RF‐Gun andHardware for emi2ance preserva7on
SuperKEKB review @ 04 Mar, 2014
Mitsuhiro Yoshida

SuperKEKB upgrade
for low emi2ance electron beam
High charge low emi2ance isrequired for SuperKEKB.

KEKB obtained(e+ / e-)SuperKEKB
required (e+ / e-)

Beam energy

3.5 GeV / 8.0 GeV

4.0 GeV / 7.0 GeV

Bunch chargee- e+ / e10  1.0 nC / 1.0 nC

e-  e+ / e10  4.0 nC / 5.0 nC

Beam emittance(γε)[1σ]2100 µm / 300 µm

6 µm / 20 µm

5 nC 10 mm‐mrad electron beam generated by RF gun.
+ 10mm‐mrad emi2ance preserva7on is required.
Quasi –travelling side couple RF‐Gun
with Yb laser system

B
J‐ARC

C

Preliminary test using DAW RF‐Gun
with Nd laser system
due to earthquake

A
10ps

30ps

1

2

3

4

5

RF‐Gun development strategy for SuperKEKB• Cavity : Strong electric ﬁeld focusing structure– Disk And Washer (DAW)=> 3‐2, A‐1(test)– Quasi Traveling Wave Side Couple => A‐1=> Reduce beam divergence and projected emi2ance dilu7on• Cathode : Long term stable cathode– Middle QE (QE=10‐4〜10‐3 @266nm)– Solid material (no thin ﬁlm) => Metal composite cathode=> Started from LaB6 (short life 7me)=> Ir5Ce has very long life >me and QE>10‐4 @266nm• Laser : Stable laser with temporal manipula7on– LD pumped laser medium => Nd / Yb doped– Temporal manipula7on => Yb doped=> Minimum energy spread• RF‐Gun– Design of RF‐Gun cavity• Quasi travelling wave side couple– Cathode– Laser– Test stand and schedule

RF‐Gun for 5 nC
20

• Space charge is dominant.
• Stable opera7on is required.
– Lower electric ﬁeld : < 100MV/m• Focusing ﬁeld must be required.

emittance(SC)̲x@5nC&90MV/m

16

Emittance (mm mrad)– Longer pulse length : 20 ‐ 30 ps

emittance(RF)̲x@5nC&90MV/m

18

emittance(total)̲x@5nC&90MV/m

14
12
10
8

Total

6
4

Space charge
RF

2
0
0

10

20

30

40

Tlaser (ps)– Solenoid focus causes the emi2ance growth.
– Electric ﬁeld focus preserve the emiMance.
Epxial coupled cavity : BNL
Annular coupled cavity : Disk and washer / Side couple

50

Pill‐box cavity

Annular coupled cavity with nose

Accelera7ng ﬁeld

Accelera7ng ﬁeld
加速電場

ビーム
Beam

Beam

=> Strong focus

Field

Ez, Er/r

Ez, Er/r=> Weak focus

Field
Focussing ﬁeldzAccelera7ng ﬁeld

Focussingﬁeld
Given forcez

Focussingﬁeld

Accelera7ng ﬁeld

Ez, Er/r

Ez, Er/r

Accelera7ng ﬁeldzAccelera7ng ﬁeld

Given forcez

Focussingﬁeld

6

Closed gap makes focus ﬁeld
Side coupled cavity is one candidate (or DAW / ACS / CDS …)

Concentrated ﬁeld
has focusing eﬀect

This structure has long drih space

This structure has focusing ﬁeld.
Long drih space is problem.
7

Design of a quasi traveling wave side couple RF gun
Normal side couple structure

Quasi traveling wave sidecouple structure

Quasi traveling wave side couple has stronger focusing andaccelerated gradient than DAW.

Quasi traveling wave side couple RF gun
This RF gun has total of seven acceleration cavities. These are divided into
two standing wave structure of 3 and 4 side coupled cavities respec7vely.
Cathode cell
To avoid beam defocusing, emi2ance
growth and ﬁeld concentra7on, a lot ofparameters were searched for design.

cathodeMaximum E‐ﬁeld at
surface: 120 MV/m

Maximum E‐ﬁeld at surface: 100 MV/m

Emi2ance: 5.5 mm‐mrad @ 5 nC
This RF gun can generate 10 nC beam

Beam tracking simula7on result
5 nC

10 nC

Emi2ance 5.5 mm‐mrad

Gun Exit
Size 0.4 mm

time=2.48098e-009

Energy [MeV]

11.7
11.6

Energy spread
0.6%

11.5

Bunch
shape

11.4
11.3

728
GPT

729

730

z

731

732

733

RF‐Gun comparison
Quasi traveling wave side couple RF gun(100 MV/m, 6mm‐mrad, 13.5 MeV)
DAW‐type RF gun(90 MV/m, 5 mm‐mrad, 3.2 MeV)
BNL‐type RF gun(120 MV/m, 11.0 mm‐mrad, 5.5 MeV)
BNL (3.8 mm)
DAW (1.7 mm)
QTW (0.2 mm)

Beam SizeCavity design
Field calcula7onRF

90 degcathodebeam

coupling cavi7es

accelera7ng
cavityNo reﬂec>on to klystronhybridMechanical design and manufacturing• RF‐Gun– Design of RF‐Gun cavity– Cathode• Advantage of LaB6
• Measurement equipment of quantum eﬃciency• Laser cleaning & Heat treatment– Laser– Test stand and schedule

Cathode : Advantage of LaB6 or Ir5Ce
Jus7n Jimenez, A Systema7c Cathode Study , Ph.D Thesis, Monterery, California

Low Workfunc7on (2.8 eV)and enough QE (10‐4)
at room temperature.
• Inac7ve in air• Recover by hea7ng or
laser cleaning•

Best choicefor SuperKEKB 5 nClong >me opera>onPhysica Scripta. Vol. T71, 39‐45, 1997.
Cathodes for Electron Guns
G. I. Kuznetsov

Condi>on
HV = 16kV
Vacuum ; 5.8×10‐6 Pa
Cleaning 7me ; 10 min

Quantum eﬃciency improvement
by Laser cleaning

QE

1500
1200

LaMz

900

LaB6
SEM‐EDX

Oxigen
OKsum

Counts1800

Carbon
LaMa

BKa

2100

CKsum OKa

2400

CKa

2700

10‐4

LaLa

Ir5Ce Cathode

600

0
0.01

1.51

2.01

2.51

3.01

3.51

4.01

4.51

keV

Ir5Ce
Carbon

8000

CKa

4000
3000
2000

0.50

1.00

1.50

IrMr

5000

IrMz

6000

CeMa
OKsum

FKa

7000

CeLa

10000

IrMa

SEM‐EDX

11000
9000

Ir5Ce@266nm

1.01

12000

LaB6@266nm
LaB6@532nm

0.51

CKsum OKa

×２０

300

Counts10‐5Lower energy density
is enough to ac7vate Ir5Ce

1000
0
0.00

10‐6
0

2.00

2.50

3.00

3.50

4.00

4.50

keV

1000
2000
3000
4000
Energy density of cleaning laser(μJ/mm2)

Non ac7va7on
QE = 5.00×10‐6

×20

Laser cleaning
Max QE = 1.00×10‐45000

No oxidiza7on is observed[SUPER‐KEKB e Linac]
Laser Power ; 233μJ/pulse（λ=266nm）
Target value ; 5nC

5.00

Life7me measurement（LaB6 / Ir5Ce）
10
QE‐4
IrCe
LaB6

10‐5
0

5

10

15

20

25

30

35

Life>me (hour)

Condi&on
Con>nuous pulse laser 200μJ@266nm)
Irrada>on => 2.5 nC emission

40

45

50

Enhancement of QE

Quantum Efficiency

×10-4
25

Laser system
Ir5Ce@213nm ・Nd:YAG laser 4th harmonics (266 nm)
Ir5Ce@266nm
・Nd:YAG laser 5th harmonics (213 nm)
Heater : Ta heater

