Quelle ultrakalten Neutronen (UCN) am pulsbaren Forschungsreaktor TRIGA Mainz sowie Studien mit UCN
Zusammenfassung der Projektergebnisse
We succeeded to establish an UCN infrastructure in Mainz and Munich, which will be of great importance for future experiments in fundamental physics with ultra cold neutrons. With support from this grant we developed a UCN source at the tangential beam tube C at TRIGA-Mainz, which provides UCN densities of 4 UCN/cm^3 in an experimental storage volume of 10 dm^3. This number is comparable to densities of the so far strongest UCN source at the high flux reactor at the Insfitute Laue-Langevin in Grenoble. With the new UCN source at the radial beam port D at TRIGA-Mz currentiy in its commissioning phase, this number will be increased by at least one order of magnitude thanks to the high thermal neutron fluence of ~ 10^14 n/cm^2 per pulse. In addition, the development of both UCN valves and sputtering techniques for UCN guides, also funded by this grant, lead to major improvements in the transport efficiency for UCN, i.e., from the source to the experiment. These improvements were included in the construction and design of the UCN source at beam port D in Mainz, as well as at the new UCN source in Munich, where also other techniques have been investigated successfully by now (outside this grant). Scientific progress has also been achieved in the understanding of UCN production and extraction mechanisms in cryo-crystals. The density of states of solid-state excitations in deuterium has been measured. Also, other converter materials have been investigated. The results of these experiments helped to understand the underlying physics processes. Again, these measurements are complemented by fundamental solid-state investigation of UCN converter materials, performed at FRM II, partially following the investigations described here. For the design of the new UCN source in Munich, many parameters were tested using the prototype setup at beam tube C in Mainz, which serves as a proof-of-principle with solid understanding to allow extrapolation to future sources with such geometry. Several technical parameters were adapted and optimized within this work. Based on results of this project, the ultra cold neutron laboratory at the neutron research reactor "Forschungs-Neutronenquelle Heinz-Maier-Leibnitz" (FRM II) in Munich will be established. The new UCN source in Munich will be able to provide up to 10'^4 UCN/cm^3 in attached storage experiments with volumes of several hundred litres, which would supersede existing UCN sources by more than one order of magnitude. This offers new possibilities and enhanced statistical and systematic precisions for experiments with ultra cold neutrons.
Projektbezogene Publikationen (Auswahl)
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Characterization of a solid deuterium converter for UCN in the framework of the Mini-D2 project at the FRM-II reactor in Munich, Dissertation, Techn. Univ. München (2007)
D. Tortorella
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Characterization of solid deuterium as a source material for ultracold neutrons (UCN) and development of a detector concept for the detection of protons from the neutron decay. Dissertation, Techn. Univ. München (2008)
A.R. Müller
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Produktion von ultrakalten Neutronen mit einem festen Deuteriumkonverter, Dissertation, Techn. Univ. München (2008)
A. Frei
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Investigation of a superthermal ultracold neutron source based on a solid deuterium converter for the TRIGA Mainz reactor. Dissertation, Johannes Gutenberg Univ. Mainz (2009)
T. Lauer
