KEK Digital Accelerator and Its Beam Commissioning
Ken Takayama High Energy Accelerator Research Organization (KEK)
Tokyo Institute of Technology
on behalf ofKEK Digital Accelerator Project Team
September 4-9, 2011 in San Sebastian
IPAC 2011
Outline of Talk1. Principle of induction Synchrotron2. Outline of KEK Digital Accelerator
2-1 ECRIS2-2 Longitudinal chopper2-3 LEBT and Electrostatic injection kicker2-4 Ring lattice2-5 Induction acceleration system
3. Beam Commissioning3-1 Injection optics3-2 Barrier bucket capture3-3 Bunch squeezing experiment3-4 Acceleration scenario
4. Expected Applications and Summary
Transformer(Induction cell)
Bunchm
onitor
Ion bunch
SwitchingPower supply
Characteristics of Induction Synchrotron
Functionally combined acceleration/confinement ->increase in the local density -> limit on a beam current
time
RF volatge
Deceleration phase
Accelerationphase
Diffusion phase
Ion bunch
Functionally separated acceleration/confinement-> increasing a freedom of beam handling
time
Pulse voltage for confinement
Pulse voltage for acceleration (set)
Ion bunch
Cascade type of accelerator complex
Linac
BoosterMain
acceleratorIon source
Ion source
Main accelerator
Single stageaccelerator
RF Synchrotron
Resonantcavity
Cavity and RF amp.with a limited bandwidth
Induction Synchrotron
Digital trigger
controller
V
RFinput
v=cβ
SW2SW1
SW3SW4
3
Takayama andKishiro in 2000
(reset)
KEK Digital Accelerator
4
4
B3
T. Iwashita et al., “KEK Digital Accelerator”Phys. Rev. ST-AB 14, 071301 (2011).
Induction accel. cell
ECRIS & HVT
LEBT
ECR Ion Source : Schematic and Output
Plasma
Mirror fields Hexapole fields
Ne
Ion Pulse
He2+, Nx+, O5+, Ne5+, Ar5+ at early stage
f = 9.33 GHzProperties:Permanent magnets10 Hz pulse mode operation
No power for guiding magnetsNo cooling water
High voltage terminal
Einzel Lens Longitudinal Chopper (1): Idea and Device
Helium
ion current (au)
Why we need a Chopper?
A long pulse from ECRIS ~ 2 - 5 msec
1 turn injection < 10 µsec
What type is desired?
Low energy operation Low cost
Low energy x-rayReduced out-gassingReduced secondary e-
Einzel lens longitudinal chopper
Voltage of Electrode (kV)
for 5 ms Ion Beam
FET switch driven 4 stages Marx generator
Longitudinal gate study
Einzel Lens Longitudinal Chopper (2): Chopping experimentat 0.4 ms at 3.0 ms
at 4.0 ms
at 5.0 ms
5 µsec
at 1.0 ms
at 2.0 ms
5 msec
Test bench
He1+ beam from ECRIS
He1+ pulses chopped at different timing
T.Adachi et al., Rev. Sci. Inst. 82, 083305 (2011)and in this conference, TUPC096
Electrostatic Injection Kicker EElectrode (+)
dx/ds(m) x
assumed 2σ emiitance:εx/εy(mm-mrad)=165/32observed 2σ emiitance:
~ 25
8
InjectedBeam
High voltage
electrode Ground Electrode
Vacuum Chamber
KickerVoltage (kV)
for subsidiaryelectrodes
Injection timing
Bending radius ρ 3.3 mRing circumference C0 37.7 mMaximum flux density
Bmax 0.84 T(1.1 T)
Accele. voltage/turn V 3.24 kVRepetition rate f 10 HzBetatron tune νx/νy 2.1/2.3
0 1 2 3 40
2
4
6
8 β-function βY
βX
F-sector
D-sector
F-sector
DA Ring Machine & Beam ParametersCombined-function type magnet (lower half)
Resonant LCR Circuit Power Supply
9
Beam envelope
ρBeam orbit
Z0(120Ω)V0
Z R CL
Induction accel. cell
V3
Switching power supply
C0
Trasmission line(40m long)
(matching resister)
DCPowerSupply
CT
Equivalent Circuit of Induction Acceleration System and Individual Instruments
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
MOSFET(rear)
Gate driver IC（rear)
Gate triggerlight signal
Gate drive power
10
Beam Commissioning (1): Injection Optics
after
Time (µsec)
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 Commissioning (2): Barrier Bucket Trapping and Life-time
Without barrier voltage pulses
With barrier voltage pulses
Fast Lossdue to Emittance Mismatch and Injection Error