QE = 2.70×10-3

20

Irradiation of shorter-wavelength laser

×15
15

QE = 9.10×10-4 (λ=213 nm, room temperature)

QE = 1.00×10-3

QE = 9.10×10-4
10

×6.5

×6

5

Heating
QE = 1.00×10-3 (λ=266 nm, 1004℃)

1
0

200

400

600

800

Cathode Temperature(℃)

1000

Irradiation of shorter-wavelength laser＋Heating
QE = 2.36×10-3 (λ=213 nm, 868℃)

Heat treatment( λ=266 nm, room temperature)Future prospects【 Current KEK A1 laser system 】
・W=10mJ/pulse @1030 nm, 20ps → 3nC/bunch・Total loss : 70 % ・transmission loss : ~50%
・loss from the miss alignment at cathode : ~60%
QE=1.54×10-4 @266nm, room temperature
To generate 5nC beams → W = 16mJ/pulse @1030nm,20ps
To generate 15nC beams → W=48 mJ/pulse @1030nm,20ps(for positron generation)
QE enhancement scheme leads to relax the laser power.

【Strategy for the new system of the QE enhancement】
CLBO+
Yb:YAG 5th harmonics
Pulse laser Heating①Irradiation of shorter-wavelength laser②Heating

The backside electron beam heating system

【 Scheme of Pre-Pulse laser Heating 】【1D thermal diffusion】

Pre-pulse (IR)→ Heating
UV laser→ photoemission

Cathode∂∂α P0 − 2σ 2
T ( z, t ) = κ 2 T ( z, t ) +
e
δ (z)
2
∂t
∂z
ρ CP π rt••

No need to develop theheater fabrications
Decrease the Dark current

Laser parameterλ1064 nmσ
2.5 nsr
4 mm
P0
45.963 MWW
288 mJ/pulse

1200
Surface Temperature (℃)

Merits(t −t0 )22

Temperature variation after irradiation
on Ir5Ce cathode
T(t)

1000
800
600
400

Shot the UV laser to generate
photoelectrons

200
0
0

Irradiation of pre-pulse

1020
t (ns)

30

40

The backside electron beam heating system【Design of New cathode plug】
A few kV

Choke structure【 Cathode jig 】

HeaterIr5Ce cathode

Further backside LD hea7ng system will be developed.

• RF‐Gun– Design of RF‐Gun cavity– Cathode– Yb Laser for spa>al & temporal manipula>on.
– Test stand and schedule

Energy spread reduc7on using temporal manipula7on
Energy spread of 0.1% is required for SuperKEKB synchrotron injec7on.

15nC

3

t
2.5

Gaussian2

σE/E (%)

5nC 10nC

20nC

1.5

1

t
5nC
10nC
15nC
20nC

Square

0.5

0
0

5

10 5nC electron
15
FWHM (ps)

20
15nC

25

30

Primary beam for positron produc7on

Nd‐doped

Proper7es of laser medium

Nd laser system for 3‐2 RF‐Gun

τ〜200μs, 40%○ 4-state laser is easy to operate.
○ High power pump LD is available.
○ Large crystal is available
× Pulse width is determined by SESAM.
(Gaussian)

LD PumpSHG(532nm) 40%
FHG(266nm) 20%
5HG(213nm) 3%

Nd:YVO4
Nd:YAG(808nm)808nm

1064nm

Yb‐doped○ Wide bandwidth => pulse shaping
τ〜900μs, 40%○ Long fluorescent time => High power
SHG(520nm) 40%○ Fiber laser oscillator => Stable
Yb‐glass
LD PumpFHG(260nm) 20%○ Small state difference
Yb:YAG(941/976nm)
5HG(208nm) 3%
× ASE
Yb:BOYS
941/976nm
1040nm
× Absorption

