electron accelerator system (atf 2009) - kek1 electron accelerator system (atf 2009) k. kubo (most...
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Electron Accelerator System(ATF 2009)
K. Kubo (Most materials are from H. K. Kubo (Most materials are from H. HayanoHayano))
Multibunch photo-cathode RF-gunHigh gradient Linac
Damping RingExtraction Line
Final Focus Test LineInstrumentation
2
ATF Introduction
Final Focus lineIP; ~35 nm beam
ATF Linac
ATF Damping Ring
Extraction line
ATF IntroductionATF = Accelerator Test Facility,
Test Facility for Linear Colliders
• Test and demonstration of high quality (low emittance, stable) beam production
• Test and demonstration of the final focus scheme of Linear Colliders
• Development of various instrumentations
• etc.
ATF Linac• Beam Energy 1.3 GeV• Up to 4E10 e-/bunch (usually 1E10)• Up to 20 bunches/pulse• Rep. rate ~6.25 Hz (usually 3.125 or 1.5625 Hz)• Acceleration system
– RF frequency 2.856 MHz (S- band, same as SLAC)– 19 accelerating structures, 3 m long each
5
6
ATF Damping RingE=1.3GeVNe=1x1010 e-/bunch
1 ~ 20 bunchesγε x= 2.5E-6 ( at 0 intensity)
γεy < 2.5E-8 ( at 0 intensity)
Extraction line and Final Focus line (ATF2)
Final focal pointσy ~ 40 nm
FF lineEXT line
Test of final focus scheme of Linear Collider
Development of various instrumentationse.g. Beam position monitors, Beam size
monitors, Orbit feedback
8
Multibunch photo-cathode RF gun• For better MB injection into DR
generation of high quality multibunch
low emittance, low energy spread, high & flat intensity
• Cs2Te cathode• Laser system; 20 bunch, 2.8ns spacing, 266nm
Nd:YVO4 (1064nm) 357MHz mode-lock laser + amplifier
• Load-lock system for Cs2Te cathode block extra cathode blocks and evaporation chamber
• KEK built gun-cavityprecise machining and blazing by KEK machine center
9
RF-gun cavity & cathode block
Cathode block with CsTe coating
End plate with cathode blockCathode block
10
Multibunch photo-cathode RF-gun
11
Gun cavity, Loadlock & Laser system
Gun cavity
Seed Laser + Amplifier
Load-lock assembly
12
RF gun beam at 80MeV• Bunch Spacing
2.8 ns (8/2.856E6 s)• Beam Intensity
~1x1010/bunch• Normalized Emittance
εy= 4~7x10-6 rad.m• Bunch length
σz= 3 ~ 6 ps• Energy spread
dE/E = 2~3% full-width• Q.E. of CsTe cathode
16% initial, 2~3% with RF ON & constant over a week
Example of beam structure
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
-2 10-8 0 2 10-8 4 10-8 6 10-8 8 10-8
20 bunch beam from RFgun
Wal
l cur
rent
mon
itor
[V]
Time [sec]
~3x109
e-/bunch
13
ATF Linac regular unit1 Klystron + 1 SLED + 2 Acc. structures + wave guide, etc.
3 m Acc.
2-iris SLED
200
MW
200
MW
g)
TOSHIBA, E371280 MW4.5 sμ
3 m Acc.
14
Klystron power supply
Klystron
85MW klystron modulatorPFN
Trigger
THYRATRON
DE-QING TRIGGER
VDC POWER SUPPLY
15
RF pulse compression (SLED)
ATFで使用されているSLED空洞
SLED 空胴からの波を考えない入力波のSLED 結合部からの反射電圧
SLED 空胴から出てくる波 の電圧
SLED の合成電圧
加速管中を通過する 電圧
ATF Linac: 4.5μs 1 μs
SLED = SLac Energy Doubler
16
Accelerator structure
S-band 2π/3 mode Disk Loaded Structure
D=35mm
t=~5mm
2a 2b
Time 0
Acc
. Fie
ld
350ps
17
regular unit rf waveform
3 m Acc.
2-iris SLED
200
MW
200
MW
Acc
eler
atin
g Fi
eld
(no
beam
load
ing)
34 MV/m
Energy gain with beam loading120 MeV 120 MeV
52 MV/m 52 MV/m34 MV/m
TOSHIBA, E3712
1st 2nd 3rd 4th
Klystron output rf power Reflection rf power from SLED+Acc.x2 Input rf power for left Acc. Input rf power for right Acc.
: : : :
80 MW4.5 sμ
3 m Acc.
