Klystron Power Supply - KEK · Accelerator Laboratory Klystron Power Supply Mitsuo Akemoto KEK Joint US-CERN-Japan-Russia International Accelerator School 2017-RF Technologies-

Accelerator Laboratory

Klystron Power Supply

Mitsuo Akemoto

KEK

Joint US-CERN-Japan-Russia International Accelerator School 2017-RF Technologies-

Oct. 16-26, Hayama, Japan

1

Accelerator Laboratory Contents

1. Klystrons

-Klystron characteristics

2. Basic Pulse Circuits

-Line-type Modulator

-Direct Switch Modulator

-Chopper circuit

-Marx circuit

3. Short Pulse Modulator

Example : KEKB Linac Modulator

4. Modulator Improvements

and Power Devices

5. Long Pulse Modulator

Example : ILC Modulator

The pulsed high voltage generator for klystron are called modulators. 2


Various types of Klystrons

3

1

10

100

1000

1 10 100 1,000 10,000

Pea

k p

ow

er(M

W)

Pulse width(µs)


Overview of

Pulsed Klystron Modulators

ILC 120kV,1700µs

KEKB 300kV,5.6µs

PAL-XFEL 400kV,8µs

SACLA 350kV,4.2µs

LCLS 360kV,5.84µs

SNS 140kV,1200µs

ESS

100kV, 3400µs

XFEL 12kV, 1700µs

4

Accelerator Laboratory Typical Klystron Parameters

Klystron type Klystron

voltage

RF output power

CW ~100 kVdc ~1.2 MW

Long pulse(~ 1 ms) ~130 kV ~10 MW

Sort pulse(~ 1 µs) ~500 kV ~200 MW

5


Klystron Characteristics

Anode

Cathode

Child's law

Ik PVk3/ 2

P=microperveance, Ik=klystron current, Vk=klystron voltage

•Klystron power Pk and power variation

Pk IkVk PVk5/ 2

PkPk

5

2

VkVk

•Klystron impedance Zk

Zk Vk

Ik

1

P Vk

•Klystron beam current Ik

Vk Ik

Zk

η=klystron efficiency

Klystron model

Equivalent circuit

6


Modulator Requirements

Compact

High-Reliability High-Efficiency

Low-Cost

7


Basic Pulse circuit

Hard-tube (Direct switch) Line-type

Suitable for short pulse Suitabe for long pulse

8


Line-type Modulator

PFL or PFN

Basic line-type modulator

Advantages •Electronics is simple.

•Short current is 2 times operating load current.

Disadvantages •Pulse width is fixed.

•Matched impedance is load impedance.

•Pulse shape is depend on load impedance.

•PFN needs to be tuned for flat pulse.

•Output voltage is half input voltage

9


Pulse-Forming Line

•Line impedance Z

Tcable 2L

u

2 r r

c

•Output pulse width Tcable

L: line length

µr: relative permeability

εr: relative permittivity

c : light velocity

Polyethylen εr=2.3 Tcable=1µs at 100 m

RG58-U(Z=50Ω, C=100pF/m, L=250nH/m), Tcable=10ns/m

Limitation

•To get a pulse width of 10µs, need a long line of 1 km.

Z

•Propagation velocity of the line u

u 1

10


Pulse Forming Network(PFN)

• Pulse Forming Network

•Characteristics impedance

•Pulse width（n stages)

•Pulse rise time

20 sections, L=1.3 µH, C=0.015 µF, Z=9.3 Ω

11

Output voltage waveform Each Capcitor voltage of PFN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

PFN Simulation

PFN: 20 sections


Load impedance

=PFN impedance

12


Direct switch Modulator

Basic direct switch modulator

Advantages •Pulse width is controllable.

•Pulse shape is good.

•Impedance matching is wide range.

•Output voltage is input voltage

Disadvantages •High stored energy.

•Short current is large current.

(crowbar circuit is used for klystron protection.)

13


Direct Switch Modulator Topology Accelerator Laboratory

・Direct Switch Modulator ・Hybrid Modulator

・Induction Adder Modulator ・Marx Modulator

High voltage SW(350 kV,310A) Middle voltage SW(50kV,2200A）＋PT(1:7)

Low-voltage SW(6kV,310A)x59 stages

Low-voltage SW(6kV,310A)＋PT(1:1) x 59 stages

Klystron: Vk=350 kV, Ik=310 A、Pw=4.2µs

14


Buck Converter(1)

The voltages and currents with time in an

ideal buck converter during steady state.

