Present Status and Future Upgrade of KEKB Injector Linac

Present Status and Future Upgradeof KEKB Injector Linac
Kazuro Furukawa, for e–/e+ Linac Group
Present StatusUpgrade in the Near Future
R&D towards SuperKEKB

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Electron/Positron Injector Linac
Machine Features
600m Linac with 59 S-band rf Stations,most of them Equipped with SLED to provide 20MeV/m
Dual Sub-Harmonic Bunchers to achieve 10ps for 10nC,and Energy Compression System for PositronBeam Characteristics
8GeV 1.2nC Electron and 3.5GeV 0.6nC x2 Positron for KEKB
2.5GeV 0.2nC for PF, 3.0GeV 0.2nC for PF-AR

Present Status

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Linac in KEKB CommissioningChallenging Projects since 1998
Commissioning (1998~)
Overcoming rf Breakdowns
at the Bunching section and Positron Capturing section (1999~2000)
Positron Injection with Dual Bunches in a Pulse (2001~2002)
Reduction of Failure Rate with Careful Managementof the Equipment and Beam Parameters, especially at rf Trip Rate (2002)
C-band R&D for the Future SuperKEKB (2003~)
Continuous Injection of both Positron and Electron Beams (2004)

Recent Operation
About 7000 hours/yearMachine-trouble time (when some part of the machine is broken): 2~3%
Beam-loss time (when beam could not be delivered): ~0.5%Routine managementof rf Power, rf Phasing, Optics Matching, Energy Spread Optimization
Present Status

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Increase of the Injection Efficiency

Feb.2005
ContinuousInjections

May.2000

Apr.2003
Dual Bunch e+
Present Status

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Continuous Injection Mode
Reliability of the Operation
Frequent Switch was not Considered in the Design
Vacuum Bellows, Mechanical Phase Shifters, etc.

Improvement in each Hardware Component,
as well as Operation Software
No Reliability Degradation is Observed
1998
1999

Year

2000
2001
2002
2003
2004
010000

20000

30000

40000

Number of Switches
Present Status

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Positron Generation with Crystalline Tungsten(Collaboration between KEK, Tokyo Metro. Univ., Hiroshima Univ., Tomsk
Polytech., LAL-Orsay)

High Intensity Positron is Always a Challengein Electron-Positron CollidersPositron Production Enhancement by Channeling Radiation in Single
Crystal Target was Proposed by R. Chehab et. al (1989)
The Effect was Confirmed Experimentally in Japan (INS/Tokyo, KEK)
and at CERN
Channeling Radiation
CrystalNucleus
Beam

ChannelCoherent Bremsstrahlung
Crystalline Positron Target

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Experiment at KEK
Positron Production Enhancement Measurement
Target Thickness Dependence(2.2, 5.3, 9mm for Tungsten Crystal, 2 ~ 28mm for Amorphous)Out-going Positron Energy Dependence (5 ~ 20MeV)
Incident Electron Energy Dependence (3 ~ 8GeV)
Single Target or Hybrid Target
Target other than Tungsten,
Crystals used for Calorimeters, Silicon, Diamond

ARC[R0]e--Gun3-GeV Experiment
ECS[61]e+-Targete--BT(PF)e+-BT(KEKB)
e --BT(KEKB,PFAR)4, 8-GeV Experiment
Crystalline Positron Target

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector LinacExperimental Setup

60oSingle Target

Hybrid TargetCrystalline Positron Target

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Typical Experimental Measurements
Ee-=4 GeV

50.5-60-40-200204060

3off-axis
210-8080

Rotational Angle [mrad]-on-axis4-60-40-200204060

80

0.6

0.4

0.20-80-60-2002040-Ee =4GeV, Pe =20 MeV/c

60

2.5

21.5

10.50-80

80-60-40-200204060

80

Rotational Angle [mrad]+Ee =8GeV, Pe =20 MeV/c0.060.06

Tungsten crystal
GEANT3
Amorphous tungsten

0.050.04

Positron Production Efficiency [%]Positron Production Efficiency [%]-40

Rotational Angle [mrad]

e+ base yield+

3

9.0mm-thickWc

0.8

Rotational Angle [mrad]

9mmWc

Ee-=8 GeV

2.2mm-thickWc

Relative Positron Yield[arbitrary unit]

11

Relative Positron Yield[arbitrary unit]

2.2mmWc

2.2mmWc

Ee-=8 GeV

9.0mm-thickWc
Relative Positron Yield[arbitrary unit]

Relative Positron Yield[arbitrary unit]

2.2mm-thickWc

0-80

9mmWc

Ee-=4 GeV

1.5

Crystal W~30%0.03

0.02

Amorphous W

0.01

0~30%

Crystal W

0.05

0.04

0.03

Amorphous W
0.02

Tungsten crystal
GEANT3
Amorphous tungsten

0.010051015

Target Thickness [mm]Crystalline Positron Target

2005101520

Target Thickness [mm]K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Results and Considerations
With Tungsten Single Crystal, the Absolute Positron Yields
were Enhanced by ~26% at Ee+=20MeV, and by ~15%(average) in the range of Ee+= 5~20MeV compared with theMaximum Yield in the Amorphous Tungsten.
Diamond Hybrid Target has been Suggested to Produce 3Times more Photons (V.N.Baier et al.), but We need >15mm
Thick Diamond while We could test only 5mm. And theRadiation Damage is Unknown.
Another Experiment is Planned just before Summer
Shutdown to Refine the Results, and The Optimized Crystalline
Tungsten is Planned to Replace the Present Positron Target.
The Design of the Target is Under way.

