KEK Digital Accelerator and Its Beam Commissioning

Transcription

1 KEK Digital Accelerator and Its Beam Commissioning Ken Takayama High Energy Accelerator Research Organization (KEK) Tokyo Institute of Technology on behalf of KEK Digital Accelerator Project Team September 4-9, 2011 in San Sebastian IPAC 2011

2 Outline of Talk 1. Principle of induction Synchrotron 2. Outline of KEK Digital Accelerator 2-1 ECRIS 2-2 Longitudinal chopper 2-3 LEBT and Electrostatic injection kicker 2-4 Ring lattice 2-5 Induction acceleration system 3. Beam Commissioning 3-1 Injection optics 3-2 Barrier bucket capture 3-3 Bunch squeezing experiment 3-4 Acceleration scenario 4. Expected Applications and Summary

3 Characteristics of Induction Synchrotron RF Synchrotron RF input Resonant cavity v=cβ Cavity and RF amp. with a limited bandwidth Induction Synchrotron Ion bunch Takayama and Kishiro in 2000 Switching Power supply V Transformer (Induction cell) SW1 SW2 SW3 SW4 Bunch monitor Digital trigger controller Cascade type of accelerator complex Single stage accelerator Ion source Linac Booster Main accelerator Ion source Main accelerator Functionally combined acceleration/confinement -> increase in the local density -> limit on a beam current RF volatge Ion bunch Acceleration time phase Deceleration phase Diffusion phase Functionally separated acceleration/confinement -> increasing a freedom of beam handling Pulse voltage for acceleration (set) Ion bunch (reset) Pulse voltage for confinement 3 time

4 T. Iwashita et al., KEK Digital Accelerator Phys. Rev. ST-AB 14, (2011). KEK Digital Accelerator 4 LEBT Induction accel. cell B3 4 ECRIS & HVT

5 ECR Ion Source : Schematic and Output f = 9.33 GHz Plasma Properties: Permanent magnets 10 Hz pulse mode operation Mirror fields Hexapole fields No power for guiding magnets No cooling water He 2+, N x+, O 5+, Ne 5+, Ar 5+ at early stage High voltage terminal Ne Ion Pulse

6 Einzel Lens Longitudinal Chopper (1): Idea and Device Why we need a Chopper? 1 turn injection < 10 µsec A long pulse from ECRIS ~ 2-5 msec Longitudinal gate study What type is desired? Low energy operation Low cost Einzel lens longitudinal chopper Low energy x-ray Reduced out-gassing Reduced secondary e - Helium ion current (au) for 5 ms Ion Beam Voltage of Electrode (kv) FET switch driven 4 stages Marx generator

7 Einzel Lens Longitudinal Chopper (2): Chopping experiment at 0.4 ms at 3.0 ms He1+ beam from ECRIS 5 µsec at 1.0 ms at 4.0 ms 5 msec at 2.0 ms at 5.0 ms Test bench He1+ pulses chopped at different timing T.Adachi et al., Rev. Sci. Inst. 82, (2011) and in this conference, TUPC096

8 Electrode (+) Electrostatic Injection Kicker E dx/ds(m) x assumed 2σ emiitance: ε x /ε y (mm-mrad)=165/32 observed 2σ emiitance: ~ 25 Injected Beam Injection timing Kicker Voltage (kv) High voltage electrode Ground Electrode Vacuum Chamber for subsidiary electrodes 8

9 DA Ring Machine & Beam Parameters Combined-function type magnet (lower half) Beam orbit ρ Bending radius ρ 3.3 m Ring circumference C m Maximum flux density B max 0.84 T (1.1 T) Accele. voltage/turn V 3.24 kv Repetition rate f 10 Hz Betatron tune ν x /ν y 2.1/2.3 Resonant LCR Circuit Power Supply 8 β-function Beam envelope 6 F-sector β Y F-sector 4 D-sector 2 0 β X

10 Equivalent Circuit of Induction Acceleration System and Individual Instruments DC Power Supply V 0 Switching power supply C 0 Trasmission line (40m long) Z 0 (120Ω) Induction accel. cell Z R C L Primary loop Switching arm S1 (7 MOSFETs in series) CT (matching resister) MOSFET board V 3 Finemet (nano-structure crystalline, Hitachi Metal) Gate drive power MOSFET (rear) Proton beam 2.5kV, 20A, 1MHz, 500nsec Development by KEK Nichicon Gate trigger light signal Cupper heat sink Gate driver IC (rear) Stacked induction cells 10 (output:2 kv/cell)

