Rongli Geng ILC Cavity Group Meeting October 25, 2011 Cost Analysis of Cavity Production/Processing Strategies Based on Recent Gradient R&D Results Rongli Geng ILC Cavity Group Meeting October 25, 2011 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

ILC Cavity Gradient Design Values Average operational 31.5 MV/m Allowable spread up to ±20% (25.2 – 37.8 MV/m) Average vertical test qualification 35 MV/m Acceptable spread up to ±20% (28 – 42 MV/m) 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

Baseline Cavity Fab. & Proc. Recipe High purity sheet Nb forming and machining Electron beam welding Light BCP Bulk EP Vacuum furnace heat treatment Rinsing Field flatness tuning Final light EP Post-EP cleaning and high pressure water rinsing Clean room assembly, evacuation and leak check In-situ low temperature bake 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

R&D Results since RDR - I RDR goal: achieve ≥35 MV/m with 80% production yield R&D results since RDR and understanding ~ 20% of cavities will fail at 20 MV/m or lower due to fabrication/material defect (bad news) Yield after one pass processing (or the typical definition of production yield) demonstrated on a global basis at ≥35 MV/m is ~ 30% at ≥28 MV/m, ~ 70%??? (Present global yield plot does not contain yield information at ≥28 MV/m – this should be fixed because 28 MV/m is an important number, i.e. the minimum acceptable gradient for vertical test) 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

ILC 36th Cavity Group Meeting 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

Cost Analysis of the Over Production Model RDR assumes 25% over production (OP), based on assumption of 80% production yield (i.e. the yield after one pass processing) at ≥35 MV/m Total number of cavities need N Total number of cavities produced 1.25*N Total cavities accepted 1.25*N*0.8=1.00*N=N Ideal model for mass production Tolerate 25% produced cavities being “thrown away” 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

ILC 36th Cavity Group Meeting Consideration of the Over Production Model for the Present Cavity Gradient and Spread Design Choice Current ILC design gradient and spread for vertical test acceptance: average 35 MV/m with allowable spread of up to ±20% (28 – 42 MV/m) This is equivalent in stating that cavities qualified to ≥ 28 MV/m are all acceptable Even though the present yield at ≥ 28 MV/m is less than 70% on a global bases, one may expect a yield of 80% at ≥ 28 MV/m can be achieved (next slide) Then the question arises: can we stick to the 20-25% over-production model in line with the RDR? 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

ILC 36th Cavity Group Meeting 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

ILC 36th Cavity Group Meeting Consideration of the Over Production Model for the Present Cavity Gradient and Spread Design Choice (continued) Cost of an accepted cavity: C = Cf + Cp Cf: Fabrication cost Cp: Processing cost Normalize cost to Cf Typical ratio of Cp/Cf=0.2 Based on cost analysis of “production style” ILC cavity processing at JLab (spread sheet available) and typical present day fabrication cost of 9-cell cavities based on small orders For future high-volume production, both Cf and Cp may go down due to value engineering, but the Cp/Cf ratio likely to stay ~0.2 So C=1.2*Cf 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

ILC 36th Cavity Group Meeting Consideration of the Over Production Model for the Present Cavity Gradient and Spread Design Choice (continued) C=1.2*Cf 25% over production Total number of cavities produced 1.25*N Total cost to get needed cavities TC_OP=1.25*N*1.2*Cf = 1.50*N*Cf Reminder: tolerate 25% of produced cavities are “thrown away” after one pass processing Ultimately one needs to know the Gradient Distribution Probability (GDP) to verify whether the current ILC gradient spread choice is compatible with the ILC average gradient choice 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

R&D Results since RDR - II R&D results since RDR and understanding A second pass re-treatment or re-processing is found effective in raising gradient and yield (good news) 100% yield at ≥ 31 MV/m is possible if a data-driven second pass re-treatment/re-processing is allowed (next slide) Three main procedures (all in hand now) for second pass Re-HPR, when cavity is field emission limited after 1st pass Re-EP, when cavity reaches ≥ 25 MV/m but quench limited after 1st pass Repair (local grinding or mechanical barrel polishing of entire inner surface), when cavity is quench limited below ~20 MV/m after 1st pass 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

Effective gradient yield improvement if a 2nd pass RT/P is allowed 16 9-cell cavities based on recent results from US ART groups 94% JLAB + FNAL + Cornell Average gradient 39 MV/m 100% yield at ≥31 MV/m + + Average gradient 39 MV/m AES6 after CBP At FNAL ✔ AES5 After Mechanical Polishing at Cornell ACC15 after at FNAL Rongli Geng LCWS11, 9/26-30, 2008

ILC 36th Cavity Group Meeting Consideration of the Re-treatment Model for the Present Cavity Gradient and Spread Design Choice Reminder: realistically assuming 80% yield at ≥ 28 MV/m after 1st pass Reminder: 100% yield at > 28 MV/m if a data-driven second pass re-treatment/re-processing (RT/P) is allowed Cost analysis if 2nd pass RT/P is allowed Total number of cavities produced N Same as the total number of cavities needed 80% of cavities acceptable after 1st pass 20-25% need 2nd pass RT/P to become acceptable Total cost to get needed cavities (assuming 25% RT/P) TC_RT/P=N*(Cf+Cp)+0.25*N*Cp = N*Cf+1.25*N*Cp=N*Cf+1.25*N*0.2*Cf TC_RT/P= 1.25*N*Cf 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

ILC 36th Cavity Group Meeting Cost Benefit Analysis Significant cost saving benefit by allowing 25% 2nd pass re-treatment or re-processing as compared to allowing 25% over production 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

Additional Benefit from RT/P Further analysis requires knowledge of gradient distribution of probability p(G) p RT/P tends to push p(G) upward, hence higher average gradient 1 G Gr Gu Gr: Rejection limit, below which cavity not acceptable Gu: ultimate limit, above which physically not possible 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting

Next Step and Required Inputs Get GDP from the available data This allows to calculate average gradient Needed for “gradient margin” analysis Get breakdown table of RT/P fractions Needed for refined cost benefit analysis Useful for RT/P strategy to be reflected in TDR Get cost spread sheet for CBP Needed for analysis of cost saving potential to insert CBP into baseline processing recipe 10/25/11, R.L. Geng ILC 36th Cavity Group Meeting