d.proch, gde meeting peking, feb.07 questions by ch. adolphsen timeline of when the gradient goal...

D.Proch, GDE meeting Peking, Feb.07

Questions by Ch. Adolphsen

• Timeline of when the gradient goal and processing recipe is frozen

• Plan for bringing industry on board (XFEL will be a big factor in this case)

• List of engineering support required (in FTEs) to finalize the dressed cavity designs and to interact with industry to build them

• Plan for how the continuing R&D program will mesh with these activities


Q1:Timeline of when the gradient goal and processing recipe is frozen

• Guess the gradient goal is 35 / 31.5 MV/m• Guess the way to this goal is S0/S1

– Tight loop effort, production type effort, basic R&D– Plus exchange of resonators in the three regions

• The tight loop effort and lab exchange is a good method to overcome lab depended deficiencies and/or to detect uncovered male functions in the lab infrastructure– But the required effort in resources seem to be

underestimated


My guess of resources needed for tight loop strategy

• Present multi-cell cavity measurements result in unpredicted scatter (FE, sometimes low quench)– The preparation chain of chemistry, HP rinsing & assembly must

be analyzed• Meaningful procedures after one good cold test:

– Repeat assembly (3 x)– Repeat HP rinsing & assembly (3x)– Repeat chemistry & HP & assembly(3x)

• Do this procedure for 6 cavities in order to pick 3 resonators for regional exchange

• Each region: – Build 6 cavities– 18 cold tests with own cavities– Another 32 cold tests with exchange cavities– In total 50 cold test at each regional infrastructure


Example of required infrastructure:DESY H3

• Active man power (FTE):– 8 EP, BCP, HPW, assembly (Axel Matheisen)– 3 cryo operation– 2 cavity inspection, tuning, assembly– 2.5 cold measurement, T mapping– 2 cavity data bank, server, software– Total 17,5 FTE

• Cavity throughput in 2006– 74 cold tests with 49 TESLA 9-cell, 25 single cell +

gun cavities


Conclusion at this point

• This R&D effort must be duplicated for the production like effort– May be not by 100%– But with new companies additional measurement and

diagnostic effort must be expected• R&D on single cells should be synchronised with

multi-cell activities• This demanding S0/S1 plan requires more

resources than are visible at this point in time– In this case de-scoping or extending the schedule

should be done in order to present a trustable plan


Q2: Plan for bringing industry on board (XFEL will be a big factor in this case)

• There are several EU companies with long time experience in cavity production

• DESY has incorporated industry in planning for– Cost reduction in Cavity fabrication– Cost reduction in cavity preparation

• XFEL is pushing for – Cavity production with performance guaranty rather

than build to print– Transfer of EP to industry

• It is more than natural to identify mutual benefit for both projects in a MoU and thus asure maximum synergetic benefit.


Q3: List of engineering support required (in FTEs) to finalize the dressed cavity designs and to interact with industry to build them

• Here a (not complete) list of issues based on XFEL preparation, to be discussed:– Nb specification 0.2 MY– Cavity structural calculations, 0.4 MY

stiffness– Completion of cavity drawing, 3D 0.3 MY– Detailed cavity fabrication spec. 0.5 MY– QA plan cavity fabrication, 0.4 MY

tolerances– Establish EDM file for cavity fabr. 1.0 MY– Design (+built) T-mapping 0.8 MY– Design (+built) eddy current scanner 1.5 MY

& tuning machine


Marc`s questions for discussion

• What RD priorities are indicated by the RDR cost? Are these different from ongoing priorities and efforts?– Cavity production yield is too low ===> S0

• Are the cost interactions of ACD known well enough to allow this prioritization?– Large / Single crystal cavities could have high gain at lower

cost; but statistics and quantitative cost numbers are missing

• Is the RDR baseline cost estimate useful for this process or is more work needed simply to refine the RDR estimate in order to prioritize the RD? Much of the RDR technical is 'immature'.– The RDR is our best guess so far, but we have to wait for S0

results before refine RDR


Marc`s questions for discussion, cont.

• How do the above interact with the design work now underway at DESY– Lower XFEL gradient might direct in different cavity

preparation technology; but involvement of industry is THE guideline for ILC

• When is down-selection information needed? What is the latest 'possible' moment at which decisions can be taken that minimizes the disruption to the most effort-intensive parts of EDR? For example CFS. I suspect the answer is now for some of the most important selections.– Marc: please give your vision

• Each RD task can be categorized based on the answer to above. How is this best done? – We have to go through the list of RD tasks with our updated

S0 knowledge, when available


Marc`s questions for discussion, cont.

