Transcript 超伝導加速による 次世代小型高輝度光子ビーム源の開発

ILC accelerator related R&D in Japan
2nd ASIA ILC R&D Seminar at KNU, Daegu, Korea
Junji Urakawa , KEK
1. Pol. e- source R&D at Nagoya U., Hiroshima U., and KEK
2. Pol. e+ source R&D at KEK, Hiroshima U., IHEP, CERN, and
LAL
reported by M. Kuriki (Also, considering conventional
source with KEKB upgrade plan, liquid Pb or crystal target)
3. Damping Ring R&D at ATF
reported by N. Terunuma
4. BDS R&D at ATF2
reported by T. Tauchi
5. SCRF R&D at STF
reported by H. Hayano and N. Ohuchi
6. Photo-cathode RF gun
7. Pulsed laser storage cavity
8. Quantum beam project
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1. Pol. e- source R&D at Nagoya U., Hiroshima U., and KEK
Production of nanosecond pol.e- beam for ILC
Laser
ILC:6.4nC/bunch
e-beam
Photocathode: GaAs-GaAsP SL
(Pol.max > 85%)
The SL active layer grown on
a laser cutting GaAs wafer
Laser energy : 6mJ （10Hz）
Bunch width(FWHM): 1.6ns
2
Bunch charge : 8nC
Space charge limit
Experiments & Simulations
Experimental data
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150kV(EXP)
150kV(GPT)
Extracted charge of 30nC/bunch
was obtained.
Extracted Charge (nC)
30
25
The experimental data is a
measurement of supply
current to the electrode.
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14.3nC/mJ
(QE~2.3%)
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Simulation data（GPT）
10
5
Bulk-GaAs (Zn:1.4x10 19/cm3)
Extracted charge is estimated from
the number of macro-particles
at 10mm downstream PC.
~775nm
0
0
10
20
30
Initial Charge (nC)
40
50
Both results are corresponding
well, therefore this simulation is
almost appropriate for calculating
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SC effect.
Characteristics of SUS and Ti-Mo electrode
SUS electrode
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1
0.8
Dark Current [nA]
Dark current [nA]
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Ti anode & Mo cathode
6
4
2
Breakdown
0.6
Breakdown
0.4
0.2
Breakdown
0
100
120
140
160
180
200
220
Voltage [-kV]
0
100
120
140
160
180
200
220
Voltage [-kV]
Advantages of Ti-Mo electrode
Dark current characteristic isn’t degraded even if many
breakdowns were occurred.
Hardly observed dark current until breakdown was occurred.
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Photocathode Lifetime
350
300
Current (nA)
250
Trans. 85~88%
200
Preliminary
150
Bulk GaAs, He-Ne 633nm, 200kV
Vacuum:4.0x10 -9Pa @Gun
100
Gun:2.7x10-9Pa
2NEG:2.0x109Pa
6.1x10-9Pa @2-NEG.Cham.
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Beam Current (nA)
F.C.(nA)
0
0
5
10
15
20
25
Time(hour)
The photocathode lifetime seems no problem under the condition
of a few micro amps beam emission.
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Long-term 200keV operation became possible by employing the
titanium anode and molybdenum cathode electrode.
Remaining R&D : A laser system which meets fully ILC
requirements.
SLAC is
developing.
Hiroshima,
and KEK are
considering.
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6. Photo-cathode RF gun
Cs2Te Photo-cathode, 1.6 Cell S-band RF Gun
Multi-bunch beam generation
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Fig.5 Momentum distribution of bunch train
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Energy (MeV)
Energy compensation for 100 bunches
41.2
41.0
40.8
40.6
40.4
40.2
40.0
39.8
TD4: 036e
TD4: 0359
TD4: 035e
0
20
40
60
80
bunch number in the train
100 bunches/pulse energy
spread is less than 0.5%.
100
Fig. 7 Upper-left : ICT signal of 100 bunches,
upper-right : 100 bunches on the OTR screen,
bottom figure : energy of each bunch in the train
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Laser Pulse Stacking Chamber, 3m long S-band accelerating tube and
Photo-cathode RF Gun
Collision point
Top view
BPM
Bending
magnet
Faraday Cup
BPM
PRM PRMQ-magnet
BPM
S-band accelerating tube (3m)
Q-magnet
Side view
Emittance measurement
ICT
PRM
BPM
PRM
Q-magnet
BPMICTsolenoid
PRM
Chicane
RF Gun
Cathode: Cs-Te
e- beam
ICT & Faraday Cup: Beam current monitor
BPM: Beam position monitor
PRM: Beam Profile Monitor 10
OTR target or Al2O3 (Cr3+ doped)
Beam energy and energy spread measurement
Emittance measurement
Collision point
εx: 3.0 [mm・mrad]
QF1
QD1
Beam current : 2.5nC/train, 3bunches
Beam profile
at Collision point
εy: 4.7 [mm・mrad]
CP1G
(OTR)
σx: 86um
σy: 36um
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Optical Circuit
e- beam
P-LW-CAV installed in APR2007.
e- beam
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X-ray Generation
43MeV end station to separate X-ray
and e-beam. 33keV X-ray is deflected
by Crystals.
