Rongli Geng - Jefferson Lab
Rongli Geng - Jefferson Lab
Rongli Geng - Jefferson Lab
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ILC SRF Cavity High Gradient R&D<br />
at <strong>Jefferson</strong> <strong>Lab</strong><br />
A Spring 2009 Update & Outlook<br />
Rong-Li <strong>Geng</strong><br />
SRF Institute<br />
Director’s Review, March 20, 2009
ILC High Gradient Cavity Processing & Testing<br />
supported by DOE HEP and US-Japan Collaboration<br />
• Program began in summer 2006. 17 Cavities Processed<br />
– Critical R&D topic for ILC.<br />
– In collaboration with FNAL and KEK.<br />
– 90% of 9-cell electropolishing (EP) processed in US.<br />
– Significant capability demonstrated - 30 EP & vertical test per year.<br />
• Established in-house multi-cell cavity high-grad. expertise<br />
– 150 hours of active EP time. Fairly stable cavity results.<br />
– Impressive gradient results recognized and valued by ILC & SRF community for<br />
future endeavor (later slides).<br />
• Potential to benefit J<strong>Lab</strong> future machine emerging<br />
– Two example of raising Q at 20 MV/m in 7-cell J<strong>Lab</strong> cavities (more later).<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
2
S0: Cavity gradient R&D<br />
S1: Cryomodule development<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
3
A5<br />
A6<br />
A7<br />
A8<br />
A9<br />
A11<br />
A12<br />
A13<br />
A14<br />
A15<br />
AES1<br />
AES2<br />
AES3<br />
AES4<br />
ICHIRO5<br />
J2<br />
max gradient [MV/m]<br />
max gradient [MV/m]<br />
J<strong>Lab</strong> Delivered Bulk Data of ART’s Contribution<br />
45<br />
to ILC Cavity Gradient Program (S0)<br />
40<br />
50<br />
45<br />
40<br />
35<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
50<br />
35<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
Summary of 9-cell Vertical Tests in U.S.<br />
A5 A6 A7 A8 A9 A11A12A13A14A15AES1AES2AES3AES4ICHI<br />
cavity<br />
J<strong>Lab</strong><br />
Cornell<br />
FNAL<br />
ANL/J<strong>Lab</strong><br />
J<strong>Lab</strong>/KEK<br />
KEK<br />
ILC goal<br />
Px goal<br />
CEBAF<br />
upgrade<br />
Graph credit: Camille Ginsburg, FNAL<br />
9-cell cavity<br />
Director's Review, March<br />
ART <strong>Rongli</strong> <strong>Geng</strong> = America Regional Team, lead by Michael Harrison<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
4
J<strong>Lab</strong> Results Push Gradient Yield Envelope<br />
- A Glimpse of Progress in Past 6 Month<br />
CEBAF upgrade<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
5
Two Big Pushes Ahead…High ILC R&D Priority<br />
Push Quench Limit:<br />
• Defects due to fab.<br />
Push Quench Limit &<br />
Field emission Limit<br />
• Surface imperfection<br />
• External contamination<br />
Past yield curves show best gradient ofJ<strong>Lab</strong> data set<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
6
The ILC Gradient Yield Goal is Challenging…<br />
- J<strong>Lab</strong> Experiences Show It Seems Possible<br />
First Pass (one light EP) Performance<br />
5 cavities from one vendor<br />
EP processed and tested at J<strong>Lab</strong> in last 8 months<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
7
Example of Quench Limit due to Defect<br />
T-mapping Identifies Hot Spot<br />
Correlated to Quench…<br />
To EBW seam<br />
200-300 µm<br />
A pit outside equator EBW<br />
at boundary of heat affected zone<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Optical Inspection Discovers Defect near Hot Spot<br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
8
Example of Field Emitter Revealed by<br />
Surface Studies: Nb-O produced by EP<br />
Nb samples EP’ed together with 9-cell cavities<br />
• High-voltage tip scans surface for field emitter map.<br />
• Integrated SEM analysis for nature of field emitter.<br />
• Solution for removal: Lowering temperature; adding 30<br />
minutes acid flow after voltage off.<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
Nb-O<br />
Dominant field emitters<br />
on as EP’ed Nb surface<br />
9
Defect Removal Development – E-beam Local Re-melting<br />
- One example of items supported by US-Japan Collaboration Fund<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
10
Look Forward: Opportunities & Challenges<br />
• Impact ILC gradient re-baseline<br />
o AAP Review at TILC09, GDE meeting at KEK, April 17-21, 2009.<br />
• Help increase US industry’s SRF competence<br />
o Specification of processing parameters to be adopted for industry application.<br />
o Train US industry for high gradient cavity processing.<br />
o Feedback knowledge (material, processing and fabrication).<br />
o Participated North America Cavity Vendor Meeting at FNAL , March 6, 2009.<br />
• Provide technology option for J<strong>Lab</strong>’s own future machine<br />
o Raise cavity Q performance at 20-25 MV/m gradient by BCP + EP.<br />
o Two examples with 7-cell HG shape cavities (next slide).<br />
• Further impacts limited for lacking of a ILC project role<br />
• Infrastructure stressed and envelope being pushed<br />
oBreakdown & bottleneck increasingly painful because of heavy use & aging.<br />
o Re-investment necessary for sustained competence in high gradient SRF.<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
11
BCP + EP Improves Q of J<strong>Lab</strong> 7-cell Cavities<br />
- A superior surface processing available in-house for CEBAF upgrade cavities…<br />
Both cavities reached quench limit with no detectable X-Ray<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
12
Final Remark: An Opportunity for Developing<br />
Next Generation SRF Processing Capability<br />
Acid<br />
EP<br />
Cathode<br />
Cleaning<br />
Ultrasonic transducer<br />
Detergent<br />
Nozzle<br />
HPR<br />
Wand<br />
<strong>Rongli</strong> <strong>Geng</strong><br />
Director's Review, March<br />
20, 2009, <strong>Jefferson</strong> <strong>Lab</strong><br />
13
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