9-cell Cavity R&D Progress and Test Plan

GAO Jie (高杰 ) ZHAI Jiyuan (翟纪元 ) YU Jing (玉静 ) LI Zhongquan (李中泉 )

ZHAO Tongxian (赵同宪 ) GU Jun (谷俊 ) HOU Mi (侯汨 ) SUN Yaolin (孙耀霖 )

ZHAO Facheng (赵发成 ) ZHANG Jingru (张敬如 ) Institute of High Energy Physics

CHEN Jinzhe (陈晋哲 ) Beijing Hejieli Science and Technology Development Co. Ltd.

YUAN Hong (袁鸿 ) Beijing Institute of Aviation Materials

First Mini-Workshop on IHEP 1.3 GHz Superconducting RF ProjectJune 10, 2009

IHEP, Beijing, China

Outline

• R&D plan & schedule• Cavity shape and material• Bare tube cavity fabrication progress• Surface preparation plan at IHEP• Vertical test issues at KEK STF• End cell and HOM coupler design

2

R&D Plan and Goal

• Bare tube 9-cell cavity IL9-0 (with pumping port)– Low loss shape, large grain niobium (Ningxia)– Fabricate and surface treat at IHEP, vertical test at KEK STF– 20 MV / m in the end of 2009 (Chemical polishing only)– 25-30 MV / m in 2010 after several test loops at IHEP– Electro-polishing in KEK STF as an alternative

• Full end group 9-cell cavity– Low loss shape, large grain niobium (Ningxia)– Start fabrication in late 2009, test in the middle of 2010– 25 MV / m in 2010– Dress and horizontal test (25 MV / m) at IHEP in 2011

• Several more 9-cell cavities in 2010-2012…

3

IL9-0 2009 Schedule

• May 15 – July 30 ： Cavity EBW– First two dumbbells in this week

• Aug. 1 – Sept. 30 ： Surface treatment in IHEP– Surface inspection, CBP, CP, Annealing, Pretuning, HPR

• Oct. 20 – Dec. 20 ： Vertical test in KEK STF– more surface treatment and pretuning in STF

4

Cavity Shape and Material

• Inner cell: Low loss shape– modified from the original low loss type in 2005

• Single cell cavity achievement– 3 Ningxia large grain cavities, made by KEK,

reached 47 MV/m by EP– 2 Ningxia large grain cavities, fabricated and

treated in IHEP, tested in KEK in March 2008 , reached 40 MV/m by CBP+CP

– 1 of the 4 fine grain cavities for reference study

5

LG LG

FG FG FG

FG

Large Grain Niobium• Advantages:

– no Q-slope at high gradient with only CP, may eliminate EP– Directly slicing from ingot, may reduce the material contamination

and cost (by multi-wire slicing)

• Disadvantages:– Mainly in fabrication and EBW: earring after deep drawing, big grain

steps, bad roundness and wall thickness uniformity…

6

9-cell cavity design

Total Length: 1247 mmEnd cell design without HOM considerationNo equator thickness trimming for EBWNext cavity will adopt equator trimming and biting structure

17 pages of drawingsMore detail discussions later

7

End Group

8

End plate and stiffening rings to strengthen the end cell

Pumping port for evacuation before and during vertical test

Pump the cavity at 2K, necessary?

STF flanges and Helix gaskets

Niobium Sheets Quality Assurance

Properties:• Chemical composition• RRR ~ 430• elongation, hardness• need more specifications and

tests

Defect Inspection:• Eddy current scan • Ultrasonic scan• got some initial results, under

further investigation9

Fabrication

Degrease and ultrasonic clean with Miro-90,

rinse

Equator roundness reshaping

Deep drawing and coining

Half cell after drawing(earring due to large grain)

Trimming

Trimmed half cellNormal length + EBW shrinkage

allowance + 1mm RF tuning allowance10

3D measurement, spring back and reshaping

Equator Roundness 0.595mm Iris Roundness 0.388mm

0°180°

270° 90°

Half cell 12# CMM CMM on 4 test half cells

Trimming jig(locating error due to spring back)

Dumbbell Reshaping jig(stiffening ring position unchanged)

Dumbbell contour, height & parallel reshaping

~1.5 mm

11

Half cell dimension and frequency measurement

12

New frequency measurement fixture

Frequency stable in kHzQ ~ 4500

Radial slots and elastic washer for good RF contact

Antenna length optimized for small perturbation and noise

The old plain and hard contact need much more press and good equator surface flatness

Easy setting and accurate measurement

This method is originated from Timergali of FNAL.

