Investigation of the Plasma delay time in PIPS detectors using the LOHENGRIN spectrometer

Abstract: This project has examined the effects of plasma delay time (PDT) and pulse height defect (PHD) for protons, tritons and alpha particles. The goal was to determine PDT and PHD for alpha particles relative to protons, by using data from a subset of measurements taken with a silicon detector of type PIPS at the LOHENGRIN spectrometer. The PIPS detectors were used in combination with an MCP to measure the time of flight (ToF) of the particles, in addition to their energies. The project involved calibrating energy and time measurements with linear calibration. As a first step, peaks were identified for each particle event in the data set. A Gaussian fit was used to determine the mean value and spread of the peak. Under the assumption that protons have zero PDT and PHD, the proton peaks were used to calibrate all the data with a linear fit. In order to determine the PDT and PHD the real values of ToF and energy for the particles had to be estimated and compared with the measurements. The LOHENGRIN spectrometer gives the real energy of the ions reaching the MCP chamber. The energy losses that occur when using the MCP were estimated with the program SRIM, used to calculate stopping-power and ranges of ions. The real ToF was derived from energy and flight path of the particles. For the flight path measurements of the experimental equipment had to be conducted, partly by the writers of this project and partly by a research team with access to the LOHENGRIN. The result presents the relative PDT and PHD of protons, alpha particles and a triton. The relationship of PDT and PHD to mass and energy is discussed. Notably the PDT was found to depend inversely on the energy of the particle. No definite trend in PHD of alpha particles relative to protons was found, thought to be due to the effect being to small to observe in this study. Empirical formulae from earlier papers were tested to compare with the result of this project. The trend of the results are supported by these formulae.