Crab Cavity Overview
Crab Cavity GroupK. Hosoyama
Crab Cavity for KEKB
Fabrication and RF Performance of Crab Cavities
Cryostat for Crab Cavity
Cool Down and High Power Test at D10 Test Stand
Tuner
Commissioning of Crab Cavities for KEKB

Crab Cavity for HER

Crab Cavity for LER

Crab Cavities for KEKB

KEKB
LER
HER
RF freq.
Cross. Ang.

Mt. Tsukuba

3.5 GeV
8.0 GeV508.9 MHz2 x 11 m rad.

Collision Point
Nikko

Tsukuba~ 1km

Tsukuba
PhotonFactoryNikko
8 SC-Cavities
Helium Ref.

2 Crab Cavities

FujiOhoConceptual Design of KEKB Crab Cavity
Coaxial InputCoupler

Crab Kick
Coaxial Coupler
Squashed Cell Shape Cavity

Top View

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

EB

Coaxial Coupler

BeamRF Absorberf > 1.3 GHz
for Monopole Modef > 1 GHz
for Dipole Mode

RF Absorber
TM010 Q < 70
TE111 Q < 20

E
Stub Support

B

Squashed Cell Shape Cavity
The squashed cell shape cavity scheme wasstudied extensively by Akai at Cornell in 1991
and 1992 for CESR-B under KEK-Cornell
collaboration.
We adopted this design as “base design”!

BeamE EBEBE
E : Electric Field
B : Magnetic FieldKEKB Superconducting Crab Cavity
Input Coupler
I.D. 240

I.R. 90

I.D. 120

I.D. 188

I.R.241.5

Coaxial Coupler

866

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

010050150
483

scale (cm)Non-axial Symmetric Structure
Thickness of 4.5 mm Nb Cavity
Reinforced by Ribs
Simplified Coaxial CouplerMilestone of Crab Cavity for KEKB
1994
1996
2005
Jan.
Dec.
2006
Jan.
Feb.
Feb.
Mar.
Apr.
May.
July

Crab 1/3 Scale 1.5 GHz Model
Crab Full Scale 500 MHz Model
Start the Fabrication of 2 Crab Cavities
RF Test of Crab Cavity HER in Ver. Cryostat Vkick = 1.9 MV
RF Test of Crab Cavity LER in Ver. Cryostat Vkick = 2.7 MV
Cool-down Test of Prototype Cryo-module
Start the Assembling of Cryo-module for Crab Cavity HER
Insertion Failure of Coaxial Coupler
Improved the Insertion Tool
Finished the Assembling Crab HER
Cool-down & High Power Test at Test Stand Vkick = 1.65 MV
Dismantle the Cryo-module
Improved RF Contact of Coaxial Coupler and Bellows

Aug. Reassemble the Cryo-module
Sep. Cool-down and High Power Test of Crab HER at Test Stand Vkick = 1.8 MV
Oct.
Assembling the Cryo-module for Crab LER
Nov. Cool-down and High Power Test of Crab LER at Test Stand Vkick = 1.93 MV
2007
Jan. 8,11 Installation of Crab Cavities for HER and LER into KEKB Ring
Jan.29,31 Start the Cool-down of Crab Cavities for HER and LER
Feb. 9,10 Start of RF Aging
Vkick = 1.7 and 1.43 MV for HER and LER
Feb. 19 Crab Kick

Construction & High Power Test of Crab Cavities
Jan. 20, 2007
K. Hosoyama

2006
March
KEKB Review

AprilMayJune

HERCool Down
May 12 – 18

JulyAug.

2007

Sept.

Oct.

Nov.

Dec.

Jan.

Feb.

MarchHERHigh Power Test
May 29 – June16

Cool Down & High Power Test

LER
Cool Down & High Power Test

Fitting Checkby Mock-up Model

Transport to D10April 26

Transport to AH
June 15
June 26
Vkick = 1.67 MV

Transport to D10 Oct.16 Nov. 14
Vkick = 1.8 MV
Transport to D10 Dec.5

Insertion
Tools

Coaxial Coupler

Cryostat Assembling

April 21
Insertion

Modification

HER

Fitting Check
HPR

HER
Reassemble

Dismantle
Reassemble&March 12
Insertion Coaxial Coupler Fitting Check
Failure!

