Crab Cavity Overview!"#$%!#&'()%%*"+,-KEK Crab Cavity R&D Group
Task Force
K.Hosoyama

KEKB Crab Crossing
New Crab Crossing Scheme
KEKB Superconducting Crab Cavity
RF Performance Test
Cryostat for KEKB Crab Cavity
Cryostat
R&D Efforts Nb-Cu Coaxial Coupler
Construction Schedule

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

New Crab Crossing Scheme
Installation of 2 Crab Cavities in “Nikko Straight Section”!
Advantage :We can use existing cryogenic system for acc. S.C. cavities
Cooling power of the cryogenic System 8 kW at 4.4K
Heat Load of Acc. Cavities~ 3kW
Enough cooling power for Crab Cavities
We decided installation of 2 Crab Cavities in “Nikko” on Feb. 2006.
FY 2004
We ordered 2 Crab Cavities from MHI.
Task Force was established!
FY 2005
We will order 2 cryostats and for the Crab cavities.

Layout of Crab Cavities In Nikko

Helium Refrigerator

Crab Cavity for LER

Crab Cavity for HERCrab Cavity in HER

Main Transfer Linepositron

Sub-transfer Lineelectron

5m

Crab Cavity

Crab Cavity in LER

Main Transfer Line
Sub-transfer Line

Acc. Cavity

Crab Cavity

Conceptual Design of KEKB Crab Cavity
Crab Kick
Coaxial Coupler
Squashed Cell Shape CavityCoaxial Input
Coupler

Top View

TM110 B-field
TM010, TE111
TM110*B
Crab Mode
Rejection Filter

EB

Beam

Coaxial Coupler

RF Absorber
RF Absorber
TM010 Q < 70
TE111 Q < 20Ef > 1.3 GHz
for Monopole Modef > 1 GHz
for Dipole Mode

Stub Support

B

Coaxial Input
Coupler

Squashed Cell Shape Cavity

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

Crab Mode
Rejection Filter

Coaxial Coupler

Beam

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

BeamE
RF Absorber
TM010 Q < 70
TE111 Q < 20We adopted this Bdesign as “base design”!

BE

KEKB Superconducting Crab Cavity
Input Coupler
I.D. 240

I.R. 90

I.D. 120

Rib
I.D. 188

Coaxial Coupler

I.R.241.5

866

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

0

Multi-pacting
10050150483

scale (cm)Non-axial Symmetric Structure
Thickness of 4.5 mm Nb Cavity
Reinforced by Ribs
Simplified Coaxial Coupler

Test Result of KEKB Crab Cavity #1
Design Esp!"!"without coaxial coupler
2.8 K

without coaxial coupler
4.2 K
$Q0!"

with coaxial coupler

#!"

"%!"

!%&"

&%'"

'%

("Esp [MV/m]

Fabrication and Surface Treatment
RF Performance Test with a Coaxial Coupler
Multipacting could be overcome by RF process.

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

Input coupler

Frequency Tuning
Magnetic Shield （ Jacket Type ） by Adjusting DistanceRFAbsorber

RFAbsorber

StubSupportI.D. 240

Coaxial Coupler

I.D.100

Bellows
Monitor Port

Liq. He

Liq. He

80 K LN2 Radiation Shield

Crab Mode
Reject Filter

Crab Cavity in Cryostat

Input Coupler

Top View
Heat Loss
80K 110 W
4.2K
15 W

Liq. Helium Vessel

Stub Support

Notch Filter

Coaxial Coupler

RF Absorber

80 K Liq. Nitrogen Shield!

"!
!

Copper Bellows#!
!!

Crab Cavity in Cryostat

Side View

Access Port for Cooling
Access Port for Liq. He
Level Sensor

Input Coupler

Liq. Helium Vessel)*%+,-./%01.-($2#$%&$''$(Notch Filter

4$((15'RF Absorber
Stub Support

80 K Liq. Nitrogen Shield
!

"!
!

3!
!!

Crab Cavity in Cryostat

Front View 1

Access Port for Cooling
Liq. N2 Out

Gas He Out

Liq. He In

Liq. N2 In

Crab Cavity

80 K Liq. Nitrogen Shield
Liq. Helium Vessel!

"!
!

#!
!!

Stub Support
!

"!
!

#!
!!

Crab Cavity in Cryostat

Front View 2
Cooling Water
Input coupler

Cooling Water

80 K Copper Shield
!

"!
!

#!
!!

!

"!
!

#!
!!

