Electron / Positron Injector Linac
Kazuro Furukawa<kazuro.furukawa@kek.jp>
for Injector Linac

Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

Linac Overview

Mission of electron/positron Injector in SuperKEKBu 40-times higher LuminosityvTwice larger storage beamà Higher beam current at Linacv20-times higher collision rate with nano-beam scheme³ à Low-emittance even at first turn³ à Shorter storage lifetimeà Low-emittance beam from Linac(à Higher Linac beam current)uLinac challengesvLow emittance e³ with high-charge RF-gunvLow emittance e+³ with damping ringvHigher e+ beam current³ with new capture sectionvEmittance preservation³ with precise beam controlv4+1 ring simultaneous injection
Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

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Linac Upgrade for SuperKEKB
u Higher Injection Beam Currentv To Meet the larger stored beam current and shorter beam lifetime in the ring
Ir5Cev 4~8-times larger bunch current for electron and positronu Lower-emittance Injection Beamv To meet nano-beam scheme in the ringv Positron with a damping ring, Electron with a photo-cathode RF gunv Emittance preservation by alignment and beam instrumentationu Quasi-simultaneous injections into 4 storage rings (PPM)v SuperKEKB e–/e+ rings, and light sources of PF and PF-ARv Improvements to beam instrumentation, low-level RF, controls, timing, etc

SuperKEKB injector Linac	
high currentgun	
low emittanceRF gun	

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

S-bandlinac	

e+ target &L-band+LAS
capture section	
Linac Upgrade Status towards SuperKEKB

1.1 GeV
Damping Ringcirc. 136 m	
Energy-spread
Compression System	
3TRF gun	FC50 Hz (e+ or e-)pulse-by-pulse
mode switching 	PFPF-ARLER 6.5 GeV e-

2.5 GeV e0.1nC x 1	

4.0 GeV e+ 4nC x 2	ECS	C-bandmodules	

HER 7.0 GeV e5nC x 2	K.F, KEK, Feb.2014.

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Linac Schedule Overview (to be updated)
RF-Gun e- beamcommissioning
at A,B-sector
Qe- = 5nC

e- commiss.
at A,B,J,C,1
Qe- = 5nC

e+ commiss.
at 1,2 Qe+ = 0.5nC (FC, DCS, Qe- 50%)e- commiss.
at 1,2,3,4,5 Qe- = 5nC

1 nC: Electron: Positron: Low current electron

Linac Upgrade Status towards SuperKEKB

non damped e+ commiss.
at 1,2, 3,4,5 Qe+ = 4nC
e- commiss. pulse-switch
at A→5 Qe- = 5nC

4 nC

2 nC

damped e+ commiss.
at 1→5 Qe+ = 4nC
e- commiss.
at A→5 Qe- = 5nC

PF-AR ecommiss.

K.F, KEK, Feb.2014.

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Fire during flux concentrator developmentu One of small problems – Cables burned by 20cm

Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

5

SLAC-SuperKEKB Workshop (Injector Linac)u Injector commissioning and issues 30'v Speaker: Masanori Satoh (KEK)u Photo-cathode RF gun 20'v Speaker: Takuya Natsui (KEK)u Positron source 30'v Speaker: Takuya Kamitani (KEK)u Timing synchronization 20'v Speaker: Hiroshi Kaji (KEK)u Linac alignment 20'v Speaker: Toshiyasu Higo (KEK)u Beam optics design for simultaneous injection 20'v Speaker: Takako Miura (KEK)

Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

6Questions and Answersu PEDD dependent on beam repetition?
v SLAC study was on single-pulse energy density³ may need further investigationu Fiber loss monitor blackening around target?
v Can be replaced routinelyu Diamond loss detector?
v Is worth comparing in the futureu Orbit stability tolerance against beam size?
v Pinhole 2mm and beam sigma 0.3mm are possible
Beam orbit jitter will be studied, as well as for emittance preservationu Rotating target/spoiler?
v Should be studied for the beam current largeru Frequency synchronization btw. linac/ring?
v All SKEKB frequencies are generated from common freq. with ring circumference compensationu Beam charge variation pulse-pulse?
v Can be importantv Technically possible with different event assignmentv Means different injection modes with different orbit stabilization for wakefieldu Target quad – pulsed ?
u Beam jitter should be smallu DR extraction angle jitterv Offset injection position/angle jitter should be small
Linac Upgrade Status towards SuperKEKB