During steady state

Buck converter circuit diagram

VL Ldi

dt

VL 1

TVLdt0

T

0

Buck converter is DC/DC power converter

which steps down voltage from its input to its

output.

15


Buck Converter(1)



During steady state


VL Ldi

dt

VL 1

TVLdt0

T

0



output.

ON

16


Buck Converter(1)



During steady state


VL Ldi

dt

VL 1

TVLdt0

T

0



output.

OFF

17


Buck Converter(2)

•Output voltage ripple

Maximum value at α=0.5

•Duty Factor

Pulse Width Modulation

•Output voltage Vc

Buck converter is DC/DC power converter which steps

down voltage from its input to its output.

<1

18


Boost Converter

Boost converter circuit diagram

Duty factor

The voltages and currents with time in an ideal

boost converter during steady state.

Boost converter is DC/DC power converter


output.

ON

19


Boost Converter

Boost converter circuit diagram

Duty factor

The voltages and currents with time in an ideal

boost converter during steady state.

Boost converter is DC/DC power converter

which steps up voltage from its input to its

output.

OFF

<1 20


Marx Generator

Marx circuit（Erwin Marx invented in 1924）

R +V

Vout

C Gap

Switch

stage

•The capacitors are charged to V through the charging resistors while the switches are open.

•The switches close and the capacitors are connected in series, producing high voltage.

•The circuit generates a high-voltage pulse by charging a number of capacitors in parallel

+ + +

Charging resistor

Multi-stage is achieved by charging the capacitors in parallel and discharging in series.

NV in N stages

21


Solid State Marx Modulator

Solid state Marx circuit

Vout

+V

+ + + Discharging Switch(DS)

Charging Switch(CS)

•The capacitors are charged in parallel and discharged in series.

•Discharge switches can be independently controlled.

•The output is controlled by sold-state elements, diode and IGBT switches.

Stage # DS DS DS

1 ON OFF OFF

2 OFF ON OFF

3 OFF OFF ON

Vout=V

Stage # DS

1 ON

2 ON

3 ON

Vout=3V

Stage 1 Stage 2 Stage 3

22


KEKB Klystron Modulator

(Line-Type)

23


KEKB Klystron and Modulator

Max. Peak Output Power 108 MW

Max. Average Output Power 30 kW

Pulse Transformer Ratio 1:13 .5

Primary Output Voltage 22.5 kV

Primary Output Current 4.8 kA

Total PFN Capacitance 0.6 µF

Pulse Rise time(10-90%) 0.8 µs

Pulse Flatness(P-P) 0.3 %

Pulse Width 5.6 µs

Thyratron Anode Voltage 45 kV

Thyratron Anode Current 4.8 kA

Thyratron Average Anode Current 1.3 A

Repetition Rate 50 Hz

Modulator Specifications

Output Power 46 MW

RF Pulse Width 4.0 µs

Efficiency 45 %

Perveance 2.1 µA/V3/2

Beam Voltage 298 kV

Repetition Rate 50Hz

Klystron Specifications

Pulse Transformer Tank

Klystron

Pulse Modulator SLED

24

Circuit Diagram of KEKB Modulator Accelerator Laboratory

• PFN-type modulator

• LC resonant charging

• De-Qing

• Single thyratorn switch

25

Charging Circuit of KEKB Modulator Accelerator Laboratory

0

2E

Vc

E

Es Ide-Q

I0

LC Resonant charging

Time(10ms/div.)