Model for Stress Analysis

Stress Analysis

Crab Cavity

31.8 [N/mm2]
28.7 [N/mm2]25.5 [N/mm2]

Tresca Stress

32.8 [N/mm2]

Stress Analysis

Helium Jacket
108 [N/mm2]

108 [N/mm2]

Tresca StressBuckling

Crab Cavity

1st Mode
Buckling Load ：0.7772 [MPa]2nd Mode
Buckling Load ：0.8500 [MPa]Buckling

Helium Jacket

1st Mode
Buckling Load ：0.3218 [MPa]2nd Mode
Bucking Load ：0.3219 [MPa]Coaxial Coupler
Stub Support

Notch Filter

Liq. HeRF Support

Inner Conductor
Nb-Cu
AlternativePumping PortGas HeNb

Temporary Support

Frequency Tuning
Frequency Tuner
Mechanical + Piezo

Input Coupler

Bellows
Stub Support
Beam

Sub He Vessel
RF Monitor

Coaxial Coupler
Main He Vessel
Cryostat Vacuum End Cell

Frequency Tuner
Front View

Side View

Test Stand for Frequency Tuner

Cryostat Vacuum Chamber

R&D Efforts Nb-Cu Coaxial Coupler
Nb-Cu Coaxial Coupler
Good cooling characteristic
Copper pipe (130 mm in Dia.) Commercially available
Designing and Fabrication of coaxial coupler are very easy
Full Size Nb-Cu Simplified Coaxial Coupler
RF Characteristic Test with Nb Crab Cavity
Full Size Nb-Cu Coaxial Coupler
Installed in Horizontal Cryostat
Designchange
More R&D time is needed
to complete the Nb-Cu Coaxial Coupler!
Nb Coaxial Coupler

Nb Spattering Setup ( Improved )Cooling Water

New Heater
Ti Sheath Heater
Ta Wire & Ceramics Pipe
3 Heater Sections
Uniform Temperature Dist.

Nb Target

RF Supply Port

Cu Coaxial Coupler

Heater
RF Shield
Prevent Discharge at Wiring

Problems
Shortage of Heater PowerElectric Insulation
Discharge at Cooling pipe
Discharge at Cabling
Cooling Water

Simplified Nb-Cu Coaxial Coupler

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

RF Test with Crab Cavity in V-cryostat

Nb-Cu Coaxial Coupler (Simplified Type)Before Nb Spattering

After Nb Spattering

Degradation of Nb-Cu Surface
Capillary vessel shape pattern

Scratch by metal scraper

Time Schedule for KEKB Crab Cavities
FY 20044
1. Proto-type1) Nb Spattering Test
2) Simplified Nb-Cu
3) Coaxial Coupler
4) Input Coupler
5) Cryostat & Tunner
6) Assembling7) Cool Down Test
8) RF Test

2. Crab #1, 2Cavities
1) Cell Forming2) Cavity E.B.W
3) Barrel P. & E.P.
4) Cold Test in V-Cryost.

5678

FY 2005

9 10 11 12 1Modification

28) Assembling9) Cool Down Test
10) RF Test
11) Installation to KEKB
Refrigerator
1) Ref. Control
2) Transfer Line
3) High Press. Reg. Law
HOM Damper
1) Damper φ240, φ188
2) Cooling Water
Test Stand
1) T.R.T
2) Power456

#2
#1

#1

#2

789 10 11 12 1

23

4

5

Welding of Jacket#1#2
EBW EP１#2Jig

ＲＦ TestEP2

AnnealWelding of Jacket
Assembling in to Cryostat

Need to Order Nb Material

File an Application to KHK & Hearing

Cool Down Test
RF Test

Review & Permission
FormingCavity Dimension
Modification of Die

Barrel Polish
TrimmingEBWWelding of Jacket

AnnealCooled Test
File an Application to KHK & Hearing

5) Coaxial Coupler
6) Input Coupler
7) Cryostat & Tunner

3

KHK :The High Pressure Gas Safety
Institution of Japan

Review & Permission

EP1 EP2

Forming/ EBWNeed to Start Action

Fabrication

AnnealEP１
EP2

Welding of Jacket

Aging

HPR

This time schedule shows the process flowof Crab cavity #1, the process of #2 follows
after 1~2 month later.

Assembling in to Cryostat
Cooled Test
RF TestInstall # 1
Install # 2

Summer Shut Down
Target Time !
Install #1, 2 at the same timeCrab Half-Cell Forming at MHI

From Y. Yamamoto Report

2000 t Press

Forming of 4 Half-Cells for Crab # 1 and # 2
Finished on Feb. 14, 2005 at Mitsubishi Heavy Industries, LTD. Kobe

Principle of Hydro-forming
Max. 2000 t

Oil Pressure 23MPa.

Press Head

Male Die
WrinkleSuppression Plate

StrokePress HeadNb Plate
5 mm tOil PanMale Die

WrinkleSuppression Plate
Over Flowed Oil

Oil
Oil

Press Bed

Before Forming

After FormingHydro-forming of half-Cell
Nb Plate
5mm tFemale Die : Oil

Male Die : Aluminum

It takes about 5 minutes to form a half-cellFinished half-cell

After forming, the shape was checked.
The dimension of the cavity was measuredby 3-D measurement system.