SRF Surface Preparation Technique

Transcription

1 SRF Surface Preparation Technique for High Gradient Superconducting Cavities A.Matheisen Deutsches Elektronen Synchrotron DESY Hamburg Germany For TTF/TESLA/XFEl community

2 Experiences for this preparation techniques gained on TTF / Tesla cavities Cavity data Standing wave structure No of cells 9 fo=1,3 Ghz Active length m HOM Couples 2 Power coupler 1 R/Q= 1036 ohm E p /E acc = 2.0 B peak /E acc =4.26 (mt/mv/m) Accelerator mode TM 010 Pi mode Power transfer KW pulsed (10 Hz) KW@35 MV/m

3 Toolboxes for cavity preparation Inputs coming form TTF collaborations CEA-Saclay/ CERN/ INFN / KEK Cleanroom Degreasing and Rinsing Clean water supply Chemistry Assembly / Personal Procedures High pressure rinsing

4 TTF Cleanroom Ground space assembly area Class m2 Class m2 Class m2 View on chemistry area View on cl 10 assembly area No 1 View on cl 100 area (storage of cavities )

5 Clean water supply Closed loop 23l/min at 4bar Liquid particle counter Ro 1400l/h L 0,5-1 µs Reservoir 4000l Polisher 25l/min L>=18 Mohm cm 0,4 µm filter UV light bacteria Point of use L>=18 Mohm cm µm filter 20l/min

6 Degreasing and Rinsing Removal of Grease, particulates, residues from former treatments UPW feed line Ultra Clean water (>= 18 Mohm cm ) +detergent ( Ticopur ) concentration 3%@Temperature 45 C 200l basin Circulation pump Filter unit Specifics: Ultrasound power: 10W/liter Circulation: system with 2 µm inline filter Volume: 200l Circulation: 40 l/min US cycle 5 Min circulation and warm up of item 5 Min US sound + circulation 5 Min US sound NO circulation 5 Min circulation

7 rinsing Clean room air CO gas solved in UPW => R limited Volume: 200l Drain line Resistivity meter Primer water:18.2 Mohm cm Filtration level: 0,02 µm Quantity: 20 l /min renewed Process steering: resistance measured at the basin exit Sequence Rinse manually by 4 bar water jet Automatic rinse up to 12,4 / 18 Mohm cm 20l/min Filter 0,02 µm UPW fed line

8

9 Test on cleaning procedure Nb sample polluted with grease and oil Not efficient cleaning After U Sound cleaning procedure

10 Chemistry BCP ( buffered chemical polishing ) Mixture by volume 1/1/2 HF/HNO3/H3PO4 2 Nb + 5 NO Nb O + 5 NO + 5 e Nb 2 O HF H 2 NbOF 5 ( lösl.) + NbO 2 F 0. 5 H 2 O ( unlösl.) H 2 O NbO 2 F 0. 5 H 2 O + 4 HF H 2 NbOF H 2 O EP (electro chemical polishing) Mixture by volume 1/9 HF/H2SO4 2 Nb SO H 2O Nb 2O H + 5 SO 4 + e Nb 2O5 + 6 HF H 2 NbOF 5 ( lösl.) + NbO 2F 0.5H 2O( unlösl.) H 2O NbO 2F 0.5H 2O + 4HF H 2NbOF H 2O

11 BCP facility 2 independent circuits Nb clean and fresh Acid for final treatment Ti used acid for Ti removal /pre cleaning Inline filter 0,2 µm T <=15 C in average during process Start T 5 C

12 EP facility First experiences gained 1 circuits Inline filter??µm 8 first experiences bad filter blocked T C in average during process Start T 30 C Current 18 V (9cell ) First experiences since commissioning June 2003

13 High pressure rinsing System Parameters Pressure :4,2-200 bar Quantity: bar Particle bar line: 0,02 µm Ultra pure water: R spec 18.2 Mohm cm Special: N2 gas overlay Standard setting: 100 bar Process duration: >2h Volume: 2000 l total per rinse Spray head 2*4 jets (8 nozzles ) Nozzle : sapphire 0,4 mm ID

