Beam Commissioningof the

KEK Digital Accelerator

• Digital Accelerator• KEK Digital Accelerator (KEK-DA)• ECR ion source and Einzel Lenz chopper• Injection Kicker• Beam Bunch Observation• Confine, Squeeze, Acceleration of the Beam• Summary

Taiki Iwashita (KEK)

HIF-HEDEP US-Japan Workshop @ Osaka Univ. Oct. 12~14, 2011

KEK-DA Collaborators

• KEK ※T. Iwashita, T. Adachi, T. Arai, D. Arakawa, K. Okamura, E. Kadokura, M. Kawai, T. Kawakubo, T. Kubo, K. Koyama, H. Someya, A. Takagi, K. Takayama, H. Nakanishi, M. Hashimoto, M. Wake

• Sokendai (Graduate University for Advanced Studies) Leo Kwee Wah

• Nagaoka University of Technology W. Jiang

• Nippon Advanced Technology K. Okazaki

• Pulse Power Japan Laboratory A. Tokuchi

Induction Cell(Transformer)

V

SwitchingPowerSupply

Digital Accelerator (DA)

Time

Confinement Voltage

Acceleration Voltage

Ion Bunch

SW2SW1

SW3SW4

Timing C

ontrol Unit

• Proposed by Takayama & Kishiro (KEK) in 2000

• Proof of principle experiments at KEK 12GeV PS in 2006

• RF cavity of conventional synchrotron is replaced by induction cell (Transformer)

• Switching power supply using high power MOS-FET is free from the limitation of band width of RF cavities and amps

• DA can accelerate all species of Ions without large injector → wide field of applications are expected

• Gate trigger signal is generated from bunch monitor signal

• Acceleration / Confinement are separeted function → Increase freedom of beam handling

IonBunch

BunchMonitor

KEK Digital Accelerator

4

B3

T. Iwashita et al., “KEK Digital Accelerator” Phys. Rev. ST-AB 14, 071301 (2011).

Induction cell

ECRIS & HVT

LEBT

HEBTExperiment AreaBeam Dump

ECRIS

Z0(120)V0

Z R CL

Induction cell

V3

Switching power supply

C0

Trasmission line(40m long)

(matching resister)

DCPowerSupply

CT

Induction Acceleration Hardware Overview

Primary loop

Finemet (nano‐structurecrystalline, Hitachi Metal)

Proton beam

Stacked induction cells（output：2 kV/cell）

2.5kV, 20A, 1MHz, 500nsec

Switching arm S1(7 MOSFETs in series)

Development by KEK・Nichicon

MOSFET board

Cupper heat sink

Cooling water

MOSFET(rear)

Gate driver IC（rear)

Gate triggerlight signal

DC‐DC converter for Gate drive power

5

Gas Feeder

Hexapole Magnet

Horn Antenna

Extraction Electrode

Mirror Magnet

Ceramic Insulatorfor pre-acceleration (14kV)

ECR Ion Source and High Voltage Terminal

• Permanent Magnet ECRIS installed inside 200kV High Voltage Terminal• He1+ is provided for acceleration experiment• C, N, O, etc can be available by changing gas

200kV High Voltage Terminal

Einzel Lenz

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.0

Ion

Beam

Cur

rent

, Ib[A

]

Micowave Power, Pin[W]

A

Microwave Power [W]

Ion Current

0.100sccm0.150sccm0.175sccm0.200sccm0.225sccm0.250sccm0.275sccm

Einzel Lenz Chopper

Control beam width by changing voltage of center electrode of Einzel Lenz

• Chop 5msec width beam from ECRIS make 5sec beam requested by acceleration scheme

Magnets

Magnets

Microwave (9.3GHz)

Gas (He, Ne, Ar)

Extraction Electrode

Einzel Lenz

+14kv 0 v

0 v 0 v

Plasma

ECRIS

5msec ion beam

5sec beam

Turn on/off Pulse HVby Solid StateMarx Generatorwith High power MOS-FET

T.Adachi et. al,. ‘‘A Solid-state Marx Generator driven Einzel lens Chopper’’, Review of Scientific Instruments 82, 083305 (2011)