• Each RD task will be funding limited, many severely. Are there some which will then necessarily come too late to be part of the EDR? What does this mean for RD funding prioritization? What does it mean for the EDR schedule? – S0 is a honest and necessary attempt to

understand the „mystery“ of performance scatter (Eacc, FE); without positive result any schedule pressure is meaningless. Unless we are willing to accept to reduce Eacc to XFEL performance??!!


Additional comment to Marc`s questions

• How to react if a new and promising technology comes over the horizon?

• Example of large grain / single crystal cavity– Obvious cost savings in Nb production– Less or no grain boundaries will reduce or

eliminate negative grain boundary effects– EP could be substituted by BCP (single grain)

G. Müller, 15.11.2006 CARE06, Frascati

Field emission scanning microscope (FESM)

PID voltage regulation

FUG power supply 5 kV, 50mA

LabVIEWprograms

Piezo motion controller PI- 920126

Motion controller Newport MM4006

PicoamperemeterKeithley 6485

3D Piezotranslator 40nm/VXYZ-motors (100nm step)

UHV system typically at 2·10-7 Pa

LabVIEW automated scans of U(x,y) for 2 nA

Scanning speed: (100×100) pixels in 1 hr

I/V curves and localization of stable emittersI/V curves and localization of stable emitters

Several W-anodes & samples


Profilometer with AFM and SEM with EDX

combined with atomic force microscope AFM

Scanning speed: (100×100) pixels in 1 min

Additional surface analysis of whole samples and relocalized areas of enhanced FErelocalized areas of enhanced FE

Optical profilometer with lateral resolution of 2 µm and height resolution of 3 nm

Scanning electron microscope SEM (XL-30) with energy dispersive X-ray analysis EDX


Emitter distribution on single crystal Nb after BCP/HPR

Alternative approach for mirror-like surfacesmirror-like surfaces: large crystal Nb+BCP30µm/HPR

PID-regulated voltage maps U(x,y) for 1 nA scanned area = 7.57.5 mm2

flat W-anode Øa = 100 µm anode voltage U = 4800 V electrode spacing z = 32 µm z = 24 µm

no emission @ 120MV/m

2 emitters @ 150MV/m 5 emitters @ 200MV/m

best FE performance of all Nb samples yetbest FE performance of all Nb samples yet


Effect of DIC on particulate and protrusion emitters

3.3 × 10-16 7.2 × 10-20S (m2)

9.6 × 10-121.6 × 10-20S (m2)

31.2147

17.4166.7

103.348.5 Eon (MV/m)

HPR+DICHPRProtrusionEon(1nA) = 77 MV/m

S particulate removed by DICS particulate removed by DIC

FE of protrusion much reduced by DICFE of protrusion much reduced by DIC

= h/r ~ w/rS ~ r2

w

r


Effect of DIC on a flake-like emitter with exposed edge

emitter of ~ 20 µm size destroyed by DICemitter of ~ 20 µm size destroyed by DICremnants emitting at higher Eon!

EDX: no foreign element detected EDX: no foreign element detected (probably oxide of Nb)(probably oxide of Nb)

2.4 × 10-13 1.2 × 10-15S (m2)

8.3 × 10-132 × 10-17S (m2)

38.051.2

35.467.4

62.854.3 Eon (MV/m)

HPR+DICHPRemitter


Correlation between FE onset field and emitter size ?

0.1 1 10 100

40

60

80

100

120

140

160

180

200

Eo

nse

t(2n

A)

scratch width or particle size (m)

scratch width (19) particle average size (19)

Eacc

= 40 MV/m

based on FE measurements and SEM analysis of 38 field emitters

(ILC)

30 MV/m (XFEL)

Evidence for correlation Evidence for correlation fast FE quality control by emitter sizefast FE quality control by emitter size

8 µm2.5 µm


Introduction

• Fourth cavity production series:- 30 nine-cells fabricated by Zanon company (incl. 3 prototypes with irregularities during fabrication)- 15 cavities of Teledyne Wah Chang Nb; 14 cavities of Tokio Denkai Nb; 1 mixed cavity (Z111)- delivery from mid 2004 to end of 2005

• “Standard” cavity preparations:- first EP of 150µm, outside etching, 800C firing,i) final EP of (40 - 50) µm, test, 120C bake, testii) final BCP (“EP+”) of 10 µm, test, (120C bake, test) => 8 cavities


Data analysis

• Comparison of maximum and usable gradient after various preparations

• Usable gradient in vertical test: Lowest value of gradient for either

- quench - x-rays exceed 10-2 mGy/min - or rf losses exceed 100 W in cw operation (comparable to app. 1

W pulsed)

=> limitation of cryogenics !!