Ti‐doped Pump τ=200μs, 40%Pump(808nm)τ〜3μs, 40%
40%

Fluorescence

Nd:YAG
SHG
Ti:Sapphire
808nm
1064nm
800nm
532nm○ Very wide bandwidth○ High breakdown threshold
TW laser is based on Ti‐Sapphire× Low cross sec7on× Short ﬂuorescent 7me => Q‐switched laser is required for pumping

Absorption

Best for RF‐Gun

Material

Nd:YAG

Yb:YAG

Ti:Sapphire

Wavelength

1064nm1030nm

660-1100nm

Fluorescent time

230ms

960ms

3.2ms

Spectral width

0.67nm

9.5nm

440nm

Fourier minimum
Pulse width
Wavelength

2.48ps

165fs

2.59fs807.5nm

941nm

488nm

Spectral width

1.5nm

21nm

200nm

Quantum efficiency

76%

91%

55%

SHG(400nm) 40%
THG(266nm) 20%
FHG(200nm) 10%

Ti:Sapphire laser system for beam monitor.

Characteris7cs of Yb doped laser• Long ﬂuorescent life7me〜1ms• Wideband• High quantum eﬃciency
X Quasi‐three level=> Absorp7on at room temperature
X Small cross sec7on
S>mulated
Fluoresce
Fluorescenceemission
ThermalspectralYb
nce
conduc>vity
cross
width
Base material
life>me [W/mK]
sec>on[nm][ms][10‐20cm2]
YAG

2

0.95

11

9

Fourierminium[fs]

120

Experimental records
Pulse
Average
width
power
[fs]
[W]
340
0.11
136

0.003

730

16

810

60

71

0.12

112

0.2

176

1.1

KYW

3

0.7

3.3

24

50

KGW

3

0.7

3.3

25

47

glass

0.63

2

‐

35

33

36

0.065

GdCOB

0.35

2.7

2.1

44

27

89

0.04

BOYS

0.2

2.5

1.8

60

19

69

0.08

86

0.3

YVO4

‐

1.2

‐

‐

‐

61

0.054

CaCdAlO4

0.55

‐

6.9

‐

‐

47

0.038

Yb
laser
system(Present
status)Yb Fiber Laser
Yb Fiber
Oscillator

Yb Fiber
Ampliﬁer

Amplitude
modulator x 2

frep=52MHz
Fiber strecher& wavelength
selec7on

frep=52MHz→10MHz
Yb Fiber
Ampliﬁer x 2(20W + 70W pump)

Pulse picker

Yb Fiber
Ampliﬁer(70W pump)

frep=10 MHz→50 Hz

λ0→1030 ‐ 1040nm

Yb:YAG laser
Yb:YAG
Regenera7ve
Ampliﬁer

Yb:YAG
Mul7pass
Ampliﬁer ×3

frep=1MHz→50Hz E=1mJ
Pulse
Compression

Rota7ng Yb:YAG

A few 10 mJ @ 1035nm
Wavelength
conversion

A few mJ @ 25

Yb:YAG
Mul7pass
AmpliﬁerYb Fiber Oscillator
LD

WDM

Yb ﬁber oscillator:‐ 30 fs is possible using non‐linear
polariza7on rota7on.

←

Remaining problem:‐ Bunch structure at higher output power.
=> SESAM is not eﬀec7ve.
=> Replace some components.
‐ Synchroniza7on performance is changing.

Transmission
grating pair←

Improved items in FY2013:‐ Transmission gra7ng=> Stable modelock (higher eﬃciency)‐ Super‐invar breadboard=> Thermal stability.
‐ Piezo mirror on large lead block=> Reduce vibra7on.