26

PFN Charging Voltage Stability Accelerator Laboratory

0

0.5

1

1.5

2

2.5

0 50 100 150 200

PF

N V

olt

age(

xV

dc)

wt(dgrees)

Stability VPFN

VPFN 0.15%

Normal PFN Voltage

Normal VPFN

25% voltage increase

VPFN

System delay

VPFN

VPFN

ab a

1 a

a=PFN regulation(5%)

b=AC line deviation(5%)

τ=system delay time(50µs)

Charging time=50ms(50Hz)

VPFN V0CDC

CDC CPFN1 cost V0 1 cost

1

LcCPFN

T 2 LcCPFN

27

Circuit Diagram of KEKB Modulator Accelerator Laboratory

• PFN-type modulator

• LC resonant charging

• De-Qing

• Single thyratorn switch

28

PFN of KEKB Modulator Accelerator Laboratory

PFN Design

Inductance of the tuning Inductor > 1µH PFN circuit diagram

•2 pallel, 20 section

•L=1.3µH, C=0.015µF

•Z=9.2Ω/2=4.7Ω

29


PFN Capacitor

W

V

1

2r0E

2

Energy Density of Capacitor

W: Stored energy (J)

V : Volume of capacitor (m3)

r： Relative permittivity

０: Permittivity of a vacuum (8.85x10-12F/m)

E : Field strength (V/m)

•No-Healing

•Self-Healing(SH)

50~100V/µm

~200V/µm

Metallicon

Evaporated thin film

Few hundreds angstrom

Dielectric film Dielectric film

Metallicon

Thin metal

~7µm

Dielectric film

Dielectric material：Capacitor thin papaer(εr~4.5)、plastic film(εr=2.0~2.3)

(J/m3)

30


Cross section of dielectric/electrode

Configulation(not to scale)

Test Capacitor

Life Test of SH Capacitor

Breakdown Capacitor Element

Lifetime : 8 Hours( 0.72 M shots)

0

50

100

150

200

250

300

105 106 107 108 109 1010

SH

NH

Ref(n=20.8)

Ele

ctri

c fi

eld

str

eng

th(V

/µm

)

Lifetime(Shots)

L

L0

V

V0

n

Accelerated Life Test Electric field strength vs Lifetime

50pps X 7,000H X 8 Years

Capacitor

Volume

1/4

Group No. Sample

No.

Structure Dielectric strength

(V/µm)

lifetime

(Hours)

1 8

1 2 10S 274 8

3 8

4 8

2 5 12S 229 11

6 12

7 102

3 8 13S 214 135

9 704

10 1332

4 11 15S 183

12 1272

13

5 14 18S 152

15

16

6 17 21S 131

18

19

7 20 24S 114

21

Breakdown capacitor inside

Test Results

31

Thyratron Switch

Inside structure of Thyratron F241

Reservoir tank

Anode

Cathode

Control Grid(G2)

Heater


Heater voltage 6.3 V

Heater current 70 A(Max.)

Reservoir voltage 2.5~6.0 V

Reservoir current 20 A(Max.)

Peak anode voltage 45 kV (Max. 50 kV)

Peak anode current 4.8 kA(Max. 10 kV)

Average anode current 1.3 A(Max.8 A)

Rate of rise of anode current 5 kA/µs(Max. 10kA/µs)

Peak control grid voltage 1.0~4.0 kV

Control grid pulse width 2 µs(at 70% value)

Specification of Thyratron F-241 Auxiliary Grid(G1)

Gradient Grid

Litton EEV ITT

L4888B CX2410K F-241

• 45 kV, 5 kA, 6 µs, 50 Hz Switching

32

Thyratron Switch Accelerator Laboratory

Driver circuit

•Keep alive has ~250 mA dc current at 100 V

•Thyratron circuit

Paschen Curve for Hydrogen

Thyratron operation region

•Breakdown voltage vs. Gas Pressure

33


Example of Thyratrons History Accelerator Laboratory

S/N: 69(95)

96-10-11: 3-4取り付け

02-11-29: HV-ON時でIkeep(H,L)ITL

03-01-07: Ikeep流れない

Example of Ranging Tube Type: CX2410K

S/N: 68(95)

96-10-11: 5-2取り付け



03-01-08: 運転時Ikeep流れない

S/N: 55(95)

96-10-11: 5-1取り付け

03-01-30: HV-ON時でIkeep流れない

Example of Ranging（Reservoir

Adjustment）

Upper

Limit

Lower

Limit Optimized

Value

Keep-alive Failure

34

Status of KEKB Thyratron Accelerator Laboratory

Operation period ( Sep. 1998〜 Feb.2008) : No. of Thyratrons=74

• Lifetime Profile • Failure Modes Distribution

Thyratron Quality ?

