Vacuum System How to Get Ready for Beam?

Transcription

1 Vacuum System How to Get Ready for Beam? V. Baglin on behalf of the team in charge of cleanning the beam vacuum in sector 3-4 CERN TE-VSC, Geneva 1. Final numbers 2. Status of sector 3-4 cleanning 3. Conclusions V. Baglin - Chamonix

2 1. Final Numbers 2

3 Sector 3-4 : Final numbers All beam lines in the tunnel have been inspected All visual and endoscopic inspections of the beam tubes and interconnects are documented V1 V2 V1 V2 Total Ok % 18 % 22 % MLI % 61 % 59 % Soot % 21 % 19 % To be done 0 0 0% 0% 0% Total % 100 % 100 % 3

4 MLI ~ OK MLI : DFBAR3 => A10R3 ~ OK : B10R 3 => A19R3 Soot : B19R3 => Q31R3 SOOT SOOT ~ OK 4

5 ~ OK MLI ~ OK : A32R 3 => B34L4 MLI MLI MLI : A34L4 => DFBAL4 5

6 Beam Screens of 3-4 Declared Cleaned C20L4.V1 Q13L4.V2 C14R3.V1 B8L4.V2 6

7 Beam Screens with MLI and Fibers QBQI 8L4.V2 A10L4.V2 B9R3.V1 QBQI 14L4.V2 A13L4.V1 QBQI 12L4.V1 7

8 Beam Screens with Soot Different types of results Traces left by the endoscope 8

9 Electron Microscopy Investigation report SEM-EDS EDS analysis of particles (EDMS ) QBBI-21R3 - V2 QBBI.21R3 line V2: Abundant presence of particles, they aggregate in macroscopic clusters. Sizes range from less than 1 µm up to 80 µm. Many have droplet shape. A dust of sub micrometric particles covers the bigger ones. The composition corresponds to the materials melted in the interconnect; two main groups of particles can be established: - Cu-rich particles with mainly Cu and some Sn and Si (possibly from brazing filler and glass fibre in the G11 around the busbar junction?) - Stainless steel-like particles, withmainlyfe,cr,ni,mobutusually also Cu that could be due to submicrometric particles covering the bigger ones. In the overall analysis the Cu is the major element. 9

10 2. Status of Cleaning in Sector

11 What remains to be cleanned in the tunnel? 53 cold masses are back to the surface from Q20R3 to Q33R3 (14 MQ, 39 MB) V2 line : 6 cold masses with soot (B19R3 -> C20R3) V1 V2 V1 V2 Total Ok % 19 % 25% MLI % 78 % 73 % Soot % 4 % 2 % Total % 100 % 100 % 11

12 Soot Removal 12

13 Beam screens with soot in tunnel : Cleanning Method Two plugs : one for horizontal and one for vertical parts of the beam screen Use of a foam-plug wet with alcohol Use of a dry foam-plug Up to 50 passages in each direction with wet foam-plug Up to 15 passages with dry plug 13 Example of C19R3.V2

14 Beam screens with soot in tunnel : C19R3 C19R3.V2 before cleanning After cleanning entrance V. Baglin mid - Chamonix 2009 end 14

15 Beam screens with soot in tunnel : Q19R3 Q19R3.V2 before cleanning After cleanning entrance V. Baglin mid - Chamonix 2009 end 15

16 Beam screens with soot in tunnel : C20R3 C20R3.V2 before cleanning After cleanning entrance V. Baglin mid - Chamonix 2009 end 16

17 Beam screens with soot in tunnel : Summary B19R3, C19R3, Q19R3, A20R3, B20R3 and C20R3 have been sweept Two vacuum systems are oxydised (C19R3 & Q19R3). The oxyde layer cannot be removed by the mechanical process. However, it is expected to have negligible impact on the vacuum performance since the outgassing rate scales like ~ exp(1/t) Four vacuum systems have been mechanically cleanned (see samples circulating in the room). Now, these 6 vacuum chambers will follow the protocol for the MLI removal (see next slides) 17

18 MLI Removal 18

19 MLI removal : 1 st step Based on automatic pumping/venting of a half-cell (52 m) A cycle : 20 s pumping, 18 s plateau, 2 second vent The pressure in the beam tube is reduced from 1 atm to 0.8 atm in 2 s (to be compared to the arc pump p down of 200 mbar/h) Air speed of 20 m/s This process is applied for 30 min (40 pumping/venting cycles) 19

20 MLI removal : 1 st step This procedure give good results i.e no more MLI are observable by endoscopy inside the beam screen Example : - Q8R4 till Q13R4 line V1 (~ 250 m) 3.2 g i.e 0.4 m g i.e 0.1 m 2 ~ 100 bits 20

21 MLI removal : 2 nd step Based on aspiration with local pertubation controlled by endoscope A nozzle blows filtered air, the MLI residues left behind the beam screen and the RF fingers are directed towards the beam aperture where they are aspired away. Time : 5 min per PIM, speed of 3 m/min along the beam screen A passage along a beam tube in a half-cell requires about half an hour 21

