Minutes of the LRFF Task Force
14th meeting on Tuesday 25/09/2012 (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, ChristineV.
1) Comments on the last minutes + Actions
- Previous actions to be done:
- Thermal evolution in the VMTSA with the huge power loss found by OK? => MG could present something at some next meetings (see Action 1 below).
- Do we need a recombination insert for the VMSDO at LSS6 (as we have at LSS2 => VMSIO and LSS8 => VMSIN)? => Contact VB to have a spare VMSDO module to make bench impedance measurements? (See Action 2 below)
- Can we find more information about the damping ferrite used in the LHC? (see Action 3 below)
- Take into account the temperature dependence of the mu' and mu" of the ferrite for the future power loss estimates.
2) Status report of this task force (EM): pdf
- EM presented the status of this task force: i) what we planned to do; ii) what was done; iii) what remains to be done
i) what we planned to do:
- Reminder on mandate.
- Exhaustive review of all the equipments with RF fingers.
- Ranking by criticality and action plan.
- First recommendations of the Task Force.
- New design and/or mitigation measures.
- List of endorsed actions presented by the Task Force => To be presented at the LMC
ii) what was done:
- Detailed follow-up of the VMTSA (issue during the 2011 run and at the origin of this task force).
- Review of past work and issue with the PIMs (what was wrong with the Plug-In Modules in the cold part of the LHC?).
- Review of past development work on RF contacts => Summary for RF fingers for the different cases encountered in the LHC.
- Past impedance studies with the RF fingers for some collimators.
- Review of equipments from TE/VSC (vacuum modules in LHC experiments and septa).
- Review of equipments from BE/BI
- Review of equipments from TE/ABT.
- Review of the wake field suppressor in the LHCb VELO.
- New design for RF fingers.
- Review of Non-Conformities in Warm Modules following the X-ray campaign.
iii) what remains to be done:
- 1) Finalize the simulations for VMTSA by:
- Introducing a more realistic gap shape (if not too difficult/long as we already see what happens) => Action 5 (OK) below.
- Introducing the ferrite to see how/if it damps the mode in case of non conforming RF fingers => Action 6 (OK) below.
- Performing simulations to study temperature and heat transfer => Action 1 (MG) below.
- 2) Finalize the review of ferrites used at CERN to damp HOMs: references, manufacturers, thermal treatments, etc.
- Ferrite people have been nominated: FritzC and ChristineV.
- The TT2-111R ferrite is recommended due to its high Curie temperature. What are the EM properties (Action 7 (ChristineV) below)? What about vacuum (Action 8 (VB) below)?
- How can we cool the ferrite if it becomes too hot? FC is in contact with some people (who exactly?) to try and improve the conduction from ferrite as most of the time only radiation is used (given the general brittleness of the ferrite we cannot apply big contact). What are the future possible solutions? (Action 9 below).
- Try and understand what happened to the ferrite of BSRT => Follow-up from MG (who made already some simulations) and BS as some modifications have been made to the 2 BSRTs and some new measurements have already be done (Action 10 below).
- 3) Finalize the validation of the new RF fingers design:
- What happens if we have a transverse offset (~ 10 mm transverse and ~ 10 mm compression in longitudinal) as this is like this that we want to use it? What about the tolerances? What about transverse plane? (See Action 11 below).
- 4) Finalize the equipments review. Anything else? (See Action 12 below).
- 5) Summarize all the issues/observations on equipments with RF fingers during the past years of LHC operation (See Action 13 below).
- 6) NC (Non Conformity) in Warm Modules => A sorting must be done by LRFF to propose the repair of critical VM and minimize the number of interventions (See Action 14 below).
- Heat treatment in general => AlessandroB will send some info with the combination of temperature and time (Action 15 below).
- VMTSA:
- VB reminded us that after LS1 there will be no VMTSA anymore as the 2-in-1 collimator will be removed and VMTSA are used only for 2-beam collimators.
- Info from VB: the RF bench is available since yesterday (the day before the meeting) so we can start to work.
- Vacuum people are testing 2 types of ferrite at the moment:
- Ferrite for TCTP (TT2-111R) => Results will be presented soon.
- Another one (8C11 I think).
- Reminder on the important question: how can we cool the ferrite? We had/have the example of the BSRT which we should try and understand in detail.
- So far, only way was radiation.
- Given the general brittlness of the ferrite we cannot apply big contact => We have bad conduction.
- As we are in vacuum => No convection.
=> We are left with radiation => We need the highest emissivity from the ferrite (it is the case) and also for the environment. Ex: Copper has a very good electrical conductivity but a very low emissivity.