11 ES Position Monitor R2 R1 Beam Commissioning (1): Injection Optics R R + R =, + R + R Z = Z Z Z Z Outside Intside R3 R4 R + = R2+R3, R - = R1+R4 Z + = R1+R2, Z - = R3+R4 Betatron tunes FFT analysis Q x =2.19 (design 2.17) Q y =2.30 (design 2.30) Beam intensity (au) after After injection error correction Time (µsec) with correction without correction

12 Beam Commissioning (2): Barrier Bucket Trapping and Life-time Without barrier voltage pulses Ion bunch circulation signal With barrier voltage pulses Ion Beam Intensity Fast Loss due to Emittance Mismatch and Injection Error Medium Loss (1.4 ms) due to COD Barrier voltage pulse Slow Loss (4 ms) due to Residual Gas Scattering

13 Beam Commissioning (3): Bunch Squeezing Experiment p/p 8 nsec/turn 0 7 msec p/p p/p > 7 msec fixed

14 Beam Commissioning (4): Mountain View of longitudinal distribution Time after injection (msec) Experimental result Injected pulse length Simulation result Crossing point Time in revolution (µsec) p/p(%) at 0 msec (injection) at 1.5 msec at 10 msec (end) off-set Barrier voltage Barrier bucket momentum spread=0.025%, off-set=0.23% (optimized so that crossing point is reproduced)

15 Induction Acceleration Scenario Technical Capability of Induction Acceleration Cell Fixed output voltage ~ 1-2 kv/cell (If magnet ramping is slow) 1) Pulse density control V acc Maximum pulse length ~ µsec/pulse Maximum rep-rate ~ 1 MHz t When requirement exceeds its capability, (If larger acceleration voltage is required) 2) Superimpose of pulses in time (If longer pulse width is required) 3) Sequential trigger in time (If higher rep-rate is required) 4) Intermittent operation V acc V acc V acc Cell B Cell A Cell B Cell A Cell A t Cell A Cell B t t

16 B(t) 0.84 T Scenario of induction acceleration/capture of He2+ and C6+ Extraction near Injection 20 msec Injection Acceleration region 100 msec t 5 msec 30 msec Vacc=ρC(dB/dt) 10 msec 40 msec 15 msec 50 msec

17 Summary and Next Step Key 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 been evaluated. 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 space Space Electronics: study on cosmic ray damages on LSI devices for deep solar-system explore missions development of cosmic-ray-resist electronics system

18 Thank you for Your Attentions Other Papers related to the KEK Digital Accelerator TUPC096 WEPS075 THP0027 Solid-state Marx Generator driven Einzel Lens Chopper Induction Sector Cyclotron for Cluster Ions Novel Switching Power Supply Utilizing SiC-JFET and Its Potential for the Digital Accelerator

19 Control of Induction Acceleration System L Matching registor Acceleration cell Beam V(t) Bunch monitor Amp. & Front End Processing 1MHz Switching Power Supply CCR For Stage change DSP PC 2 USB DSP Cable between Accelerator tunnel and CCR CT current(induced voltage) Beam bunch signal R signal DSP PC 9 USB Optical fiber Module to transfer to optical signals Cable between CCR and Accelerator tunnel Signal distributor for intermittent operation Pulse generator NIM logic circuit DSP (Digital Signal Processor) Calc. T(t)=L/V(t) Set Timer T(t)

20 Betatron Iron york From Betatron to Induction Synchrotron / Cyclotron dψ MURA 50-MeV FFAG (1964) V = E dl = ( Ψ B ds) Fulx density dt Exciitation coil Excitation Coil (primary) N S Initial Accel. in FFAG Synchrotron (KEK, 2006) Vacuum chamber Top view Orbit f < 1-3 MHz (first Betatron) r Topological modification Cyclotron f < 1 Hz (burst ~ 1 khz) Linear induction accelerator with Kerst 10kA, 50-MeV ATA (LLNL, 1983) for more history K.Takayama and R.Briggs (Eds.) Induction Accelerators (Springer, 2010 October)