Intensity and Profile Measurement for Low Intensity Ion Beams in an Electrostatic Cryogenic Storage Ring

The cryogenic storage ring CSR is a 35 m circumference electrostatic ring, designed for molecularand atomic physics experiments at MPI-K Heidelberg. It will operate at pressures down to 10 mbar and temperatures <10 K. The beam intensities will be in the range of 1 nA to 1 μA, particle energies with between 20 300 keV. An intensity measurement for coasting beams below 1μA requires magnetic field detection devices, which are much more sensitive than existing DC beam transformers. The highest sensitivity is currently achieved using 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/Hz. Recently a resolution of 40 pA/Hz 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 mbar.