1. 3-CELL TEST RESULTS & 9-CELL PLAN Howie Pfeffer 11/13/13

4.  900 V/cell, 8.3 ohm load – no problem?!

5.  Turn-on Ringing, cells switching within 600ns

6.  Run just 2-cells - simplify  Bottom (ground-level) cell switching in 2 nd place – measurements easier.  Isolated charging circuits with high-value resistors – eliminate other possibilities.  Still had oscillations when spaced less than 600 ns.

7.  Turn-on Ringing, cells within 600ns

8.  After various failures, started to suspect problem due to diode turn-off before diode is fully on.  Seen similar problems with FETs – turning them off shortly after turning them on.  If so, then problem should go away if diode is at higher current during turn-off.

11.  Switching at 300 amps

12.  Switching at low currents

13.  “ON” time is important

14.  3-cell switching at 100 amps

15.  3-cell simultaneous turn- on at 300 amps.

16.  No problems with 3-cell operation as long as initial turn on timing is done properly.  Simultaneous turn-on yields 2700 volts with 250 ns rise time (10% - 90%).  9-cell construction under-way

18. Beam Top Tilt (Adj.):+/- 5 kV Beam Voltage Step :15 kV/usec Flattop/Beam Reg.:+/- 25 V Repeatability:+/- 10 V Max. spark Energy:< 5 Joules Pulse rep rate:15 Hz Maximum Output:35 kV Maximum step size:1.5 kV Load Resistance:~100 ohm Beam Length/Time:110 usec Load (Tube) Voltage 40-Cell Marx Output 12-Cell Reg. Output

19.  Nine steps up to 8 kV  Load = 100 ohms.  First step on for 2 us before subsequent steps.  One step followed by 8 cells simultaneously.  Uses existing driver electronics.  Delays between control edges and outputs.  Short circuit protection  Delay turn-off by 8 us after receiving trip signal. This allows overcurrent circuits on gating boards to turn off slowly.

20.  Interleaved Regulator operation  Uses Matt’s circuit.  Doesn’t require ultimate resolution.  Pulse one cell ON, then make 4 kV 8-cell interleaved pulse.  1 us spacing, 2 us minimum time, 8 us cycle, 96 us pulse length.  Filter circuit?  Short circuit response  F reeze signals for 8 us then turn OFF.

21. Program Voltage Load Voltage TriangleSquare Wave

24. UnfilteredFiltered

25.  Short circuit testing  Critical function – there will be arcs  Charging diode transients during pulse  Diode Qrr results in reverse current during turn-off  Charge inhibit function  Ensure charge switch and main switch are never on at the same time - disaster

26. SPARK CURRENT AND ENERGY WITH NO CURRENT LIMITTING 37,000 amps 55 Joules (50 volt arc) 18 usec

27. Main Switch Charging Switch Capacitor Charged to 950 volts Current

28.  9-Cell construction on-going  All 9 cells individually tested  Controls for ramping complete  Regulation mode controls being designed  Goal: start system testing in late January