Calibration and Theory of EUV Detectors: The PHEBUS EUV Detector on BepiColombo and the Exceed EUV Detector on SPRINT-A
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Calibration of extreme ultraviolet (EUV) instruments utilized in space missions is essential in order to determine detector properties and optimize their design. Under the supervision of Professor Yoshikawa, this study has looked into Resistive Anode Encoders (RAE). Part of the thesis study the RAE readout mechanism and the role of RAE shape, readout technique, electrode position, sheet resistivity and intrinsic capacitance and its effect on detector positional resolution and image distortion. The goal of the study is to increase knowledge of Micro channel plate (MCP) and RAE based detectors so that it can be applied in primarily the development of the PHEBUS and EXCEED detectors and also in future EUV detectors developed at the University of Tokyo. A general conclusion that RAE of Professor C.W Gear's circular arced terminated design utilizing charge ratio as readout technique is favourable from both resolution and distortion perspectives is made. In order to determine the distortion the RAE and MCP assemblies has been irradiated by a deuterium source through a fixed grating. The Gear anode is found to have an ideally linear position response over the majority of the anode area and shows small signs of positive radial distortion, known as barrel distortion. When designed as a rectangle the effective area of the detector diminishes and the barrel distortion increases. The report also includes a study on determination of correct pulse shape amplifier time constants for optimized operational resolution. A conclusion is drawn, that RAE resistivity and intrinsic capacitance governs the charge diffusion speed through the anode resistive layer and the correct choice of shaper time constant to match the charge diffusion speed, as well as frequency of incoming particles are the key elements in a high resolution distortion free RAE based detector. The study includes a series of experiments on RAE charge diffusion and charge injection techniques. The reason for previously unknown RAE charge leakage is explained and has through experiments with probe injected charge been identified to be an error in charge injection technique rather than an error in the anode itself. Theory on correct probe injection is presented stating that injection of charge should be done with a probe with minimized probe tip area. This result shows that injection of charge through a probe tip is not suitable for resistive anode surfaces due to their mechanically brittle nature. Further research into electron gun injection of charge is suggested as an alternative. Measurements of overall detector capacitance have been made utilizing a number of electronic circuits. A Schering bridge is proved to be partially successful and a AVR based timing circuit is shown to be superior in measurement accuracy. The capacitances between the different MCP stages and towards ground is found to be in the range of 30 pF - 150 pF which fit previous calculations made by Dr. Kazuo Yoshioka.
Place, publisher, year, edition, pages
2013. , 100 p.
Technology, EUV, BepiColombo, Phebus
IdentifiersURN: urn:nbn:se:ltu:diva-47358Local ID: 4e9d3ffe-4724-46c0-99c5-5dbeec135a58OAI: oai:DiVA.org:ltu-47358DiVA: diva2:1020679
Subject / course
Student thesis, at least 30 credits
Space Engineering, master's level
Validerat; 20131210 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved