1	KEKB Review 2013	

Positron Source Upgrade	(FC	
  modulator	
  development	
  is	
  covered	
  by	
  M.	
  Akemoto's	
  talk	  )	

KEKB injector linac
Takuya Kamitani	
Positron Source Upgrade (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-)	Bunch
Compressor	

S-bandlinac	

Energy-spread
Compression System	
3T
RF 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	

positron target relocation from 2-1 to 1-5
for energy margin in DR injection	

1-3	
 1-4	
 1-5	
 1-6	
 1-7	
 1-8	
 2-1	
 2-2	
 2-3	
 2-4	
 2-6	
 2-7	
 2-8	
FODO singlet system	

target	 solenoid	Q triplet 3m	

normal S-band	

LAS
Large Aperture S-band
accelerating structure	Positron Source Upgrade (Takuya Kamitani)	

Q triplet 5m	

3-2	

Positron Capture Section (PCS)	

3

KEKB e+ capture section	
l QWT system (2.0 T x45mm+ 0.4 T x8m)
air-core pulse coil
DC solenoidsl KLY1 (S-band) -> 2 x 1m 12 MV/m, aper 2a = 27 -> 25 mml KLY2 (S-band) -> 2 x 2m 10 MV/m, aper 2a = 25 -> 21 mml beam energy at capture section exit : 80 MeV
N(e+)/N(e-) = 10 % at 3.5 GeV linac-end
N(e+)/N(e-)/E(e-) = 2.5 %/GeV

SuperKEKB e+ capture section	
l AMD system (5.0 T x200mm+ 0.4 T x15m)
Deceleration capture	
flux concentrator
DC solenoidsl KLY1 LAS -> 2 x 2m 14 MV/m, aper 2a = 32 -> 30 mml KLY2 LAS -> 4 x 2m 10 MV/m, aper 2a = 32 -> 30 mm We omit L-band components
and redesign PCS with alll beam energy at capture section exit : 120 MeV
LAS configuration which canN(e+)/N(e-) = 49 % at 1.1 GeV DR give sufficient e+ yield and
LAS	
  :	
  Large	
  Aperture	  	
  satellite elimination.
N(e+)/N(e-)/E(e-) = 14 %/GeV
	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  S-­‐band	
  structure	Positron Source Upgrade (Takuya Kamitani)	

e+ source issues discussed here	1) target & beam-spoiler designfor protection against target destruction2) Flux Concentrator system development(magnet, modulator, detachable girder)
3) Capture parameter optimization one+ yield and satellite particle elimination4) e+/e- compatible optics design anddirect e+ injection without DR

Positron Source Upgrade (Takuya Kamitani)	

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(1) Positron
Production Target &Beam-Spoiler	

Positron Source Upgrade (Takuya Kamitani)	

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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 mmpulse QM	l injection e- beam on axis to preserve low emittancel primary e- beam 2~3 mm off axis
(target offset 3.5 mm, FC offset 2.0mm)
e+ yield degradation by this offset
should be evaluated with full 3D tracking simulation
Positron Source Upgrade (Takuya Kamitani)	

7.0 mm
FC aperturetarget shape & thermal analysis	
n target design is ongoing

KEKB	
  e+	
  target	

consideringcooling efficiency analysis andfield reduction by eddy currentn target size should fit in theavailable space
between a yoke and FC

ANSYS	
  calcula7on	
  by	
  L.	
  Zang	  Positron Source Upgrade (Takuya Kamitani)	

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target destruction issue 	
FLUKA	  &	
  yield	
  calcula7on	
  by	
  L.	
  Zang	  We should enlarge design spot size 0.5 mm -> 0.7 mm for safety margin
at a cost of 10 % yield degradation	
Positron Source Upgrade (Takuya Kamitani)	

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target protection	
target	spoiler	primary	  e-­‐	

e+	
hole	

hole	
thickness	
  t	

injec7on	
  e-­‐	

distance	  D	

n beam spoiler to maintain spot size σx ,σy> 0.7 mm on targetn avoid too small beam spot on spoiler & on target,

need monitoring spot sizes and focusing magnet settingsn D & t should be optimized considering beam line layoutn at a distance D = 3.0 (m), thickness t = 0.5 (mm) for Al plate

Positron Source Upgrade (Takuya Kamitani)	

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10	

(2) Flux Concentrator
system development

Positron Source Upgrade (Takuya Kamitani)	

SLAC-type Flux Concentrator	
n First prototype is fabricatedwith helps of drawings fromSLAC and IHEPn it is for stand-alone test with asimplified vacuum chambern started a test operation andfield measurement with aprototype modulatorn conductor is made of HRSC
copperprototype-­‐1	
SLAC-­‐type	
  FC	

parameters	  	

length	

100	
  mm	

outer	  diameter	

100	
  mm	

inner	  diameter	
  (min.)	

7	
  mm	

inner	  diameter	
  (max.)	