Pulsed laser stacking chamber
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Laser Undulator Compact X-ray (LUCX)
Project at KEK-ATF
43MeV Multi-bunch beam+ Super-Cavity = 33keV X-ray.
X-ray
Detector
Multi-bunch
photo-cathode
RF Gun
S-band Acc. Structure
Beam size at
CP 60mm in s
Multi-bunch e- beam 300nC at gun
Storage
Laser power
40kW,
7psec(FWHM),
next step :1MW
At present, laser waist size is 30mm in
s. We should reduce both beam size at CP
down to 30mm.
33keV X-ray generation based on inverse
Compton scattering was started from May
14
2007 with Super-Cavity.
7. Pulsed laser storage cavity
From two-mirror cavity to four-mirror cavity under
International collaboration with LAL.
50 ｍJ / pulse, waist = 8 mm
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Considering two-mirror cavity,
reflectance R, transmissivity T, and losses L where R+T+L = 1
by energy conservation.
The “bounce number” b which is defined from the round-trip
power loss in a cavity, ∝ e−1/b. FSR : free spectral range
If R=R1=R2
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Storage of laser pulse
Perfect resonance : Llaser = L cavity
Resonance condition :
The relationship with
laser and cavity :
Imperfect Resonance : L laser ～ L cavity
The enhancement
factor is the function
of reflectivity, Δl and
laser pulse width.
Not resonance : L laser≠ L cavity
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Achievement on related technique
JFY2003
CW Laser wire beam size monitor in DR
300mW 532nm Solid-state Laser
fed into optical cavity
14.7µm laser wire for X scan
5.7µm for Y scan
(whole scan: 15min for X,
6min for Y)
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Laser wire block
diagram
Free spectral range
:532nm/2=266nm
Line width=0.3nm
optical cavity resonance is kept by piezo actuator
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Experimental results（Pulse Laser Storage）
Laser:
Mode Lock: Passive
SESAM
Frequency:
357MHz
Cavity length:
0.42 m
Pulse width: 7.3 p sec
(FWHM)
Wave Length:
1064 nm
Power:
~ 6W
SESAM: SEmi-conductor Saturable Absorber Mirrors
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Ext. Cavity:
Cavity:
Cavity length:
Mirrors:
Reflectivity:
Curvature:
Super Invar
420mm
99.9%, 99.9% (maybe, 99.98%)
250 mm (ω0 = 180μm)
super invar
62φ
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・Finesse: R = 99.98%
Finesse =πτc/l
PD
PBS
PBS
τ:decay time
c: light verocity
l: cavity length
P.C.
Trans.
τ~ 3.0μsec
F ~ 6300
JFY 2004
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-ray Generation with Laser Pulse
Stacking Cavity (Hiroshima-Waseda-IHEP-KEK)
1.Achieve high enhancement & small spot size
2.Establish feedback technology
3.Achieve small crossing angle
4.Get experinence with e- beam
We should detect
20 ’s/collision.
pulse stacking
cavity
in vacuum chamber
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Mirror damage which is caused
by peak power density on the mirror.
Storage average
power 40kW or more
(maybe 120kW)
Laser size on mirror
440 mm
Then, reduce waist
size from 160 mm to
60 mm.
Laser size on mirror
1174 mm
Waist size in sigma from
80 mm to 30 mm
damaged coating size ~100 mm
Depth (p-p) 5.5 mm
Good coating spherical mirror damage threshold :
Average power density on mirror ~10 MW/cm2
Peak power density on mirror ~10 GW/cm2
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REO and SOC mirror threshold are a little small :
6.7 GW/cm2 and 1.6 GW/cm2
We designed asymmetric reflective mirror configuration
to increase the coupling : 99.7% and 99.9% .
Then, we found damaged mirror was low reflective one.
When we introduced burst mode operation for x-ray generation
with F.L. pumped amplifier, we might increase average power
in the cavity until 120kW. It means ~20GW/cm2.
Now we keep 40kW average power with larger beam size
1174 mm on the mirror ,which corresponds 0.8GW/cm2.
