Crab Cavity R&D and Future Plan!"#$%!#&'()%%*"+,-KEK Crab Cavity R&D GroupK. Hosoyama, K. Hara, A. Kabe, Y. Kojima, Y. Morita, H. Nakai
A. Honma, A. Terashima, K. Nakanishi
MHIS. Matsuoka, T. Yanagisawa

KEKB Crab Crossing
Installation of Crab Cavities in Nikko
Characteristics of KEKB Crab Cavity
Fabrication and RF Performance Test
Cryostat for KEKB Crab Cavity
R&D Efforts 1 Cryostat
R&D Efforts 2 Nb-Cu Coaxial Coupler
Road Map to Beam TestKEKB Crab Crossing
The crab crossing scheme allows a large crossing angle collision
without introducing any synchrotron-betatron coupling resonances. 1, 2)
1)
2)

R.B.Palmer, SLAC-PUB-4707,1988
K.Oide and K.Yokoya, SLAC-PUB-4832,1989!"#$%&'%()*+,#-+./#-.01)2#3
4@!
@'%()+*78

B@!

A*81)+*78;?CC#DE
4%.56*7-*''181*7;?C;#DE

Required kick 1.44 MV

non-crab crossing-+*88179#:79'%####,;;#<#=#>#+.5?3;?C;#DE;?CC#DE

Installation of Crab Cavities in Nikko Straight Section
Installation of Crab Cavities in “Nikko Straight Section”!
Beam Test : Operation under high beam current
Advantage :We can use existing Cryogenic System for KEKB Acc. Cavities
Cryogenic System (8 kW at 4.4K)
Heat Load of KEKB Acc. Cavities ~ 3kW

Layout of Crab Cavities in Nikko Tunnel
Nikko Straight Section
LER

D10

D11HER

Crab Cavity
for LER

Crab Cavity
for HER

D10 Straight Section

Transfer LineConnection PortLER

e-Acc. Cavities

Crab Cavity

e+HERCrab Cavities
Installed in
KEKB Ring

HER$#'#+"$%,'()$!"'&!("%$&!

!"#$%$"!"""!!"*ElectronLER+!#!

!!"!$("%)"%"")$!"""%$"!"#$%$&!

!("#""*Positron

5mLER

Crab Cavity././01234!"#$#%&'#()*+,-Crab Cavity

Designed by Kanazawa

Conceptual Design of KEKB Crab Cavity
Coaxial Input
Coupler

B
Crab Mode
Rejection Filter

EB

Beam

Coaxial Coupler

RF Absorber
RF Absorber
TM010 Q < 70
TE111 Q < 20E

f > 1.3 GHz
for Monopole Modef > 1 GHz
for Dipole Mode

Stub Support

B

Coaxial Input
Coupler

The squashed cell shape cavity schemeB
was studied extensively
by Akai atECornell in 1991 and 1992 for CESR-B
under KEK-CornellB collaboration.

Squashed Cell Shape Cavity

Crab Mode
Rejection Filter

Coaxial Coupler

Beam

RF Absorberf > 1.3 GHz
for Monopole Modef > 1 GHz
for Dipole ModeE
Stub Support

Beam

E

We adopted this design
as “base design”!
B

RF Absorber
TM010 Q < 70
TE111 Q < 20B

E

Superconducting Crab Cavity
Input Coupler
I.D. 240

I.R. 90

I.D. 120

I.D. 188

Coaxial Coupler

I.R.241.5

866

I.R. 20
I.D. 30
Monitor Port

010050150483

scale (cm)Non-axial Symmetric Weak StructureThickness of 4.5 mm Nb Cavity
Reinforced by Ribs

Cold Test Stand for KEKB Crab Cavity
He Refrigerator for KEKB
superconducting Acc. cavities

Liq. He Dewar
12,000 L

Clean room

Vertical cryostat

The crab cavity is
set in the verticalcryostat

The crab cavity is taken out from clean room
to install into the vertical cryostat.

Test Result of KEKB Crab Cavity #1
Design Esp!"!"

without coaxial coupler

2.8 K

Q0

without coaxial coupler
4.2 K

with coaxial coupler

$!"

#!"

"%!"

