Crab Cavity

GroupCrab Cavity Overview
K. Hosoyama

Crab Crossing Scheme New Crab Crossing Scheme
KEKB Superconducting Crab Cavity
Construction Schedule
Fabrication of Crab Cavities for LER & HER
RF Performance Test
Cryostat for KEKB Crab Cavity
HOM Damper
Input Coupler
Frequency Tuner
Connection of Inner Conductor / Coaxial Structure
SummaryKEKB Crab Crossing
The crab crossing scheme allows a large crossing angle collision without
introducing any synchrotron-betatron coupling resonances. 1, 2)
1)
2)

Original Crab Crossing Scheme
4 Crab Cavities
at Colliding Section

R.B.Palmer, SLAC-PUB-4707,1988
K.Oide and K.Yokoya, SLAC-PUB-4832,1989

RF Deflector( Crab Cavity )HER

LERElectrons

Positrons

1.44 MV
Head‑onCollision

1.41 MV

Crossing Angle(11 x 2 m rad.)non-crab crossing

New Crab Crossing Scheme
2 Crab Cavities
at “Nikko” Section

Beam-bunch wiggle around the whole ring!

Advantage: We can use existing cryogenic system for Acc. S.C. cavities

1.41 MV

1.44 MVLayout of Crab Cavities In Nikko
Helium Refrigerator
8kW at 4.4 K
Crab Cavity for LER

Crab Cavity for HER

D10

D11Main Transfer Line
Main Transfer Line

Sub-transfer LinepositronelectronAcc. Cavity
5m
Crab Cavity

Crab Cavity

Conceptual Design of KEKB Crab Cavity
Top View

Crab Kick
Coaxial Coupler
Squashed Cell Shape Cavity

Coaxial InputCoupler

TM110 B-field 1.44 MV
TM010, TE111
TM110*

B
Crab Mode
Rejection Filter

EB

Coaxial Coupler

Beam

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

RF Absorber
TM010 Q < 70
TE111 Q < 20B

Squashed Cell Shape Cavity
The squashed cell shape cavity scheme
was studied extensively by Akai atCornell in 1991 and 1992 for CESR-B
under KEK-Cornell collaboration.

BeamEEBE

B

We adopted this design as “base design”!

EE : Electric Field
B : Magnetic FieldKEKB Superconducting Crab Cavity
Frequency

501.7 MHz

R/Q

46.7 ΩG

220

Input Coupler
I.D. 240

I.R. 90

I.D. 120

Rib
I.D. 188

I.R.241.5

Coaxial Coupler

866

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

Multi-pacting
0100

50150
483

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

Esp / Vkick14.4 MV / m / MV

Hsp / Vkick

415 Oe / MV

Construction Schedule of KEKB Crab Cavities
FY 2004

FY 2005A S O N D J F

M A M JJFY 2006

A S O N D J

Cavity Cold Test

Fabrication of LER, HER Cavities Start

Mile Stone

March 19, 2005 K. Hosoyama

Good Result

LER

Prototype Cryostat
4/27
Prototype #2 Cold Test

1) Cryostat2) Assembling3) Cold Test

Crab LER, HER
Cavities
1) Cell Forming2) Cavity E.B.W.
3) Surface Treatment
4) Cold Test

6/7 6/23

Esp = ~40 MV/m
Welding of Jacket

Cryostat AssemblingFile an Application to KHK & Hearing
Review & Permission
FormingCavity Dimension
Modification of Die

Coaxial Coupler: Inspection by KHK
KHK :The High Pressure Gas Safety
Institution of Japan

Input Coupler
Freq. Tuner

Welding of Jacket
Installation to Cryostat
2/27 at KEK Cold & RF Test

EP１

HIP

Cold & RF Test

Final
Installation
Assembling

EP2

EP１
EP2Aging
Input Coupler for LER, HER
Tuner for LER, HER

HOM Damper

Cold & RF Test at Test Stand

EP1
EP2
EP2 2/8 at KEK
Cold & RF Test
12/20
Barrel PolishForming/ E.B.W. HER

Input Coupler PrototypeAgingNotch Filter

OKPre-tune EP1 EP2
AnnealForming/ E.B.W. LER

Review & Permission

Cold & RF Test

Final Assembling
2/ 6 – 10
11/29 Leak ! Cold Test

Pre-tune
E.B.W. HER

File an Application to KHK & Hearing

A O

11/2 D10 Test Stand

Cold Test
BarrelPolish Anneal 11/18
1/12
11/29

E.B.W. LER

Trimming

Cold Test

JInstallation

Good Result

HER

Proto-type

M A M J

FDriving Test

Notch Filter for LER, HER
Baking AssemblingHigh Power Test

Tuning

HOM Damper
Cryogenic System
1) Transfer Line KEKB
2) Transfer Line D103) Cryogenic Control
VacuumCooling Water
RF System

