6月25日 High-Performance Gamma Spectrometers for Fusion Plasma Diagnostics

报告题目：High-Performance Gamma Spectrometers for Fusion Plasma Diagnostics

报告时间：6月25日（星期四）下午14：00-15：30 

报告地点：4号楼5楼中间会议室

报 告 人：Prof.Alexander Shevelev

报告人简介：

Dr.Alexander Shevelev, from Ioffe Institute of the Russian Academy of Sciences, works on runaway electrons and fast ions at the GLOBUS-M2, TUMAN-3M, FT-2 (RF), JET (UK), and ASDEX Upgrade (Germany) tokamaks, participated in and supervised the development of diagnostic equipment for plasma facilities based on the use of gamma-ray, HXR, and neutron spectrometry methods, supervised nuclear physics research at the cyclotron of the Ioffe Institute. He is a member of the Russian diagnostic team in the ITER Project and leader of the Gamma-ray Spectrometry group in the Ioffe Institute, member of the Diagnostics and Energetic Particle ITPA expert teams. He published more than 100 publications in peer-reviewed scientific journals.

报告简介：

This report focuses on developing gamma-spectrometry methods for diagnosing energetic particles, in terms of both instrumentation and experimental data analysis. It is impractical to use standard laboratory equipment when conducting measurements under fusion experiment conditions, such as in the presence of a tokamak's stray magnetic field and high levels of neutron and gamma-ray background. This requires the use of advanced methods for radiation detection, digital signal processing and experimental data analysis algorithms. 

The development of silicone photomultipliers (SiPMs) could solve the problem of detector sensitivity to magnetic fields. However, issues remain regarding the devices' gain linearity and radiation hardening. Detectors equipped with modern SiPMs can achieve a high count rate of up to 10⁶ counts per second while maintaining gain stability and energy resolution. 

The problem of radiation resistance in photodetectors can be solved by transmitting light over significant distances via optical fibres with acceptable losses using modern methods. Semiconductor detectors, such as HPGe, have demonstrated their ability to provide accurate information on the energy distribution of fast ions in experiments at JET, thanks to their high energy resolution. In order to use them in next-generation facilities, however, the problem of accurately estimating the dead time of measurements must be solved by applying new methods of digital signal processing.  In order to effectively use gamma-ray spectrometers for plasma measurements, it is necessary to study their characteristics at particle accelerators. This talk presents the results of test measurements of various types of detectors, including LaBr3 scintillation detectors with both traditional photomultiplier tubes (PMTs) and SiPMs, as well as semiconductor HPGe spectrometers on a cyclotron ion beam.