!%

&"

Esp [MV/m]

&%

'"'%

("Multipacting in Crab Cavity with Coaxial Coupler
Reflected Power

10:43

Reflected Power

11:25
EmittedPower

RF Power On

RF Power On

Transmitted Power

Transmitted Power

Reflected Power

11:45

11:15
Reflected Power
Emitted Power

Transmitted PowerRF Power On

RF Power On
Transmitted Power

Emitted PowerSummary & Future Plan 1
Crab Cavity # 1, 2
Fabrication and Surface Treatment
RF Performance Test with a Coaxial Coupler
Multipacting could be overcome by RF process.
We have established these techniques!
Prototype Cryostat
Detailed Design and Fabrication
Fabrication of End Plate
Start of Construction
Complete and Cold Test End of FY 2004Collaboration with KEK Machine-Shop

Conceptual Design of Cryostat for KEKB Crab Cavity
Frequency Tuning by Coaxial Coupler
28.3 kHz / mm
Stub-Support ---- Mechanical Support & Cooling of Coaxial Coupler Tip
Jacket-type Helium Vessel

Top View

Input coupler

Frequency Tuning
Magnetic Shield （ Jacket Type ） by Adjusting Distance

RFAbsorber

RFAbsorber

StubSupport

I.D. 240

Coaxial Coupler

I.D.100

Bellows
Monitor Port

Liq. He

Liq. He

80 K LN2 Radiation Shield

Crab Mode
Reject Filter

Cryostat for Crab Cavity (Top view)
DE->?98;-@(89'&:Input Coupler

Liq. Helium Vessel6&-7&**&'/01->?

2899(:;

Stub Support
Notch Filter!"#$/6&->?

Coaxial Coupler=6&-<8;%&''()*RF Absorber
2899(:;@(AB4A'-/4?&-2;8C-2899(:;/01-<8;+,-.-/01-234&'5

80 K Liq. Nitrogen Shield

0F

HFF
scale (m)1GFFF

Cryostat for Crab Cavity (Side view)
Input Coupler

Access Port for Liq. He
Level Sensor
Access Port for Cooling+C-*E*FC-*@,*G*H0/

A-B<&,(B&)*.022%3/

C-*D-66-)

Stub Support
Notch Filter$3&1*$&>(/?
$%&'(&)*$%02)-3@,20/*$%02)-34-))%56

RF Absorber$%&'(&)*+(,-*./01*.022%3/

Liq. Helium Vessel
80 K Liq. Nitrogen Shield

78*9*+:;*.<(-)=

0!

#!!

scale (m)1"!!!

Cryostat for Crab Cavity (Front view)!"##$%&

Scale')''('''

R&D Efforts 1

CryostatSeamless Cu Bellows
For Frequency Tuning --- Thin wall (0.4mm) Cu Bellows(Nb-Cu)Forming of Thin End Plate
End Plates for Cryostat
φ600, 920 : for Helium Vessel
φ1200: for Vacuum Vessle

Fabrication of Bellows

Press Unit andPressure Water Pump

Fabricated 5-cell Bellows

Set the Female Die

Female Dieand Outer
Guide Pipe

Fabrication of End Shell
φ 1200, 1.5 t SUS 316L
End Shell for Vacuum Vessel

φ 600, 1.5 t SUS 316L
End Shell for Helium Vessel

φ 920, 2 t SUS 316L
End Shell for Helium Vessel

R&D Efforts 2Nb-Cu Coaxial Coupler

Nb-Cu Coaxial Coupler( Designing and Fabrication is very easy ! )1.5 GHz Nb-Cu Cavities
RF Characteristic Test in Nb Coaxial Cavity
Optimization of Nb Spattering
Full Size Nb-Cu Simplified Coaxial Coupler
RF Characteristic Test with Nb Crab Cavity
Full Size Nb-Cu Coaxial Coupler
Installed in Horizontal Cryostat
Input Coupler
Fabrication of Prototype

Nb-Cu Spattering Cavity
1.5 GHz Nb-Cu Cavity

Temperature 300 ~ 350 0C
Ar Gas
0.2 PaRF Power 100kW 13.56 MHz

RF coupler

HeaterRadiation shield
Vacuum chamber
Magnet
SUS316L

SUS316L
C1011

Cu cavity
Nb target

Nb-Cu 1.5 GHz Cavity

%

Q0!"

$!"

#!"

02468
Esp [MV/m]

101214

Simplified Nb-Cu Coaxial Coupler

Assembled Cu Coaxial Coupler
Electro-polished Cu Coaxial Coupler
High Pressure Rinsing
Nb Spattering
High Pressure RinsingElectro-polishing

RF Test with Crab Cavity in V-cryostat

Clean Room for Cavity and Cryostat Assembling
Clean Room ( Class 100 )for Cavity AssemblingHigh Pressure Pure
Water Rinsing
Clean Roomfor Cryostat Assembling

Clean Roomfor Nb-Cu Spattering

Road Map to Beam Test
Jan.

2003

2004

Dec. Jan.

Crab Cavity #1

Dec. Jan.

2005

DesignDec. Jan.

E.P.
Crab Cavity
Cold Test
Cryostat

Crab Cavity Prototype
Ｃｒｙｏｓｔａｔ

Coaxial Coupler(Prototype)

Assembling

Installation

Coaxial Coupler (Prototype)Nb-Cu R&D

Assembling

Cold Test

Vac.
RFCryogenics
ControlCold Test

Beam Test

Vac.
RF
Cryogenics
Control