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Autoren:
Dickmann, Marcel 
Dokumenttyp:
Dissertation / Thesis 
Titel:
Radio Frequency Energy Elevation and Characterization of a Pulsed Positron Microbeam 
Betreuer:
Dollinger, Günther, Univ.-Prof. Dr. rer. nat. habil. 
Gutachter:
Dollinger, Günther, Univ.-Prof. Dr. rer. nat. habil.; Brusa, Roberto S., Prof. Dr. 
Tag der mündlichen Prüfung:
17.11.2017 
Publikationsdatum:
07.02.1018 
Jahr:
2017 
Sprache:
Englisch 
Schlagwörter:
Forschungsreaktor Garching II ; Rastermikroskop ; Schnittstelle ; Positronenquelle ; Positronenstrahl ; Energieverlust ; Strahlqualität ; Hochschulschrift 
Stichwörter:
Positron Annihilation Lifetime Spectroscopy Microscope Microprobe Radio Frequency Elevator 
Abstract:
This thesis concerns the implementation of the renewed Scanning Positron Microscope (SPM) interface, including the positron elevator, at the high intensity positron source NEPOMUC at the Munich research reactor FRM II. The interface transfers the NEPOMUC beam into a pulsed microbeam of high brightness in order to reach the stringent requirements of the microscope. With the SPM itself it is possible to measure spatially resolved positron annihilation lifetime spectra in order to investigate defects for material science. The in-pile positron source NEPOMUC provides a once-re-moderated positron beam of 3.0 · 107 e+/s , 20 eV kinetic energy, about 2 mm diameter and a transverse phase space volume in the range of 4.2 mm2eV·me. To generate a beam spot of ≤ 2 µm on the sample, the SPM requires a phase space of less than 0.7 mm2eV·me. For this reason, the interface is equipped with an additional re-moderation stage, which enhances the beam brightness. With every additional component, however, the manual beam alignment becomes more delicate and time consuming. Therefore, devices for beam characterization and automated beam alignment have been developed and applied with great success. Furthermore, a serious problem is that every re-moderation step leads to a loss of several keV total beam energy. Limitations, which issue from the low beam energy and the restricted space between microscope and interface, prevent an increase of the kinetic beam energy by a conventional radio frequency accelerator. Thus, we developed a new device, which increases the potential beam energy without altering any other beam parameters. To stress the differences we call the setup elevator. This final device is indispensable to operate the SPM at NEPOMUC. To verify that the high beam quality, which is achieved by the SPM interface, gets not lost as a result of the energy elevation, we etermined the transverse phase space as 0.012 mm2eV·me for an 1-keV-elevated beam. The results show that the elevator concept and design work. In addition, the elevator is also of advantage for other positron beam facilities, since it offers the possibility to bias source and sample on the same potential. 
DDC-Notation:
539.7214 
Fakultät:
Fakultät für Luft- und Raumfahrttechnik 
Institut:
LRT 2 - Institut für angewandte Physik und Messtechnik 
Professur:
Dollinger, Günther 
Open Access ja oder nein?:
Ja / Yes