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R/D Status in Japan
Moderate Enhancement ~ 1000
Moderate spot size
~ 30 micron
Simple cavity stucture with two mirrors
Get experinence with 43MeV and 1.3GeV e- beam
Laser Undulator Compact X-ray
(LUCX) Project at KEK-ATF
43MeV Multi-bunch beam+
Super-Cavity = 33keV X-ray.
Expected X-ray is generated.
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8. Quantum beam project
Characteristic of proposed machine
Compact (less than 10m) quasi-monochromatic (less than 1%)
High Flux ( 100 times than Compact normal Linac X-ray：1011 photons/sec 1% b.w.）
High Brightness (1017 photons/sec mrad mm 0.1% b.w.）
Ultra-short pulse X-ray （40 fs ~）
2
2
Key technology
is
SCRF
acceleration
technology
Structural
genetic analysis,
Nano-material
evaluation,
Highly fine
X-ray Imaging
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http://mml.k.u-tokyo.ac.jp/
SCRF Cavity
Ultra-low loss(10nΩ)
long pulse acceleration
high intensity and low emittance
Pulsed laser storage
Storage energy : 100 times
Beam size < 8 mm
Laser Inverse Compton scattering
High intensity, high quality, monochromatic X-ray
Photo-cathode RF gun
Low emittance beam 3mmmrad
Short pulse, 162.5MHz bunch train
400 times by CW operation : ERL
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Pulsed Laser Storage
From 2-mirror cavity to 4-mirror cavity
0.5 ｍJ / pulse, waist = 30 mm
50 ｍJ / pulse, waist = 8 mm
Beam orbit control
Achieved by ATF
Laser wire waist： s ~ 3 mm
Electron beam size： s ~ 2
mm
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Organization & Responsibility
Compact and reliable Multi-beam Klystron R&D
Committee for project
evaluation
High power RF
Compact Klystron
Main Institute
KEK
Hiroshima U.
Laser storage
RF Gun
Photo-cathode
Toshiba
高安定電源供給
Hitachi
SC RF Accelerator development
システム構築・運転、性能測定
若手教育
ATF, STF
Pulsed Laser Storage
DC High Voltage Source
高安定電源供給
JAEA
直流高電圧電子源
High Quality and Intensity e- source カソード
ERL電子源試験装置
Waseda U.
X-ray detector
Laser Compton Exp.
Compact Accelerator
U. of Tokyo
Photo-cathode
Input coupler
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Annual Schedule and Budget
Item
2008
2009
2010
2011
2012
S. Cavity Development
($1.5M/year),
HRF + Cly
($0.8M/year)
Upgrade of SC Cavity performance
Compact RF power source system
Control system for SCRF
Electron Source
($0.5M/year)
High Q and long life photo-cathode
500 kV DC High Voltage
High Intensity Beam Generation
Pulsed Laser Storage
System ($0.4M/year)
X-ray Detector
($0.1M/year)
Construction of Test
Accelerator・Confirm
the performance
Design and R&D on laser storage
X-ray Detector
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Impact by Compact High Brightness Photon Beam
1) 第2世代放射光源の性能が 実験室へ！
構造ゲノム解析
＠A大学
ナノマテリアル評価
＠B企業研究所
高精細X線イメージング
＠C病院
2) サブピコ秒X線源を 実験室へ！ → 高速過渡現象の研究
溶液中の化学反応、 タンパク質の機能、 衝撃破壊、
３) 放射性廃棄物中の同位体検出
光誘起相転移
（エネルギー・環境問題解決へ）
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Target of component technology
technology
Electron
source
Present status
300 nC/pulse
Target
Key points
48,000 nC/pulse
(2010-2012)
Pulse laser, new photocathode
1 msec pulse length
10,000nC/pulse
(2008-2009)
SC Cavity
Pulse: 25 MV/m
CW: 12 MV/m
Pulse: 30 MV/m
CW: 20 MV/m
無欠陥・清浄表面、
高精度電子ビーム溶接、
高精度成形、
無欠陥材料
Pulsed laser
storage
0.5 mJ/pulse,
Waist: 30 mm
50 mJ/pulse,
Waist: 8 mm
4-mirror optical cavity
Colliding
control
mm beam orbit
control
Sub- mm beam
orbit control
環境の安定化、
高速フィードバック制御。
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Quantum beam project(2008-2012) approved by MEXT
Compact high brightness X-ray source using SC Cavity
Photo-cathode RF Gun
Pulsed Laser storage Cavity
30 MeV/m SC. 9 cell Cavity
Decelerating Exp.
X-ray Detector
ERL R&D
25 MeV まで加速
decelerate to 1MeV
He refrigerator
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