Modification
Tuner Check
Dismantle

Dec. 21
Vkick = 1.93 MV

LERAssemblingInstallation into Tunnel

Cool Down & High Power Test

Tuner Structure
RF Contact

Beam Test
HER LERRF Contact
Design & Test

Mock-up Model

KEKB Summer Shutdown

KEKB Winter Shutdown

Fabrication and RF Performance Test of Crab Cavity• Fabrication of two crab cavities for LER and HER started in Jan. 2004
and finished in Nov. and Dec. 2005.
•The crab cavities for LER and HER were cold tested in vertical cryostat.
The test result of crab cavity for HER was satisfactory.
Vkick = 1.9 MV
The result of crab cavity for LER
was no good at 2nd and 1st Test.
We could improve the RF performance,by removing “lint” and EP2 processing.
Vkick = 2.7 MVFabrication Procedure of Crab Cavity
Crab Cavity CellMHIKobe

Nb SheetBeam Pipe & Flange

Tokyo Denkai

Nb Sheet

5 mm t RRR = 180

Half Cell Hydro-forming

Rolle

Mechanical Polishing & Trimming
Electron Beam Welding
Grinding of Welding PartKEKTsukuba
NomuraPlating
KanumaBarrel Polishing~ 100 µm

Electro-Polishing

EP 1~ 100 µm

Cell Equator

Electro-Polishing

EP 2~ 5 µm

High Pressure Water Rinsing
80 bar. 60 min.

High Pressure Water Rinsing
Assembling for Cold TestKinzoku
Giken
Mito

Annealing

700 oC x 3 hr

Cold Test in Vertical Cryo.

Forming and Barrel Polishing

Barrel Polishing
Nov. 11, 2005 at KEK
Forming of 4 Half-Cells for CrabCavity for LER and HER
Feb. 14, 2005 at Mitsubishi Heavy
Industries, LTD. Kobe

Polishing Time 312 Hr

Electro Polishing & Annealing

Crab Cavity:
Rotating ~ 1 rpm
Cathode:Aluminum Straight Pipe
Electro Polishing at Nomura Plating Ltd.

Titanium Box

EP 1 ~ 100 µm
EP 2~ 5 µm
Annealing at 700oC for 3 hours
at Kinzoku Giken Ltd.

High Pressure Rinsing and Assembling for RF Cold Test

Set Flanges of Beam Pipes and Ports
in Class 100 Clean RoomNozzle

High Pressure Water Rinsing
by 80 bar Ultra-Pure waterRotation & Up-Down Motion

Test Result Crab Cavity for HER

Test Result Crab Cavity for LER
X-Ray

Nov. 18

1st Test

H.P.R.
Nov. 29
EP2

Re-processing

Jan. 13 Test
Recovered !

2nd Test

Field Emission

Cryostat for Crab Cavity•Jacket type helium vessel is adopted for the cryostat design of KEK crab cavity.

•Nb-coaxial coupler is inserted in the cell of part of crab cavity
to extract a LOM and HOMs, andto adjust frequency, i.e. as for frequency tuner.

•Assembling the coaxial coupler to the cryostat was very “tough job”.
We could not connect the bayonet type joint of coaxial coupler.
We could assemble it by using improved Insertion tool.

•RF contact of the connection parts were improved.

Conceptual Design of Cryostat for KEKB Crab Cavity
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

Crab Mode Reject
Notch Filter

Bellows

Monitor Port
80 K LN2 Radiation Shield

Sub Liq. He Vesse

at
LER 1.6 A
1300 bunch

Jacket-type Helium Vessel
Coaxial Coupler
Frequency Tuning
Stub-Support -- Mechanical Support & Cooling of Coaxial Coupler
Jacket-type Helium Vessel

Jacket Type Helium Vessel

Prototype

Large Beam Pipe

Input Coupler Port

Jacket Type Helium Vessel

Jacket Type Magnetic Shield
Permalloy 3t

Crab Cavity & Coaxial Coupler in Cryo-module
Support Rod
Jacket Type Main He vessel
SUS316L

