Minutes of the LRFF Task Force
6th meeting on Tuesday 24/04/2012 (09:00-11:00 max, 6-R-018)
LRFF members: Alessandro Bertarelli (AlessandroB), Alexej Grudiev (AG), Benoit Salvant (BS), Elias Metral (EM), Fritz Caspers (FC), Giuseppe Bregliozzi (GB), Hugo Alistair Day (HD), Jose Miguel Jimenez (JMJ), Marco Garlasche (MG), Mike Barnes (MB), Olav Ejner Berrig (OB), Oleksiy Kononenko (OK), Oliver Aberle (OA), Ralph Assmann (RA), Raymond Veness (RV), Rhodri Jones (RJ), Roberto Losito (RL), Sergio Calatroni (SC), Stefano Redaelli (SR), Vincent Baglin (VB), Vittorio Parma (VP), Wim Weterings (WW).
Present/Excused: AlessandroB, AG, BS, EM, FC, GB, HD, JMJ, MG, MB, OB, OK, OA, RA, RV, RJ, RL, SC, SR, VB, VP, WW.
1) Comments on the last minutes + Actions
- Question: we said that Au plating should be used at cold and Ag if bake-out. Why? => Due to diffusion of Cu in Au and then the Au layer disappear.
- For the MKI, SS is being used because the bake-out has to be done at even higher temperature (~350 deg) => Why? Use SS (instead on Cu-Be) but still with Au plated. See Slide 27 of Sergio, coming from manufacturer.
-Reminder: 1000 h of bake-out was made assuming 20 years of LHC operation and 1 bake-out per year of ~ 50 h (i.e. 2 days).
- PIM => Review of all the types, geometries... => MiguelJ.
2) Equipment review: some equipments from BE/BI (RV): pptx
- 9 months in this job => RF contacts in BI.
- Some assumptions: Only the circulating rings of the LHC considered, only equipments designed and/or provided by BI. Include both mobile and static contacts.
- All the info provided by RV has been summarized at http://emetral.web.cern.ch/emetral/LRFF/InfoOnLHCEquipmentsWithRFfingers/RFContactsInLHCBeamInstrumentation/RFContactsInLHCBeamInstrumentation.htm.
- BTVS: 2 design concepts
1) both beams inside the vacumm chamber => Double beam.
- Specifications: movement up and down. AlOx screen for low intensity and OTR screen for high intensity. Very rare (1 or 2 last year). In front of MKI and next to TDI.
- We had pb with them last year => talk at LMC in February. They are 6-7 mm long and are static ones. Don't know yet the cause => Could be more mechanical etc. as a first observation than a heating problem. The fingers are still flexible.
- When it is bake-out it is open. These are Au plated fingers whereas we do some bakeout.
- Plan to be done for LS1.
- For the moment it was said that we don't use them during this run.
- It is typically for extraction and injection.
- Comment from VB: We should remove these objects which cannot be completely bake out (due to screen etc) and they are close to equipments very demanding for out gassing.
- These are important in case of injection/extraction pb.
- There are RF contacts all along the moving parts.
- Proposition to NEG coat.
- Copper plated
- Observations: 6 with missing and 1 has been repaired.
- Do we have a spare to make a wire meas?
- The pb was known because the VAC people opened otherwise we would have not seen that.
2) 1 beam aperture:
- Vertical movement, 2 screens.
- More axially symmetric.
- No pb known but were not physically inspected.
- Comment from AlessandroB: are they close to radioactive area => OK as it is in front of TDI and not after. Recommendation: pay attention to the motorization etc, when it is close radioactive area => General degradation. SEUs are less critical for motors. Reminder: SPS motors could not be used for LHC collimators because they were not enough radiation hard.
- BSRTM:
- 2 of them in pt 4.
- The mirror could be put close to the beam, ~ 12 sigmas.
- 2 different contacts: round fingers (circular short contacts) => In antichamber. They are Cu-Be.
- Heating seen during last MD.
- Reminder from last year from RJ: with high-intensity it is moving. When the mirror is moved in it is heating and when the mirror is outside it is OK.
- Reminder from RJ: It is a dielectric coated mirror. It was to make it less transparent or use a traditional Berylium mirror as used in the past. In LEP it was cooled at the SR was huge..
- A lot of simulations were already done.
- All this was for moving contacts.
- Now for the static contacts:
1) Wire scanner (BWS).
- Which material?
- Cavity not screened of course.
- No heating issue for the moment.
2) BGI:
- It operates at High Voltage.
- Discussions with Mariusz yesterday.
- Some RF fingers.
- No heating issue for the moment.
- It was NEG coated to reduce e-cloud.
- VB mentioned that he can see similar vacuum pressure rise as TDI.
3) Schottky:
- RF contact with the beam pipe. Again helicoidal spring. It was designed in the US.
- Structure resonates at 4.8 GHz (but it is designed for that...)
- It is not coated so we will have e-cloud issues with the 25 ns.
- Summary:
- Monitors with moving RF contacts
- 18 monitors.
- 3 different design concepts.
- Monitors with Static RF contacts
~ 12 monitors.
- 3 different design concepts.
- Currently observed issues
- (Mechanical?) problems with BTVST-type design.
- (Heating) problem with BSRT mirror-type design.
- Reminder: we need the 3D drawings!
3) Actions to be taken for the next meeting
- Old actions.
4) Miscellaneous
- The next (7th) meeting will take place on 08/05/2012 between 09:00 and 11:00 (max.) in room 6-R-018 => Agenda:
1) Equipment review: some equipments from TE/ABT (MB and WW).
- See preliminary agendas for the next meetings.
Minutes by E. Metral, 25/05/2012.