Test results of gyrotron power supply of KSTAR* ECH system

2004. 4. 24성균관대학교 (자연과학캠퍼스), 수원

배영순, 이한구, 정진현, 남궁원, 조무현포항공과대학교

박재안포스콘

2004년 80회 춘계물리학회

*Work supported by KBSI

Abstract• The KSTAR ECH system uses a CPI 84 GHz gyrotron which is designed with

the CPD (Collector-Potential-Depression) scheme. The gyrotron is capable of generating 500 kW RF power driven by 80-kV, 25-A electron beams. The gyrotron of the CPD type requires two power supplies, a cathode power supply (CPS) and a body power supply. The cathode power supply produces electron beams of 25 A. The cathode-body potential difference of 80 kV is maintained by the body power supply between the cathode and the gyrotron body. Therefore, the body power supply is called the acceleration power supply (APS). The nominal applied voltage and output current of the CPS are -80 kV and 30 A, respectively, and those of the APS are +100 kV and 100 mA, respectively. The gyrotron operation voltages are -56 kV at the cathode by the CPS and +24 kV at the body by the APS with respect to the collector at the ground potential. The system was tested with a resistor of 2.5 kΩ as a dummy load. We also confirmed that the fast switch-off prior to the high voltage crow-baring is capable of limiting the arc energy transfer less than 6 J using an in-house built arc-test zig. Conclusively, this test showed the power supply is properly designed and can be used for the gyrotron operation. In this paper, we present the detailed test skills and the test results.

KSTAR ECH system

Power monitoringmiterbend

Polarizermiterbends

AluminumTank load

Waveguideswitch

Arc detectormiterbends

miterbendWaveguideswitch

84-GHz, 500 kWGyrotron31.75-mm corrugated

waveguide

AluminumTank load Turbo

pump

A

Diamondwindow

5 kV DC break

Bellows

Launcher gear assembly

RF gate valveLauncher

input

L-box

Launcher assembly

•Transmission line components:1. Eight miter bends-One power monitoring miter bend-Three Regular miter bends-Two Arc detector miter bends-Two polarizer miter bends

2. Two pump-out tees3. Two waveguide switches4. Two bellows5. One 5 kV DC break6. One RF gate valve7. One Diamond window8. Two water loads

84-GHz, 500 kW gyrotron

• Specifications of Gyrotron (CPI VGB8084)

– Frequency: 84 GHz with 0.1 GHz bandwidth

– Power: 500 kW with duration of 2 sec pulse

– Gun Type: Diode-gun with cathode of 40.6 mm-radius

– Cavity mode: TE15,4,1 (31-kG focusing field)

– α = 1.4 (80 kV and 25 A)

– Collector Potential Depression

• Cathode-Collector Voltage: -56 kV

• Cathode-Body Voltage: -80 kV

• Beam Current: 25 A

– Heater voltage: 28 V, Heater current: 9 A

– Efficiency: 40 %

– RF output mode: TEM00 Gaussian mode with linear polarization

– Diamond window: edge-cooled single-disk with 2.0-inch (50.8 mm) aperture and 0.059-inch (1.5 mm) thickness

80 in

ches

(~ 2

met

ers)

Schematic circuit drawing of power supply

qCathode-Collector Power Supply (CPS)• -85 kV, 30 A • Pulse width: 10 µs ~ 10 sec• Crowbar switch system: Two ignitrons

with each trigger modules• Rise time: ~ 4 µs, Fall time: ~ 4 µs

qAcceleration Power Supply (APS: Cathod-Body Power Supply)• 100 kV, 100 mA• Pulse width: 10 µs ~ 10 sec• Rise time: ~ 4 µs, Fall time: ~ 4 µs

Configuration of power supply

Cathode

Body

CollectorVCB panel

Inverter stacks

Rectifier

Filter Deck

Cathode HVS APS

APS HVS

Heater PS

CPS 단독 테스트

APS

HVS

HVS

RG58To Oscilloscope(collector current)

30 kVClampMOV

2.2 kΩ

VC

iC

CT

Rise time: 16 µsec (for -30 kV)Fall time: 40 µsec Ripple: 1 kV / 8.8 kV *100 = 11 %Ripple 주기: 2.6 ms (379 Hz)(Inverter 주파수: ~ 800 Hz)

2.6 ms

VC

High Voltage ON/OFFON time: 2.4 secOFF time: 11 sec

500 µH

100 Ω

CPS

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r

APS 단독 테스트

APS

HVS

HVS

RG58To Oscilloscope(collector current)

30 kVClampMOV

2.2 kΩ

VB

iC

CT

VB

High Voltage ON/OFFON time: 3.4 secOFF time: 1sec

Rise time: 25 µsec (for + 26 kV)Fall time: 12 msec Overshoot:∆T ~ 460 µsec, ∆V ~ 1 kV

500 µH

100 Ω

∆T

∆V

CPS

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r

연동 운전 및 MOV test

Pearson CT (only measures fault current)

APS

HVS

HVS

RG58

RG58

To Oscilloscope(collector current)

30 kVClampMOV

2.2 kΩ

* APS 출력 증가시키며 VB 의 최대허용 전압 30 kV 유지되도록 MOV clamp기능 확인

VB

VC

To Oscilloscope(cathode currentshould be zero)

iB

iC

CTPearson CT

HV coaxial cable

Positive output for Electron flow

Direction of Arrow

HV coaxial cable

CPS

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r

Ch1: VC

Ch2: VB

Ch4: IC

Arc test

iFAULT

i FA

ULT

iFAULT

APS

HVS(OC set: 30 A)

HVS

RG58

Spark gapswitch

- 56 kV

+ 24 kV

To Oscilloscope

* Arc test는 crowbar test, clamp diode test, Pearson CT fault test 를 동시에 수반하는 테스트임.

test wire(sustaining energy: 6 J)

ClampDiode40 kV PIV

To Oscilloscope(arc current)

VB

VC

iC

CT

E/O Trans

Matrix Board

CTCT

HVS OFFHV OFF(Inverter OFF

VCB OFF)C

PS

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r

Crowbar OFFComp set: 20 A

VC = -56 kV,VB = +24 kV

VC = -30 kV,VB = +25 kV

Ch1: VC

Ch2: VB

Ch3: IARC

Gyrotron power supply electronics

collector currentmetering shunt(0.5 Ohm)

Pearson CT (only measures fault current)

Cathode

Collector

iC

iC

iC

iFAULT

i FA

ULT

iFAULT

BodyiB

APS

Body currentMetering shunt(100 Ohm)

E/O Trans

HVS

HVS

RG58

RG58

RG58

To OscilloscopeTo “Fast Interlock Signal Pre-processor (FISPP)”And To Oscilloscope

O/E Trans

30 kVClampMOV

* Arc current between the cathode and body will be a major fault current

ClampDiode40 kV PIV

Positive output for Electron flow

Direction of Arrow

CPS

HV floating

To “Fast Interlock Signal Pre-processor (FISPP)”

iC