Waveform of rf-power
18
Beam Loading
励起する電磁波の強さは
バンチの電荷量に比例する
ビームがつくった電磁波は空洞の共振モードで存在し続け、後方のバンチに減速力を与える。
Electric particles induce electro-magnetic fields in cavity.Accelerating resonance mode field survive long time and decelerate following particles.
Another point of view:Electric particles are accelerated, means they get energy from fields in the cavity.Field energy in cavity is reduced and following particles feel less acceleration.
Beam Loading
• Beam loading makes bunch by bunch energy difference in multibunch operation.
• The difference can exceed energy acceptance of following beam line (linac to ring transport line) and damping ring (about 1%)Beam loading compensation for mitigate
the effect.
20
ΔF Beam Loading compensation
後ろのバンチほど加速される
ビームローディングによって後ろのバンチほどエネルギーが下がる
Schematic explanation
regular RF
+-ΔF
Beam monitors in Licac
• Strip line BPM (beam position monitor)• Screen monitor (beam profile)• Beam current monitor• Streak camera (bunch length)
22
Linac stripline Beam Position Monitor
23
Screen monitor image
24
Beam current monitor
beam
beam
V
ビームダクト 絶縁ビームダクト 抵抗
Current trans Wall current monitor
25
Streak camera for bunch length measurement
掃引電極
slit MCP
掃引回路
掃引電極
光電面
レンズ
トリガー信号
加速電極スリット 蛍光面
蛍光面上のストリーク像
SpaceTime
MCPPhoto-cathode screen
Streak image
掃引波発生回路
OTR light
26
Damping Ring
Circumference 139 mE=1.3GeV
Old Extraction Line
27
B Combined function bending magnet
main Quad magnet
FOBO arc cell for low emittance
Defocus in horizontal plane: Reduce horizontal emittance and horizontal damping time
sextupole magnetssteering magnets
sub quad magnet
DR FOBO arc cell
photo
29
Injection/Extraction
QM
5R.1
(ZV
10R
)
QF5
2T
QM
10R
.1
QF5
3T
QD
52T
ZV51
T
QM
9R.1
QM
8R.1
QM
7R.1
QM
6R.1
ZH
50T
KIX
KII
BS
1X
BS
2X
BS
3X
BS
3T
BS
2T
BS
1T
Biμ
B0
Be
入射ビームリングのビーム
ヨーク
コイル(A ) コイル(B )
Septum magnet (DC)
L
C C
フェライト
電極
Kicker magnet (pulse)
extraction kickerinjection kicker
From Linac
EXT Line
Damped RF cavity
S. Sakanaka, et al., PAC1993, p1027
32
Low Emittance tuning• Optics modeling by beam based way
Q-magnet strength correction in model
• Beam based BPM offset measurementQ, SX trim excitation & bump orbit to orbit response
• COD correction• Dispersion correction• Coupling correction
horizontal kick to vertical response, then skew corrector
Alignment of magnets and Performance of BPM are essentially important.
33
Vertical Emittance history by 2004
Target Y emittance = 1.0 x 10-11 at 0 intensity(1% from X)
10-12
10-11
10-10
10-9
8/1/97 8/1/98 8/1/99 8/1/00 8/1/01 8/1/02 8/1/03 8/1/04
Single bunch emittance history
Y emittance (EXT wire, SR)Y emittance (LW)
Y e
mitt
ance
[rad
.m]
Date
RFg
un2µ
m B
PM
210m
A li
mit
DR
IonP
ump
20µm
BPME
XT
line
MB
ope
ratio
n
star
t MB
rad.
shie
ld
rad.
shie
ld
X e
mi c
onfir
med
GL
CT
A
rad.
shie
ld
refine beam tuning10-12
10-11
10-10
10-9
8/1/97 8/1/98 8/1/99 8/1/00 8/1/01 8/1/02 8/1/03 8/1/04
multibunch emittance history
Y emittance by Ext wire
Y emittance by LW
proj
ecte
d Y
em
ittan
ce [r
ad.m
]
Date
210m
A li
mit
2µm
BPM
RFg
un
DR
Ion
Pum
p
star
t MB
MB
ope
ratio
n
radi
atio
n sh
ield
radi
atio
n sh
ield
GL
CT
A
radi
atio
n sh
ield
Recent Vertical Emittance history
2008 - 2009
0
10
20
30
40
50
60
Nov/1/2007 Mar/1/2008 Jul/1/2008 Nov/1/2008 Mar/1/2009 Jul/1/2009
εy (pm) X-SR
SR-ILW
ε y (pm
)
Beam Monitors in Damping Ring
• Button BPM (96 BPMs in the ring)– One shot orbit– Averaged orbit (closed orbit). (Only 20 out of 96
BPMs now. To be improved.)– Turn-by-turn (Oscillation. Tunes.)
