NUMI Power Supply Regulation WBS Power Supply System Level 3 Manager Nancy Grossman FNAL June 28, 2001

NUMI Internal NuMI Review June 28, 2001 Power Supply Regulation Page 2 Overview of Regulation Needs 7 Magnet Strings with regulation requirements ranging from 55 ppm to 400 ppm.  55 ppm means +/- 55 ppm relative to the flattop operating current (RMS).  V105 string requirement is 60 ppm, close to the tightest requirement.  Discussion will center around simulations of the V105 string. 3 sources of current variation for magnet strings:  720 Hz power supply voltage ripple being applied to the magnets.  Line voltage changes.  Load changes. Simulations of a particular power supply (or series of power supplies) can be used to see the effects of these changes on the resulting flattop current.

NUMI Internal NuMI Review June 28, 2001 Power Supply Regulation Page Hz Ripple Effect 720 Hz line ripple effect on the PS currents is shown in the table below.  Not acceptable  Need filters for each string  Refurbish existing filters  Have costed 3, have claimed 7 for NuMI.  Estimated cost to remove, refurbish and install: ~$10k/string (extra $40K)

NUMI Internal NuMI Review June 28, 2001 Power Supply Regulation Page 4 Line Voltage and Load Changes Simulations were run for the NuMI V105 string, assuming a constant reference voltage. 5% change in line voltage was easily corrected for at the level of ~25 ppm with standard voltage regulation. (most variation one would expect) 5% load change (resistance) gave a 240 ppm current variation.  Corresponds to about a 10 0 C change in the copper in the magnet or the LCW changing 15 0 C  Other magnet strings would have similar results most likely.  Not acceptable.  Need additional regulation.  HOLEC transductor ($5K/string)  Special FNAL regulation electronics ($5K/string)  Both are designed and installed in the Main Injector  This combination of electronics would give another factor of ppm

NUMI Internal NuMI Review June 28, 2001 Power Supply Regulation Page 5 Line Voltage and Load Changes Three strings are still above the required specifications. So now what?

NUMI Internal NuMI Review June 28, 2001 Power Supply Regulation Page 6 Additional Factor of Bandwidth Each string will be tuned for maximum bandwidth. 20 Hz is assumed in the previous calculations. 40 Hz is frequently achieved (but not guaranteed).  Gives a factor of 2 in current stability. Auto-tune Load changes are typically slow changes and thus Auto-tune can correct for these. One could then argue why do you need the extra power supply regulation too?  Auto-tune does not always work.  Needs beam and working beam position monitors to work.  Assumes next beam pulse like the previous one.  Experience at FNAL where significant beam control is needed says do both.  Since the power supply regulation is also driven some by groundwater concerns, we want something that is always working.

NUMI Internal NuMI Review June 28, 2001 Power Supply Regulation Page 7 Other Primary Beam Power Supplies Quadropole power supplies (20 KW PEI’s):  Standard regulation is at +/- 0.05% of the maximum current (100 or 200 amps)  Corresponds to up to +/-0.44% variation in operating current.  Believed to be sufficient. Main Injector Trim Magnet power supplies:  Standard regulation is at +/- 0.1% of the maximum current (15 amps)  Believed to be sufficient.

NUMI Internal NuMI Review June 28, 2001 Power Supply Regulation Page 8 Summary NuMI power supply regulation levels will be achieved by:  Filters on all 7 strings.  HOLEC and FNAL Electronics on all 7 strings.  Auto-tune.  Tuning for maximum bandwidth. Cost increase to NuMI:  ~$40k for 4 additional filters (refurbished)  ~$70k for 7 sets of HOLEC/regulation electronics (one for each string) Other slightly less expensive (and perhaps more effective) options may be designed by Fermilab before NuMI runs, in which case we would certainly use them. Studies in the Main Injector P1 line will also help us to better define the level of regulation one obtains with a HOLEC transductor and special regulation electronics.