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In this study, the thermal behavior of a cryogenic heat pipe was experimentally investigated. The cryogenic heat pipe is a conventional type of a heat pipe (wicked heat pipe). The heat pipe studied here utilizes a cryogenic fluid as its working fluid and operates at low temperatures. To carry out the experiments, commercially available heat pipes that use water as the working fluid and are typically intended for use at room temperature were utilized. This study replaced the working fluid with either N2 or Ar. The heat pipe consists of copper and has a diameter of 6 mm, a length of 200 mm, and a thickness of 1 mm. The wick structure comprises sintered powder copper and grooves. The study investigated the impact of the filling ratio of the working fluid and the inclination angle of the cryogenic heat pipe. The N2− and Ar-heat pipes both exhibited an overall thermal resistance (Rth) value of 0.20 and 0.25 K/W, respectively, during normal heat pipe operation mode. It was found that the filling ratio of the working fluid had a significant impact on both the maximum heat transport capability, Qmax, and the overall thermal resistance of the heat pipe. Moreover, the inclination angle also had an effect on Qmax, with an angle greater than 10 ˚ when the evaporator section is positioned below the condenser section being found to notably increase the value of Qmax. [ABSTRACT FROM AUTHOR]

Superconducting radio frequency (SRF) cavities made from niobium and cooled with liquid helium are becoming key components of many particle accelerators. The helium vessels surrounding the RF cavities, portions of the niobium cavities themselves, and also possibly the vacuum vessels containing these assemblies, generally fall under the scope of local and national pressure vessel codes. In the U.S., Department of Energy rules require national laboratories to follow national consensus pressure vessel standards or to show "a level of safety greater than or equal to" that of the applicable standard. Thus, while used for its superconducting properties, niobium ends up being treated as a low-temperature pressure vessel material. Niobium material is not a code listed material and therefore requires the designer to understand the mechanical properties for material used in each pressure vessel fabrication; compliance with pressure vessel codes therefore becomes a problem. This report summarizes the approaches that various institutions have taken in order to bring superconducting RF cryomodules into compliance with pressure vessel codes. [ABSTRACT FROM AUTHOR]