52	
  mm	

peak	
  current	

12	
  kA	

pulse	
  width	5	  µs	
  (half-­‐sine)	

peak	
  ﬁeld	3.9	
  T	

inductance	

1.0	
  µH	

Positron Source Upgrade (Takuya Kamitani)	

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FC material choice	n candidate material OFC & HRSC
Heat Resistance, high Strength & Conductivity copper(Mitsubishi Material co.)n vibration measurement gives

similar resultn avoid hardening of copper bymanual pressingn difference in impedances(80 % conductivity in HRSC)n decision will be made with resultsof operation tests ofprototype-1 (HRSC)
prototype-2 (OFC) under fabrication

Positron Source Upgrade (Takuya Kamitani)	

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FC slit machining at KEK	n Slit machining was performedat KEK machine workshop
with an electrical discharge
wire cutting machine.
n 0.15 mm thick wiren 0.2 ~ 0.25 mm slit gap
n special wire path shape witha sapphire pulley devised for
FC fabrication

Machining	
  by	
  T.	
  Takatomi	
  &	
  N.	
  Okada	Positron Source Upgrade (Takuya Kamitani)	

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FC test stand	n started operation on 2013/2/26
n low current operation (1.36 kA)

in the air for field measurementn high current operation (~6 kA)
in a vacuum will start soon	Positron Source Upgrade (Takuya Kamitani)	

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FC modulator (prototype)	
n modulator with thyratronn [1] prototype modulator

Ipeak = 6 kA for FC tests andfor initial commissioning(2013 Dec. -> 2014 Jun.)n [2] operation model modulator
Ipeak = 12 kA for FC tests andfor commissioning(2014 Oct. -> )n half-sine 5 µsec pulsen stability 0.3% p-p	
Details	
  on	
  the	  modulator	
  is	
  covered	
  by	
  M.	
  Akemoto's	
  talk	Positron Source Upgrade (Takuya Kamitani)	

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quick detachable girder	
n FC girder is designed to bequick detachable tominimize worker's radiationdose in FC exchange work.
n wave guide disconnection
in distant position from FCn quick coupling vacuum
flangen quick couplingwater, electricity connection	

Solton	  Co.	
  Staubli	  Co.	
Positron Source Upgrade (Takuya Kamitani)	

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17	

(3) Capture parameter
optimization one+ yield andsatellite elimination

Positron Source Upgrade (Takuya Kamitani)	

Capture Section with LAS	KLY	
  1-­‐5	
target+FC

KLY	
  1-­‐6	

SLED	

SLED	
Solenoids

LAS 10 MV/m
acceleration	

LAS 14 MV/m
deceleration & phase slip	
Large Aperture
S-band structure(LAS)n LAS with SLEDs for sufficient field gradientn breakdown issue of LAS in solenoid fieldn non sharp-peaked RF pulse shape	

Positron Source Upgrade (Takuya Kamitani)	

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why no L-band in PCS ?	
n L-band first introduced for larger acceptancen Later, L-band found useful for satellite particle eliminationn However, L-band components are costly	n Recent simulation study shows capture section of all LAS

can give sufficient satellite particle elimination as L-bandn e+ capture with high-field deceleration is effective in thiselimination
	Positron Source Upgrade (Takuya Kamitani)	

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high-field decel. eliminate satellites	

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satellite	
  fracUon	
  with	  Acc	  mode	
  
is	
  10	
  Umes	  larger	  &	
  over-­‐scaled	
  !!	

ﬁeld	
  >=	
  14	
  MV/m	  preferable	
Positron Source Upgrade (Takuya Kamitani)	

e+ capture simulation	

21l capture	
  tracking	
  simula7on	
  with	
  
GPT	
  by	
  F.	
  Miyahara	
  &	
  L.	
  Zang	  l beam	
  line	  op7cs	
  design	
  with	
  
SAD	
  by	
  T.	
  Miura	  l beam	
  line	  tracking	
  simula7on	  with	
  SAD	  by	  N.	
  Iida	n capture parametersoptimized with thesimulationsSee	
  external	
  movie	
  ﬁle,	
  capture-­‐anim1.avi	
  !!	
n deceleration capture
with RF phase-slip
gives less satellite
particles
Anima7on	
  by	
  F.	
  Miyahara	
  Positron Source Upgrade (Takuya Kamitani)	

satellite formation	

See	
  external	
  movie	
  ﬁle,	
  capture-­‐anim2.avi	
  !!	

Anima7on	
  by	
  F.	
  Miyahara	
  n in deceleration capture, satellites are mainly generated

by low-energy particles at accel. structure gapn high-field deceleration can avoid this trap
Positron Source Upgrade (Takuya Kamitani)	

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23	

(4) e+/e- compatible
beam optics design &direct e+ injection
without DR	

Positron Source Upgrade (Takuya Kamitani)	

before	  DR	

e+ beam line (1-6→2-8) & optics	

24	

SAD	
  calcula7on	
  by	
  T.	
  Miura	
  quads	  are	
  densely	
  placed	
  in	
  FODO	  to	
  accept	
  large	
  emiYance	
  e+	

to
DR	

emiYance	
  halo	  collimators	
  x3	

PCS	

1-7(LAS)	
 1-8(S)	
matching	  secUon	

FODO	

2-1	
 2-2	

2-3	

2-4	

2-6	
triplets	

Positron Source Upgrade (Takuya Kamitani)	