Summer Shut Down

Summer Shut Down

KEKB Shut Down

Fabrication ofFabrication of Transfer Line Transfer Lineby Hitachi Ltd.
for D10 Test StandControl for Cryogenic System

Summer Shut Down

Related Talks•
••
•
••
•
•

RF characteristics of crab cavity
FR couplers of crab cavity
Cryostat, jacket, etc.
Peripheral devices
HOM absorbers
Horizontal test of crab cavity
RF system for crab cavity
Installation of crab cavity

Y. Morita
K. Nakanishi
H. Nakai
H. NakaiY. Morita
Y. Yamamoto
K. Akai
M. OnoFabrication of Crab Cavity
1) Full Scale Prototype Crab Cavity

500MHz2 Nb Cavities # 1 & # 2# 2 has was Installed
into Horizontal Prototype Cryostat

2) KEKB Crab Cavity

509MHz2 Nb Cavities for LER, HER
Finished the Fabrication
Cold Tested in Vertical Cryostat
Now under Installation into Horizontal Cryostat

Forming at Electron Beam Welding at MHI
Beam Pipes wereFabricated by E.B.W.

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

Barrel Polishing at KEKPolishing Time 312 Hr
Remove about 0.15 mm along the cell equator

Measurement of Resonant Frequency

Electro Polishing & Annealing

Crab Cavity:
Rotating ~ 1 rpm
Cathode:Aluminum Straight Pipe

Titanium Box

Annealing at 7000C for 3 hours
at Kinzoku Giken Ltd.

Transport & Assembling for Cold Test

Arrive in KEK from Nomura Plating Ltd.

Assembling in Clean Room in AH

High Pressure Rinsing at KEK
New HPR Facility at KEK

Transition FlangeHigh Pressure Water Rinsing
by 80 bar Ultra-Pure water
Rotation & Up-Down Motion

NozzleTransition Flange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 isset in the verticalcryostat

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

Test Result Crab Cavity #HER

Test Result Crab Cavity #LER
X-Ray

Nov. 18

1st Test

H.P.R.
Nov. 29
EP2
Jan. 13 Test
Recovered !

2nd Test

Field Emission

Inspection

Inside the Cavity

Small Beam Pipe
Trace of RibInp
ut C

A Whisker Like Foreign Material
was found at the heating spot !
ouplerPortPictures of Electron Microscope
Lint of Cotton Wiper?

［断面］加速電圧：10kV

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

Input coupler

Frequency Tuningby Adjusting Distance

Magnetic Shield （ Jacket Type ）RFAbsorber

RFAbsorber

StubSupport~ 18 kW
I.D. 240~ 8 kW

Coaxial Coupler

Main He Vessel

I.D.100

Bellows

Crab Mode
Reject Filter

Monitor Port
80 K LN2 Radiation Shield
atLER 1.6 A1300 bunch

Sub Liq. He Vesse

Cryostat for Crab Cavity

Input Coupler

Top View

Liq. Helium Vessel
SUS Support Pipe
Stub Support

Notch Filter

Coaxial Coupler

RF Absorber

80 K Liq. Nitrogen ShieldAluminum
End Plate

Copper Bellows
Aluminum
End PlateCrab Cavity in He Vessel (3D)
Support RodJacket Type Main He vessel
SUS316L

Jacket Type Sub He vessel

Tuning Rod
Input Coupler

Notch Filter

Crab Cavity Cell
RF Absorber
Coaxial Coupler (Nb)
Extract TM010, TE111 Mode
Frequency Tuning

