Next-Generation Perturbed Angular Correlation Spectroscopy
Matthias Nagl
Doctoral thesis
Date of Examination:
2014-05-13
Date of issue:
2014-06-12
Advisor:
Hofsäss, Hans Christian Prof. Dr.
Referee:
Hofsäss, Hans Christian Prof. Dr.
Referee:
Krebs, Hans-Ulrich Prof. Dr.
Referee:
Krause-Rehberg, Reinhard Prof. Dr.
Persistent Address: http://hdl.handle.net/11858/00-1735-0000-0022-5EE5-B
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Abstract
English
Time differential perturbed angular correlation (TDPAC) spectroscopy is a nuclear solid-state physics method with unique advantages: Due to the penetrating power of gamma radiation used as information carrier, it allows studying of probe atoms' surroundings inside bulk material and under extreme conditions. It is sensitive to magnetic fields and electric field gradients at the probe nuclei's sites. This work aims at extending the scope of this well-established method by exploiting technological advancements. A newly developed software driven digital spectrometer reaches better performance and provides an improved measurement workflow, which increases the output and quality of measurements, compared to other spectrometers. Comprehensive simulation based studies concerning the properties and behavior of scintillation detectors as well as the performance of digital signal processing approaches for the analysis of these detectors' anode signals were conducted. These studies provide a deeper understanding of performance-limiting factors and allowed reaching of extraordinary time as well as energy resolution values of 219.8 ps and 3.30 % (both FWHM) for the spectrometer using the usual Co-60 and Cs-137 benchmarks. A new method for the automatic compensation of detector gain drift complements the other improvements of the measurement process. For the exploitation of new opportunities arising due to the spectrometer's improved performance and the availability of exotic nuclides at production facilities like ISOLDE (CERN), a database-driven nuclide search software was implemented. This software permits the identification of suitable candidate nuclides and thereby extended the selection of possible probe elements. Three new implantation chambers allowing for measurements involving exotic probe nuclides at ISOLDE were developed and are also presented in this work.
Keywords: PAC; TDPAC; Spectrometer; Detector Simulation; Scintillation Detector; Gamma-Gamma; Drift Compensation; Probe Nuclides; ISOLDE; Solid-State Physics; Software Defined Spectroscopy; Digital