Yb FiberYb Fiber Main Ampliﬁer

Yb Fiber Pre Ampliﬁer

From Yb Fiber Oscillator

LD

LD

Stretcher

Pulse
PickerEO

Stretcher
Yb Fiber Ampliﬁer

To Regenera7ve Ampliﬁer

Yb:YAG thin disk Laser
Yb:YAG disk
10 % doped
2mm thickness

Yb disk laser

350

30% eﬃciency was achievedat room temperature Yb:YAG

300

Eout (mJ)

250
200
150
100
50
0
0

200

400

600

800
Epump (mJ)

940nm LD (2.4 kW / module)

Regenera7ve ampliﬁer using Yb disk laser

1000

1200

1400

=> 4kW=> 10kW x 6

Large regenera7ve ampliﬁer for 2‐bunch
opera7on

100ns (2-bunch)+20ns (Pockels cell speed) = 36m=> round trip + polarization => resonator length > 9m : 2.25m×3 + 0.75m×4
Input

R=3m (f=1.5m)

λ/4

R=3m

φ9

R=1.5m

R=1.5m

φ 4.5

φ 4.5

λ/4

λ/4
f=200mm

Outputf=75mm2.25m

f=300mm

f=100mm

φ 1.5

Main Ampliﬁer

UV conversion (BBO SHG+FHG)=> 2 mJ maximum @ 260 nm
Typical charge distribu7on
Current situa7on:‐ Instability=>‐ No spa7al shaping‐ No compressor

Laser instability is caused by:‐ RF Synchroniza7on of oscillator.
=> FPGA & electric modulator.
‐ ASE of ﬁber ampliﬁer.
=> Mul7‐stage ﬁber ampliﬁer.
‐ Gain instability of regenera7ve ampliﬁer.
=> In‐vacuum regenera7ve ampliﬁer.
‐ Poin7ng ﬂuctua7on (Vibra7on ?)=> Higher output power and cut the edge.

R&D for be2er performance of Yb disk laser• 1035nm band is diﬃcult to use for ampliﬁer.
– Thermal lens
– Absorp7on– Low gain

Integrated sta7on
LD• We got good performance for1035nm Q‐switch laser.
Seed=> Cascade Yb laser is good candidate. (1050nm)••••

Very small thermal lens eﬀect.
Less absorp7on.
Higher excita7on density.
LD sta7on => Easy to maintain LD stacks.

1050nm940nm
Yb:YAG
1035nm

Yb:BOYS
Yb:CaF2

Yb:BOYS
Yb:CaF21050nm1050nmUV conversion efficiency improvement
Reference [1]Nd:YAG Laser [1]Pulse width : 3.5 ns
Max Energy : 400 mJ/pulse
single longitudinal mode
single transverse mode (top-hat)Reference [2]【 Conversion efficiency of fundamental wave 】
Nd:YAG Nd:YAG Nd:YAG Nd:YAG
1ω
2ω
4ω
5ω
BBO CLBO CLBO
250 mJ 90.3 mJ 50.2 mJ 36.0 mJ

Crystal
10 Hz
70.71 %
conversion
14.4
36.12 20.08
efficiency (%)
100 Hz
250 mJ 90.3 mJ 44.9 mJ 19.8 mJ
44.10 %
conversion
7.92
36.12 17.96
efficiency (%)

【 QE of Ir5Ce photocathode 】
QE = 1.54×10-4@266nm
QE = 9.10×10-4@213nm

×6【 The optimal combination 】

Photocathode: Ir5Ce compound
Laser : 5th harmonics (CLBO)[1] K.Deki , et al., “CsLiB6O10 (CLBO)を用いた193nm光源の開発”, 光技術情報誌「ライトエッジ」No.18[2] Yap YK, et al., "High-power fourth- and fifth-harmonic generation of a Nd:YAG laser
by means of a CsLiB(6)O(10).", Opt Lett. 1996 Sep 1;21(17):1348-50.

• RF‐Gun– Design of RF‐Gun cavity– Cathode– Laser– Test stand and schedule• 3‐2 RF‐Gun for preliminary test & PF injec>on• A‐1 RF‐Gun

A‐1 RF gun‐ Quasi‐travelling wave side couple RF‐Gun‐ Yb based laser system

Installed RF‐Gun

Chicane for bunch compression
30ps => 10ps

Exis7ng DC‐Gun & pre‐buncher

Installed RF gun
Cathode
90 de

g Hyb

rid

Laser port

A‐1 RF gun results
5.6 nC was achieved.
However beam proﬁle is not good.