Jacket Type Sub He vessel

Support Pipe
Tuning Rod
Input Coupler

Notch Filter

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

Stub Support

Coaxial Structure Detailed

Temporary Mechanical Support
for Assembling

Notch Filter

Nb-Coaxial Coupler
Cooled by Liq. Helium

RF Absorber

Stub SupportBA

Nb-Coaxial Coupler
Cooled by Liq. Helium

Joint Part

Copper Plating SUS Inner Conductor
Cooled by Water

Assembling of Coaxial Coupler

Crab Cavity (Cryostat) Side

Bayonet Type Connection
Step 1 Insert
Step 2 Rotate Clockwise 30 degree

Notch Filter Side

New Insertion Setup
Notch Filter (~100kg)
Vacuum Pumping
Port 20.4 kg1) Rigid structure2) Easy to adjust position and axis direction

Alignment of Coaxial Coupler

Decide the axis of the coaxial coupler
set in the cryostat by using transit.

Align the axis of the coaxial coupler
which will be connected to the coaxial
coupler of cryostat side.

RF Contact
Type： Spiral
Material： BeCu
Spring Constant： 14kg/φ94mm（0.5kg/cm）

Mechanical & Electrical Properties of RF Contact
Spiral TypeRF Contact

July 14, 2006
I.D.94mm用

y = 2.8577x - 24.475

300

O.D.148mm用

0.60.55

Resistance(mΩ)
抵抗値（mΩ）

Deformation(µm)
ダイヤルゲージ読み(μm)

250Contact Resistance

200150100500.50.45

Without RF Contact

0.40.35
0.30.25
0.20.150.1000204060
荷重(N)
Load(N)

8010012020406080

荷重（N) ( N )Load100120

Cool-down and High Power Test at D10 Test Stand•

Crab cavity for HER and LER were cool down without leakage.

•Resonant frequency could adjust to operating frequency of 508.9MHz.

•Vkick = 1.8 MV and 1.93 MV respectively,
exceed the design value of 1.44 MV.

•Qo – values at design kick voltage were higher than 1x109.

•Cavity and coaxial coupler was cooled stably during the high power test.
Cryogenic system worked very well.

•Frequency tuner of crab cavity HER work very well.
Phase stability of crab cavity HER is good.

•Phase stability of crab cavity LER is no good!

Move to Test Stand for Cool-down & High Power Test
April 26, 2006 1stOct. 16, 2006 2ndMt. Tsukuba

Crab cavity for HER

Dec. 6, 2006
Crab cavity for LER

Test Stand for Crab Cavity at D10 Station
Control System for RF Test
Acc. Cavity

Sub-transfer Line
Crab Cavity

HER
May 12 – June 16 1st TestOct. 24 – Nov. 17

2nd Test

LER
Dec. 13 – Dec. 28

Sub-transfer LineHigh Power Test

High Power Test for Crab Cavity HER & LER
Crab Cavity HER
Input Power

Crab Cavity LER
120kW

Input Power55kW

Vkick

1.80MV

Vkick

VacuumVacuumTemperature

Temperature

1.93MVFrequency Tuning•

Resonance frequency of the cavity can be changed by1) deforming the cavity cell shape for pre-tuning, and2) changing insertion depth of coaxial coupler for tuning.

•The insertion depth can be changed by two tuning rods in parallel.
These rods are driven by “main tuner”.
Head position of coaxial coupler can be changed by “sub tuner”.
The sub tuner drives one tuning rod and shakes the head of coaxial
coupler in horizontal direction.

•••

Tuning mechanism described above work very well for crab cavity HER
but, not good for crab cavity LER.
We tried
1) reinforcement of the mechanical structure, and
2) improve the sliding mechanism to reduce friction, but not effective.

•We are now planning to reinforcement of “support bolts”.

