MPI Heidelberg, Germany – Accelerator

Cooling system for the Cryogenic Storage Ring (CSR) at Max-Planck-Institute in Heidelberg, Germany

At the Max-Planck Institute for Nuclear Physics in Heidelberg, a next-generation electrostatic storage ring (CSR) is under construction. In contrast to existing electrostatic rings, the vacuum chamber of the Cryogenic Storage Ring CSR will be completely cooled down to temperatures below 5 K. The main advantage of the low-temperature storage ring walls is that black-body radiation incident onto the stored particles is strongly reduced. Correspondingly, only the lowest rotational levels will be occupied in radiatively active molecules and new classes of experiments, such as rotational and vibration state control of molecular ions and their interaction with ultra-low energy electrons, will be possible. Moreover, the low-temperature walls act as a large cryo-pump, which should result in a vacuum in the 10-15 bar range. This leads to unprecedented long storage times, reaching several minutes, for low-energy molecular ion beams.

The CSR together with a refrigerator is forming a unit to be cooled and warmed up simultaneously as one common system. The cooling concept which has been engineered, designed, and built by Linde Kryotechnik AG, is based on a low-cost system for maximum cooling power and will deliver 21 W below 2 K or 13 W below 1.8 K respectively. It consists of a cold box with almost no changes to a standard liquefier cold box for 4.5 K. The expansion and subcooling down to 2 K, respectively 1.8K is handled in a separated cold box, the connection box, which is located very close to the ring so that the distance for the 2 K transport tube is very short. The herein under Figure presents schematically the layout of the whole system, which consists of the CSR itself, the Helium recycle compressor, the process vacuum unit- both installed outside of the building in a machine container, the helium buffer and the two above mentioned cold boxes.