.The preliminary energy resolution of 241Am is?58.8%@59.6 keV.At last,the requirements,the design and the performance of the front-end electronics for PandaX-? experiment are summarized in this paper.In addition,the shortages of the current design are put forward,and some suggestions are made for further improvement.