Abstract. The HPGe detector assembly of gamma-ray spectrometer cooled by Stirling cycle cryocooler is under consideration. Modal analysis based on the compiled dynamic model was carried out. The natural frequencies and modes shapes for HPGe detector with relative efficiency 15 % mounted by supports made from composite G-Etronax and CESTILENE HD 1000 were calculated by Solidworks simulation. The frequencies of the axial mode are in range of 200-600 Hz where electrical interferences caused by mechanical vibrations (so-called microphone noise) has a large impact on the resolution of spectrometer. It is shown that for cryostat cap the lowest natural frequencies determined by the thickness of input window lay in higher frequency range. The validity of the adopted model was confirmed by the experiments. The calculated natural frequencies of the detector assembly are compared to the harmonics of cryocooler's vibration. The results obtained are useful to identify the interferences source in electrical circuits of spectrometer at its adjusting.

This paper describes the results of a complex simulation of nitrogen boil-off recondensation in a hybrid cooling device for High Purity Germanium (HPGe) detectors. The OpenFOAM platform-based software was used. The proposed finite-volume axisymmetric 2D model combines cooling processes occurring in the considered three-phase medium, including a liquefier condenser (solid), nitrogen boil-off (gas) and the resulting condensate (liquid). At the beginning of the simulation condenser and gas temperatures are set above the condensation point while the end time is set such that the system reaches a quasi-steady state. For conical and hemispherical condensers, the energy consumption for the following processes occurring in the operating mode such as: condenser cooling; cooling of adjacent boil-off nitrogen vapors; their condensation; the gravity-driven flowing; condensate film subcooling and subsequent partial re-evaporation from its surface are compared. The visualizations of the temperature field of the finite-volume model and the velocity vectors of nitrogen vapors adjacent to the condenser are presented. The calculated integral mass recondensation rates were confirmed experimentally on a commercial hybrid cooling device, taking into account the actual equivalent characteristics of the liquefier on the Stirling cryocooler used.

This paper presents the design of an easily portable spectrometer using high purity germanium (HPGe) detector -HandSpec. The key challenge in the design of a lightweight spectrometer is to minimize its heat losses so that efficient electric cooling could be used instead of bulky dewars. The design process has been largely based on experimental investigations. In this study, a digital twin of the HandSpec cryostat using computational fluid dynamics (CFD) method is developed to support the design and optimization of the physical prototype. K: Cryogenics and thermal models; Detector design and construction technologies and materials; Gamma detectors (scintillators, CZT, HPGe, HgI etc); Simulation methods and programs 1Corresponding author.

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Using mass spectrometry methods, the composition of residual gases and its temporal dynamics in experimental cryostats for HPGe detectors of gamma radiation, have been investigated. The studies were carried out for a vertical dipstick cryostat with vacuum chamber of small volume (1200 cm3) and an U-type cryostat having its vacuum chamber combined with vacuum cavity of a Dewar vessel (total volume 36500 cm3). Results of residual gas analysis are presented, showing the effect of Combogetter on a composition of residual gases of warm cryostats. Its use as an auxiliary getter for cryostats with HPGe detectors, maintaining a vacuum during storage or transportation, is considered.