Status of ILC WG5 Asia Activities Kenji Saito

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Status of ILC WG5 Asia ActivitiesKenji Saito

• Before Snowmass
• Effort for principle identification of 45MV/m
  by single cell cavities
• Effort for demonstration of 45MV/m LL 9-cell
  cavities
• After Snowmass
• More concentrated on single cell cavity study
• 1) Establish our preparation recipe
• 2) Find a cure against multipacting
• Preparation for STF cryomodule instruction of
  LL 9-cell cavities

Changed the original RD plane
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ILC WG5 Asia Strategy and RD Issues

• Push gradient higher for the future ILC energy
  reach
• Needs enough margin on 35MV/m operation
• Cavity operation cost saving by 10 by LL cavity
  shape
• Industrialization Conventional baseline
  fabrication and advanced Nb/Cu clad seamless
  cavity for cost down

KEK decided to develop the LL shape 9-cell cavity
for ILC and demonstrate the high gradient
(45MV/m) module operation in STF at least by the
CDR.
Need a wide dynamical range tuner for larger
Lorenz detuning Need a higher power (500kW) input
coupler

• RD Issues
• 45MV/m high gradient cavity
• Wide dynamical range tuner system
• 500kW high power coupler
• Baseline fabrication, Nb/Cu clad seamless cavity
  fabrication

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ILCWG5 Asia Manpower
Cavity fabrication and Vertical Test Nb
material(M.Wake) Cavity fabrication(H.Inoue,
K.Saito, T.Saeki) Preparation(K.saito,
T.Saeki) Vertical test(T.Saeki, T.Higo,
N.Toge) Bonding of SUS/Nb(F.Furuta) Aluminum
sealing(F.Furuta) Cavity design(Y.Morozumi) HOM(Y.
morozumi, T.Higo, S.Noguchi) Structure
analysis(H.Yamaoka) International
collaboration(K.Saito)
International Collaboration DESY,INFN-Milan, INFN
LNL,SLAC,FNAL,JLAB,Cornell
Asia WG5 PAL,IHEP, Beijing uni
K.Saito
Pre-tuning/Tuner Mechanical design
(Y.Higashi) Structure analysis (H.Yamaoka)
WG5 K.Saito (Deputy T.Higo)
Y.Higashi
FTE 10 persons
Niobium material (M.Wake)
M.Wake
500kW high power input coupler Coupler
design(S.Kazakov, H.Matsumoto) Fabrication(S.Kazak
ov, H.Matsumoto) Brazing(N.Kudo) High power
test(H.Matsumoto, S.Kazakov) Internatinal
collaboration(H.Matsumoto)
WG2 H.Hayano (STF)
H.Matsumoto
K.Tsuchiya
45MV/m cryostat Cryostat design (K.Tsuchiya,
A.Terashima
Nb/Cu clad seamless cavity Forming machine
design(K.Ueno, K.Enami)
K.Ueno
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RF Critical Field analyzed by K.Saito
Vortex nucleation model
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from J.Sekutowicz lectuer Note
Cavity Design
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48.5
46.5
4.26
KEK Proposal TESLA shape was designed in 1992
optimizing Ep/Eacc against field emission. Now
field emission is not a hard limit by KEK recipe
(EPHPRBake process ). Gradient is limited
critical magnetic field. Cavity shape has to be
optimized on Hp/Eacc and Ep/Eacc for high
gradient and high Q.
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Not yet 45MV/m
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ICHIRO 9-cell cavity (KEK)
Already completed 4 cavities and cold test
started
Beam pipe flange SUS316L
He jacket base plate SUS316L
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• Eacc limited around 21MV/m, due to MP ?
• Lower Qo (expected value 21010),
• loss at end stainless blind flanges
  (simulation by Morozumi)

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After the Snowmass
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Successful principle identification of Eacc gt
45MV/m by single cell cavities on last Sep (KEK)
ILC Gradient ACD
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Breakthrough to push Eacc 50MV/m
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Multipacting
46.5MV/m
Needed RF processing for 45min
90min
X-ray
Transmitted power
T 3min/div
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Establishment of Recipe by single cell cavity
study

• Single cell study
• Establish recipe Fabricate new 6
  single cell cavities
• Find a cure against MP
• NOT Optimization of EP condition, which was done
  15 yeas ago.
• Suspected Issues

Low QA with EP acid control Concentration
of HF Contamination in Acid, specially
Sulfur Low QA with rinsing water quality
control
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Investigation of rinsing water QA

• Monitoring Water Quality Parameters
• Resistivity, Particle, Bacteria, TOC
• Good result on some cavities
• with Resistivity 6.5 MW _at_ KEK PW
• Use 0.1 0.2 mm inline filter
• TOC, Bacteria high priority parameters to be
  investigated

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Method for investigation with TOC and Bacteria
CO2 filter
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MP source, gaseous or solid ?
Gaseous
Reset effect of MP processing after warm-up
e-
A
B
A
B
2K Nb surface
300K Nb surface
Solid Memory effect of
MP processing after warm-up
e-
A
A
B
B
2K Nb surface
300K Nb surface
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Matrix of Single Cavity Study and Status
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Preliminary Summary from on going Single cell
study
Reliably demonstrated 50MV/m high gradient
performance 1) Reproduced by repeated cold
tests with/without vacuum re-evacuation
2) Kept the performance after high pressure water
rinsing with ultra-pure water Rinsing
water quality strongly correlates to cavity
performance HPR with UPW can recover the
degraded performance by low quality water
rinsing By new RF processing of MP, the
processing time is within 15 minutes now
for both RE and LL, which looks not a serious
problem After warm-up, MP processing time
reduced to one half
We will collect lots of information on
Preparation Recipe by TESLA/GDE Meeting in
Frascati.