0

2

4

6

8

10

0 10 20 30 40 50 60 70 80

CX2410KF241L4888B

Nu

mb

er o

f T

ub

es

Time(kHours) Keep alive Failure

G1 discharge

High voltage Break

Down

Reservoir Failure

Others

35

Maintenance activity for Thyratrons

•Acceptance Test

Break down rate < 0.05/ hour after operating for 100 hours.

Switching Jitter < 10 ns

Anode delay time

•Exchange new thyratron in advance

Most Important modulators ( such as buncher section)

at intervals of two years(~14,000 hours) , Exchanged one is reused.

•Checking and adjustment

Reservoir current, keep-alive current, if necessary, adjust or exchange.

•Regular maintenance

Ranging(reservoir voltage adjustment)、check of jitter and pulse timing

at intervals of one year

Thyratron MTTF : 34,00 hours (as of 2011)


To maximum lifetime, and to minimize cost.

36

Klystron waveforms

Klystron voltage, current, RF waveforms


37

• Modulator failure distribution

Total operation time : 6322 Hours

Machine failure time : 114 Hours


Operation Statistics of KEKB Modulator

•Keep-alive current tuning

•Thyratron failure

•Air cooling fan

Modulator availability=0.997

Modulator failure time = 17.6 Hours

• Linac failure distribution(2007)

53% of RF failure

Reliabilty of an RF system is directly linked to

the linac availability. 38


Modulator Improvements

By Power Devices

Example :

Charging Power Supply

High-Power Solid-State Switch


39

PFN Charging Power Supply Accelerator Laboratory

•Transformer core size

S

Ns

Np

S VP

N p f

Vp : Primary voltage

Np : Number of primary turns

S : Core cross section

f : AC frequency

•LC Resonant Charging（f=50 Hz)

HV transformer : very Large

•Switching Power Supply(f=30 kHz)

HV transformer : very Small

Transformer core 40

Switching PS (DC-AC-DC Converter) Accelerator Laboratory

Es= 45 kV, fr=50 pps

60µs 30µs(33 kHz)

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

7.7 7.75 7.8 7.85 7.9 7.95

Char

gin

g C

urr

ent(

A)

Time(ms)

-10

0

10

20

30

40

50

-0.5

0

0.5

1

1.5

2

2.5

-10 -5 0 5 10 15 20 25

PF

N V

olt

age(

kV

)

Ch

argin

g C

urren

t(A)

Time(ms)

Block Diagram of Inverter Power Supply System(Toshiba) Expanded pulse top trace of the charging current

Input Power

Section

Inverter

section

High Voltage

Section

Modulator Control System

DC AC(33kHz) DC

41

Down-sizing of KEKB Modulator Accelerator Laboratory

1.8ｍ 4.7ｍ

Compact modulator Original modulator

LC Resonant Charging（f=50 Hz) ー＞ Switching Power Supply(f=30 kHz)

•Reduce the modulator size by one-third of the existing modulator.

•Switching power supply technology is essential to reduce modulator size.

42

Switching Power Supply Accelerator Laboratory

Item Main Sub

Charging voltage Vc（(kV) 43 43

Average charging current Iav(A)

1.57 0.2

PFN capacitor C(µF) 0.62 0.62

AC frequency f(kHz) 40 70

Voltage stability（％） 0.15 0.015

Charging time(ms) 17 -

Charging power(kJ/s) 34 5

TC C Vc

Iav

Sub Power Supply

Main Power Supply

Design parameters

Two type inverter power supplies have been developed at KEK.

V

V

Iav

V C f

V : Charging voltage

Iav : Average charging current

C : Capacitance

f : AC frequency

•Charging voltage stability

43

PFN Voltage Stability Measurement

(Main power supply)

112.9V

Voltage stability=112.9V/43kV=0.26%(P-P) for 10K times 44

PFN Voltage Stability Measurement

Main + Sub power supplies

12.3V

Voltage stability=12.3V/43kV=0.029%(P-P) for 10K times 45


Thyratron Replacement Switch Accelerator Laboratory

Thyratron •Short life time(~34khoures)

•Reservoir voltage Tuning(Ranging)

Solid-State Switch •Long life time(?)