Gate Open +11kVGate Close +17kV

EL chopper: Simulation / Experiments5mS He1+ Ion Beam

-2.00E-06

0.00E+00

2.00E-06

4.00E-06

6.00E-06

8.00E-06

1.00E-05

1.20E-05

-2.00E-03

-1.00E-03

0.00E+00

1.00E-03

2.00E-03

3.00E-03

4.00E-03

5.00E-03

6.00E-03

7.00E-03

8.00E-03

After TWT Amp Trigger (S)

Ifc (

A)

5μS Chopped Beam

0.00E+00

2.00E-06

4.00E-06

6.00E-06

8.00E-06

1.00E-05

1.20E-05

1.40E-05

1.60E-05

1.80E-05

5.00E-06 7.00E-06 9.00E-06 1.10E-05 1.30E-05

Ifc (

A)

0.4mS delay

1mS delay

3mS delay

7 8 9 10 11 12 13 14 15 16 17 180

2

4

6

8

10

12

14

Einzel Lens Voltage, V1/KV

Ion B

eam

Curr

ent, Ib/

μA

Ib Vs V1

IGUN Simulation：17kV of center electrode can stop 14keV beam

5sec width beam bunchTest bench results

5msec He1+ ion beam

[sec]

(Veridical)

Luminescent Plate+ CCD camera

Wire profile monitor（Horizontal）

BM2BM1

BM3Q1(F)

Q2(D)

Q3(F) Q4 (D) Q5(F) Q7(F)Q6(D)

Horizontal Vertical

βx

βy

Beam Profile measurement at beam transport line

EAnode (+)

InjectedBeam

s

x

Simulated phase space motioninside the field

x(m)

dx/ds

Electrostatic Injection Kicker

Anode （＋） Ground

Vacuum Chamber

SubsidiaryElectrodes

SubsidiaryElectrodes

HV

(kV

)

Kicker voltage profile

Time (ms)

First Beam of KEK-DA

12s from Chopper trigger

5s

Bunch Monitor

Chopper Trigger2nd turn is stoppedby luminescent plate in the ring

Circulating Beam

15mV

1msec

Beam Confinement with Barrier Bucket(without acceleration)

Vbb on

Beam is alive 10 msec later from injection

Vbb offBeam decays at 10 msec later from injection

Medium Loss (1.4 ms)due to COD

Slow Loss (4 ms)due to Residual Gas Scattering

Loss by Residual Gas: neutralized &stripped & scattering

Fast Lossdue to Emittance Mismatch and Injection Error

Ion Beam Intensity

Neutralization (capturing e‐)

Being stripped, Losing e‐

Ion bunch

ion

Residual gas in vacuum

Charge‐state change

Beam Loss

Injection Optics

after

Time (sec)

Beam intensity (au)

Outside Intside

R1R2

R3 R4

ES Position Monitor

ZZZZZ

RRRRR ,

R+ = R2+R3, R- = R1+R4

Z+ = R1+R2, Z- = R3+R4

FFT analysis

Betatrontunes

Qx=2.19 (design 2.17)

Qy=2.30 (design 2.30)

After injection error correctionwith correctionwithout correction

Beam monitor

TOF calculationT(t)=L/V(t)

SetTimer T(t)

Amp. &Front EndProcessing

1MHz switching power supply

Waveshaping

BeamL

V(t)

DSP (Digital Signal Processor)

Optical Convertermodule

CCR(Central Control Room)

Induction Acceleration Cell

Optical fiber

Control System of induction Acceleration in KEK‐DA

PC for DSP control

USB

Beam timing pulse

NIM

 Logic circuit

Matchingresistance

Oscilloscope for monitoring inductionoutput voltage

Signal divider(for alternativeOperation)

ECRIS Pulse chopper timing signal

R monitor Beam bunch signal

Timing pulse

Rsignal

Bunch Squeeze Experiment

time

time

Barrier Voltage

Beam Bunch

Injection

3.5msec

7msec

Barrier Voltage

DSP (Digital Signal Processor) changes timing ofBarrier Voltage by 8nsec/turn

(by T.Iwashita and T.Adachi)