=> Try to have around the ferrite materials with the highest emissivity.
=> We have to treat each case by case, one cannot give a number like this.
- VB said that we could show curves depending on the emissivity. Emissivity depends on the shape.
=> AG reminded us that some people need a number => What is a critical number?
- ChristineV mentioned that in some cases ferrite is in oil and in this case we could rely on convection.
- AG mentioned example in KEK they put some copper to keep the ferrite.
- FC mentioned also the deposition of ferrite on some materials etc.
=> What is the correct figure of merit: Watt / volume? (Action 16 below)
- Ferrite in BSRT => VB mentioned that they are looking at the outgassing of the current ferrite installed. In the past it was 8C11.
- Thermal conductivity of ferrite is no so good => Better than ceramics but SiC is better.
- Any other equipments => VB still need to show collimators modules and sectors valves (Action 12 below).
- Alessandro will present the collimators themselves => From phase 1 to phase 2 => 1 h talk (Action 12 below).
- Another conformity in the LHC => Left of point 2 (TCLIA) => VB will send me a link (Action 18 below). It is carbon and it is 2-in-1 beam. It is a non-conformity but it is not a pb for operation. The TCLIA does not need the 5th axis so we don't need the VMTSA... AlessandroB mentioned nevertheless that they designed it with the 5th axis.
- NC in warm modules: VB asked to open all the vacuum sectors but in case of missing time we should provide a list of less critical equipments.
- There should be a report written at the end of this task force with all the guidelines etc. and a summary of the activity which took place (Action 18 below).
3) Actions
- Old actions.
- New actions:
- Action 1 (MG): Study of the thermal evolution in the VMTSA with the huge power loss found by OK.
- Action 2 (OB): Perform bench impedance measurements on a spare VMSDO module to see if we need a recombination insert for the VMSDO at LSS6 (as we have at LSS2 => VMSIO and LSS8 => VMSIN).
- Action 3 (All the equipments groups): Can we find more information about the damping ferrite used in the LHC?
- Action 4 (Impedance team): Take into account the temperature dependence of the mu' and mu" of the ferrite for the future power loss estimates.
- Action 5 (OK): Introduce a more realistic VMTSA gap shape (if not too difficult/long as we already see what happens).
- Action 6 (OK): Introduce the ferrite in the VMTSA to see how/if it damps the mode in case of non conforming RF fingers.
- Action 7 (ChristineV): Measured TT2-111R ferrite's properties: EM-wise?
- Action 8 (VB): Measured TT2-111R ferrite's properties: vacuum-wise?
- Action 9 (FC): How can we cool the ferrite if it becomes too hot? FC is in contact with some people to try and improve the conduction from ferrite as most of the time only radiation is used (given the general brittleness of the ferrite we cannot apply big contact). What are the future possible solutions?
- Action 10 (MG and BS): Try and understand what happened to the ferrite of the BSRT. Follow-up from MG (who made already some simulations) and BS as some modifications have been made to the 2 BSRTs and some new measurements have already be done.
- Action 11 (OB and BS): What happens if we have a transverse offset (~ 10 mm transverse and ~ 10 mm compression in longitudinal) with the new RF fingers as this is like this that we want to use it? What about the tolerances? What about transverse plane? Simulations and measurements (with the brand new bench) to be performed.
- Action 12 (All the equipments groups): Did we really review all the equipments with RF fingers? VB still need in particular to show collimators modules and sectors valves. AlessandroB will also review the collimators themselves. Others?
- Action 13 (All the equipments groups): What are all the issues/observations on equipments with RF fingers during the past years of LHC operation?
- Action 14 (EM and all task force): NC (Non Conformity) in Warm Modules => A sorting must be done by LRFF to propose the repair of critical VM and minimize the number of interventions.
- Action 15 (AlessandroB): Info about heat treatment with the combination of temperature and time.
- Action 16 (AlessandroB): Try and figure out a figure of merit for the power loss in ferrite (Watt / volume?) vs emissivity (from ferrite and environment)? etc.
- Action 17 (VB):There is another nonconformity in the LHC (left of point 2, TCLIA) => Send info (exact position, pictures, etc.).
- Action 18 (EM): Write a report at the end of this task force with all the guidelines etc. and a summary of the activity which took place.
5) Miscellaneous
- The next (15th) meeting will take place on 16/10/2012 between 09:00 and 11:00 (max.) in room 6-R-018 => Agenda:
1) Measured TT2-111R ferrite's properties: EM-wise (ChristineV) and vacuum-wise (VB).
2) Follow-up of actions from last meeting (everybody).
- See preliminary agendas for the next meetings.
Minutes by E. Metral, 12/10/2012.