•No tuning

•No heater & reservoir PSs

46


Thyratron Replacement Switch Accelerator Laboratory

Many companies and Laboratories are currently developing various semiconductor switches

to replace the thyratrons.

Semiconductor Switches Technical Approach

•Series connection for high-voltage

•Parallel connection for high-current

•Array of semiconductor devices

47


APP Thyristor Switch(SLAC) Accelerator Laboratory

41cmx４１cmx８６cm（H） 2Px16S

C. Burkhart, et. al, “Development of a solid state thyratron replacement for the LCLS

klystron modulator” Pulsed Power Conference, 2013. 48


25kV SI-Thyristor Switch(PPJ) Accelerator Laboratory

25 kV, 5kA, 10µs, 10 Hz

6Px10S SI-Thyristors Switch

Size : 300(W)x150(D)x500mm(H)

F. Kamitsukasa, et. al, “Development of a High-Power Solid-State Switch for a Klystron” Annual Meeting of Particle

Accelerator Society of Japan 2013. 49

45kV 6kA Solid-State Switch

KEK has evaluated Turn-on characteristics of SI-thyristor

and has designed and built a 45 kV solid-state switch and

successfully operated for 57 hours( 5 M shots).


50

SI Thyristor Accelerator Laboratory

92 mm

SI Thyristor

Structure of SI Thyristor

SI Thyristor （Cathode）

Anode

Cathode

P

e

P++

ne

n-

Buried Gate

Current Flow

Channel

Diagram of the on-state SI thyristor

Diode for Inverse Current Isolation Band

Gate Electrode

Wafer

Gate

•Voltage 4.0 kV

•Turn off current 600A

•RMS current 600A

•dI/dt 150kA/µs

•Normally-on type device Vg=-20V

51

Low Inductance Test Circuit Accelerator Laboratory

Photography of the test circuit

Equivalent circuit

Circuit inductance(~136nH)

Capacitor

Diodes

SI-Thyristor and Gate driver circuit

Tune-on Test •Low-inductance

•Coaxial structure

Gate driver circuit

and

SI-thyristor

52

Turn-on characteristics of SI-Thyristors Accelerator Laboratory

- Peak current 10kA

- Peak dI/dt 110kA/µs

- Switching time(90-10%) 128ns

Anode current dI/dt waveform

Anode voltage and current waveforms

Peak anode voltage and Peak di/dt vs. Applied voltage

Test Results

53

45kV 6kA Semi-Conductor Switch Accelerator Laboratory

Switch assembly

Gate driver circuit

and

SI-thyristor Basic circuit diagram

15 SI-Thyristors connected

in series

700 mm

• Hold-off voltage 45 kV

• Peak current 6,000 A

• Pulse width 6 µs

• Repetition rates 50 pps

• Device SI-Thyristor[NGK :RS1600PA40T1(4kV)]

• Connection 15 devices in series

• Insulation Oil

• Cooling Forced oil cooling

54


High-Power Test Circuit Accelerator Laboratory

Operation Parameters • Peak output power 136 MW

• Hold-off voltage 45 kV

• Peak current 6 kA

• Pulse width 6 µs

• Repetition rates 25 pps

• di/dt 10 kA/µs

Performance test at ATF

55

Accelerator Laboratory Accelerator Laboratory Dead-Short Circuit Test

56

Accelerator Laboratory Accelerator Laboratory Switching Waveforms

Klystron Arc-down Normal operation

57


Thyratorn vs. Solid-State Switch Accelerator Laboratory

Switching Current Switching Voltage

Thyratron Switching Time(90-10%): 40 ns

Solid-State Switching Time(90-10%): 208 ns

Thyratron : EEV CX1536

58


Switch Losses of Solid-State Switch Accelerator Laboratory

Details of switch lossesPFN

Voltage

(kV)

PFN

Stored energy

(J/pulse)

Switch

Losses

(J/pulse)

Balance

resisters

(J/pulse)

Gate

Circuits

(J/pulse)

Devices

(J/pulse)

20 162 9.4(5.8%) 0.98(10.5%) 0.8(8.5%) 7.6(81.0%)

30 365 21.3(5.8%) 1.92(9.0%) 0.8 (3.8%) 18.6(87.2%)

40 648 32.8(5.1%) 2.77(8.5%) 0.8 (2.4%) 29.2(89.1%)

45 820 41.1(5.0%) 3.10(7.4%) 0.8 (2.4%) 37.2(90.7%)

•Switch losses were measured by calorimetry.