3 nC beam delivery was achieved.

37

Emi2ance measurement
Q scanVer7calHorizontal

Using 30 um screen at 25 MeV

Normalized emi2ance
X: 24.1 ±7.2 mm‐mrad Y: 11.1 ±1.8 mm‐mrad(Large horizontal emi2ance is due to laser incident angle.)

Emi2ance measurement
Wire scanner at B sector

Normalized emi2ance
X: 95.0 ±27.4 mm‐mrad Y: 42.0 ±31.1 mm‐mrad(including the beam posi7on ji2er.)

Summary of RF‐Gun• RF‐Gun cavity– Quasi travelling wave side couple structure is underopera7on.

• Cathode– Room temperature Ir5Ce cathode has enough QE.
– Laser cleaning & laser injec7on angle is eﬀec7ve.
– R&D for the QE improvement.

• Laser & control– Yb based laser system : A‐1 RF‐Gun• Yb‐ﬁber :Precise RF synchroniza7on.
• Yb‐disk ampliﬁer:
High power output.
• Temporal manipula7on
Under experiment.

– Stability / Control:

Improved but not enough.

Hardware development
for emi2ance preserva7on

Hardware for emi2ance preserva7on• Alignment– Ini7al alignment using laser tracker(will be presented by Kamitani)– Con7nuous monitor (HLS, Wire) + Ac7ve mover– Beam based alignment• Temporal manipula7on– Laser pulse shaping– Bunch compression– Addi7onal hardware to compensate longitudinal
wakeﬁeld• Beam diagnos7cs for oﬀset injec7on– RF DeﬂectorRequirement for alignment• 0.3 mm is not enough with oﬀset injec7on.
• 0.1 mm in sector• 0.3 mm in global• Alignment• Ini7al alignment using laser tracker.
• Con7nuous monitor (HLS + Wire) => Ac7ve mover.
• Beam based alignment• Orbit measurement without accelera7on and magnet• Low charge (only dispersion) & high charge (wake)measurement• Higher order wakeﬁeld monitor

Hard ware alignment status• Girder alignment– Done with laser PD, we assume σ<0.3mm• Accelerator structures– Aligned on the girder reference points– Mostly and can be σ<0.1mm• Q magnets– Set on a bridge aligned w.r.t. adjacent girder ends
– Reflector bases are being mounted on old magnets.
– New magnets are equipped with them.
– Alignment can be checked by laser tracker .
– Evaluation should also be done by beam.
– Independent girders for magnets should be developed if needed.
2013/11/11

T. Higo SuperKEKB WS

44

Present situa>on on short‐distance (local) alignment
Hard ware alignment on a 10m girder

6

)&!*

2334
"#%

B

B2-H
0.136

GH

G&

"

G%

GF

G(

CDE%
!"#&

CDEF

!"#$

CDE&

CDE(

!"#%

"

&"""

%"""

$"""

'"""

+,-./0123456

B

(""""

B

)%!*

>??@
"#%

B4-H
G&

GF

GH

G%

"

!"#&

CDE&

CDE(
!"#%

!"#$

CDEF

CDE%
C

"

&"""

%"""

$"""

789:;<=

DEF$

DEF%

DEF'

"#%

DEF&

"

G$

G%

G&

'"""

GH

G'

!"#%

"

$"""

'"""

("""

)"""

89:;<=>
*'!+

?@@A

%""""
?@@A

B4-V

"#&

"#&

G(

"#$

!"#$

C

2334

+,-./01

A

*$!+

0.228

0.266
,-./01234567

"#&

B2-V

?@@A
"#&

,-./01234567

789:;<=>?@AB

5

"#$

"#%

G%

!"#$

DEF$

DEF%

!"#%

"

