Power Systems for the Rhic First Sextant Test

The first sextant test of the RHIC project is an opportunity to evaluate the many systems that must work together for the accelerator to operate. For the main dipole string, the actual main quadrupole power supply with its DSP regulator and output circuit compartment will be used. Temporary supplies will be used for the main quadrupole string, quadrupole offset, and quadrupole shunt supplies. This will let us both measure the performance of the main supply as well as determine the interaction among other power elements in the circuit. Correction elements will also be powered. The actual gamma-T power supplies will be used, as well as temporary supplies for the dipole correctors and sextupole supplies. Some of these units are required for beam to be transported, others are to be operated without beam to measure their performance, and how they interact with their superconducting loads. The power supply equipment, and that of other systems, required an infrastucture of AC power and output cable distribution in the RHIC tunnel, outlying service buildings, and interconnecting the tunnel to the service buildings. This note will describe the performance of the RHIC power supply systems during the sextant test, and the experience gained from this exercise. 1 MAIN POWER SUPPLIES Each of the main power supplies consists of a single regulator controlling two power modules. The “ramp” power module has a high output voltage and is used to ramp the current from injection level to storage level. The “flattop” power module has a lower output voltage and is used to maintain the current at fixed levels. When the commanded current slope exceeds 10 Amps/sec the regulator automatically switches from the flattop to the ramp power module, this is referred to as “cross-over”. The regulator uses digital firing boards to time the firing pulses to the SCRs. Loop compensation and realtime sub-harmonic correction of the output voltage are carried out by a digital signal processor (DSP). The DSP calculates a firing count that is sent to the firing board at a 720 Hz rate. Twelve correction counts, one for each SCR pair, are calculated and sent to the firing board at a 3 Hz rate. The firing board adds the appropriate correction to the firing count and uses this adjusted value to fire the SCR pairs. The sextant test provided an opportunity to test the stabilty, cross-over, and sub-harmonic correction capabilities of the power supplies on a load approximating that of the main quadrupole string. The regulator used during the sextant test was a prototype. The digital boards had been fabricated as printed circuit boards, but the analog signal conditioner boards used were the prototype boards. The final regulator will be housed in a temperature controlled enclosure, this was not available for the sextant test.