ProjectedProjected

Squeezing in Mountain View & its projection

1st turn2nd turn3rd turn

Hundreds of turnAt injection

Stop squeezing at 7ms

Beam bunch

Simulated Phase Space Motion of Squeezing Experiment

tBarrier Voltage

bucket

Beam Density Profileat Injection

End of Squeezing

5s

1.5s

momentum spread=0.025% off-set=0.23%

ms s

Experiment Simulation

At injection

Cross point

final

t

t

t

1st turn

125th turn

820th turn

5 sec 5 sec1st turn

125th turn

820th turn

1st turn

820th turn

Comparison: Experiment VS. Simulation

estimated fromExperiment

Analog Devices

Beam monitor

300MHz

Amp. &Front EndProcessing

1MHz switching power supply

Beam

L

V(t)

FPGALess overhead,much compact than present DSP systemOptical 

Convertermodule

CCR(Central Control Room)

Induction AccelerationCell

Optical fiber

Replace DSP by FPGA (Next Generation)

PC for FPGA control

JTAG

Beam timing Signal

Matchingresistance

Signal divider(for interm

ittentOperation)

ECRISChop timing signal

Xilinx Vertex5400MHz

ADC

Oscilloscope for Monitoring inductionoutput voltage

R monitor

Rsignal

Timing Signal

Beam bunch signal

Induction Acceleration In minimum B fields

max

max

2

max

2

Sweep distance in the horizontal direction:

(1)

where1.4 m

4 cmAllowed maximum momentum spread:

4 2.8 10140

Meanwhile,1

px D sp

D s

x

pp

p Ep E

20

2 402 3

2 30

6

4

(2)

where12

2 1 200 keV2 1.07 104 931 10 keV

4 931 0.2 10 keV

3.724 10 keV

1 0.8 keV0.8

1.07 10

acc

A m c Q e V

Q eVA mc

E A mc Q eV

E Q eV N turn Np Np

3

6

2

3

=2 10 (3)3.724 10

2.8 10 14 turn2 10

N

N

No acceleration voltage

with 0.8 kV acceleration voltage

13 turns 

xmax

Ion Beam expected at KEK-DA

Species Z Q EnergyMeV/u

PPP PPS (10Hz)

He 4 2+ 88.0 2.1×1010 2.1×1011

O 16 6+ 50.4 7.0×1010 7.0×1011

Ne 20 6+ 32.6 7.0×1010 7.0×1011

Ar 40 8+ 14.6 5.3×109 5.3×1010

2010-2012 Bmax=0.84T, 10Hz operation、200kV injection

2012- （Magnet upgrade, install Laser Ablation Ion Source）

Bmax= 1.1T, 10Hz operation、200kV injection

Species Z Q EnergyMeV/u

PPP PPS (10Hz)

He 4 2+ 146.8 1.8×1010 1.8×1011

3He 3 2+ 248.5 1.75×1010 1.75×1011

C 12 6+ 146.8 5.8×109 5.8×1011

Ar 40 8+ 120.5 1.9×109 1.9×1010

Fe 56 26+ 127.8 1.3×109 1.3×1010

Au 197 79+ 96.8 4.4×108 4.4×109

Summary• KEK-DA started beam commissioning from June 2011• Fortunately damage from earthquake was very limited• 10～20A of He1+beam is provided from ECRIS• Barrier trapping, bunch squeezing, acceleration

experiments are going on

Next Plan• Accelerate & Extract Helium beam including He2+

• Accelerate N, O, Ne, Ar, etc.• Build a new application line

T. Iwashita et. al, "KEK digital accelerator"Physical Review Special Topics - Accelerators and Beams, July 2011 Vol.14, Issue 7

T.Adachi et. al,. ‘‘A Solid-state Marx Generator driven Einzel lens Chopper’’, Review of Scientific Instruments 82, 083305 (2011)