(""""
>??@

$"""

G'

G&

G$

"

DEF&

'"""

GH

DEF'

("""

89:;<=>

)"""

%""""
?@@A

Reference bars (blue) are set typically within 0.1mm.
Ver < 0.2mm
Hor. up to 0.5mm slope

Systematic error may exists in H by 0.5mm, while
V stays 0.2mm from reference bar.
T. HigoK. Kakihara, 22 Nov. 2012

KEKB Review 5 March 201345

Laser straight over 500m as a reference

Laser systemwith tilt
feedback

500m
vacuumpipe

Spot size
4σx~21mm
4σy~18mm

Can be used as a straight line.
The line connecting points at the ARC exit and BT entry
is kept with FB.
2013/11/11

T. Higo SuperKEKB WS

46

Laser PD meas. 9/10〜9/16 Vertical
0.1mm

Ver. ~0.65㎜/V

Junc7on‐ 0.1mm#2=A1D2013/11/11

Sensor posi7on
横軸：センサー位置
T. Higo SuperKEKB WS#2=PD‐R001D
47

Accelerator structure alignment
on a girder, measured w.r.t. PD arms
Examples showing the present
status: Sta7s7cs of three units(C1, C2, C3)
Horizontal
Average = 2 microns
Stand. Dev. = 16 microns

Easy adjustment by shimming
Ver>cal
Average = 5 microns
Stand. Dev. = 51 microns

A li2le tedious but can be
adjusted by screw bolts
2013/11/11

T. Higo SuperKEKB WS

48

Hydro leveling system (HLS) for con7nuous monitor

HLS

HLS

C‐2 girder

C‐3 girder
Expansion Joint

HLS

C‐4 girder

HLS

C‐5 girder

Long term measurement of girder height
400

Height diﬀerence from average height
300

C‐5
200

100

C‐5

11/17 => reference (zero)

C‐4

Height [ μm ]00.7 mm

‐100

‐200

‐300

Daily varia7on
C‐3

‐400

‐500
11/17

11/27

12/7

12/17

12/27

1/6

=> Con7nuous monitor & Ac>ve movers are required !!

Ac7ve mover• Eccentric Cam Movers
5mm stroke, 125nm resolu7on

Speciﬁca>on
StrokeX ‐ axis
Y ‐ axis
Z ‐ rota7on± 2.5 mm
± 2.5 mm
± 0.42°

Resolu7on
X ‐ axis
Y ‐ axis
Z ‐ rota7on~ 125 nm
~ 125 nm~ 9.5 x 10‐7 °Geometry (X Y Z)

320 x 800 x 189 mm

Withstand load

12000 N

Weight170 kg

500 kg withstand load testAc7ve mover installa7on plan for girderPreliminary test for higher order transverse wakeﬁeld monitor
Accelera7ng structure

BPM

TM12 : 8.728 GHz
Dipole mode
DBM
Synchronized RF
８〜12 GHz(Base RF: 10.38 MHz)IQ

90 degHybridMagic T

Bunch compression
for 5nC electron & primary electron for positron produc7on
5nC electron

Streakcamerain Laser system

StreakcameraB
J‐ARC

RF‐Gun (5nC〜10nC)
with pulse shaping using Yb laser system.

A
10ps

30ps

1

2

4ps

C

3

4

5

StreakCamera(will be installed)

StreakcameraPrimary electron for positron produc7on

B
J‐ARC

RF‐Gun (10〜20nC)

A
30ps

RF‐Gun (5nC〜10nC)

30ps

30ps

C

1

2

3

4

5

X‐band RF Deﬂector for
Bunch Sliced Transverse Emi2ance Monitor
RF‐Deﬂector (TM110 Cavity Chain)z eVdeflectorωRF Δt  πΔxscreen = β deflector β screen sinφ=  deflector →screen

Ebeam
2

 

y

σ x = β screenε screenxΔxscreen / σ x =β deflector  eVdeflectorωRF Δt 
ε screen 
Ebeam


t

σ y (t ) = β yε y (t )Vdeflector = 10MV , f RF = 2.856GHz, Δt = 10 ps, β deflector = 10m→ Δxscreen / σ x = 3
Vdeflector = 15MV , f RF = 11.424GHz, Δt = 10 ps, β deflector = 10m→ Δxscreen / σ x = 18

Installa7on to the monitor beam line at 3rd switch yard (end of LINAC)=> feedback to the ini7al oﬀset to compensate the transverse wakeﬁeld.