measurement with the old fixture: Freq. jump ~ 30 MHz, Q < 900

13

58.0 58.2 58.4 58.6 58.8 59.0 59.2 59.4 59.6 59.8 60.0 60.2 60.4 60.6 60.80

2

4

6

8

10

12

14

16

18

Design 59.09 mm

Nu

mb

er

of h

alf

cells

Half cell length / mm

guo zhao chen zhao/e total

Mean 59.36 mm

Half cell No. Height / mm 0 mode Freq./ MHz

#07 59.14 1,277.935 #08 59.90 1,281.722 #09 59.42 1,278.667 #10 58.29 1,281.501 #11 59.12 1,277.938 #12 59.70 1,277.574 #13 59.50 1,278.406 #14 59.69 1,277.871 #18 59.00 1,279.563 #19 58.66 1,278.512 #20 58.96 1,278.981 #21 60.60 1,278.994 #23 59.45 1,275.428 #24 59.39 1,276.386 #25 59.38 1,275.623 #27 59.67 1,277.149 #28 59.20 1,274.419 #29 59.72 1,278.763 #30 59.51 1,277.715 #31 59.55 1,277.553

1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286

0

1

2

3

4

5

6

7

8Tuning Target1279 MHz

#18#24

#23,25 #8,10

Theoretical1277 MHz

Nu

mb

er

of h

alf

cells

Half cell frequency / MHz

Mean1278 MHz

75%

#28

Half cell height and frequency data

14

Half cell CP and EBW

15

• (Degreasing and ultrasonic cleaning) • CP 20 μm (40-60℃!) (away from silicon products, plastics like Teflon, fingerprint

… !)

• Rinse with UPW until 10 MΩ cm• Dry in class 10 clean room• Ultrasonic clean and 3 μm CP at iris, rinse• Put in container filled with argon gas• Send to BIAM for EBW (many details…)

– Refer to DESY specification 2005

f / MHz

L / mm

1299.500

1300.000

1297.350

1

102

3

4

5

6

EP or CP

Pressure

Permittivity

Temperature

LHe Pressure

Cryomodule Vacuum

Pretuning Target

Cavity in Cryomodule

Iris Shrinkage& Deformation

DumbbellTrimming

Equator Shrinkage

Pretuning

Pretuning LengthTolerance Range Half cell Length

HALF CELLS9-CELL CAVITY

7

8

9

Stiffening Ring Shrinkage

DumbbellDeform and Reform

Annealing

EP or CP

CBP

15

11

12

13

14

DUMBBELLS

Dumbbell Reform Length Target

Dumbbell LengthTarget

Measurable Frequency Point

Unmeasurable Frequecy Point

Controllable Frequecy Change

Uncontrollable Frequency Change

Tuning Available Region

EP or CP limit

Horizontal Test Tuner Tuning Range, typically Slow tuner 500 kHz, Piezo 1 kHz

Cavity Length Range(~ 2 mm)

Field Flatness Tuning

Cavity Vertical Test

VT Power Source Range

0 Tuner Preload (HT)

5 to 2

0

-1

-2

-1

13

Key Frequency Point

Final Frequency Target

Cavity Frequency Change and Control

16

Frequency Changing Effects Δf kHz

f fmax fminhalf cell ΔL

mm

half cell L Lmax Lmin Notes Related

Parameters

Horizontal Test Target 1,300,000 1,300,530 1,299,470 57.69 58.04 57.34 RT 23

Helium vessel welding & Tuner preload

500 1,300,000 1,300,530 1,299,470 0.08 57.69 58.04 57.34 After performing the

effects Humidity / % 40

Cryomodule evacuation 100 1,299,500 1,300,030 1,298,970 0.00 57.61 57.96 57.26 Pressure / hPa 101.325

Helium Pressure Decreases 150 1,299,400 1,299,930 1,298,870 -0.02 57.61 57.96 57.26 Vertical test condition 9-cell k(f-L)

kHz/mm 350

Temperature Decreases 1885 1,299,250 1,299,780 1,298,720 -0.05 57.63 57.98 57.28 formula

Half cell k(f-L) kHz/mm 6300

Cavity evacuation 415 1,297,365 1,297,895 1,296,834 -0.02 57.68 58.03 57.33 formula

