BL

B.A. Looman

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Master thesis (2020) - B.A. Looman, H. van der Graaf
The goal of this research is to characterize thin membranes used as transmission dynodes (tynodes) for electron multiplication. A stack of tynodes could be used in a novel ultra fast soft photon counter. A combination of a charge sensitive TimePix1 CMOS chip and a pulsed electron gun were used as part of a setup deemed Tytest. The pixel chip was calibrated using a surrogate function that is fitted to the single pixel responses of 76 different pixels. The calibration is used to perform Transmission Secondary Electron Yield (TSEY) measurements on a 20 nm thick alumina membrane. The maximum TSEY value observed is 2.76 ± 0.64 for a incident energy of 1675 eV. The maximum TSEY value seems to be at higher incident energies which cannot be reached using our setup. A unexplained spread in electrons being emitted by the tynode is observed.
The second part of this research was to create a stack of tynodes which can be used to convert a single electron into a measurable signal. The goal is to stack the tynodes using a self aligning mechanism and measure the misalignment. A ZEISS Axio-zoom V16 light microscope in combination with two µm precision manipulators placed in a clean room at Nikhef in Amsterdam is setup in this research used to stack tynodes. The aim was to have a misalignment better than 5 µm, and this setup a misalignment of 4.1±1.3 µm was measured. It’s important to note that only the misalignment between two tynodes is measured, since no more were readily available.
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We measure the transmission secondary electron yield of nanometer-thick Al2O3/TiN/Al2O3 films using a prototype version of a Timed Photon Counter (TiPC). We discuss the method to measure the yield extensively. The yield is then measured as a function of landing energy between 1.2 and 1.8 keV and found to be in the range of 0.1 (1.2 keV) to 0.9 (1.8 keV). These results are in agreement to data obtained by a different, independent method. We therefore conclude that the prototype TiPC is able to characterise the thin films in terms of transmission secondary electron yield. Additionally, observed features which are unrelated to the yield determination are interpreted. ...