X‐band RF‐Deﬂector (U.S. / SLAC)‐1 m structure same as the RF‐deﬂector for LCLS

Input Power : 10MW
Deﬂec7ng Voltage : 15 MV

X‐band Klystron (KEK)‐ Based on exis7ng
9GHz, 4 MW klystron‐ 250 kV, ηP=0.7‐ 10 MW output‐ 2 window

1.5 m RF ‐ Deﬂector
1 m RF‐deﬂector
Window
10 MW
KlystronSummary of hardware for emi2ance preserva7on• Alignment– Ini7al alignment using laser tracker– Con7nuous monitor (HLS, Wire) => Ac7ve mover– Beam based alignment• Temporal manipula7on– Laser pulse shaping– Bunch compression– Addi7onal hardware to compensate longitudinal wakeﬁeld• Beam diagnos7cs for oﬀset injec7on– RF Deﬂector– One shot emi2ance monitor

BackupYb‐ﬁber & Yb solid state laser development
Yb Fiber Main-Amplifier
70W

LD
Pump

λ/4 λ/2

Yb Fiber Pre-Amplifier

Solid-state Amplifier Yb:KGW

2.5µJ


100Hz

LD
200W

10W

Pump Laser

3mJ

Frequency doubling LBO
517nm

BBO

Yb Fiber Oscillator
LD

~30ps
0.5mJ
Spectral Range
Adjustment

1035nmWDM

Prism Pair

Intensity [a.u.]

Spectrum of Seed (52MHz)

980

990

1000

1010

1020 1030 1040
Wavelength [nm]

1050

1060

1070

1080

Oscillator & pre‐ampliﬁer are already working.

259nm

Regenera7ve Ampliﬁer

DAW (Disk and Washer) type RF‐Gun
Electric ﬁeld focus

Large coupling

Strong focussing ﬁeld
Curved surface cathodefor low emi2ance.

CathodeLow electric ﬁeld

Emi2ance
6 mm‐mrad（5 nC）

Beam size (σ)
1.2 mmBunch length (σ)
8 psecFabrica7on of DAW RF‐Gun

Adjust with spacer
on cathode rod

Reﬂec7on ra7o

G = 0.119

Coupling

β = 1.27

Q factor

Q0 = 6007.3

Loaded Q

QL = 2646.4

3‐2 RF‐Gun

3‐2 Laser hut

3‐2 RF‐Gun (2011/10)

・52MHz Oscillator
・DPSS Module
・AO + EO x 2 pulse picker

Cathode LaB6 => Ir5Ce （2012/03)
LaB6

Ir5Ce

Laser injec7on with angle （2012/05)

Nd based laser system• Nd:YVO4 oscillator + Nd:YAG mul7‐pass ampliﬁer

30 ps (10 mm)

5nC was achieved !

• 4 mJ @ 266nm => 1.5 mJ on cathodeQ‐scan=> 14.1 mm‐mradfor 1nC(Preliminary)

計測結果
300

C‐2下流側水面高さを基準とした、他水管傾斜計水面高さの変動
200

100

C‐5

11/17 日の状態を初期値ゼロとした

C‐4

水面高低差 [ μm ]

0

‐100

‐200

‐300

水面低下は、水管傾計の高さが上がったことを意味する

‐400

C‐3
‐500

‐600
11/17

11/27

12/7

12/17

12/27

1/6

Beam diagnos7c sta7on
ScreenDeﬂetorPF pulse bend