• SR (Synchrotron Radiation) monitors– Visible light
• profile (beam size)• interferometer (beam size)• streak camera (bunch length)
– X-ray profile (beam size)• Laser Wire monitor (beam size)
36
New clip-circuit modulefast base-line clip
~1GHz wide-band widthwith low noise
DR button BPM and New clip-circuit
37
Vertical dispersion Improvement
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
0 20 40 60 80 100
Y dispersion before BPM improvement (26Nov2002)Y
dis
pers
ion
[mm
]
BPMnumber
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
0 20 40 60 80 100
Y dispersion after BPM improvement (20May2003)
Y d
ispe
rsio
n [m
m]
BPMnumber
New Electronics
38
X to Y coupling Improvement
-200.0-150.0-100.0
-50.00.0
50.0100.0150.0200.0
0 20 40 60 80 100
dY by ZH2R 26Nov2002
dY[m
icro
n]
BPMnumber
-200.0-150.0-100.0
-50.00.0
50.0100.0150.0200.0
0 20 40 60 80 100
dY by ZH4R 26Nov2002
dY[m
icro
n]
BPMnumber
-200.0-150.0-100.0
-50.00.0
50.0100.0150.0200.0
0 20 40 60 80 100
dY by ZH2R 20May2003
dY[m
icro
n]
BPMnumber-200.0-150.0-100.0-50.0
0.050.0
100.0150.0200.0
0 20 40 60 80 100
dY by ZH4R 20May2003
dY[m
icro
n]
BPMnumber
New Electronics
39
Stored Beam – 10 minute time scale; ATF lifetime ~ few minutes
beam position read-out vs. beam intensity:
scattered plot : existing analog circuit.
line plot : digital read-out introduced for test.
aiming εy ~ 1 pm
Digital read-out
Analogue read-out
DR BPM resolution improvement by digital read-out system (SLAC, FNAL, KEK)
40
Beam oscillation measurement by TBT-BPM
Tune measurement with 4K memory
Slow oscillation meas.with 64k memory
41
42
Layout of the SR-interferometer
Synchrtron light Polarizer
Band pass filter
Double slit
f=600mmLens
Interferogram 7m
CCD
1.6.1997 T.Naito
a D
L L
1.3m
0
y
I = πaJ0{1+ exp[−(2πDaλL0
)2]• cos(2πDyλL )}
SR interference beam size monitor
Interference pattern
43
Beam image (x:39µm, y:7.3µm)X-ray SR beam size monitor(Tokyo Univ., KEK)
44
X-ray SR profiles
X profile Y profile
39.27 +/- 0.53 [μm] 7.30 +/- 0.12 [μm]
εxXSR = 1.8 x10-9 , εy
XSR = 1.1 x10-11
( ~ 3 x109 bunch intensity)
After subtracting dispersion effect
Laser wire beam size monitor in DR
Laser Wire
electron - photon collisions
electron beam
gamma-raysgamma-ray detector
Principle
46
Laser wire beam size monitor in DR
14.7µm laser wire for X scan5.7µm for Y scan(whole scan: 15min for X,6min for Y)
300mW 532nm Solid-state LaserFed into optical cavity
47
Laser wire block diagram
optical cavity resonance is kept by piezo actuator
48
Beam profile by Laser wire
σe2 = σmeas
2 - σlw2
εβ = σe2 – [η(Δp/p)]2 β:measured by Q-trim excitation
49
50
51
Single Bunch emittance
εx = 1.8x10-9 ( εxn = 4.5x10-6)
εy = 0.7x10-11(εyn = 1.7x10-8) at 9x109 intensity
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0 2 109 4 109 6 109 8 109 1 1010
Horizontal Emittancex emittance (run B)x emittance (run D)simulation (0.4% coupling)
x e
mitt
ance
[10-9
]
bunch intensity [electrons/bunch]
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0 2 109 4 109 6 109 8 109 1 1010
Vertical Emittancey emittance (run B)y emittance (run D)simulation (0.4% coupling)
y e
mitt
ance
[10-1
2 ]
bunch intensity [electrons/bunch]
52
Bunch Length by SR monitor streak camera
15
20
25
30
35
40
0 2 109 4 109 6 109 8 109 1 1010 1.2 1010
bunch length(runD') [psec]bunch length(runE') [psec]bunch length(runF') [psec]simulation (0.4% coupling)simulation (6% coupling)simulation (3% coupling)
Bun
ch L
engt
h (r
ms)
[pse
c]
Bunch Intensity [electrons/bunch]
