The Study Of Signal Extraction And Track Reconstruction Of A GEM-TPC Prototype

Time Projection Chamber (TPC) is a high precise charged particle tracking detector. It can provide both 3D spatial coordinates and particle tracks to get dE/dx information. With high ability of particle identifying, it has been widely used in a lot of high energy physics experiments. TU-TPC, constructed successfully at Tsinghua University, is the 1st TPC prototype based on GEM readout in China. For its good performance, it will provide a basis for future and improvement.TU-TPC readout electronics, improved from the MDC electronics of the BESâ…¢of IHEP, is used to extract information on arrival time and charge of each channel and provide the raw data for off-line analysis. Served as TU-TPC readout electronics, it has several faults as follow:1. During the data acquisition, charge is computed by method of digital integral based on FADC results, so it does not contain information on waveform samples in raw data. But only waveform samples information is needed when track reconstruction during off-line analysis. On the other hand, in order to compute Q value more accurately, operations of baseline assessment and noise elimination are needed. It also requires waveform information in the raw data.2. In the MQT circuits, charge Q and T are measured separately, and it causes that Q can't correspond with T in the same channel. The events that Q and T is not one-to-one correspondence have to be thrown away during track reconstruction. For these reasons, DAQ system, include hardware and software, is improved partly to fulfill readout requirements of TU-TPC.In the dissertation, the method of information extraction and track reconstruction was studied systematically. The following works were accomplished:1. The upgrade of TU-TPC readout electronics system, including hardware and software. After upgrade of electronics, the waveform samples and drift time information can be read by DAQ system. It also resolves successfully the problem of correspondence between Q and T.2. Off-line data analysis. In this step, several digital filters were designed based on Matlab or ROOT tools to estimate and subtract baseline, eliminate noise.3. Track reconstruction. Based on Doublefit platform, ROOT tool and LCIO framework,3D tracks of charged particle were reconstructed successfully. Using performance analysis program, perfonnance parameters such as x-direction resolution, z-direction resolution, diffusion constant, were computed in the following step. It shows TU-TPC has excellent performance and can be well capable of readout for GEM-TPC. In the final part of the dissertation, the performance of the prototype was studied systematically with different conditions, such as diffusion constant and spatial resolution. The results show TU-TPC performance parameters are improved obviously through improvement of electronics and signal optimization. Therefore, the accomplishment of this article will be important for the following research of GEM-TPC readout.