6/Nov/2012 TTC Meeting 2012 @J-Lab 1 Improvement of cavity performance by T-mapping/X-ray-mapping,...

6/Nov/2012 TTC Meeting 2012 @J-Lab

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


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Measured(Fabricating) Cavities MHI-01~04 Phase-1 (already done)

MHI-05~09 S1-Global (already done, except for MHI-08) MHI-10, 11 S0 plan (already done) MHI-12, 13 Quantum Beam (under beam operation) MHI-14~22 Phase-2 (CM-1 assembly will start next

year) MHI-23~26 Under fabrication @Mihara MHI-A, B, C New fabrication method (presented by F. Inoue) HIT-01, 02 New vendor TOS-01, 02 New vendor KEK-00, 01 In house (presented by T. Saeki) IHEP-01 International Collaboration AES-001 Commissioning test (first test)


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Sequence of cavity process


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Two weeks per one cycle

Optical inspection

f0 & Field flatness

measurement

surface treatment

(bulk EP∼100μm)

annealing

pre-tuning

V.T.

as received from a vendor

Optical inspection

surface treatment

(light EP ∼20 or 5μm,

Degreasing, HPR) Cryomodule

testfailur

e

success

☠

F.F. > 96%

Cure for Failed Cavity


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V.T.

optical inspection

local grind

EP (20μm)

optical inspection

EP (5μm)

After V.T. After local grind After 20μm EP

equator iris

Radiation monitor measured at top flange of cryostat

T-map X-ray-map

Items for evaluation / improvement

of cavity performance


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I. T-mapping/X-ray-mapping

II. Optical inspection (Kyoto Camera)

III. Local Grinding Machine

“San-shu No Jingi”(three imperial treasures)


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T-mapping/X-ray-mapping System

396 carbon resistors182 PIN photo diodesRadiation monitor

Optical Inspection (Kyoto Camera)


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This tool was developed by Kyoto University and KEK.After some improvements, many defects were observed easily.

Before LED improvement

After LED improvement

Local Grinding Techniques


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equator

iris

HITACHI method

Automatic grinding machine

Handy grinding

Categorization of Problematic Defect


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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


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Type I: Defect on bead of Equator

MHI-05, 09, 10, 15, 16 and TOS-02 were limited by Type I.MHI-05 MHI-09 MHI-10

MHI-16MHI-15 TOS-02

27.1MV/m 27.0MV/m23.8MV/m

22.5MV/m 20.8MV/m 31.2MV/m


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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-14 MHI-15 MHI-18

MHI-22MHI-20 MHI-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)


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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-07 MHI-11 MHI-18

MHI-19

18.1MV/m(explosion)


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Type IV: Defect at other location

MHI-08, 15 and TOS-02 were limited by Type IV.MHI-08 MHI-15 TOS-02

Irregular pit(edge of equator bead)

Bump shape 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/m31.5MV/m17.0MV/m

Improvement of cavity performance by local grind


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MHI-14 MHI-15

MHI-20 HIT-02

15 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


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Summary of Effect of Local Grind at STF

Cavity Change of Gradient [MV/m]

Location of problematic

defect

grind method

Limit cause in last V.T.

MHI#8 16 27(1st 2nd)

#2 equator(edge)

by machine

Cell #2 heating (other location)

MHI#10 26 20(2nd 3rd)

#1 & #9 equator(on bead)

by hand & machine

Cell #1 heating(other new defect)

MHI#14 13 >37 @π(2nd 3rd)

iris #8-#9(edge)

by hand Power limit

MHI#15

23 >33(1st 2nd)

#2 equator(on bead)

by machine

Cell #9 heating(new defect)

29 >36(2nd 3rd)

#9 equator(on bead)

by machine

Cell #9 heating due to heavy F.E.(new defect)

18 >36 @π(3rd 4th)

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)


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defect

grind method


MHI#18

31 10(1st 2nd)

beam pipes (on bead)

by machine Cell #1 heating

10 30(2nd 3rd)

iris #2-#3 (edge)

by machine Cell #2, 3 heating due to heavy F.E.

(new defect)

30 36(3rd 4th)

iris #1-2, 2-3, 3-4 by HITACHI method

power limit due to heavy F.E.

MHI#19 26 37(1st 2nd)

iris #5-#6 (edge)beam pipes (on

bead)

by machine Cell #4, 5 heating

MHI#20

9 29(1st 2nd)

iris #2-3, 3-4, 5-6, 6-7, 8-9 (edge)

#5 equator (on bead)beam pipes (on bead)

by machine power limit due to heavy F.E.

29 35(2nd 3rd)

iris #1-2, 2-3, upstream beam

pipe

by hand Cell #2 heating by heavy F.E.

MHI#22 32 36(1st 2nd)

iris #5-6, 6-7, 8-9beam pipe (on

bead)

by machine Cell #1 heating


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The local grinding technique is very important for the improvement of cavity performance!!



defect

grind method


TOS#2 31 >38(1st 2nd)

#7 equator(on bead)

by machine

Cell #7 heating

TOS#2 38 >39(1st 2nd)

#8 away from equator

(Not on bead)

by machine

Cell #8 heating

HIT#2 >35 >41(1st 2nd)

Every irisbeam pipes

by HITACHI method

Power limit with heavy field emission


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Summary of cavity affected by defect

05

06

07

08

09

10

11

12

13

14

15

16

17

18

19

20

21

22

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.

Q0 – Eacc Curve for STF-2 Cavities


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MHI-12, 13, 17 and 21 reached the ILC specification without any grinding, because of no problematic defect.

Max. Achievable Gradient of MHI/HIT


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Max. Achievable Gradient of MHI/HIT


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EP EP EP EPLG+EP LG+EP LG+EP LG+EP LG+EP LG+EP LG+EP LG+EP

40.7 36.2 36.6 35.7 33.8 38.4 36.2 37.2 35.1 38.9 35.8 40.9 MV/m

Comparison of radiation level for EP / LG+EP


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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.


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Thank you for your attention


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6/Nov/2012 TTC Meeting 2012 @J-Lab 1 Improvement of cavity performance by T-mapping/X-ray-mapping,...

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