KEKB Review 2014	

Positron Source Upgrade	
KEKB injector linac
Takuya Kamitani	2SuperKEKB Injector	
SuperKEKB injector	
1.1 GeV
Damping Ringcirc. 136 m	

low emittanceRF gun	

3.5 GeV
10nC x 2 (prim. e-)
5nC x 2 (inj. e-)	BunchCompressor	

S-bandlinac	

Energy-spread
Compression System	
3TRF gun	

50 Hz (e+ or e-)pulse-by-pulse
mode switching 	

PF	AR (later)
6.5 GeV e-

2.5 GeV e0.1nC x 1	LER, AR	

4.0 GeV e+
4nC x 2	ECS	e+ target &LAS capture section	

7.0 GeV e5nC x 2	HER	DR	LAS : Large Aperture S-band structure	

1-3	

1-5	 1-6	 1-7	 1-8	 2-1	 2-2	 2-3	 2-4	 2-6	 2-7	 2-8	target	 solenoid	
LAS modules	

FODO singlet system	

Q triplet 3m	

3-2	

Q triplet 5m	

S-band modules	

en#re	  re-­‐arrangement	  of	  beam-­‐line	  components	  in	  this	  region 	  	  (in	  progress)	
KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

SuperKEKB positron source	

3	

primary
e- beam	
positronproduction
Target	BridgeCoils	

FluxConcentrator	
e+ beam	
KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani)

4	target offset & beam hole	side	  view	
primary e-	bridge coils	

DC QM	

spoiler	
target	rear	  view	solenoid	

Accel.
structure	

targetdiameter
4.0 mmtargetoffset
3.5 mm	

e+	
beam
hole	

injection e-	
Flux
Concentrator	

pulse ST	

2.0 mmFC offset

holediameter
2.0 mm
7.0 mm
FC aperture

pulse QM	l injection e- beam : on axis to preserve low emittancel primary e- beam : 2.7 mm off axis
(target offset 3.5 mm, FC offset 2.0mm)
KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

5	e+ yield degradation by target offset	
n e+ yield degrades ~50 %by offset e+ generationn it can be improved to 78 % byu utilizing transverse kick byproper orientation of FC slitu e- incident position optimization
FC field map (Bx)	
0.010

Bx	

0.005

Bx [T]

0.000-0.005-0.010target	  center	  posiBon	FC2 data Bx
CST BxBx-­‐max	  =	  	  0.15	  T	  @	  12	  kA	

-0.015-0.020-200204060

80

10 0

Longitudinal Position [mm]data	  by	  Zang	  Lei	KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

6	

beam spoiler	
3m	  distance	

n beam spoiler to enlarge beam

spot on target to be σx ,σy> 0.7 mm
to avoid target destructionn spot size monitoring screen Al2O3(0.14 mm thick)+ scattering Al foil (0.25 mm thick)[total material thickness = 0.05 X0]screen	  &	  scaDerer	

target	e+	

primary	  e-­‐	
injecBon	  	   hole	e-­‐	  beam	

KEKB Review (2014.03.04)

hole	spot	  size	  camera	

Positron Source Upgrade (Takuya Kamitani) 	

FC Test-stand at KLY gallery	7	test	  operaBon	  of	  FC	  assembly	  started	  2013/12/17	  at	  test-­‐stand	  before	  installaBon	  into	  beam-­‐line	

parallel	  plate	  power	  line	

Flux
Concentrator
assembly	snubber	circuit	
coaxial	cables	
KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

FC test stand fire accident	

8	n fire accident during operation test on

2013/12/21, 22n power cable burned at the connection
to snubber circuitn improved cable connection and new
snubber circuit under fabricationn restart test operation in April 2014
beam line installation in May 2014
improved	  connecBon	  	  design	

KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

Positron Capture Section	
SLED	SLED	KLY	  1-­‐5	9	KLY	  1-­‐6	target+FC

LAS : Large Aperture
S-band structure	LAS 10 MV/m
acceleration	

LAS 14 MV/m
deceleration & phase slip
& acceleration	
Large Aperture
S-band structure(LAS)

Solenoidsn LAS with SLEDs for sufficient field gradientn breakdown issue of LAS in solenoid fieldn needs careful RF conditioning	

KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

161412108642010-3

Eacc[M V /m ]R FW idth

2000
1500
1000
5000RF WIDTH (ns)Eacc[MV/m]

unit 1-5 RF conditioning history	

CC_̲15_̲LA

Pa

10-4
10-510-6Solenoid
Current[Amps]

