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 Project June 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) – 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 … 3

IL 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 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 mm End cell design without HOM consideration No equator thickness trimming for EBW Next cavity will adopt equator trimming and biting structure 17 pages of drawings More 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 investigation 9

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 cell Normal length + EBW shrinkage allowance + 1mm RF tuning allowance 10

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 kHz Q ~ 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 <

Half cell No.Height / mm0 mode Freq./ MHz # , # , # , # , # , # , # , # , # , # , # , # , # , # , # , # , # , # , # , # , 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

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Frequency Changing Effects Δf kHz f fmaxfmin half cell ΔL mm half cell LLmaxLmin Notes Related Parameters Horizontal Test Target 1,300,0001,300,530 1,299, RT23 Helium vessel welding & Tuner preload 5001,300,0001,300,530 1,299, After performing the effects Humidity / %40 Cryomodule evacuation 1001,299,5001,300,030 1,298, Pressure / hPa Helium Pressure Decreases 1501,299,4001,299,930 1,298, Vertical test condition 9-cell k(f-L) kHz/mm 350 Temperature Decreases 18851,299,2501,299,780 1,298, formula Half cell k(f-L) kHz/mm 6300 Cavity evacuation 4151,297,3651,297,895 1,296, formula Half cell pi mode k(f-Le) kHz/mm other effects 01,296,9491,297,480 1,296, Free frequency before cryomodule installation Half cell 0 mode k(f-Le) kHz/mm Vertical test Lorentz force detuning -441,296,9491,297,480 1,296, Half cell pi mode k(f-Lir) kHz/mm Vertical Test antenna -181,296,9931,297,524 1,296, Half cell 0 mode k(f-Lir) kHz/mm 1324 Second CP or EP -4001,297,0111,297,542 1,296, Free frequency before vertical test CP,EP,CBP k(thickness – f) kHz / μm -10 Pretuning 01,297,4111,297,942 1,296, Pretuning target. Pretuning included in later steps Vertical test Lorentz force coefficient Hz / (MV/m) 2 -2 Frequency estimation

Frequency Changing Effects Δf / kHz ffmaxfmin half cell ΔL / mm half cell L LmaxLminNotesRelated Parameters Anealing / outgasing1001,297,4111,297,9421,296, Gradient MV/m 35 First CP or EP-8001,297,3111,297,8421,296, Horizontal test LFD k Hz / (MV/m) 2 1 CBP -8001,298,1111,298,6421,297, Second CP EP thickness / μm 40 Equator welding 6341,298,9111,299,4421,298, First CP EP thickness / μm 80 Equator trimming 01,298,2771,298,8081,297, CBP thickness / μm80 Iris welding 3401,298,2771,298,8081,297, Equator EBW one side shrinkage/ mm -0.2 Equator RF tuning allowance ,297,9371,298,4681,297, Equator RF tuning allowance 1 Equator EBW shrinkage allowance -6341,301,1071,301,6381,300, Equator EBW shrinkage allowance 0.2 Iris EBW shrinkage allowance -3401,301,7411,302,2721,301, Iris EBW shrinkage allowance 0.2 original designed half cell pi mode 1,302,0811,302,6121,301, Iris EBW one side shrinkage -0.2 original designed half cell 0 mode 1,282, Equator Trimming0 Equator RF tuning allowance 0 mode ,279,424Half cell tuning0 Equator EBW shrinkage allowance 0 mode -5311,278,8939-cell length error1.5 Iris EBW shrinkage allowance 0 mode 2651,279, Half cell length error cell frequency error250 Half cell frequency error530 Frequency estimation (cont.)

（ 58.16±0.35 mm ， ±0.53 MHz ） cell 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: DB ij (HC i -HC j ) 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 21

Cell matching (cont.) Equator trimming length Make inner cell pair C ij (HC i -HC j ), so finally we have the half cell H i configuration in the 9-cell cavity half cell sequence n The end cells are tuned separately by the similar method 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, (2008)] – 6 frequencies 23

Pretuning Pretuning machine under fabrication Deliver in July 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 pull f0f0 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, H 2 O 2, 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