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TS01 Klystron Modulator Minh Nguyen May 20, 2014 Beam Voltage Stability Improvements

TS01 Klystron Modulator

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TS01 Klystron Modulator. Beam Voltage S tability Improvements. Minh Nguyen May 20, 2014. TS01 current modulator status. TS01 modulator has been running without PFN voltage regulation. Klystron beam voltage stability measures ~ 1000 ppm (rms) at 300kV, 120Hz - PowerPoint PPT Presentation

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Page 1: TS01 Klystron Modulator

TS01 Klystron Modulator

Minh NguyenMay 20, 2014

Beam Voltage Stability Improvements

Page 2: TS01 Klystron Modulator

TS01 current modulator status

• TS01 modulator has been running without PFN voltage regulation. Klystron beam voltage stability measures ~ 1000 ppm (rms) at 300kV, 120Hz

• Restore existing de-Q’ing regulation chassis #1 and #2 and measure PFN voltage and beam voltage stability at various voltage levels and pulse repetition rates• 30, 33, 35, 38, and 41kV (PFN from Ross HV divider)• 240, 260, 280, 300, and 320kV (Beam voltage)• 10, 30, 60, and 120Hz

2

Page 3: TS01 Klystron Modulator

Stability measuring device

7 ppm resolution

3

Page 4: TS01 Klystron Modulator

TS01 stability at 120Hz PRR

Beam Voltage (kV)

Sta

bilit

y (p

pm)

4

220 240 260 280 300 320 3400

50

100

150

200

250

300

BVPFN

Page 5: TS01 Klystron Modulator

TS01 short-term PFN/BV stability

Stability (ppm)

PR

R (H

z)

41/320kV38/300kV35/280kV33/260kV30/240kV

5

1010101010

3030303030

6060606060

120120120120120

0 50 100 150 200 250 300

Beam VoltagePFN Voltage

Page 6: TS01 Klystron Modulator

6

Motivation for TS01 improvements

• Klystron beam voltage stability is mainly dependent on modulator PFN voltage stability and thyratron operating conditions

• PFN voltage with original de-Q’ing regulation circuitry is stable within 120 – 150 ppm (rms)

• Fine PFN voltage regulation can be achieved by the use of a low power, high frequency capacitor charger (HVPS) in conjunction with existing high power resonant charger. The HVPS charges and regulates PFN capacitor voltage - on top of the resonant voltage – up to 0.5% target voltage

• Two previously upgraded modulators in the Linac 21-1 and 24-8 have shown to improve beam voltage stability to < 100 ppm

Page 7: TS01 Klystron Modulator

7

Scope of TS01 modulator upgrade

• Install a new 50kV TDK-Lambda HVPS to charge the PFN capacitors in parallel to existing resonant charger

• Install new PFN voltage regulator chassis and Ross HV divider to provide voltage regulation for both the resonant charger and the TDK-Lambda HVPS

• Install and modify other components to improve the beam voltage stability• Tail clipper to reduce klystron backswing voltage• SCR thyratron driver to provide negative bias on thyratron grid 2• Thyratron grid drive circuit to minimize trigger rise and delay time

• Replace the thyratron if necessary after assessing the performance of the upgrade

Page 8: TS01 Klystron Modulator

Upgraded modulator circuit diagram (in red lines)

Modulator Output: 360 kV, 420 A , 151 MW peak, 91 kW ave. @ 120 Hz

8

Page 9: TS01 Klystron Modulator

Some upgraded components

PFN Voltage Regulator Chassis

De-Q SCR trigger On/Off

switchVref input

PFN voltage feedback

120Vac In PFN voltage monitor

Tail Clipper Assembly

Inhibit signal monitor

HVPS control

9

TDK-Lambda 50kV Capacitor Charger(402-OEM series w/ blank front panel)

Modified SCR Thyratron Driver

Page 10: TS01 Klystron Modulator

Upgraded Linac modulators

Ross Divider

TDK Charging Resistors

TDK Reverse Voltage Protection Diode

Tail Clipper

PFN Voltage Regulator Box (Outside of Cab 3)

TDK 50kV HVPS

Power Transformer 3-Phase600Vac In, 208/120Vac Out

Circuit Breaker 208Vac / 20A

10

Page 11: TS01 Klystron Modulator

Mod 21-1 PFN voltage stability measurements

Zoom –in PFN VoltageRegulated by de-Q only (50V/div)

Zoom –in PFN VoltageRegulated by HVPS (50V/div)

Before Upgrade After Upgrade

PFN voltage stability=739uV/8.8V= 84 ppm (rms) PFN voltage stability=106uV/8V= 13 ppm (rms)

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Page 12: TS01 Klystron Modulator

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Mod 21-1 Beam voltage stability measurements

BV stability: 2.63mV/64V= 41 ppm (rms)BV stability: 10mV/69.9V= 143 ppm (rms)

Before Upgrade After Upgrade

Page 13: TS01 Klystron Modulator

Mod 21-1 performance after HVPS upgrade

Typical PFN voltage stability in a 10-minute period

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2011

12

13

14

15

Intervals (30sec)

Stab

ility

(ppm

)

13

Page 14: TS01 Klystron Modulator

Tail clipper performance

BV scale: 50kV/divPFN volt scale: 5kV/div

Klystron backswing voltage before and after tail clipper installation

14

Effects of thyratron random recovery on beam and PFN voltages

Page 15: TS01 Klystron Modulator

Thyratron grid 2 voltage after upgrade

-- 75Vdc bias on grid 2 ~ 1nS time jitter

15

Beam voltageTrig rise time after

Trig rise time before

Page 16: TS01 Klystron Modulator

16

TS01 upgrade schedule

• TDK-Lambda 50kV HVPS purchase requires 14wks of lead time. To meet the UED@ASTA project schedule, we have to borrow/move this HVPS and other upgraded components as needed from Linac modulator 24-8

Page 17: TS01 Klystron Modulator

17

TS01 cost estimate

M&S (not including new thyratron) $25,000

Engineering (Electrodynamics, APSE, and TestLabs Dept) 200 $22,000

Coordination 16 $1,760

APSM and TestLabs Technicians 160 $13,600

Cost Total $62,360