- Action 1 (Impedance team): Try and fully understand the ~ 200 MHz resonance in the case of bad top/bottom contacts => First results will be presented on 03/04/12 => Done. To be continued.
- Action 2 (EM): Contact Pierre Strubin and summarize the past work on the PIM and PIM working group => Done on 27/03/12. Pierre will come himself on 17/04/12 to give more detail.
- Action 3 (EM): Contact Sergio Calatroni to summarize the past work on RF contacts => Done. SergioC will talk on 03/04/12.
- Action 4 (AlessandroB): Send mentioned notes about mechanical and heat tretments etc. to EM to put them on the web site.
- Action 5 (Owners of LHC equipments with RF fingers) => Requested info for the equipments' review:
(1) name of the equipment,
(2) number of such equipments,
(3) exact locations of these equipments,
(4) some real pictures with clear explanations (on some slides) of each relevant pieces etc.: with materials used (coating's parameters in case of coating, i.e. thickness and resistivity), contact force, how it should work in practice (elongated vs. contracted, static vs. dynamic etc.),
(5) functional specifications (if any) and impedance contact person (if any),
(6) real 3D drawings for further electromagnetic simulations to compute the impedances,
(7) are there (and if yes, where? etc) some spare equipments on which bench impedance measurements could be performed (and with which time scale)?
- Action 6 (VSC): What is the PIM stroke?
- Action 7 (VSC): Confirm that the SSS have been displaced by 2 mm such that the RF fingers are now more compressed.
- Action 8 (BS and OB for impedance team): Contact VB to prepare the bench impedance measurements on the ALICE vacuum module called VMABA.
- Reminder on current plan for the impedance team => Work on 2 parallel things:
- VMTSA (where issues were observed in operation in 2011) => Try and fully understand the bench measurements (comparing in particular with simulations).
- ALICE VMABA (where no issue was observed in operation in 2011 and which is quite simple) => Perform first bench impedance measurements to see if we find some problems. Then benchmark with simulations to validate our procedure.
- Action 9 (EM): Check with StefanoR and RalphA if we still need the fifth axis on the TCT collimators (as it complicates considerably the situation with the RF fingers).
- Action 10 (WW): Check if for the MKI stainless steel was chosen for the RF fingers (instead of CuBe) and if yes, why (maybe a good conductivity is not needed...).
- Action 11 (AG): Review of past impedances studies with the RF fingers for the collimators.
- Action 12 (?): How can we cool the ferrite if it becomes too hot?
- Action 13 (HD): Contact VB to have a spare VMSIO module (recombination of circulating B1 and injected B1) to make bench impedance measurements.
- Action 14 (Impedance team): 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.
- Action 15 (EM and FC): Review of past specifications for the PIMs DC contact resistance and thickness of copper / good conductor layer on some equipments.
- Action 16 (HD and OB): Perform a bench impedance measurement of the VMTAB module with a wire.
- Action 17 (OK): Continue the simulations of the VMTSA with old RF fingers (instead of new RF fingers) with HFSS to try and benchmark the wire measurements made in the past.
- Action 18 (MG): > 6 kW of power loss were predicted by OK for the VMTSA 2nd type bad contact (10 mm gap) with the new RF fingers. What about the thermal evolution with this huge power loss?
- Action 19 (impedance and equipments teams): We should give to Cedric Garion some requests for some (mobile) equipments and he could see, based on his experience, if he can propose some realistic parameters for his new RF fingers design.
- Action 20 (HD and OB): Perform a bench impedance measurement of this new RF finger design prototype with a wire.
- Action 21 (VB): Send a note on another kind of RF fingers in KEKB.
- Action 22 (BS): Follow-up of the LHCb Upgrade (in LS2) and impact on the LHC impedance if the radius is reduced from 5.5 mm to 3-4 mm.
- Action 23 (OB and BS): Follow-up for 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?
- Action 24 (OK): Finish the simulations for VMTSA by introducing a more realistic gap shape (if not too difficult/long as we already see what happens) and introduce the ferrite to see how/if it damps the mode in case of non conforming RF fingers.
- Action 25 (BI): Can we find more information about the damping ferrite used in the LHC?
- Action 26 (Impedance team): Take into account the temperature dependence of the mu' and mu" of the ferrite for the future power loss estimates.
- 14th meeting (25-09-12) => We restart the numbering of the actions at 1 (important actions to be finalized before concluding this Task Force):
- 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 (mu' decreases with temperature, but what about mu"? What about the ratio?).
- 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? => Done on 16/10/12.
- Action 8 (VB): Measured TT2-111R ferrite's properties: vacuum-wise? => Done on 16/10/12 (but update needed after new measurements required => See Action 20 below).
- 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.
- Action 19 (EM and impedance team): Practical recommendation for the ferrite's thickness to be used.
- Action 20 (VB): Update of the estimated outgassing flow of 1 TCTP collimator after new vacuum test of the TT2-111R ferrite with increased thermal treatment temperature.
- Action 21 (ChristineV and FC): OliverA mentioned that the dimensions of the ferrite used for the vacuum tests are smaller than the ones used by ChristineV and FC for their EM measurements => Might be good also to measure this ferrite to see the effect of a smaller length.
- Action 22 (EM): Question from VB: what is the beam behaviour with some pressure bumps in LSS3 and 7? => VB et al. will redo the outgassing tests and then they will present the vacuum profiles.
- Action 23 (FC and AG): Are there equipments with RF fingers under the responsibility of the RF group?
- Action 24 (VB): Send the detailed list of all the LHC non-conformities.
- Action 25 (VB and BS): Send the list of all the issues/observations on equipments with RF fingers during the past years of LHC operation.
- Action 26 (Impedance team): Plot on the same graph the penetration depth vs. frequency of the (few available) ferrites to see which ferrite should be used depending on the resonance frequency.