Nuclear physics experiments typically involve the collection and analysis of detector signals produced by the interaction of subatomic particles with matter to deduce various quantities. When heavy ions are involved, Si Detector signals are distorted by the formation of a plasma-like cloud from the interaction between the heavy ions and the detector material. The signal amplitude is reduced and delayed, two effects known as Pulse Height Defect (PHD) and Plasma Delay Time (PDT). A recent experiment was performed at the Institut Laue-Langevin(ILL) experimental nuclear reactor facility in Grenoble, using the LOHENGRIN mass spectrometer, to study these walk effects. The purpose of this project is to use a subset of the data to perform pulse shape analysis and develop a parametrization of the pulse waveform in order to better understand the PDT and PHD and how the pulses are affected. Initially, the PDT and PHD are estimated for masses 90, 100, 130 and 143 u using already established methods. The pulse waveforms are then investigated and a suitable parametrization of the pulse waveform is developed. The region around the pulse onset, which is important in extracting the timing characteristics of the pulse, is found to be described rather well by the Landau function. The Landau function parameters are further investigated and correlations with pulse shape characteristics are discussed. Finally, this novel parametrization is used as an alternative approach to estimate the PDT for the same masses as initially. Comparisons between the two methods indicate that the PDT is actually a combined effect of the physical plasma delay and the walk effects introduced by the underlying triggering routine that is used during offline analysis.

The goal of the project was to simulate a typical silicon detectorresponse in an experiment made at the Tandem lab in Uppsala. The plasma delay time was analyzed by simulating the experiment. Three different models of the plasma delay time were introduced and their effects on time of flight measurements were studied. A continuation of the main goal was to see if the inserted PDT models could be extracted from the simulations when being treated as a pseudo experiment, to see theoverall effectiveness of the experiment. When comparing the final simulations with actual measurements, it was concluded that the main properties of the detector response had been featured and that the simulations were successful. The successful extraction of the inserted plasma delay times and their dependencies on energy also proved that the experiment was a good one. The result of the project was that one of the models seemed to have a strong mass dependence, however with no clear dependence on the energy. The other two models showed a somewhat similar dependence on energy. One of the two models also showed a relatively weak mass dependence.

When an atomic nucleus undergoes fission, two fragments with different mass and kinetic energy are emitted. The highly unstable fission fragments (FFs) evaporate prompt neutrons soon after the nucleus splits. A precise measurement of both, the mass yield distribution of the FFs and the average prompt neutron emission, $\bar{\nu}$, is important not only for current nuclear technologies but also for the development of future technologies such as Generation IV nuclear power plants. Moreover, the experimental determination of the mass yield distributions, both pre- and post-neutron emission, is valuable for testing fission models. Additionally, a precise measurement of the average neutron multiplicity as a function of the FFs mass, <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?$%5Cbar%7B%5Cnu%7D(A)$" data-classname="equation" data-title="" />, is crucial in the understanding of how the excitation energy is shared between nascent FFs.  The VElocity foR DIrect particle identification spectrometer (VERDI) is designed to achieve pre- and post-fission mass distributions with resolutions between 1-2 u. VERDI is a double-energy double-velocity instrument that consists of two arms. On each arm is operated one Microchannel Plate detector (MCP) for the collection of the FFs start time and up to 32 Passive Implanted Planar Silicon (PIPS) detectors for the stop time and energy detection of the FFs. However, challenges in the experimental measurements with VERDI arise due to the high degree of ionization (plasma) in the detector material from the interaction with the FFs. The plasma causes a delay in the charge carriers' migration for the signal start, known as the plasma delay time effect (PDT). Furthermore, the recombination of charge carriers in the plasma causes a shrinking in the signal's height, known as pulse height defect (PHD). This phenomenon leads to inaccuracies in the measurement of FFs mass distributions and increased systematic uncertainties.  Previous studies on PDT and PHD have shown varying behaviors across different detector types, which motivated dedicated studies in the type of PIPS detectors used in VERDI. An experimental campaign to characterize the PDT and PHD in PIPS detectors was conducted in the LOHENGRIN recoil separator, which is part of the ILL nuclear facility in Grenoble, France. Measurements of FFs in a range of masses between 80 u and 149 u, with energies between 20 MeV to 110 MeV, were taken to fully characterize six PIPS detectors. The resulting PDT and PHD values were 1 ns to 4 ns and 2 MeV to 10 MeV respectively. The PDT and PHD exhibited consistent energy and mass dependencies across the detectors, which enables the possibility of an event-by-event correction of VERDI data. In this thesis, the basis for discussing the results of the studies of the PDT and PHD effects will be presented.