METHODS AND INSTRUMENTATION FOR MEASUREMENT OF LOW ION BEAM CURRENTS AT CRYRING

In many CRYRING experiments an accurate measurement of the circulating ion beam current is essential for determination of, for example, absolute cross sections. However, the current produced from the ion source can be very low, below 1 nA. Various detector systems have been developed for the storage ring, CRYRING, to measure both bunched and coasting beams by using the overlapping ranges of these systems. BUNCHED-BEAM CURRENT MEASUREMENTS Bunched beam parameters: duty cycle: 10-60%, frequency range: 40 kHz-1.5 MHz For bunched beam measurements a Bergoz Beam Charge Monitor with Continuous Averaging (BCM-CA) and an Integrating Current Transformer (ICT) were installed in 1997 giving 200 µA full scale range and 20 nA RMS resolution. Newer electronics (a low noise, high gain preamplifier, moved closer to the ICT, and a 10 Hz low pass filter) has improved the measurements made with the Bergoz transformer. The full-scale range has been lowered from 200 µA to 5 µA, with 1 nA RMS resolution. An example of the increased sensitivity of the modified system can be seen in Fig. 1.