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Several Workshop around Injector Linacu Technology choice for beam position monitor (BPM)v Indispensable for emittance preservationv ~10micron precision (~100micron in KEKB linac), about 100 BPMs, event controlsv Experts from SLAC, Steve Smith and Andrew Youngv Many valuable discussions for filter design, digital signal processing, etc.
v One of the developments was chosen for performance, operation, and budgetu Laser and photo-cathode RF gun workshopv 6 presentations, 16 participantsv The same objectives of low emittance and higher stabilityv Injector linac is unique on higher beam charge and lower energy spreadv Should exchange technology/information continuouslyu Accelerator structure processing workshopv 22 participantsv Many discussions on duration (more than a month), and the systemv No baking necessary, longer processing and better monitors, better interlock needed
Linac Upgrade Status towards SuperKEKB

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Improved beam optics designuPulsed quad addition – Simultaneous injectionuFODO → Doublet – Emittance preservationuOrbit correction simulationuFurther emittance preservation even withalignment tolerancesuOptimization for budget …

Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

9KEK e-/e+ Injector LINAC	
B	

1.5 GeV e-	C	

10 nC x 2 (for LER)
5 nC x 2 (for HER)
0.3 nC x 1 (for AR)
0.3 nC x 1 (for PF) 	
low emittance
1.1 GeV
RF gun	A	1	2	e+	  target	  	same	  energy	

DR	l e-/e+ beams are delivered to 4-rings withdifferent current & energy.
l Beam	  accelera7on	  modes	  must	  be	  switched	  by	  50	  Hz	  pulse-­‐by-­‐pulse	  for	  top-­‐up	  injec7on.	

3	4	5	e-­‐:Chicane	

4.219	  GeV	  e-	Decelerate	

1.1 GeVe+	  target	  	 e+	

HER:	  7	  GeV	  e-­‐	  	  	5	  nC	  x2	AR:	  6.5	  GeV	  e-­‐	0.3	  nC	  x1	

LER:	  2.5	  GeV	  e+	4	  nC	  x2	PF:	  2.5	  GeV	  e-­‐	0.3	  nC	  x1	

1.5	  GeV	  C	1	2	3	

4	5	

Beam optics should satisfy the fast beam-mode switching.	
Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

Result of e-p fittinge-­‐	

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e+	

K.F, KEK, Feb.2014.

Emittance Preservationu If Device is off center of the beamv Focusing magnet (quad) kicks the beam bunchv Accelerating structure (cavity) excites wakefield, to bend the tailu Distorted bunch in banana shapev Emittance dilution or blow-upv Depending on the beam optics and the beam chargeu Orbit correction is crucial to preserve the emittance
Sugimoto et al.

Beam
Focusing
MagnetAcceleratingStructure
Transverse distribution in time direction

Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

12Emittance Dilution
uOffset injection may solve the issueuOrbit have to be maintained precisely
Mis-alignment leads to Emittance blow-up

Orbit manipulation compensates it

100 samplesSugimoto et al.
Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

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Alignment	  Error	  vs.	  Emi>ance	  Growth	  	<Tracking	  Condi7on>	
Calculated	  by	  	  H.	  Sugimoto	• Positron	  is	  transported	  from	  DR	  outlet	  to	  LINAC	  end.	
• Alignment	  error	  is	  given	  in	  quads	  and	  cavi7es.	  
• The	  orbit	  correc7on	  is	  performed	  by	  assuming	  the	  center	  of	  the	  quads	  and	  BPM	  are	  exactly	  the	  same.	  
• Initial Emittance@Outlet of DR	  =6.5 µm / 89 µm (Vertical / Horizontal)
Ver@cal	Horizontal	

Zoom	e+	  norm.	  ε	  at	  LINAC-­‐end	  should	  be	  less	  than	  	  20	  µm	  /	  100µm	  (	  Ver.	  /	  Hor.)	

Linac Upgrade Status towards SuperKEKBl Triplet	  and	  doublet	  give	  almost	  same	  results.	  
l In	  triplet	  and	  doublet,	  misalignment	  of	  300µm	  is	  acceptable.	  
l In	  FODO	  la`ce,	  signiﬁcant	  emibance	  growth	  is	  seen.	  
K.F, KEK, Feb.2014.