Half cell pi mode k(f-Le) kHz/mm -3170

other effects 0 1,296,949 1,297,480 1,296,419 0.00 57.70 58.05 57.35 Free frequency before

cryomodule installationHalf cell 0 mode k(f-Le) kHz/mm -2657

Vertical test Lorentz force detuning -44 1,296,949 1,297,480 1,296,419 0.00 57.70 58.05 57.35 Half cell pi mode

k(f-Lir) kHz/mm -1700

Vertical Test antenna -18 1,296,993 1,297,524 1,296,463 0.00 57.70 58.05 57.35 Half cell 0 mode

k(f-Lir) kHz/mm 1324

Second CP or EP -400 1,297,011 1,297,542 1,296,481 0.00 57.70 58.05 57.35 Free frequency before

vertical test

CP,EP,CBP k(thickness – f)

kHz / μm-10

Pretuning 0 1,297,411 1,297,942 1,296,881 0.00 57.70 58.05 57.35

Pretuning target. Pretuning included in later

steps

Vertical test Lorentz force

coefficient Hz / (MV/m) 2

-2

Frequency estimation

Frequency Changing Effects Δf / kHz f fmax fmin

half cell ΔL

/ mm

half cell L Lmax Lmin Notes Related Parameters

Anealing / outgasing 100 1,297,411 1,297,942 1,296,881 -0.06 57.70 58.05 57.35 Gradient MV/m 35

First CP or EP -800 1,297,311 1,297,842 1,296,781 0.00 57.76 58.11 57.41 Horizontal test LFD k Hz / (MV/m) 2 1

CBP -800 1,298,111 1,298,642 1,297,581 0.00 57.76 58.11 57.41 Second CP EP thickness / μm 40

Equator welding 634 1,298,911 1,299,442 1,298,381 -0.20 57.76 58.11 57.41 First CP EP thickness / μm 80

Equator trimming 0 1,298,277 1,298,808 1,297,747 0.00 57.96 58.31 57.61 CBP thickness / μm 80

Iris welding 340 1,298,277 1,298,808 1,297,747 -0.20 57.96 58.31 57.61 Equator EBW one side shrinkage/ mm -0.2

Equator RF tuning allowance -3170 1,297,937 1,298,468 1,297,407 1.00 58.16 58.51 57.81 Equator RF tuning allowance 1

Equator EBW shrinkage allowance -634 1,301,107 1,301,638 1,300,577 0.20 57.16 57.51 56.81 Equator EBW shrinkage allowance 0.2

Iris EBW shrinkage allowance -340 1,301,741 1,302,272 1,301,211 0.20 56.96 57.31 56.61 Iris EBW shrinkage allowance 0.2

original designed half cell pi mode 1,302,081 1,302,612 1,301,551 56.76 57.11 56.41 Iris EBW one side shrinkage -0.2

original designed half cell 0 mode 1,282,081 56.76 Equator Trimming 0

Equator RF tuning allowance 0 mode -2657 1,279,424 Half cell tuning 0

Equator EBW shrinkage allowance 0 mode

-531 1,278,893 9-cell length error 1.5

Iris EBW shrinkage allowance 0 mode 265 1,279,158 58.16 58.51 57.81 Half cell length error 0.35

9-cell frequency error 250

Half cell frequency error 530

Frequency estimation (cont.)

57.0 57.5 58.0 58.5 59.0 59.5 60.0 60.5 61.0

1275

1280

1285

1290

1295

1300

1305

1310

Tuning Target

Dumbbell Equator Trimming

mode

Fre

qu

en

cy /

MH

z

Half cell Length / mm

0 mode

Cavity Cell Pretuning Region

57.0 57.5 58.0 58.5 59.0 59.5 60.0 60.5 61.0

1275

1280

1285

1290

1295

1300

1305

1310

1270

1271

1272

1273

1274

1275

1276

1277

1278

1279

1280

1281

1282

1283

1284

1285

1286

012345678T

unin

g T

arge

t12

79 M

Hz

#18

#24

#23,

25#8

,10

The

oret

ical

1277

MH

z

Number of half cells

Ha

lf ce

ll fr

eq

ue

ncy

/ M

Hz

Mea

n12

78 M

Hz

75%

#28

（ 58.16±0.35 mm ， 1297.937±0.53 MHz）0 0

0 L L

tan ( ) ( )

2 2

f ff

f Q Q

min.

max.

Phase

Phase

Field Flatness [%] 1 100%

1

N

100%

cmax. cmin.

ci

E E

Ecell frequency difference and filed flatness ， 99.96%

Dumbbell and cavity tuning

19

Dumbbell matching• Criterion

– Similar iris average diameter and wall thickness– Exclude the pre-matched* cell-pair C’

ij

*Pre-matching: cell matching before dumbbell welding and measurement, supposing the length of the half cell does not change due to reshaping.