• Analysis of- final EP- vs. BCP (“EP+”) - treatment- comparison before and after 120C bake

• Not strictly following “first/last/best test” like in data base=> Choice of “reasonable” test (see add. transparencies) (e.g. ¾ of all cavities first test used before bake)


Usable gradient before and after bake

• Usable gradient before and after after 120C bake:Usable gradient before + after bake

28.7

24.9 24.5

32.6

28.3

24.7

31.029.6 29.7 29.4

14.5

23.5

0

5

10

15

20

25

30

35

40

Cavity

Max

. Gra

die

nt


Summary of Results

• Broad scatter of both, Eacc,max and usable gradient in vertical

and Chechia tests !!!

• Final EP:7 of 17 tested cavities are quench limited below 25 MV/m !!=> 3 cavities (Z83 (pre-series with fabrication problems), Z86 + Z93) with “real” quench=> 4 cavities have field emission => FE induced quench e.g. Z104 ??=> only 2 (Z83, Z104) of these cavities had T-mapping investigation !!!

• Final BCP (“EP+”):7 of 8 tested cavities are limited between 26 MV/m and 30 MV/m=> very reproducable ??=> but Z111 only shows 16 MV/m limited by quench in equator region !!


Summary of Results II

• 120C-bake often gives no improvement in Eacc due to quench

limitation !!(but nevertheless some improvement in Qo (cryo losses!!))

• 3 cavities lost significant performance from vertical test to Chechia => assembly and cleaning procedure!!

• Many cavities show significant field emission => preparation process not reproducable !!

• re-processing with only HPR helps:Z103 little improvementZ87 LH welding + HPR, vertical test => some improvementZ94 big improvement!!

D.Proch, GDE meeting Peking, Feb.07Jacek Sekutowicz, DESYOctober 18th, 2006

Ep/Eacc=1.894

Bp/Eacc=4.308 mT/(MV/m)

(R/Q)=104.6 Ohm

G=277.43 Ohm

D.Proch, GDE meeting Peking, Feb.07Jacek Sekutowicz, DESYOctober 18th, 2006

Ep/Eacc=1.71

R=42mm

Ep/Eacc=1.99 Ep/Eacc=1.74

R=40.03mm

Bp/Eacc=4.23 mT/(MV/m)

(R/Q)=1011.5 Ohm

G=271.56 Ohm

All data by p-p 2% FF


0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50 60

KEK & TESLAKEK singleDESY single

Eacc [MV/m]

KEK Eacc = 43±5 MV/mTESLA Eacc = 34±4 MV/m

0

0.2

0.4

0.6

0.8

1

1.2

500 1000 1500 2000

KEK & TESLA

KEK singleDESY single

Hp [Oe]

KEK Hp = 1538± 185 OeTESLA Hp = 1460±147 Oe


Comparison of DESY and KEK single results

KEK recipe

CBP+CP+Anneal+EP+HPR+Baking

DESY recipe

EP+Anneal+EP+HPR+Baking

0

1

2

3

4

5

6

50 100 150 200

Nu

mb

er

B peak [mT]

AVE. =146STDEV =15

DESY

FE, Q-slope are removed

BCP are removed

N=12

N=32Eacc=43.5+-4.8MV/m for ICHIRO

Eacc=37.3+-4.1MV/m for TESLA

Eacc=35.2+-3.6MV/m for TESLA

EP technology is close between KEK and DESY. But still there is 6% margin for DESY, if they use KEK recipe.

DESY can be push up the gradient about 6%, which guaranteed the BCD acceptance performance with high yield(>90%).

Included pilot run

0

1

2

3

4

5

6

50 100 150 200

Nu

mb

er

B peak [mT]

AVE. =155STDEV =17

KEK

Using DESY/ Detlef Reschke’s data.

d.proch, gde meeting peking, feb.07 questions by ch. adolphsen timeline of when the gradient goal...

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