Positron SourceuHigh current positron is requireduPositron capturing with flux concentrator (FC)and large aperture s-band structure (LAS)uDeceleration field to reduce satellite bunchesuPinhole beside target for electron beamuProtection system with beam spoilers

Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

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Positron beamline under construction
SLEDtarget+FCKLY
1-5

LAS 14 MV/m
deceleration & phase slip& acceleration

SLED

KLY
1-6
LAS : Large Aperture
S-band structure

LAS 10 MV/m
acceleration

Solenoidsl primary e- 3.2 GeV, 10 nC x 2 bunch, 50 Hzl tungsten targetl AMD system (5.0 T x 200mm+ 0.4 T x 15m)
Flux Concentrator DC solenoidsl KLY1 2m LAS x 2 (14 MV/m), aperture 2a = 32 -> 30 mm (typical S-band ~20 mm)l KLY2 2m LAS x 4 (10 MV/m), aperture 2a = 32 -> 30 mm Deceleration capture	l e+ beam energy at capture section exit : 110 MeV
e+ yield: N(e+)/N(e-) = 49 % at 1.1 GeV DR
Linac Upgrade Status towards SuperKEKB

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Flux Concentrator Assembly
FC assembly

primary
e- beampositronproduction
Targetquick detachable power & water connection
to minimize worker's radiation doseFlux
Concentrator
BridgeCoilse+ beam
Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

1718	e+/e- beam switching at target
side	  view	
10 nC
primary e-	bridge coils	

DC QM	 spoiler	target	rear	  view	solenoid	

LAS Accel.
structure	

targetdiameter
4.0 mmtargetoffset
3.5 mm	e+	beamhole	

5 nC injection e-	
Flux
Concentrator	

pulse ST	
pulse QM	

2.0 mmFC offset

holediameter
2.0 mm
7.0 mm
FC aperture

Two possible schemes of beam switching by orbit bump	1) e+ on-axis, e- offset-> e- emittance growth by solenoid kick induced orbit2) e- on-axis, e+ offset
we take this scheme.	
-> e+ yield degradation (50% -> 10%)
T.Kamitani
Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

Photo-cathode RF-gun DevelopmentuA1 RF-gun (GR_A1) under testvBig progresses are quasi-traveling wave sidecoupled cavity, Ir5Ce photo-cathode, Yb fiber laservLongitudinal laser pulse manipulation is necessaryfor energy-spread and stability managementvShould understand those many new components forreal stable operationv5-nC per bunch was re-confirmed with newconfigurationv600-m transport was confirmed (with small charge)

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Linac Upgrade Status towards SuperKEKB

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GR_A1 : 5.1 nC / bunch

Horizontal position /mm

Vertical position /mm

Charge /nC

Charge Trend / Stability

Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

Beam Trend / Stability

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K.F, KEK, Feb.2014.

Horizontal / Vertical stability

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K.F, KEK, Feb.2014.

u600m beam transport from RF-gun with QTWSC

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Dual-layer Controls

Virtual Accelerator-based Controlsu Multiple closed loops were installed on each PPM VA
independentlyv Tested at KEKB
e− Gun"e– BT (PF: 2.5GeV, 0.1nC)"

PF Injection

ARC"

e+ Target"e− Gun"Event-basedControl System

ARC"

KEKB-LER Injection

Primary e– (4GeV, 10nC)

e+ BT (KEKB: 3.5GeV, 0.6nC)"

e+ Target"e− Gun"ARC"

KEKB-HER Injection
e+ Target"e– BT (KEKB: 8GeV, 1.2nC)"

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K.F, KEK, Feb.2014.

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Event-based
Control Systemu Four PPM VAs at least
for SuperKEKB project(maybe withadditional PPM VA
for stealth beam)

Every
20 ms

F.B
e− GunARC

F.B

PF Injectione– (2.5GeV, 0.2nC)

F.B
e− GunARC

Damping ring

SuperKEKB-LER Injection

F.B

e– (3.5GeV, 10nC)

F.B

e+ Targete+ (4GeV, 4nC)

e− GunARC

SuperKEKB-HER Injection

F.B

e– (7GeV, 5nC)
e− GunARC

F.B

PF-AR Injection

F.B
e– (6.5GeV, 5nC)

Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

SummaryuSteady progress towards first MR injection in 2015
uWill make staged improvements before 2017uWill finish disaster recovery in 2014uWill balance between final beam quality and stable
and staged operationuWill select optimized route depending on available
resources

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K.F, KEK, Feb.2014.

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Mt. Tsukuba

Thank you
SuperKEKB
dual rings
PF-ARPF

Linac Upgrade Status towards SuperKEKBInjector
LinacK.F, KEK, Feb.2014.

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Linac Upgrade Status towards SuperKEKB

K.F, KEK, Feb.2014.

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