10-70800
600
400
20000100 200 300 400 500 600 700 800
Hours

1-­‐5	  unit	  	  RF	  condiBoning	  	  	100 200 300 400 500 600 700 800
hours

in	  solenoid	  ﬁeld	

16141210864202000
Eacc[M V /m ]R F	 W idth	 [ns]

1500
1000
500010-3

RF Width [ns]Eacc [MV/m]

unit 1-6 RF conditioning history	

CC_16_LA

Pa10-410-510-610-7

Solenoid
Current[Amps]

0800
600
400
2000100

200300400 500
hours

600

700

800

1-­‐6	  unit	  	  RF	  condiBoning	  	  	0100 200 300 400 500 600 700 800
hours

in	  solenoid	  ﬁeld	

16141210864
20Eacc[M V /m ]2000

R F	 W idth	 [ns]

1500
1000
SLED ON500
010-3

CC_17_LAPa

10-410-5outgassing	  issue	  at	  low	  ﬁeld	  level	  by	  mulBpactoring	  in	  	  input	  coupler	  cavity	

1-­‐7	  unit	  	  10-6-710

RF Width [ns]Eacc [MV/m]

unit 1-7 RF conditioning history	

0100 200 300 400 500 600 700 800hours

RF	  condiBoning	  	  	in	  FODO	  quads	

construction photo (1)	13n LAS structures and solenoids arecarefully installed in the positron
capture section units 1-5, 1-6.	

KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani)construction photo (2)	14	

densely	  placed	  quads	  for	  focusing	  	  large-­‐emiDance	  positrons	  KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

construction photo (3)	15	FC	  &	  target	  to	  be	  installed	  	  here	

quads	  around	  the	  acc.	  structures	  for	  short	  interval	  	quads	  and	  steerings	  	  interleaved	
KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

e+ beam optics after DR	n in sector 3, 4, 5 after DR,Outlet	  of	  DR	pulse quads & steerings will be
used for e-, e+ mode dependent
flexible optics designn triplet/doublet/FODO designs arecompared for magnet spec.
determinatione+	16	

opBcs	  calculaBon	  by	  	  T.	  Miura,	  H.	  Sugimoto	
90deg.	

Triplet	90deg.	

Doublet	u FODO: bestu doublet: betteru triplet: NG90deg.	

n from emittance growth issue,FODO	

triplet/doublet are preferredbecause of smaller beta-function(see next slide!)n finally doublet is chosen

KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

e+ emittance growth	Ver#cal	

Horizontal	

zoom	

calculaBon	  	  by	  H.	  Sugimoto	

17	n emittance growth for FODO issignificantly largern average beta-functions areβx,y ~16 m for doublet/triplet
βx,y ~36 m for FODO
(see previous slide!)n small beta-function is essential
to suppress emittance growth	
KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

e+/e- compatible optics	

18	SAD	  calculaBon	  by	  T.	  Miura	  Sector-C	

e+/e-­‐	  compa#ble	  op#cs	  with	  DC	  quads	

pulse	  quads	  for	  mode	  dependent	  	  op#cal	  seAng	

Sector-1	

Sector-3	

Sector-2	

Sector-4	

Sector-5	

target	l in	  e+/e-­‐	  compa#ble	  op#cs	  in	  Sector-­‐1,	  2,	  e-­‐	  have	  βx,y	  ~	  36	  m	  or	  larger	  l e-­‐	  emiOance	  growth	  in	  this	  region	  should	  be	  worried	  l design	  considera#on	  started	  for	  addi#onal	  pulse	  quads	  	  KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani) 	

schedule	

KEKB Review (2014.03.04)

19	

Positron Source Upgrade (Takuya Kamitani) 	

Summary	20	1) e+ beam-line construction started last summer andto be almost completed in April 20142) target & spoiler to be installed in May 2014
3) FC power cable system reconstruction in progress
after the fire accident
test operation at KLY gallery in Apr/May 2014installation in tunnel in May 2014
4) LAS structures (in capture section units and one FODO unit)
in RF conditioning5) pulse quads and steering in preparation for Sector-3, 4, 5
in doublets system for emittance growth suppression(installation ~ 2015 summer ? depending on budget situation)6) additional pulse quads considered in Sector-1, 27) we will start e+ commissioning in June 2014
(with constraint of half FC current and half DC solenoid current)

KEKB Review (2014.03.04)

Positron Source Upgrade (Takuya Kamitani)