2-7	

2-8	

a[er	  DR	e+ beam line (3-1→5-8) & optics	

25	

SAD	
  calcula7on	
  by	
  T.	
  Miura	  l to	
  switch	
  opUcs	
  ﬂexibly	
  for	
  e+/e-­‐/PF/AR,	
  pulse	
  quads	
  are	  preferable	  l triplets	
  are	
  replaced	
  by	
  FODO	
  and	
  beam	  pipe	  aperture	
  is	
  reduced	
  to	
  half	  to	
  relax	
  pulse	
  quad	  speciﬁcaUon	
  and	
  cost	
beam
from
DR	

Sector-3	

Sector-4	

Sector-5	

quads	  are	
  sparsely	
  placed	
  for	
  small	
  emiYance	
  e+	
  from	  DR	
Positron Source Upgrade (Takuya Kamitani)	

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e- beam optics	

SAD	
  calcula7on	
  by	
  T.	
  Miura	
  Sector-C	

e+/e-­‐	  compaUble	
  opUcs	
  
with	
  DC	
  quads	

pulse	
  quads	
  for	  mode	  dependent	  	
  opUcal	  se`ng	Sector-1	

Sector-3	

Sector-2	

Sector-4	

Sector-5	l e+/e-­‐	  compaUble	
  (compromised)	
  opUcs	
  in	
  Sector-­‐1,	
  2	
  of	
  DC	
  quads	
  area	
  
	
  	
  	
  (e+	  oriented	
  opUcs	
  with	  adjustment	
  for	  e-­‐	
  matching)	
  l e-­‐	  oriented	
  opUcs	
  se`ng	
  in	
  Sector-­‐3,4,5	
  by	
  pulse	
  quads	
  l small	  acceptance	
  in	
  Sector-­‐3,4,5	
  is	
  suﬃcient	
  for	
  small	
  emiYance	  e-­‐	
Positron Source Upgrade (Takuya Kamitani)	

direct e+ injection w/o DR	
n in early design stage, LER injection w/o DR is not expectedn in sector-3, 4, 5, acceptance becomes smaller

by introducing pulse quads,v [1] triplet->FODOv [2] smaller aperturen this acceptance is sufficient for small emittance e+/e-,
but not for large emittance e+n very low e+ transmission in sector-3, 4, 5	

Positron Source Upgrade (Takuya Kamitani)	

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28	

beam loss of large emittance e+	
SAD	
  tracking	
  by	
  N.	
  Iida	  No	
  CollimaUon	
  Case	  gradual	
  beam	  loss	
  &	
  acUvaUon	

e+	
  intensity	
  at	
  linac-­‐end	
0.355nC	CollimaUon@1-­‐8	
  Case	  localized	
  beam	  loss	0.346nC	

Positron Source Upgrade (Takuya Kamitani)	

e+ intensity
at BT-line
will be ½ byenergyacceptance	e+ injection with old quads ?	
SAD	
  tracking	
  by	
  N.	
  Iida	  29	

OpUon	  to	
  achieve	  higher	
  e+	
  transmission	n Existing triplets in

sector-3, 4, 5 withlarge aperture (a = 10 mm)gives larger beamtransmission in linacn cannot switch optics
pulse-by-pulse withDC magnetsn budget constraint on
pulse quad fabricationand installatione+	
  intensity	
  at	
  linac-­‐end	 transmission
efficiency at
3.41	
  nC	
BT-lineshould be
evaluated !!	
Positron Source Upgrade (Takuya Kamitani)	

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Schedule & Summary

Positron Source Upgrade (Takuya Kamitani)	

e+ schedule for next 1 year	

31	

n components development & fabricationn e+ capture section installation (2013 Jul, Aug, Sep)vDC solenoids & LAS installationn e- commissioning from A1-gun to linac-end (2013 Oct)n e+ target installation (2013 Nov)ve+ target, FC & FODO (Sector-1, 2) installationn e+ commissioning (2013 Dec-2014 Jun)

[Constraints]
e- intensity 5 nC (~ 10 nC)v beam repetition ~ 1 Hz radiation limit, w/o shield around targetv FC current 6 kA (half of full spec.) prototype half spec. modulatorv DC solenoid currents 325 A (half of full spec.)
water & electricity facilities are not yet upgradedv pulse quads not yet installedv

Positron Source Upgrade (Takuya Kamitani)	

Summary	1) target & spoiler design is ongoing2) FC prototype-1 started test operation
with a prototype (half spec.) modulator
3) Capture section with no L-band designed
for sufficient e+ yield and satellite elimination4) e+/e- compatible optics in Sector-1, 2 andindependent optics with pulse quads in Sector-3, 4, 5
designed5) direct e+ injection w/o DR gives large beam loss inlinac6) development, fabrication and installation ofcomponents will be performed for 1-st stage e+commissioning at 2013 December.
Positron Source Upgrade (Takuya Kamitani)	

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