Frequency Tuning Mechanism
Tuning RodTop View

Support Pipe

Input Coupler

Buckling?
Add Expansion Rods!
Driving Plate

Sub Tuner

Main Liq. He Vessel

Mechanical

Pick up Probe
BellowsLoad Cells
BeamMain Tuner
Mechanical + Piezo
Stub Support

RF Monitor

Coaxial Coupler

Main Tuner : Frequency Tuning
Sub Tuner

Sub Liq. He Vessel~30 kHz / mm: Adjust Position of Coaxial Coupler

Cryostat Vacuum End Cell

Frequency Tuner

Support Bolt
Add Expansion Rods!

Base Plate
Driving Plate
Main Tuner

Sub Tuner

Test Stand for Frequency Tuner

Frequency Tuner Crab Cavity for HER

by A. KabeResonance Frequency

Frequency Tuning by Main Tuner

Load [kg]Main Tuner Position (mm)Main Tuner Position (mm)Adjustment of Coaxial Coupler Position by Sub Tuner
By adjusting coaxial coupler on the axis of crab cavity,
the crab mode can be prevented going out.
The coupler position can be controlled by sub-tuner.

by A. Kabe

Frequency Tuning by Piezo Tuner

by A. Kabe

Phase StabilityImprovement of phase stability by expansion rods

Phase stability could be improved by RF feed back system

2 degree30 degree

0.3 degree

0.5 degree

Installation & Commissioning Schedule for CrabCavities
January

814February

2128

4

Jan. 8Installation
Alignment
Jan. 15, 16
Vacuum Chamber

HER( D10 )

Jan. 26
Coupler Aging
200kW

18254Feb. 10
Helium Gas Leak at recovery line
Bypass LineFeb. 6
Tuner Test

Jan. 18,19
Wave GuideMarch11Feb. 5
fo AdjustJan. 29
Cool down

Jan. 17
Tuner Test

Crab Cavity

Jan. 28, 2007
K. Hosoyama

Vkick=1.5
Vkick=1.44

Feb. 9Cavity Aging (day time)Jan. 9,10
Tuner Re-assembling
Jan. 11
Installation

Crab Cavity

Jan. 31
Cool down

Alignment
Jan. 17, 18
Vacuum Chamber

Feb. 8
Tuner Test

Jan. 19
Tuner Test

LER

Feb. 6Feb. 7fo Adjust

Vkick=1.4( D11 )

Jan. 22, 23
Wave Guide

Jan. 15 - 19
T.R.T. & Piping

Jan. 31
Coupler Aging
150kW

SCC Acc.

Jan. 26
Cool down
Jan. 24
Jan. 19
Gastight test Inspection for High Press. Regulation Law

Vkick=1.43

Feb. 10
Cavity Aging (day time)

BeamFeb. 13
LER 30mA
HEL 30mA
31 bunch 30mA

Belle Monday Meeting

Feb. 19
Crab Kick
LER 1 MV
HER 1.4 MV

50 bunch
LER 48 mA
HER 60 mA

11Commissioning of Crab Cavities for KEKB••••••

Crab cavity for HER and LER were installed in KEKB ring and cool down
successfully.
Resonant frequency could adjust to operating frequency of 508.9MHz.
Kick voltage of crab cavity HER and LER reachedVkick = 1.6 MV and 1.5 MV respectively,
exceed the design value of 1.44 MV.
RF phase tuner of crab cavity LER did not work well.
But by using the RF feed back system, we could control within the design value.
Crab kick was confirmed by streak camera.
Crab crossing has started!

Troubles:• Cold helium gas leak at connection part of recovery pipe.
Tighten the connector and set a heater at connection part.
• Lack of cooling power at coaxial coupler.
Add bypass line to increase the gas flow.
•Frequent break down by vacuum burst at input coupler of crab cavity for LER.
Need warm up ???

Cooling He Gas & Cooling Water
Cooling Water
Input Coupler

Main He Vessel
Sub He Vessel

Cooling Water

Liq. He In
RFAbsorber

Coaxial Coupler
Bellows

Notch Filter

RFAbsorber

Beam

Stub SupportGas HeRF Monitor
Gas HeCooling Water

Cooling Water

Control Valve
BypassFlow Meter