ANL, Argonne, USA
With the increased radioactive beam capabilities brought by new CARIBU (Californium Rare Isotope Breeder Upgrade) in ATLAS facility, highest charge breeder efficiency of ECR is desired. Experimental study shows that the best efficiency could be achieved when high voltages (up to 50KV) of two platforms (CARIBU and ECR) are only different within less than 1V. We have developed a system with some innovative ideas implemented to measure the required tiny voltage difference ratio (~0.002%) precisely and to protect the system too. High voltage (HV) filter is designed to protect it from severe HV sparks and multiple level of relays with high precision medium HV divider are used to protect it from possible power supply failure. Homemade HV divider is used for rough measurement and control. Measurement results are converted to optical signals and then used to control power supplies to achieve the desired platform voltages. The system has been partially tested and will be used in the future.
ANL, Argonne, USA
The ATLAS National User Facility is world’s first CW superconducting linac and provides variety of ion beams for nuclear physics experiments for the past 30 years. The accelerator is being continuously upgraded to extend the scientific reach. A new normal conducting CW RFQ capable to provide total voltage up to 2.1 MV for the heaviest uranium ions has been added in the front of the SC linac in order to increase efficiency and intensity of both stable and radioactive ion beams. The RFQ has been fully integrated into the ATLAS and it is routinely operated since January 2013. A new cryomodule of high-performance 72.75 MHz SC QWRs has been built and currently it is being commissioned off-line. New design and fabrication techniques have been applied for production of QWRs which resulted to new record voltages up to 4-5 MV per cavity and low residual resistance of 2-3 nOhm at 2K as was demonstrated in individual cold testing of several QWRs. Primary purpose of the new cryomodule is to increase intensity of accelerated stable ion beams. Beam commissioning will take place at the end of year after substantial modification of the booster area including radiation shielding.