Stub Support

Prototype Cryostat
1) Jacket Type Helium Vessel

to Check the Leak Tight

2) Input Coupler

to Check Thermal Contraction

3) Without Coaxial Structure
Assembled in KEK
Leak at In-Seal of Beam Pipe Flange!
Nov. 29, 2005

Disassemble and Reassemble

Cool Down Test

OK !
Feb. 6-10, 2006

What cause the Leakage?
Transition Flange

Welding

SUS Jacket

SUS Transition Flange

Niobium – SUS
by Indium Seal
Force

Helicoflex
Beam Pipe Nb
In - Seal

Force
In the Case ofVertical Cryostat Test

Force
In the Case of Jacket Type Cryostat

Magnetic Shield (Jacket Type)

Permalloy 3t

Segmentation
Crab Cavity

3t

10

R60
D100127

D100
D600
R300

R300
R600300300300

D320

Large Beam PartD32090Large Beam Pipe
250
D100250

D328
20127

Cell Part

Crab Cavity Cell
5612720D278

Small Beam Pipe

D270200

Small Beam Part

Jacket Type Helium Vessel

PrototypeHelium Vessel for Small Beam Pipe

Helium Vessel for Large Beam Pipe

Installation of Input Coupler 1
Input Coupler for KEKB Crab Cavity(Prototype)

RF Window

FlangeConnection
to Crab Cavity

CoverFlange
Connection
to Cryostat
80K Shield

Simulation for Installation of Input Coupler

Assembling of Large Beam Pipe

Took a Picture after finish a Good Job.

Prototype Cryostat

Test Stand for Crab Cavity at D10 Station

Sub-transfer Line

Sub-transfer LineHOM Damper

Ferrite RF AbsorberSame as HOM Damper
for KEKB Acc. SC cavity
Baking and High Power Test
have been finishedCavity 0.7 V/pC
Taper 0.04 V/pC
Damper 0.3 V/pC
Total: 1.04 V/pC
HOM power: 20.5 kW(1.6 A, 1300-bunch)by Y.Morita
Supported by Acc. Cavity GroupT. Furuya

Input Coupler

3 input couplers were high power tested

by K.Nakanishi and Y. YamamotoSupported by Acc. Cavity GroupS. Mitsunobu
Cooling Water

RF Window

4.4 K

300 K

Cooling Water

one is installed in Prototype
one in Crab Cavity #HER

TW: 200kW
SW: 100kW

Frequency Tuner
Frequency TuningPiezo + Motor Drive
Piezo 0.3 mm
Motor 6 mm
Under 600 kg Load
Position ofCoaxial coupler
Motor DriveCoaxial Structure Stub Support

Assembling of Stub Support Part

Helium Jacket for Stub Support

Coaxial Structure

Connection of Inner Conductor
Nb Coaxial Coupler

HOM Damper

Gate Valve

Notch Filter

Bellows
TunerConnection Part

Crab Cavity (Cryostat) SideHow to connect inner conductor
Step 1 Insert
Step 2 Rotate Clockwise 30 degree

Notch Filter Side

Set Up for Connection of Coaxial Structure
Inner Conductor 8.8 kg
Inner Conductor Nb
25.5 kg

Notch Filter (~100kg)

Vacuum Pumping Port
20.4 kg
Inner Conductor
38 kg
HOM Damper
55 kg

RotateSlide

Could not connect !
Need Precise Alignment
Position of Axis
Direction Axis

The Coaxial Structure is Heavy.
Insertion Tool
Not Strong Support Structure
No Precise Adjustment Knob

Need Modification

Inner Conductor（Room Temperature Part）

36 kg

Inner Conductor (Cold Part)

Problem at connection part
Good RF Contact ?
Need Finger Contact ?
---------

Summery• We could fabricate and cold tested 2 full size crab cavitieswhich have satisfactory RF performance for KEKB crab.
• A prototype cryostat for crab cavity was fabricated and coldtested at D10 test stand.
• A cryostat of crab cavity HER was fabricated.
• Insertion of the coaxial structure to the cryostat is now
underway. We are struggling with this job.
We need modification of insertion tool !
• The other key components; input coupler, HOM damper,
taper chamber, tuner, vacuum system, transfer lines, coolingwater, … are ready to integrate to the crab cavity.
• These 2 crab cavities will be installed in KEKB after cool
down and high power test at D10 test stand.