53
Energy Spreadby beam size monitor at EXT dispersive point
4.5 10-4
5.0 10-4
5.5 10-4
6.0 10-4
6.5 10-4
7.0 10-4
7.5 10-4
8.0 10-4
8.5 10-4
0 2 109 4 109 6 109 8 109 1 1010 1.2 1010
Energy Spread (runD)Energy Spread (run E)simulation (0.4% coupling)simulation (6% coupling)
Ene
rgy
Spre
ad
Bunch Intensity [electrons/bunch]
54
Multibunch Y Emittanceby Laser wire
Multibunch Projected Y emittance < 1% from X
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
0 2 109 4 109 6 109 8 109 1 1010
Vertical Emittance (Inc. Multibunch)
y emittance (single, runB)y emittance (single, runD)simulation (0.4% coupling)y emittance (20 bunch projected)
y e
mitt
ance
[10-1
2 ]
bunch intensity [electrons/bunch]
0.0 100
5.0 10-12
1.0 10-11
1.5 10-11
2.0 10-11
2.5 10-11
0 5 10 15 20
Multibunch Y emittance by LW (23April2004)
Y emittance (1.5E9 bunch intensity)Y emittance (4.6E9 bunch intensity)
Y e
mitt
ance
of e
ach
bunc
h [r
ad.m
]
bunch number
4.6x109 bunch intensity
1.5x109 bunch intensity
55
56
MB-BPM electronics
• Bunch by bunch, turn-by-turn acquisition8bit, 357MHz sampling, +/-250mV inputSum/diff circuit :
ATT for sum ch, ATT+19dB Amp. for diff. ch
three chassis : Fast S/H (RF) + S/H control (logic) + CAMAC interface
• Long memory128kB/ch --> 20bunch, 6.4k turnapplying FFT for each bunch,
then bunch oscillation and its phase can be observed
• Expected resolutioncentered beam : ~3µm at 1x1010 intensity (thermal noise resolution)1mm offset beam : ~16µm at 1x1010 intensity (bit resolution)
Fast kicker R&D (KEK,DESY,SLAC,LLNL)
Key technology for ILC damping ring
2005 - 2008Demonstration of very fast pulse kicker by using the electron beam in ATF damping ring.
R&D with several pulsers
2007〜Design of the beam extraction system by fast kicker
2009〜Trials of beam extraction
Rise time = 3.2ns(1%~100%)Fall time = 4.0ns(100%~1%)
ILC DR Injection/ extraction Kicker speed Limit of number of bunches
Bunch spacing in linac: ~300 nsCompressed in damping ring as short as possible
Circumference/bunch spacing = max. bunch number / pulse
Kicker field
Extract (inject) bunch by bunch using very fast kicker magnet.Kicker speed determine the bunch spacing
circumference/number of bunches
Bunch number may be limited by other effect: e.g. electron cloud instability in positron ring, fast ion instability in electron ring.
300 ns
extractionMain Linac
Damping Ring
Strip-line kicker
Auxiliary Septum Beam extraction trial
2008 DecemberInstalled in DR
2009 JanuaryFirst trial (2 weeks)
Postponed in June.Pulsers were broken when we fired for the beam extraction.System was removed from DR.
Fast Kicker hardware and Plan
Multi-bunch beam in ATF2
Multi-bunch in ATF2 by fast kicker30 bunches with 308 ns spacing60 bunches with 154 ns spacing
• Demonstrate the beam extraction• Check the reliability-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
-600 -400 -200 0 200 400 600 800
(Single bunch) x 3 Train Extraction
BP
M S
igna
l
Time (nsec)
154ns spacing
1↓1↓
2 >2 >
1) Ch1: 10 mV 50 ns 2) Ch1: 100 mV 50 ns Thy. Current 1 Amplitude Droop at 300ns
3 bunches, 154ns spacing
308ns pulse width
Present ATF kicker(Pulse magnet kicker system)
Bunch structure at ATF2 by Fast kicker
Cavity Compton ( R&D for Cavity Compton ( R&D for pol.epol.e++ ))All equipments are installed into the DR on 12th Sep. 2007.The first signal was detected on 30th Jan. 2008.All equipments are installed into the DR on 12th Sep. 2007.The first signal was detected on 30th Jan. 2008.
