6/Nov/2012 TTC Meeting 1 Improvement of cavity performance by T-mapping/X-ray-mapping, optical inspection and local grinding Kirk

Outline  Introduction  List of Measured (Fabricating) Cavity  Sequence of Cavity Process at STF  Recent Cavity Performance  3 Important Items for Evaluation and Improvement  Examples of Effect of Local Grinding Technique  Summary 6/Nov/2012 TTC Meeting 2

Measured(Fabricating) Cavities  MHI-01~04Phase-1 (already done)  MHI-05~09S1-Global (already done, except for MHI-08)  MHI-10, 11S0 plan (already done)  MHI-12, 13Quantum Beam (under beam operation)  MHI-14~22Phase-2 (CM-1 assembly will start next year)  MHI-23~26Under  MHI-A, B, CNew fabrication method (presented by F. Inoue)  HIT-01, 02New vendor  TOS-01, 02New vendor  KEK-00, 01In house (presented by T. Saeki)  IHEP-01International Collaboration  AES-001Commissioning test (first test) 6/Nov/2012 TTC Meeting 3

Sequence of cavity process 6/Nov/2012 TTC Meeting 4 Two weeks per one cycle Optical inspection f 0 & Field flatness measurement surface treatment (bulk EP ∼ 100 μ m) annealing pre-tuning V.T. as received from a vendor Optical inspection surface treatment (light EP ∼ 20 or 5 μ m, Degreasing, HPR) Cryomodule test failure success ☠ F.F. > 96%

Cure for Failed Cavity 6/Nov/2012 TTC Meeting 5 V.T. optical inspection local grind EP (20μm) optical inspection EP (5μm) After V.T.After local grindAfter 20 μ m EP equatoriris Radiation monitor measured at top flange of cryostat T-mapX-ray-map

Items for evaluation / improvement of cavity performance 6/Nov/2012 TTC Meeting 6 I.T-mapping/X-ray-mapping II.Optical inspection (Kyoto Camera) III.Local Grinding Machine “San-shu No Jingi” (three imperial treasures)

6/Nov/2012 TTC Meeting 7 T-mapping/X-ray-mapping System 396 carbon resistors 182 PIN photo diodes Radiation monitor

Optical Inspection (Kyoto Camera) 6/Nov/2012 TTC Meeting 8 This tool was developed by Kyoto University and KEK. After some improvements, many defects were observed easily. Before LED improvementAfter LED improvement

Local Grinding Techniques 6/Nov/2012 TTC Meeting 9 equator iris HITACHI method Automatic grinding machine Handy grinding

Categorization of Problematic Defect 6/Nov/2012 TTC Meeting 10 Type I: Defect on bead of Equator Cavity performance is limited certainly (worst case) Type II: Defect on bead of Iris Heavy F.E., sometimes with explosive event Type III: Defect on bead of End-cell/Beam-pipe F.E., sometimes with explosive event, but not understood well Type IV: Defect at other location Not on bead or far away from equator

6/Nov/2012 TTC Meeting 11 Type I: Defect on bead of Equator MHI-05, 09, 10, 15, 16 and TOS-02 were limited by Type I. MHI-05MHI-09MHI-10 MHI-16MHI-15TOS MV/m27.0MV/m 23.8MV/m 22.5MV/m20.8MV/m31.2MV/m

6/Nov/2012 TTC Meeting 12 Type II: Defect on bead of Iris MHI-06, 09, 14, 15, 18, 19, 20, 22 and HIT-02 were limited by Type II. MHI-14MHI-15MHI-18 MHI-22MHI-20MHI-09 When a cavity has such a defect at iris region, the heavy field emission occurs certainly. 20.8MV/m (explosion) 18.1MV/m (explosion) 9.7MV/m 9.0MV/m 31.5MV/m 27.0MV/m (explosion)

6/Nov/2012 TTC Meeting 13 Type III: Defect on bead of End-cell/Beam-pipe Type III probably limited the performance of MHI-07, 11, 18 and 19. Not understood whether these defects are actually problematic, or not. 251° 261° 270° 278° 214° 223° 232° 242° MHI-07MHI-11MHI-18 MHI MV/m (explosion)

6/Nov/2012 TTC Meeting 14 Type IV: Defect at other location MHI-08, 15 and TOS-02 were limited by Type IV. MHI-08MHI-15TOS-02 Irregular pit (edge of equator bead) Bump shape Sputtered ball? MHI-08 had the rare defect after 1st V.T. The defect shape is like a triangle and deep pit. MHI-15 and TOS-02 had a bump defect somewhat away from equator. They are considered as the sputtered ball during the EBW process. 38.2MV/m 31.5MV/m 17.0MV/m