130 W/˚C

•Total switch loss is 41J/pulse.

•Main loss is devices(91%)

Oil cooling system

59


Long Pulse Modulator

Example : ILC Modulator


60

ILC Modulator Specification

61


Parameter Value

Pulse Voltage 120 kV

Voltage Regulation 1%(p-p)

Pulse Current 140A

Pulse Length(flat-top) 1.6 ms

Total Pulse Energy 27 kJ

Repetition Rate 5 Hz

Average Output Power 135 kW


Capacitance of Direct-switch Modulator

•Capacitor Storage Energy (WC)

•Output pulse Energy (WP)

•Droop(D)

Droop

Droop(%) Wc/Wp Ratio

0.5 100

1 50

20 2.8 R

C

Switch

C

R Dr

Capacitor Size vs. Droop

62


Waveform function of Droop Compensation

Droop compensation circuit

The electric charge of Capacitor q(t), the circuit

equation is given by

Solve the equation at initial condition t=0, V0, q(t)

is

Calculating from the equation, in the condition q(0)=C V0 at t=0,

i(t) is given by

In the condition i(t)=V0/R, VB(0)=0, VB(t) is given by

Load waveform

63

Bouncer Circuit

• LC resonant circuit

V

0 t

VR

VBounc

er

VOUT


64


Design Parameters of STF Modulator#2,3

• Peak Output Power 16.8(12.0) MW

• Secondary Output Voltage 120(130) kV

• Secondary Output Current 140(92) A

• Pulse width 1.7 ms

• Flat-top width > 1.5 ms

• Rise time(10-90%) ~ 0.1 ms

• Flatness < ±0.5%

• Repetition Rate 5 pps

• Pulse Transformer Ratio 1:15

• Capacitor Bank 2000 µF<20%droop>

• Energy deposit in klystron

from gun spark < 20 J

• Main Switch

Voltage 8.8(9.5) kV

Current 2100(1380) A

( )=5MW Klystron 65

50 kJ/s

Switching PS

Pulse Transformer

1:15

Kly

stro

n

LC Bouncer Circuit

IGBT Main Switch

20S4P

Capacitor Bank

2 mF

Main Cabinet

AC 420V 3ø

L 0.3 mH

C 2mF

100 µH

STF#2 Modulator Circuit Accelerator Laboratory

Compact Switching PS

Self-healing-type capacitor

Compact pulse transformer

IGBT Main Switch

IGBT

1600V,600A

20S4P

IEGT

Switch

STF#3

66

Overview of STF Modulator #2 Accelerator Laboratory

50kW Switching

PS Pulse Transformer

Storage Capacitor IGBT Switch Bouncer

Circuit

Klystron

3.8m(STF#3) 67

Main cabinet is 4.2m wide x 2.2m deep x 2.2m high


IEGT Switch for STF#3 Modulator

ＩＥＧＴＩＧＣＴ

Device ST2100GXH24A

（toshiba）

5SHY35L4511

（ABB）

Voltage 4.5kV 4.5kV

Turn-Off

Current

5500A 3800A

RMS

Current

2100A 2200A

di／dt 5000A／μs 1000A／μs

Outline φ125mm post

26.5mm t

φ85mm post

26.5mm t

Gate Voltage Drive

20W Power

Current Drive

100W Power

IEGT Switch Assembly

Comparison of IEGT and IGCT

ＩＥＧＴ（Injection Enhanced Gate Transistor）

6 stack IEGTs Snubber Circuit

Transformer

for gate driver

PS

Gate Driver

Size：900 mm W x 920 mm D x 685 mm H

68

• Switch 9 kV, 2100A, 1.7 ms, 5Hz

• Redundancy of one-series

• Detect a short circuit fault for

each IEGT device


Pulse Transformer

Klystron

Resistance

R=120kV/140A

=857Ω

tr 2.2 Ll

R

Ll(Leakage inductance)

A Vs

Ns B

A

•Cross section of Core(A) •Pulse Rise time(tr)

Ll 1

2 H 2 dvNs

2

Ns

Ll tr R

2.2

100s 857

2.2 39mH

Np

120kV 1.7ms

~2T(dc-bias）

Core size is optimized by rise-time of ~100µs

69


Pulse Transformer(2)

Cores

• 25 Cores used for JHF pulse transformer were

reused in total number of 39 cores for cost saving.