Crystalline Positron Target

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector LinacUpgrade Towards Simultaneous Injection(Collaboration Working Group between PF, KEKB, Linac and Others)Requirements
One Linac is used for 4 Storage Rings (Time Sharing)Switching between KEKB and other Modes takes ~3 minutes because ECS
Magnets have to be standardized.
Machine Studies in PF and/or PF-AR Interrupt the KEKB Continuous Injection.
PF Needs Top-up (Continuous) Injection in the Future for Advanced
Measurement.

Possible Solution
Simultaneous Injection Scheme
is Strongly Suggested.
Beam Switches pulse-by-pulse
could be Employed.
Needs Pulse Bend. Magnetto Kick PF Beam

Simultaneous Injection

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Fast Beam SwitchesFast Change of the Magnetic Field is Difficult
Common Magnetic Field (Quad and Steering Magnets) should be Used.
Energy Adjustment can be Achieved with Low-level rf Controls.
With Additional Circuits and Controls.

The Beam is Accelerated up to ~5.3GeV
then further Accelerated to 8GeV for KEKB,or Decelerated to 2.5GeV for PF.

"2.5 GeV" e- optics

Preliminary Testby Y.Onishi
Simultaneous Injection• Energy = 2.7 GeV (SC61H)= 3.6x10-4 m• γεx• γεy = 6x10-5 m

8 GeV e- optics• Energy = 8 GeV (SC61H)• γεx = 2.5x10-4 m• γεy = 4x10-5 m
K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Upgrade Overview
Upgrade would be Carried in 3 Phases
Phase-I: Construction of New PF-BT Line Summer 2005
Phase-II: Simultaneous Injection between KEKB e– and PF e–
Phase-III: Simultaneous Injection including KEKB e+ (,PF-AR)It was decided to be Carried out as Soon as Possible.

Simultaneous Injection

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

PF Beam Transport Optics Design
The New PF-BT Optics Design is FixedSpare Parts are Collected based on the Design, if Exists
Other Components are being Designed or being FabricatedPhase-I Components (except Pulse Bend) will be Installed at this Summer

Energy Spread Monitor

Simultaneous Injection

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

C-band R&D towards SuperKEKB
Higher Luminosity in SuperKEKB
(1) Squeezing Beta at Interaction Region
(2) Increase of Beam Currents(3) Crab Cavities
(4) Exchange of Energies of Electron/Positron to Cure e-Cloud Issues
etc.

For Linac (4) is the Major Challenge as well as (2)Higher Gradient Acceleration with C-band Structure is Considered toAchieve 8GeV Positron

~24 rf Stations will be Converted
From: Single S-band rf Station + 2m x 4 Acc Structure = ~160MeV
To: Dual C-band rf Station + 1m x 16 Acc Structure = ~320MeV==> 8GeV Positron can be Provided

Dumping Ring to Meet the IR Design will also be Employed
C-band R&D

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Advances in C-band R&D
Apr.2002-Aug.2003.
Design and Installation of
First rf Station
First Acc. Structure
Basically Scale down of S-band One

First Accelerated Beam (Oct.2003)
~38MV/m at 43MW

Sep.2003-Aug.2004.
Design and Installation of
First LIPS type rf Compressor (SLED)TE038 mode

Further Improve for Real Operation

Accelerated Beam withrf Pulse-Compressor
~42MV/m at ~56MW (12MW from Kly.)

C-band R&D

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

C-band Components
Klystron & Pulse Modulator
Compact (1/3 size), Cooling and IGBT breakdown Issues Solved

rf Window
Mix (TE11+TM11) mode Traveling Wave, 300MW Transmission

rf Pulse Compressor
TE038 mode (instead of TE015), Q0=132,000, 200MW Achieved in Test

Accelerating StructureBased on half-scale of S-band Structure
2/3p Traveling-wave, Quasi-constant-gradient, ElectroplatingBecause of such Simple Design, a few Trips / hour Observed
Expected to be Solved in the Next Summer

rf Low-level and booster KlystronMay need Modification in Real OperationC-band R&D

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector Linac

Improvements in Coming Summer
Four Accelerating Structures are under Fabrication
Designed in KEK, and Fabricated in KEK or MHI

Several Features are Applied especially at Coupler
Standard or Non-standard (Full-length) Coupler Cell
Thick and Smooth Shape Coupler Iris
Coupler Axis offset for Field CorrectionElectro-polishing at Coupler
Constant ImpedanceC-band R&D

K.Furukawa, Feb.24.2005.

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Present Status and Future Upgrade of KEKB Injector LinacSummary
Operational Improvements and Future Projects are Carried
with Balancing between them
Continuous Injection Surely Improved KEKB LuminositySimultaneous Injection Project will Help both KEKB and PF
Advanced Operation, and also Other Rings in FutureOriented Crystalline Positron Target may Enhance Positron
Production
C-band R&D for Future SuperKEKB Advances Steadily but
relatively Rapidly, and the Results seem to be Promising

K.Furukawa, Feb.24.2005.

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