• Make dumbbell pair: DBij (HCi-HCj)i is the marker numbers on the half cells

• Will be done next week

20

Cell matching• Criterion

– Similar equator diameter and thickness– Smallest cell frequency deviation

– Pretuning available range

2151

3

( 3,5...15 half cell nummin ber of the 9-ce 2

ll cavity)n n

n

f ff n

min

max

1

min 1 max1

: measured half cell length after dumbbell welding, reshaping and equator trimming

: minimum target cell length

: maximum target cell length

: measured hal

2

n

c

c

n

n n

c n n c

L

L

L

f

f ff

L L L Lk

1

f cell frequency after dumbbell welding, reshaping and equator trimming

: cell target frequency

: cell frequency length coefficient

f

k 21

Cell matching (cont.)

• Equator trimming length

• Make inner cell pair Cij (HCi-HCj), so finally we have the half cell Hi configuration in the 9-cell cavity half cell sequence n

• The end cells are tuned separately by the similar method

'

2

'1

1 2

'

: half cell length after dumbbell welding and reshaping

: half cell frequency equator trimming coefficient

( )

i

i ii

i i i

L

k

k L L f fL

k k

L L L

22

Dumbbell frequency measurement

• Dumbbell π mode and 0 mode frequency• Determine the individual half cell frequency with perturbation

method [Sun An etc., RSI 79, 104701(2008)]

– 6 frequencies

23

Pretuning

• Pretuning machine under fabrication• Deliver in July 2009• 9-cell copper cavity for machine test• Machine design parameters

– resolution ： 2 μm （ 9-cell cavity freq. change 600 Hz）– max. clamp plates distance ： 2 cells– max. tuning length ： 8 mm– max. force ： 10 kN– displacement sensor ： electronic meter– stress sensor ： N/A– CW frequency and phase shift measure

with N.A. for field flatness bead pull0 0

0 L L

L

tan ( ) ( ),

2 2

30 , 100kHz, 3751(1.3GHz)

f ff

f Q Q

f Q

f0

Ψ

24

Surface Preparation Plan

• Install in stainless steel jig• CBP 150 μm (must do due to large grain steps, inner surface inspection)

• Ultrasonic degreasing and rinsing• First CP and rinsing (inner 80 μm, outer 20 μm)

– Close loop, acid temperature control

• Annealing• Pretuning• Install in vertical test titanium jig and degreasing• Flange CP and Second CP 20 μm• Hot bath rinsing (degreaser, H2O2, alcohol for EP)*

• HPR and dry in class 10 clean room• Fill with Argon gas (what gaskets?) and shipping to KEK STF

25

Vertical test issues at KEK STF• Jig dimension and interfaces

– Hanging holes, HPR interface holes– VT hanging stand holes

• Pretuning (clamp plates? others?)• CP (must, where to do?)• Annealing (if needed, STF Ti box)• EP (if needed, cathode rod diameter?)

• HPR• Input coupler and antenna (use STF’s, coupling check?)• Helix gaskets (reliable but expensive, easy to demount? use STF’s?)

• Pumping port transition• T-mapping• Inspection of inner surface (Kyoto camera rod diameter?)

HPR

VT

Hanging holes or hanging rings?

26

Online pumping during vertical test?

• At low temperature, the cryo-pumping of the cavity overtakes the online pumping.

• Without online pumping, the increased residual gas is 1.25×10-3 Torr·L, which will cause a negligible increment on the adsorbed molecule number of the cavity surface.

• Maybe the online pumping can be omitted.

• More details in the memo “About online pumping during vertical test” by XIAO Qiong (肖琼 ) of the vacuum group

27

Vertical test time and plan

• STF available test time (several choices between Oct. and Dec.) :– ? – ?

• Drawings (flanges), interfaces and jig fixed: this meeting• Pretuning clamps fabrication: IHEP, July• CP and EP issues: KEK, August• Input coupler and antenna: KEK, June• Helix gasket: KEK, June• Pumping port transition: IHEP, July• T-mapping and inspection: KEK and IHEP, September

28

Full end group 9-cell cavity design and HOM coupler simulation

29

Summary

• IHEP’s first 9-cell cavity will finish fabrication and EBW in July , and hope to get the first test result at the end of 2009 in collaboration with KEK STF. This will be a milestone.

• Large grain niobium cavity fabrication has many special issues, dimension and frequency control is important and needs more investigation.

• SCRF facilities upgrade should be promptly driven by the cavity R&D progress and requirement, which is urgent for sustainable R&D at home

30