Design And Development Of The Plastic Scintillator Detector Of DArk Matter Particle Explorer

Since first proposed by F. Zwicky in 1933, the existence of dark matter has been confirmed by a large amount of astronomical observations. Although the dark matter hypothesis has been accepted by most of the astronomical community and plays a central role in the standard Big Bang cosmology model(i.e. ΛCDM model), the composition and particle nature of dark matter have puzzled the scientists for a long time and continue to stimulate the interest in dark matter research. The Standard Model of particle physics doesn’t have a viable dark matter candidate which posses all the basic properties of dark matter; on the other hand, many new theories beyond the Standard Model have predicted new particles that turn out to be excellent dark matter candidates. Thus, the detection and study of dark matter particle could be used to verify these new theory, and may even start a new revolution in physics.The DArk Matter Particle Explorer(DAMPE) is a satellite-borne dark matter exploration program which is proposed and developed by China independently. It is one of the most powerful dark matter particle detectors in space, with the broadest energy convering range and highest energy resolution. Based on the indirect detection method,DAMPE aims to search and study dark matter particle by recording the energy spectrum of high-energy gamma ray and electron in the Te V scale, which might be the products of dark matter annihilation or decay.The Plastic Scintillator Detector(PSD) is one of the key sub-detectors of DAMPE.It provides two functions as follows: 1) e/γ identification in combination with the BGO calorimeter of DAMPE; 2) charge measurement for cosmic ions with Z = 1～20. The major work of this doctoral thesis is about the design and development of PSD, which is structured as follows:PSD adopts plastic scintillator as the detection material and accomplishes its functionalities by measuring the deposited energy of incidenct particle in it. To reducethe rate of e/γ misidentification, PSD adopts a modular design strategy and consists of 82 detector modules which form two layers that are perpendicular to each other. On the other hand, the application in space environment imposes special requirements for the design of PSD. Chapter 2 gives a brief introduction about the working principle together with the design of PSD.The large dynamic range readout design is one of the key technologies of PSD.Based on PSD’s functionalities, it was estimated that each detector module should cover a dynamic range from 0.1 MIPs to 1400 MIPs. Thus, we designed and implemented a readout scheme based on the double-dynodes signal extraction from the photomultiplier tube. This design was tested and verified thoroughly using both cosmic ray and relativistic heavy ion beams. These work are presented in Chapter 3.PSD adopts the photomultiplier tube(PMT) as the readout device. To obtain the optimal detector performance, it’s common to carry out a detailed PMT characterization before usage. We designed and built a dedicated PMT test bench, and measured the characteristic curve against voltage of the relative gain and dy58 ratio of all the candidate PMTs of PSD. These work are described in Chapter 4.? Space-borne experiments demand higher stability and reliability of the components of PSD. We have established a strict quality control procedure and applied it in the PSD construction process. Chapter 5 gives a detailed description about this process, with a focus on the test, selection, production and qualification of the PMT and the plastic scintillator bar submodule.After the assembly, PSD needs a complete and detailed test to obtain its performance parameters. For this purpose, we built a dedicated test bench for the cosmic ray calibration of PSD on ground. Chapter 6 gives a short description about this test bench, and presents the preliminary results of PSD calibration including pedestal noise, MIP response, energy resolution, attenuation curve, detection efficiency and position resolution.DAMPE was launched on 17 December 2015 and entered its orbit successfully.During the in-orbit tests, the performance of PSD was stable and satisfies all the design requirements.