14

15 Procedures d e live ry acceptance in s p e c tio n an n e alin g and titanis atio n degreasing and rins ing tita nium BCP in s id e 8 0 µm outside 20µm in s e rtio n to oven C annealing in s e rtio n to oven C tita nis a tion tita nium BCP in s id e 8 0 µm outside 40µm tuning of field profile niobium BCP in s id e 2 0 µm 1st high pres s ure rins e assembly of flanges +leak te s t 2nd and 3rd high pressure rins e RF acceptance tes t for tank welding tan k w e ld in g cleaning +degreasing ventilation of c a vity w ith innert gas electron beam w elding of titanium rings frequency control and adjustment TIG w e ld in g o f Nb to Ti connection frequency control and field profile w elding of h e liu m v e s s e l leak test of ta nk s ys te m com ponent te s t adjustment of HOM a n te n na s cleaning +degreasing BCP niobium circuit inside 20µm 1st high pres s ure rins e assembly of flanges +leak te s t 2nd and 3rd high pressure rins e in s e rtio n o f pow er-coupler assembly of tune r acceptance tes t for module assembly module as s e m bly cleaning +degreasing alignment of cavity n for module ventilation of cavity assembly of connecting bellow assembly of cavity n+1 a lig n me n t o f coupler port distance general leack check alignment and frequency control assembly of me ch.tune rs, in s u la tio n, ma g n e tic s h ie ld in g assembly of vacuum vessel assembly of pow er-coupler warm part module te s t / mod u le in s ta lla tio n

16 EDMS Processing cycles Total 46 work packages

17 Processes

18 Assembly / Personal Personal: Defined procedures for handling /assembly

19 Test of procedures by air particle counters Top flange cavity probe Tube connecting to the first air counter Connecting to the second air counter disassemble two screws first disassemble first four screws ,3 0, ,3 0, : : :50 10 :57 11:0 5 11:12 15:2 5 15:3 2 15:4 0 15:4 7 15:55 16 :0 2 time time

20 Vertical measurements - Undressed resonator - Vertical bath cryostat - Power coupler variable high Q antenna 3*10 9 => 2* HOM feed not installed - Rf measurements Test mode CW operation - Eacc calculated from power measurement power from calibrated pick up signal - Qo calculated from decay signal RF off Some results Horizontal measurements - Undressed resonator - Horizontal cavity vessel= bath cryostat - Power coupler - variable antenna 3*10 6 => 8* HOM feed and antenna installed - Rf measurements Test mode pulsed 1-10 Hz operation - Eacc calculated from power measurement power from calibrated pick up signal - Qo calculated He losses

21 horizontal test s Multipacting Results of vertical test s

22

23 Results of vertical test s

24

25 Cavity Performance versus time and events / reproducibility E (MV/m) Nov. 98 Mrz. 99 Aug. 99 Verteilung aller 9 Zeller HF Messungen Distribution of vertical Rf test results 1 Jan. 00 Jun. 00 Nov Apr. 01 Sep. 01 Fe onset Eacc max E (MV/m) Nov. 98 Distribution of vertical test results AC series Verteilung aller Messungen an AC Cavities Mrz. 99 Jan. 00 Jun. 00 Nov. 00 Apr. 01 Aug. 99 Sep. 01 Fe onset Eacc max

26 35 Correlation of Verteilung test results aller and 9 Zeller man power 1 HF Messungen 2 E (MV/m) Fe onset Eacc max 0 Nov. 98 Mrz. 99 Aug. 99 Jan. 00 Jun. 00 Nov. 00 Apr. 01 Sep. 01 Peronalsituation für den Betrieb des Reinraumes 98 99=<1 99=>2 99=>3 00=>1 00=>2 00=>3 01=>1 01=>2 01=>3 02=>1 02 =>2 1 Reinraum z z z z z D D D D D D D 3 Reinraum z z z z z z z z z z z z 2 Reinraum z z z z z Z (1-3 Jahre) z z 4 Reinraum z z z z z z z Z (1-3 Jahre) z z 5 Reinraum z z z z z z z Z (1-3 Jahre) z z 6 Reinraum D D D D D D z z 7 Chemie D D D D D D D D D D D D Eingearbeites Personal Einarbeitungszeit nicht besetzte Stelle Z= Zeitvertrag D= Dauervertrag

27 Results of vertical test on AC cavity series Start up of DESY EP

28 Some comments on reproducible high gradients / low field emission levels on srf cavities Material and fabrication High quality Nb available Improved and high standard cavity fabrication available Tools are available BCP for Eacc~ 30 MV/m Epeak 60 MV/m Electropolishing for Eacc MV/m Epeak MV/m Gives improvement on surface /cleaning quality High pressure rinsing to fight field emission BUT! Facility has to be under control /intensive QC necessary Sequences and personal structure Preparation sequences are tested Test set up for assembly build up and applied Well trained personal!!!

29 Experiences on other than Nb surfaces CU => Gun cavity for TTF / Power coupler / connecting bellows In first order bad results CU surface oxidized strongly during treatments Chemical treatments more complicated Different results on different CU qualities Most critical: Impact on UP water / CO from air start strong oxidations on Cu Changes : Chemistry => citric acid in use for final chemistry Drying => Ultra pure alcohol for fast drying Oxidation=> N2 inert gas overlay on UP water rinsing basin HPR => strong N2 gas overlay on tank and rinsing cane But we still do not have lots of experiences and need more investigations Results on Gun cavity : Improvement compared to standard treatment low dark current was seen