• Material is 0.22mm thick silicon steal ribbon.

• 4.4 tons in weight

STF#1Specifications of Pulse Transformer

• Primary voltage 21.7 kV

• Primary current 588 A

• Primary impedance 36.8Ω

• Secondary voltage 130 kV

• Secondary current 98 kV

• Secondary impedance 1327 Ω

• Flat-top pulse width 1.5 ms

• Rise-time(10-90%) 40µs

• Pulse droop < 3%

• Step-up ratio 1:6

• Pulse repetition rate 5pps

Design Feature

• DC bias

• Auto winding

• Heater transformer is isolation transformer type.

Core assembly

70


Pulse Transformer(3)

Pulse Transformer assembly

巻き線方式

1

23

4

65T65T167T 158T65T

1710mm 660mm

Design Values(Secondary side）

• Primary inductance : 60 H

• Leakage inductance : 20 mH

• Distributed capacitance : 570 pF 1255mm

Ll=28 mH@ABB

Main Pulse Transformer：4.8t

Tank：1.84t

Oil：2.5t

Total weight：9.14t 71


Klystron Voltage Waveforms（STF＃２）

Es=7.0 kV, Pw=1.7 ms, fr=5 pps

Bouncer trigger optimization

72



Td=456 µs

5 MW Klystron Operation（STF＃２）

Rise-time(10-90%)=0.92 µs 73


Klystron Voltage Flat-top Waveform（STF＃２）


Td=456 µs

74


Klystron waveforms at Breakdown（STF＃２）

Es=9.0 kV, Pw=1.7 ms, fr= 5 pps

W 100V Ik dt

Energy deposit in klystron

from gun spark

W=2.0 J < design value

Arc voltage＝100 V

75


P2 – Marx Modulator(SLAC)

• 32 Cells

• 3.75 kV Nominal Cell Voltage

• N+2 Redundancy (4 kV Max)

• 350 µF Cell Capacitance

• One-cell 20% Droop Compensation

• Active, closed-loop control regulates output

voltage

• Air Cooling/Insulating(No oil)

• Independent Charging Supplies

• FPGA-based Diagnostic/Control Module

• Compatibility with two-tunnel design

• High availability

• Low-cost

• Ease of maintenance

• Portability of design to future applications

P2 Marx Design Considerations

RF System Overview

76



• SLAC P2 Marx Cell Cell Output Current

Cell Output Voltage

Main IGBT Vce

PWM Inductor Current

+

+

+

Correction Scheme

2 cells switching in phase 2 cells switching

180o out of phase

Ripple

Cancelation

77

Droop compensation circuit



Layout

283 cm H

168 cm D

347 cm W

Marx cell : 22.7 Kg

Oil-free

Easy access

78



Performance

79



•Arc-down test at full output power by a self-break oil gap across the load.

•Assuming a 200 V arc, we calculate a deposit of less than 10J.

電力効率（TDR）

80

Marx-type Modulators

81


• Marx Topology : Charge in parallel, discharge in series

• Features: Modularity, Electrostatic Adding, Independent module control

and Low-voltage sub-units

• Marx-type modulator is expected to have high availability and low-cost.

DTI Marx Modulator

for ILC

SLAC P2 Marx Modulator

for ILC Ampegon Pulse Step Modulator

for XFEL

KEK Marx Modulator

82


620 V

20 kHz

420 V

50 Hz

3φ

Isolation

Step-up

Transformer

Kly

stro

n

• Marx Unit: – 6.4 kV output pulser with four Marx

cells at -2 kV each – Marx Cell has a step-down converter

with a switching frequency of 50 kHz

– Flat pulse voltage is formed with a PWM modulation

• Charging system:

– Independent unit charging through 20 kHz isolation step-up transformer

– Each unit is charged up to -2kV and the input voltage of the Marx unit is regulated.