Cavity-Compton Setup (IP)
γ-ray detector (shared with LW)
62
EXT and FF Line beam diagnostics
Stripline BPMCavity BPMScreen monitorOTR monitorWire scannerLaser Interferometer
63
Tungsten (carbon) wire scanner
64
multibunch wire scannergamma detection system
65
66
OTR Monitor (SLAC)
( 76.6 µm , 9.5 µm )
beamtarget
microscope
67
ODR Monitor
ODR Target chamber
ODR Target Holder
Observation of visible light ODR
68
69
70
Cavity BPM
beam
cavitywave guide
Dipole mode RF field is induced by beam with offset.Field strength ~ proportional to offset.RF is extracted through slit and wave guide and detected.
TM 110 mode
Beam position monitors for ATF2, made by PAL (Korea)
photo by Toge
IP BPM test model
IP-BPM (KNU, KEK)R&D will be continued at ATF2. It should be re-installed.
Low Q IP-BPMKEK IP-BPM
Position sensitivity test performed, consistent with expectationBunch separation achieved in 154 ns interval
Beam test at ATF extraction line@0.7x10^10 e/bunch, dynamic range: 5 um
Achieved resolution8.72 +-0.28(stat) +-0.35(sys) nm
to 2nm Stabilization of Temperature, Stabilization of extracted beam
IP Beam Size Monitor (Tokyo, KEK)• Commissioning was started by Laser wire mode (horizontal scan).
• Searching the collision of laser and beam next slide
• Setup for Interference mode (vertical scan)• 2 and 8-degrees crossing will be done in this spring.• 30 and 174-degrees crossing will be done until next fall.
Scan range:
Crossing:
Beam size monitor for ATF2-IP(Tokyo Univ., KEK)
FFTB result
Result in FFTB at SLAC
Installation at ATF2-IP (2008/5)
by Terunuma
Experimental data of IP BSM
Not yet. . . . . . . . .
Post-IP Wire Scanner (SLAC)• FFTB carbon wire scanner was installed at post IP.
• Witting for a beam commissioning (next week)
• 10 micron Tungsten Wires (H, V and 45° scanning)• better signal for large initial beam sizes
• 5 micron Carbon Wires (V and +-1.3° scanning)
Oxford, Daresbury, QMUL, SLAC, KEK, DESY, CERN
Kicker BPM 1
Feedback
BPM processor
Driveamplifier
BPM 2
BPM 3
e-
History of latencyFONT1 (NLCTA) : 67nsFONT2 (NLCTA) : 54nsFONT3 (ATF) : 23ns
FONT : Fast feedback R&D
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
-600 -400 -200 0 200 400 600 800
(Single bunch) x 3 Train Extraction
BP
M S
igna
l
Time (nsec)
154ns spacing
3 bunches, 154ns spacing
FONT4, Digital feedback (ATF)
FONT (Re-installation) at ATF2Dedicated location at ATF2. • New beamline layout with three pickup BPMs (KEK) and
two Kickers (SLAC) are installed.• Commissioning will start in next week.
Pulsed Laser Wire R&D(RHUL, Oxford, KEK)
ILC design requirement:< 1 um laser wire scanner
2007/Jan
σ~8um2008/May
σ~3.8umRealize the 1 um beam size scanning in FY2008, by implementing improvements in the electron beam optics and improved laser diagnostics.
Pulsed Laser Wire at ATF2(Re-installation)
Dedicated location at ATF2.• Laser system is under moving to new hut.• Collision system in the beamline will be re-installed until
fall.
New location forLaser wire
Laser hut
ATF2 - LC Final Focus test
Goals of ATF2 project• Demonstration of the focusing method of ILC
– ~40 nm RMS vertical beam size– Will be confirmed using Shintake-monitor
• Demonstration of beam stabilization– ~2 nm vertical jitter– Feedback using nano-BPM (beam position monitor
with nano-meter resolution)
T.Tauchi, EPAC08
Hardware system at ATF2
86
ATF2 Construction Schedule
ATF2 Beam
Floor Refurbishment2007/8/20 2007/9/4
ATF2 construction
2007/9
2007/10
2007/12
ATF2 construction
2008/2 2008/9: new EXT
2008/5
International Contribution (1)ATF2 Q-magnet Setup
Concrete Base Stand (KEK)
FFTB mover (SLAC)
QBPM(Cavity BPM)(KEK,PAL)
Q magnet (KEK,SLAC,IHEP)
QBPM electronics(SLAC)
(2008/6)
International contribution (2)
High Availability PS (SLAC)
FF dipoles, quadrupoles (IHEP)Sextupoles (SLAC)
Infrastructures, Cables (KEK)
Magnet mover system andQBPM readout (SLAC)
International contribution (3)
Final Doublet systemMagnets and Movers(SLAC)Supports and Table (LAPP)
S-band BPM (KNU)
IP-BSM (Tokyo Univ.)
ATF2 beam line
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