SCC upgrade~ Superconducting Accelerating Cavity ~KEKB-MAC2005
Feb. 22, 2005

T. FuruyaKEKB-MAC2005

SCC Upgrade

KEKB-SCC- The peak luminosity of KEKB has reached 150% of the design value.
- The beam intensity of HER reached 115%.
Contents
1) Achievements of KEKB-SC
2) Activity for upgradingKEKB-MAC2005

SCC Upgrade

Achievements of KEKB-SC

Historical aspects
1998 Commissioning with 4 SC’s in D11-site.
1999 Coupler power test: 380kW to the beam.
Physics run start.
2000 Installation of the next 4-cavities in D10-site.
2001 Lpeak= 6.9 x 1033 cm-2s-1
with beams of HER/LER = 0.8A/1.0 A.
HOM of each SC reached 5kW.
2002 Lpeak = 8.2 x 1033 cm-2s-1 .
Beam of HER reached 1 A.
2003 Lpeak = 1.06 x 1034 cm-2s-1
The max. current of HER reached 1.1 A in1184 bunches.
HOM of each SC reached 10kW.
- Capacity of cooling water was increased
to 20kW.
SC-Vc test up to 2MV using D11B cavity.
Lpeak = 1.13 x 1034 cm-2s-1
with beams of HER/LER = 1.18A/1.56 A
2004 Continuous Injection mode
1.25A in 1293 bunches induced 16kW of HOM.
2005 Lpeak = 1.5 x 1034 cm-2s-1 with 1.27A(HER)…. still growing up …..

KEKB-MAC2005

SCC Upgrade

Achievements of KEKB-SC

RF power at 1.27 A

total of D10

D10 cavities

Power delivered to the beam (kW)Power delivered to the beam (kW)-RF power of 2.4 MW was transferred to the beam by 8 SC cavities.

total of D11

D11 cavitiesKEKB-MAC2005

SCC Upgrade

Achievements of KEKB-SC

RF power absorbed by HOM dampers at 1.27 A- A beam of 1.27 A in 1293 bunches induces the HOM of 14 - 16 kW for each module. (σz=7mm)- The ratio of SBP / LBP is 7 kW / 9 kW.
LBP damper
HOM power of SBP + LBP (W)SBP damper

HOM of D11 cavitiesKEKB-MAC2005

SCC Upgrade

Achievements of KEKB-SC

Summary of figuresdesignachieved

84 at the commissioning
8 since Set. 2000

Beam intensity

1.1A in 5000 bunches

1.27 A in 1293 bunches

Bunch length

4 mm

6 - 7 mm-> 2.5 MV/cavity(2 – 2.8 MV/cavity)

RF voltage with beam

1.5 MV/cavity

1.2 – 2 MV/cavity

Q-value1 x 109 at 2 MV

0.5 – 2 x 109 at 2 MV

RF power transferred to thebeam> 250 kW/cavity

300 - 350 kW/cavity
400 kW/cavity in max.

HOM power

5 kW at 1.1 A

14 - 16 kW at 1.27 A

Number of SC cavities

Max RF voltage w/o beam

KEKB-MAC2005

SCC Upgrade

Activity for upgrading

1. Spare module* Because of the increase of a beam current, the SC system has no margin of RF power.
* A prototype module constructed for the beam test in 1996 was modified as a spare module of
KEKB in the last summer.
* The module will be cooled at a test stand soon.

Prototype module in TRISTAN AR.

KEKB-MAC2005

SCC Upgrade

Activity for upgrading

2. Input coupler* Required RF power in SuperKEKB is 460 kW/cavity.
* Traveling wave of 500 kW was successfully supplied at a test stand in 2003.
* To increase the coupling strength, the vacuum gasket of the outer conductor was replaced tothin one in the last summer shutdown.

- Qext of 5 x 104
D10A, D10B, D10C
D11C
-Qext of 7 x 104
D10D
D11A, D11B, D11D

KEKB-MAC2005

SCC Upgrade

Activity for upgrading

3. Power test of a HOM damper* Power test was carried out to the spare dampers of SBP and LBP.
* Absorbed power up to 18 kW for SBP damper and 25 kW for LBP damper did not damage theferrite surface, which correspond to the HOM power at 2 A in 1300 bunches in HER.
* The surface temperature reached near 200C.
* Out gas rate should be measured as the next step.
* In SuperKEKB, the HOM of 60 kW has to be absorbed by a pair of the dampers.
To reduce the temperature rise of the surface,
the dampers with a thin ferrite cylinder (2-3 mm)
will be fabricated and tested.KEKB-MAC2005

SCC Upgrade

Activity for upgrading

4. HOM damper trouble: vacuum leakage of the D11A-LBP damper* At the end of the last year, one of the HOM damper had a vacuum leakage at a welding seamof the flange. (D11A-LBP)* Troubled damper was replaced to new one in this winter shutdown.

Troubled damper was replaced to newone in the tunnel.

KEKB-MAC2005

SCC Upgrade

Activity for upgrading* During replacement of the dampers, we could inspect the ferrite surface.
* No damage or cracking was observed on both SBP and LBP dampers.

Vacuum leakage happened at EB-welding
between SUS and Cu.

Inside view of the D11A cavity

KEKB-MAC2005

SCC Upgrade

Activity for upgrading

5. Cracking of HOM damper in CRAB-dummy chambers* Both SiC and ferrite absorbers had been installed in crab-dummy chambers of D01-section andD02-section in Tsukuba-area.
* The damage of these dampers were found in October and December.
* Ferrite size: 170 mm ferrite cylinder with the diameter of 240 mm.

Ferrite damper of D01 section.

Ferrite damper of D02 section.KEKB-MAC2005

SCC Upgrade

Activity for upgrading….. as a preliminary results……
Both simulation of loss factor and temperature measurements showed the absorbed power of
only 4 kW at the maximum beam intensity.
Ultra-sonic scanning showed a lot of cracking of the ferrite.

D01 ferrite

D02 ferrite

Spiral cracking suggests that caused by winding of cooling pipe from the out side.

KEKB-MAC2005

SCC Upgrade

Summary

6. Summary* Beam intensity of HER has increased to 1.27 A.
* SC cavities can provide the voltage of 1.4 MV/cavity and 300 – 350 kW/cavity to
the beam of 1.27 A.
* Coupling of the input coupler has been increased on 4 cavities. (7 x 104  5 x 104)
* The HOM absorbed by the damper reached 16 kW/cavity.
 SBP / LBP = 7 kW / 9 kW
 No damage was observed on the dampers of D11A cavity.
* Power test at a test stand showed no damage of the ferrite surface up to 18 kW for
SBP damper and 25 kW for LBP damper, which correspond to the HOM power at 2A in HER.
* Cracking of the D02-ferrite suggest the improvement of the damper fabrication
process should be established.