Study of the EMI shielding of a dipstick facility for the Leiden Cryogenic b.v. model CF-400 Cryogenic-Free Dilution Refrigerator

Abstract

This Master Thesis was accomplished during the period 1st of September 2008 and 13th February 2009 at SRON (Netherlands Institute for Space Research) in Utrecht. SRON has purchased a new cryocooler for cryogenic detector development. The cool down time of the whole cooler is about 36 hours. In order to be able to measure more efficiently, there is a strong need to be able to perform small tests while the cooler remains cold. For this reason the cooler is equipped with a dipstick provision which allows samples to be entered without warming up. Tests have been performed with a dipstick cooling down to 4 K. In the first period of this master thesis assignment, several possible designs were discussed with regard to the most performance dipstick unit which allows experiments to be performed at 20 mK level. However, during the study of several design options, a dipstick provision for cryogenic detector development was designed and manufactured by Leiden Cryogenics. As a consequence the assignment in SRON changed, and the second phase of this master thesis was to adapt the dipstick purchased by SRON to the TES requirements. To achieve the goals of the thesis it was first necessary to have the CAD models of the dipstick. The software used was Pro/Engineer wildfire 4.0 and some visits to Leiden Cryogenics BV were done in order to finish the models of the dipstick and know exactly the operation of it. The cooler with the dipstick will not be delivered to SRON until some months after the author finishes the assignment in the Institute; however, in order to be able to start to use the dipstick when the cooler is delivered to SRON this study is done. This Master Thesis explains how to EMI shield this new dipstick in two Faraday cages and makes a detailed study of the heatloads at the first thermal contact between the cooler and the dipstick with the aim to reduce the temperature at this stage below 9K.