The Application And Research Of The Digital Waveform Sampling Technology In Particle Detection

Positron Emission Tomography(PET) can monitor the distribution of irradiation dose and the position of heavy ion beam in the treatment of the heavy ion tumor radiotherapy and introducing time of flight(TOF)information in PET can reduce the data processing time and improve the image quality of the image reconstruction. During the development and application of the TOF-PET system for the heavy ion tumor radiotherapy monitoring, the traditional discrete electronics readout system is with the charaters of large scale, complex circuit, high power consumption, low measurement accuracy and poor reliability, and it is unable to meet the demand for TOF-PET system. Therefore, it is necessary to design and develop a new high integration and low cost readout electronics system. Based on the requirement, cooperation with nuclear electronics research group, we have developed a digital waveform sampling system with the DRS4 chip(Domino Ring Sampler chip version 4) as the core, which is based on the switched capacitor array(SCA) technology. It can sample 16 channel signals in cascade mode, have on-board coincidence measurement function and can be used to obtain accurate TOF and energy information.The TOF-PET timing calibration system, composed of La Br3 scintillation detector, is successfully developed. The application of DRS4 and subsequent data processing methods are researched and developed. The experimental results imply that the coincidence time resolution(178 ps) and energy resolution(3.42%@511 ke V) acquired by the DRS4 system and with the digital waveform analysis algorithm, are better than the time resolution(250 ps) and energy resolution(4.2%@511 ke V) acquired by the traditional CAMAC system in comparison.The prototypes of TOF-PET detector are successfully developed, which consists of La Br3 crystal array, position sensitive photoelectric multiplier tube and simplified readout circuit. The DRS4 system is firstly used to test the performance of the prototypes. Compared to the CAMAC system, the black scattered points on PET crystal flood image obtained by using DRS4 system are more clear and easy to segment and the SNR(signal to noise ratio) is higher. The DRS4 system achieves better energy resolution(14.9%), position resolution(0.74 mm) and coincidence time resolution(750 ps) in comparison with the CAMAC system. The results verify the feasibility of the application of the DRS4 system in TOF-PET and the aim of developing the DRS4 system is achieved.Based on the excellent performance in the experiments, we have used the DRS4 system for the first time in domestic for lifetime measurement of excited states in nucleus and the experiment of in-beam particle identification. Fast timing method is successfully used to measure lifetime of excited states and the results are similar to the assessed lifetime posted by the NNDC(National Nuclear Data Center). In the in-beam particle identification experiment, the proton beam, α beam, 12 C beam and the secondary beam produced by 28 Si are measured, and the different particles can be identified.In this paper, the DRS4 digital waveform sampling system and the digital waveform analysis algorithms are studied and successfully used in several applications. These experimental results indicate that the DRS4 system and the digital waveform analysis algorithm have higher measurement accuracy compared to the traditional CAMAC system for the energy and time measurement. Also the system has a large number of advantages like high density of channels, simple circuit, high integrated density, small size, small transmission noise, low cost, easy debugging and information lumped-analytical, which complies with the design requirements for TOF-PET readout electronics.