Power Supply Design Howie Pfeffer Mu2e Extinction Technical Design Review 2 November 2015

Basic Specifications (Eric, 9/30/15) Howie Pfeffer/Power Supply Design 2 11/2/15 Mu2e Magnet Specification Pole width [m]0.09 Pole gap [m]0.018 Length [m] mu_01.26E-06 L [H]5.44E-06 B/I [T/A]7.00E-05 Frequency [kHz]N_cellsPeak Field[Gauss]Peak Current [A]Peak Voltage [V]Power (W) E E E E+03

Power Supply Requirements Minimize voltage-to-ground on magnets Provide continuous 300 kHz excitation Resonant system to minimize size and cost of power supply Real time resonance control Phase jump required Howie Pfeffer/Power Supply Design 3 11/2/15

Power Supply Specifications Howie Pfeffer/Power Supply Design 4 11/2/15

Load Parameters for 300 kHz  Total Magnet Inductance16.32 uH  Required Capacitance18 nF  Total Losses7.20E+03watt (Magnet and capacitors)  Scaled from prototype magnet measurements (~ 1 kW per ½ meter magnet.  Cable losses about 1200 watts Howie Pfeffer/Power Supply Design 5 11/2/15

½ meter magnet resonant circuit testing Howie Pfeffer/Power Supply Design 6 11/2/15

Approach  Use existing design Booster Corrector  H-Bridge, Switch mode Power Supply  3-4 Supplies Required  Design/build/commission  Matching Transformer  PS Controls  Resonant Controls  Cabling Howie Pfeffer/Power Supply Design 7 11/2/15

Power Supply Block Diagram Howie Pfeffer/Power Supply Design 8 11/2/ Apk/61 Vpk 116 Apk/122 Vpk

H-Bridge, Switch-Mode Power Supply Howie Pfeffer/Power Supply Design 9 11/2/15

Working Group Members Howie Pfeffer/Power Supply Design 10 11/2/15

Modifications needed to operate a Booster corrector power supply at 300 kH 1) Installed a larger DC - DC converter to power the bath tub driver for the FETs. 2) Changed the gate network from a resistive drive of 4.7 ohms to a lower R (3.3 ohms) in parallel with a diode. This decreases the gate turn on by a bit and makes the turn-off faster than the turn-on. 3) Built a low level drive circuit to accept a on-off drive from an square wave generator and create the on - off gate drive to both bridges with a 0.2usec delay between upper FET off to lower FET on. For reference the standard drive has a 0.6usec delay. Howie Pfeffer/Power Supply Design 11 11/2/15

PS Testing A dummy load was fabricated from parts on hand. The parameters of the dummy load are L_series = 56.5uH, C_series = 4.95nF and R_series = 10 ohms. Thus: f_o = 1/2*pi*sqrt(L_s*C_s) = 301kHz Q = (2*pi*f_o*L_s)/R_s = 10.7 Howie Pfeffer/Power Supply Design 12 11/2/15 Conclusions: 1) Prototype unit is capable of driving a ~300kHz load. 2) At a current of +/- 20 amps in the load you should expect about 20 degC rise of the air cooled heat sink. 3) With this measurement I would estimate that the unit could drive +/- 30 amps and deliver ~3,000 watts to the load with a single unit. 4) Number of power supplies needed will depend on how far off resonance will be allowed during operation.

Modified booster corrector driving ½ meter prototype magnet Howie Pfeffer/Power Supply Design 13 11/2/15  The required drive power increased from 1000 W to 1500 W over the span of 2 years.  This was tracked down to the resonant caps degrading.  Temperature measurements indicated that the PS could easily handle twice the power.

Real time resonance control  Measured stability of resonant frequency of prototype system was about +/ % over a period of 4 hours and a ferrite temperature range of 13 degrees C.  This corresponds to a +/- 0.1% change in inductance or capacitance.  The data was taken after a 10 minute warm-up of the system.  An adjustable inductor of +/- 0.7 uH will allow for a resonant frequency change of +/- 0.5%. This is ten times the change we have seen during our testing. Howie Pfeffer/Power Supply Design 14 11/2/15

5.1 MHz Testing  Extrapolated to the 3-magnet system (20 Apk),  R at resonance = 7.74 ohms  5:2 step-down transformer  Input to transformer ~50 ohms  Only one RG220 coax cable  Drive power ~ 1547 watts  3 x 2 x (2/3 * 2) 2 x 145 Howie Pfeffer/Power Supply Design 15 11/2/15  ½ Meter prototype magnet  I= 10 Apk, V=29 Vpk, 4 capacitors 0.9 nF each  4:1 Step-down transformer  Power = 145 watts  R at resonance = 2.9 ohms  Input to transformer ~ 50 ohms

Magnet frequency response Howie Pfeffer/Power Supply Design 16 11/2/15 Computer simulation (24 – cell) compared to measurement Note that the currents at 5 MHz are not uniform throughout the magnet due to transmission line modes. 5 MHz

½ meter prototype magnet model Howie Pfeffer/Power Supply Design 17 11/2/15 Calculated phase and amplitude of currents at different points in the ½ meter prototype magnet.

1 meter magnet model Howie Pfeffer/Power Supply Design 18 11/2/15 Calculated phase and amplitude of currents at different points in the 1 meter magnet.

Phase jump simulation, 300 kHz Howie Pfeffer/Power Supply Design 19 11/2/15 Phase Magnet Current 1 microsecond phase jump 1 mS

Conclusions  Modified Booster corrector supplies are capable of driving the 300 kHz magnet system  Tuning of resonant frequency looks doable.  Phase jump looks doable  4.5 MHz magnet system can be driven by a 2 kW RF amplifier. Field varies along the length of the magnet but is not a problem.  Would like to measure the frequency response, inductance and losses in a new 1-meter prototype magnet. Howie Pfeffer/Power Supply Design 20 11/2/15