MPI-K, Heidelberg
At the Max-Planck-Institute for Nuclear Physics in Heidelberg a cryogenic electrostatic storage ring (CSR) is under construction, which will be a unique facility for low velocity and in many cases also phase-space cooled ion beams. Among others the cooling and storage of molecular ions in their rotational ground state is planned. To meet this demand the ring must provide a very low level of blackbody radiation and a vacuum in the XHV range (10-15 mbar) which is achieved by cryogenic cooling of the ion beam vacuum enclosure to 2-10K. The beam current will be in the range of 1 nA -1 μA. The resulting low signal strengths together with the cold environment put strong demands on the amplifier electronics. We plan to make use of a resonant amplifying system. Using coils made from high purity copper, we expect quality factors of ~1000. The mechanical design has to provide stability of the alignment against thermal shrinking when switching from room temperature operation to cryogenic operation. A prototype pickup has been built in order to test resonant amplification and the mechanical design with a wire. The amplification principle will be tested in the MPI-K’s Test Storage Ring.
MPI-K, Heidelberg
The cryogenic storage ring CSR is a 35 m circumference electrostatic ring, for molecular- and atomic physics experiments at MPI-K Heidelberg. It will operate at pressures down to 10-13 mbar and temperatures <10 K. The beam intensities will be in the range of 1 nA to 1 uA, particle energies are between 20 - 300 keV. An intensity measurement for coasting beams below 1 uA requires magnetic field detection devices, which are much more sensitive than existing DC beam transformers. The highest sensitivity is currently achieved with DC SQUID based cryogenic current comparators (CCCs). At GSI, a prototype of such a CCC was successfully tested in the mid 90’s, reaching a resolution of ~250 pA/Hz1/2. Recently a resolution of 40 pA/Hz1/2 could be achieved under laboratory conditions at Jena University, however, the CCC sensitivity in an accelerator environment depends strongly on efficient shielding and mechanical decoupling. We describe our work on adaptation and improvement of the CCC beam transformer for the CSR. Furthermore a concept for an ionisation profile monitor is discussed, which in addition to low beam intensities, has to cope with extremely low gas densities at 10-13 mbar.