Improvement of cavity performance by local grind 6/Nov/2012 TTC Meeting 15 MHI-14MHI-15 MHI-20 HIT  37 MV/m 23  36 MV/m 9  35 MV/m 35  41 MV/m The radiation level also decreased drastically! Best record in STF

6/Nov/2012 TTC Meeting 16 Summary of Effect of Local Grind at STF Cavity Change of Gradient [MV/m] Location of problematic defect grind methodLimit cause in last V.T. MHI#8 16  27 (1 st  2 nd ) #2 equator (edge) by machine Cell #2 heating (other location) MHI#10 26  20 (2 nd  3 rd ) #1 & #9 equator (on bead) by hand & machine Cell #1 heating (other new defect) MHI#14 13  π (2 nd  3 rd ) iris #8-#9 (edge) by hand Power limit MHI#15 23  >33 (1 st  2 nd ) #2 equator (on bead) by machine Cell #9 heating (new defect) 29  >36 (2 nd  3 rd ) #9 equator (on bead) by machine Cell #9 heating due to heavy F.E. (new defect) 18  π (3 rd  4 th ) iris #3-#4 (edge) iris #7-#8 (edge) iris #8-#9 (edge) by hand & by machine Power limit MHI#16 21  >34 #1 equator (on bead) by machine HOM #2 pre-heating (transient state)

6/Nov/2012 TTC Meeting 17 Summary of Effect of Local Grind at STF Cavity Change of Gradient [MV/m] Location of problematic defect grind methodLimit cause in last V.T. MHI#18 31  10 (1 st  2 nd ) beam pipes (on bead) by machine Cell #1 heating 10  30 (2 nd  3 rd ) iris #2-#3 (edge)by machineCell #2, 3 heating due to heavy F.E. (new defect) 30  36 (3 rd  4 th ) iris #1-2, 2-3, 3-4 by HITACHI method power limit due to heavy F.E. MHI#19 26  37 (1 st  2 nd ) iris #5-#6 (edge) beam pipes (on bead) by machine Cell #4, 5 heating MHI#20 9  29 (1 st  2 nd ) iris #2-3, 3-4, 5-6, 6-7, 8-9 (edge) #5 equator (on bead) beam pipes (on bead) by machinepower limit due to heavy F.E. 29  35 (2 nd  3 rd ) iris #1-2, 2-3, upstream beam pipe by handCell #2 heating by heavy F.E. MHI#22 32  36 (1 st  2 nd ) iris #5-6, 6-7, 8-9 beam pipe (on bead) by machine Cell #1 heating

6/Nov/2012 TTC Meeting 18 Summary of Effect of Local Grind at STF The local grinding technique is very important for the improvement of cavity performance!! Cavity Change of Gradient [MV/m] Location of problematic defect grind methodLimit cause in last V.T. TOS#2 31  >38 (1 st  2 nd ) #7 equator (on bead) by machineCell #7 heating TOS#2 38  >39 (1 st  2 nd ) #8 away from equator (Not on bead) by machineCell #8 heating HIT#2 >35  >41 (1 st  2 nd ) Every iris beam pipes by HITACHI method Power limit with heavy field emission

6/Nov/2012 TTC Meeting 19 Summary of cavity affected by defect I ☻☻☻☻☻ II ☻☻☻☻☻☻☻☻☻ III ☻☻☻☻☻☻ IV ☻☻ MHI-12, 13, 17 and 21 had no problematic defect, and they reached the ILC specification easily! But, the other cavities had the problematic defect, which is categorized to Type I, II, III and IV. And, we had to remove these defects for the improvement of the cavity performance by the local grinding method, because these defects are never removed by the EP. For only Type I, we can evaluate the correlation between the quench field and the defect profile. But, it is difficult to evaluate by the same way for the other three types. † Yellow shows the cavity without problematic defect.

Q 0 – E acc Curve for STF-2 Cavities 6/Nov/2012 TTC Meeting 20 MHI-12, 13, 17 and 21 reached the ILC specification without any grinding, because of no problematic defect.

Max. Achievable Gradient of MHI/HIT 6/Nov/2012 TTC Meeting 21

Max. Achievable Gradient of MHI/HIT 6/Nov/2012 TTC Meeting 22 EP LG+EP MV/m

Comparison of radiation level for EP / LG+EP 6/Nov/2012 TTC Meeting 23 only L.G.+EP cavities only EP (partly L.G.+EP) cavities

Summary  Cavity R&D has been carried out since 2008 at STF.  For evaluation of cavity performance, T-mapping/X-ray-mapping and optical inspection system are very important.  For improvement of cavity performance, local grinding technique is effective, and also suppression of F.E.  Problematic defect is categorized to four types. 6/Nov/2012 TTC Meeting 24

Thank you for your attention 6/Nov/2012 TTC Meeting 25