• System: – N+1 redundancy

– Air insulatated, water cooled, No oil

Inverter

Charging System

Marx Unit #20 10kW Inverter

Charging PS

Marx Unit #19 10kW Inverter

Charging PS

Marx Unit #02

Marx Unit #01

10kW Inverter

Charging PS

10kW Inverter

Charging PS

-120 k V

140 A

1.7 ms

5Hz

-6.4 k V

140 A

1.7 ms

5Hz

2.0 k V

20kHz

0.00m 0.40m 0.80m 1.20m 1.60m 2.00m -150.00K

-120.00K

-80.00K

-40.00K

0.00K

10.00K

v(r340) (V) t (Secs)

MARX80ver2.CIR

Simulated output voltage waveform

System Block Diagram

-2.0 kV

DC

KEK Marx Modulator View

83


Size 1.6 m(D) x 3.3 m(W) x 2.3m(H)

Marx Unit

Charging

system

Tests with a dummy load were ready at end of this March. Quarter of the modulator full charging power(50kW) is

available.

Marx Unit

84


•Marx unit is the semiconductor Marx generator and consists of four Marx cells and a control circuit board with FPGA to control the each cell. •Marx cell is a step-down converter.

Block diagram of Marx unit

Marx cell (Step-down converter)

455mm×650mm×382mm(H)

Parameter Value

Input voltage 2.0 kV

Output voltage -6.4 kV

Capacitor droop 20%

Number of Marx cell 4

Marx unit parameters

85

Marx cell parameters

SiC FET 3P2S

SiC SBD 2S

IGBT 1.33uF

550Ω

0.133uF

48uH

400mm×300mm×75mm(H)

充電経路 SiC FET 3P2S

Opt.i/F Opt.i/F

IGBT

Filter L

Filter C

Storage capacitor C

Marx Cell

SiC SBD 2S

Marx Cell Accelerator Laboratory

Parameter Value

Input voltage -2.0 kV

Output voltage -1.6 kV

Capacitor voltage droop 20%

PWM frequency 50 kHz

Circuit diagram of Marx cell

SiC power devices(1.2 kV FET, SBD) were selected

because of its higher breakdown voltage, low on-

resistance and fast switching speed.

Energy conversion efficiency is about 93%.

SiC Power Device(Si vs. SiC) Accelerator Laboratory

IGBT：IXGK75N250

2500V, 75A FET：SCH2080KE

1200V, 40A

2S3P

SiC

•Frequency：50 kHz、Duty cycle :75%、Charging voltage :1 kV

ON

•Reduce chopper switching loss by one-third comparing with Si device

Si Switching loss(1 cycle)

86

87

Charging and Pulsing in Marx unit

Charging Pulsing


DC

-2kV

(input)

DC

-2kV

(input)

-6.4kV

Pulse

Charging switch Chopping switch

Droop Compensation

88


Output droop can be compensated by PWM control.

Output voltage droop of Marx cell

Droop ratio: 20%

PWM duty cycle is increased from 76% to

95% in proportion to time.

Ripple Cancelation

89


PWM1CELL Stage1

Dis-Charge90°

180°

270°

90°

180°

270°

2us 10us

Duty_Start Duty_Stop

Pulse Width=1.7ms

CHG

PWM2CELL Stage2

Dis-Charge

PWM3CELL Stage3

Dis-Charge

PWM4CELL Stage4

Dis-Charge

Repetition Frequency

-Order=5Hz

PWMFrequency

PWMFrequency

In the same way, modulator output ripple can be reduced by unit

phase shift control.

Timing chart of four-cell gate signal Output voltage ripple of Marx unit

Each cell gate signal is shifted by 90 degrees. Ripple ratio : 52% 6%(for Marx unit)

The output ripple of the unit can be reduced by cell phase shift control.

Charging voltage=1300 V, Vp=80 kV, Ip=90 A, Pw=1.7 ms, Ripple=0.6%(p-p)

High voltage Test at Dummy Load Accelerator Laboratory

90


Thank you for your attention！

91

Klystron Power Supply - KEK · Accelerator Laboratory Klystron Power Supply Mitsuo Akemoto KEK Joint US-CERN-Japan-Russia International Accelerator School 2017-RF Technologies-

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