22 Nozzle demonstration : QQEI.11L4 22

23 MLI Harvest : Beam Screen Alone Example of A8L4.V2 1 st passage ~ 100 bits 2 nd passage ~ 100 bits 3 rd passage ~ 20 bits The efficiency decrease with the number of passages The 1 st method is not efficient anymore Debris size range from 1 x 1 to 2 x 2 mm 2 23

24 MLI Harvest : PIM Alone Example of QBBI.8L4.V2 1 st passage ~ Too many bits (500) Debris size range from 1 x 1 to 5 x 5 mm 2 Time ~ 5 min / PIM QBQI 12L4.V1 Most of the debris recovered by the nozzle are coming from the PIM 24

25 MLI Harvest : A8L4+QBBI+B8L4 2 passages ~ 250 bits 5 passages 20 bits The tooling efficiency decrease with the number of passages 9 passages 4 bits 2 per dipole! 25

26 MLI Harvest : Tooling Efficieny 4-5 passages will allow to remove 95 % of what can be removed by the tool 8-10 passages will allow to remove 99 % of what can be removed by the tool 26

27 MLI Harvest : How many and where remain the debris? Statistic ti ti was performed in the lab on 20 PIM from sector 3-4. Under analysis. The nozzle allows to remove 90 to 99 % of the MLI debris The remaining MLI debris are located in «corners» probably for ever! We can expect the same situation for the beam screen / cold bore case A MLI particle will probably find its place for ever in the coaxial space 27

28 Tunnel Work 28

29 Organisation Two fronts : removal of MLI, removal of soot Two teams Cleaning activities started beginning of January Procedure for MLI and soot removal have been set up All QQBI interconnects have been open to allow MLI removal and perform PIM s consolidation in the meantime 29

30 Procedure Soot front : - mechanical cleanning - aspiration/ venting for 30 min - 5 to 10 passages of aspiration under nozzle perturbation - final endoscopy for qualification MLI front : - aspiration/ venting for 30 min - 5 to 10 passages of aspiration under nozzle perturbation - final endoscopy for qualification All steps are documented 30

31 Status The 6 magnets with soot have been sweeped MLI 1 st step : DFBAR3 => Q16R3 is done Q27L4 => DFBAR4 is done 30 % remain to be done MLI 2 nd step : A8L4 => Q8L4 is done 99 % remain to be done Still to be defined if 5, 10 or 15 passages are required Rate of progress : - < 1h per passage and per beam line and half-cell - about 4 (2) half-cell per week and per team for 5 (10) passages 31

32 Vacuum Sectors at Room Temperature (A7R3, A7L4) 32

33 Recovery of room temperature vacuum sectors Sectors A7R3.R R and A7R3.B were at 1 mbar after the incidentid Sectors A7L4.R and A7L4.B were at mbar After 3 days of pumping down, the sector A7R3.B is at mbar So, these vacuum sectors are under pure He atmosphere (as expected) V. Baglin - Chamonix

34 Inspections Opening parts of the vacuum sector A7R3.R&B and the sectors A7L4.R&B did not revealed any traces of debris, only normal contamination could be identified by electron microscopy (EDMS , ) Endoscopy of magnet Q6R3 and Q6L4 did not show any traces of debris Vacuum sectors A7L4.R&B are activated this week and ready for operation Vacuum sectors A7R3.R&B will be activated in two weeks 34

35 Magnets at the surface 35

36 Surface Front Some magnets to be installed in sector 3-4 are «new» - Insertion of new beam screens Other magnets are «re-used» - Cutting and insertion of new beam screen - Soot sweeping and cleanning with the SMI2 washing machine Give very ygood results for the inner beam screen Inspection of the outer coaxial space is under way 36

37 Conclusions Systematic inpections revealed debris of soot and MLI all along the arc Soot is removed by a mechanical action with a foam-plug MLI is removed first by a pumping/venting mechanism and second by a combination of a nozzle and pumping mechanism No traces of debris have been found outside the arc Room temperature vacuum sectors are under commissioning On the MLI front : still a lot of work to do in the tunnel The objective of the coming weeks is to release sectors for PIMs interconnection 37

38 Acknowledgments A. Mongelluzzo; M. Thiebert; L. Leggiero; I. Wevers; J-F Ecarnot; H. Neupert; J. Cave; W. Vollenberg; B. Teissandier; M. Malabaila; H. Kos for the endoscopic inspections B. Jenninger, A. Sinturel, E. Mahner for the design, procurement and validation of the pumping/venting systems and nozzle systems B. Henrist, A Vidal, G. Schneider, E. Page, J. Finelle for their comittement to the repair of sector 3-4 Industrial support : FSU and AL43 teams HNINP collaboration for the endoscopies after cleanning J-M Jimenez for his constant support 38