Medium Loss (1.4 ms)due to COD
Slow Loss (4 ms)due to Residual Gas Scattering
Barrier voltage pulse
Ion bunch circulation signal
Ion Beam Intensity
Beam Commissioning (3): Bunch Squeezing Experiment
8 nsec/turn
0 – 7 msec
> 7 msec
∆p/p
∆p/p
∆p/p
fixed
Time in revolution (µsec)
Time after injection (m
sec)
Beam Commissioning (4): Mountain View of longitudinal distributionExperimental result Simulation result
∆p/p(%)
3
1.50
momentum spread=0.025%, off-set=0.23% (optimized so that crossing point is reproduced)
at 10 msec (end)at 1.5 msecat 0 msec (injection)
Barrier voltage
Barrier bucketoff-set
Injected pulse length
Crossingpoint
Induction Acceleration Scenario
4) Intermittent operation3) Sequential trigger in time2) Superimpose of pulses in time
Fixed output voltage ~ 1 - 2 kV/cell
Technical Capability of Induction Acceleration Cell
Maximum rep-rate ~ 1 MHz
Maximum pulse length ~ 0.5 - 2 µsec/pulse
tttCell A
Cell B
Cell BCell A
Cell A Cell B Cell A
Vacc Vacc Vacc
1) Pulse density control
t
Vacc
When requirement exceedsits capability,
(If magnet ramping is slow)
(If larger acceleration voltage is required)
(If longer pulse widthis required)
(If higher rep-rate is required)
near Injection
5 msec
10 msec
15 msec
20 msec
30 msec
40 msec
50 msec
Scenario of induction acceleration/capture of He2+ and C6+
t
B(t)
Acceleration regionInjection
Extraction
Vacc=ρC(dB/dt)
100 msec
0.84 T
Summary and Next StepKey devices newly developed for the KEK-DA have been confirmed
to work in the desired manner.
Permanent magnet ECRIS operated in the pulse mode.Einzel lens longitudinal chopper was demonstrated for the first time.Electrostatic injection kicker worked with sufficient performance.Induction acceleration system operated in the rapid cycle synchrotron mode
Beam commissioning started in early June.
Basic machine properties such as Tune, COD, or Injection errors have beenevaluated.
Barrier bucket beam handling has been examined.Induction acceleration study will be started after summer shutdown.
(Test acceleration was officially approved in the mid-July.) Next step: Heavy ion beams from the KEK-DA will be delivered to Applications
“Laboratory Space Science using Virtual Cosmic Rays” from this winter.
Astrobiology: manifest a role of cosmic ray on production of life in spaceSpace Electronics: study on cosmic ray damages on LSI devices for deep
solar-system explore missionsdevelopment of cosmic-ray-resist electronics system
Other Papers related to the KEK Digital Accelerator
TUPC096 Solid-state Marx Generator driven Einzel Lens ChopperWEPS075 Induction Sector Cyclotron for Cluster IonsTHP0027 Novel Switching Power Supply Utilizing SiC-JFET and Its
Potential for the Digital Accelerator
Thank you for Your Attentions
Bunch monitor
Calc.T(t)=L/V(t)SetTimer T(t)
Amp. &Front EndProcessing
1MHz Switching Power Supply
Pulse generator
Beam
L
V(t)
DSP (Digital Signal Processor)
Module totransfer to opticalsignals
CCR
Acceleration cell
Optical fiber
DSPPC×9
USB
DSPPC×2
USB
DSP
Cable betweenCCR andAccelerator tunnel
NIM
logic circuit
Matchingregistor
CT current（Induced voltage）
Cable betweenAccelerator tunnel and CCR
Signaldistributorfor interm
ittent operation
For Stage change
Control of Induction Acceleration System
Beam bunch signal∆R signal
From Betatron to Induction Synchrotron / Cyclotron
Exciitation coilFulx density
Iron york
N
S
Betatron
Top viewOrbit
r
( ) dV E dl B dsdtΨ
= ⋅ = − Ψ ≡ ⋅∫ ∫
（first Betatron)
Vacuum chamber
with Kerst
f < 1 Hz(burst ~ 1 kHz)
f < 1 - 3 MHz
ExcitationCoil (primary)
Synchrotron(KEK, 2006)
Cyclotron
MURA 50-MeV FFAG (1964)
Initial Accel.in FFAG
Topologicalmodification
Linear inductionaccelerator
10kA, 50-MeV ATA (LLNL, 1983)
K.Takayama and R.Briggs (Eds.)“Induction Accelerators” (Springer, 2010 October)
for more history
