Hilcker, Michaela (2020)
A superfluid liquid helium target for electron scattering experiments at the S-DALINAC.
Technische Universität Darmstadt
doi: 10.25534/tuprints-00012811
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

The aim of this work was to develop a superfluid helium target for electron scattering experiments at the S-DALINAC. The target consists of a multistage helium cryostat including target cell and corresponding scattering chamber. It is initially filled with liquid helium at boiling temperature and then cooled down to 1.8 K via vapor pressure reduction. The infrastructure of the QCLAM spectrometer provides a set of basic conditions for the design. Difficulties in handling liquid helium provide further challenges. After the delivery of the required components, the cryostat had to be assembled and tested. The development of a suitable cooling procedure was a particularly critical point. The functionality of the cryostat was demonstrated in a following experiment. The assumed advantages of superfluid helium instead of liquid helium at boiling temperature as target material were confirmed. A commissioning experiment at the QCLAM spectrometer was performed. By evaluating the spectrum of elastically scattered electrons, the target thickness could be measured experimentally. It agrees with the geometric manufacturer's specifications. During the experiment, the focusing of the electron beam on the target was difficult. Therefore, simulations on a modified target cell geometry with an increased target area were performed.

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