- Action 1 (everybody): List of (professional) travel plans for 2013 sent to EM before 04/02.
- Action 2 (everybody): Summer student project proposals for 2013 => Submit your request electronically and send the proposals to Delphine before 04/02.
- Action 3 (NM and BS): Start to think / prepare a possible workshop on impedance in 2014 (Spring => Should be a good time because we need a first estimate of the HL-LHC impedance by November this year).
- Action 4 (everybody): Send info to EM about computing resources used (which ones? names? for which code(s)? additional info etc.) and needed in the future.
- Action 5 (e-cloud team): Explore the difference in photoelectrons between the ECLOUD and PyECLOUD codes in dipole fields.
- Action 6 (e-cloud team): One useful output of the ECLOUD-PyECLOUD codes could be the number of e- on average over the machine which is inside the proton bunch. We have the central density but it is not enough for some estimations.
- Action 7 (FS): Check (asap) all the LIU requests and deadlines from PSB, PS and SPS linked to space charge and update them (if necessary) in agreement with all the involved/responsible people to set up a realistic plan (if necessary).
- Action 8 (XB and AB): Clarify the situation with the stability diagram in the presence of both octupoles and LR beam-beam => Done (see minutes of 80th meeting on 24-04-13).
Action 9 (BB team): Check/follow with JJ et al. all the beam-beam issues with Pb ions and if this is true that we will need to collide and squeeze for stability issues (and if yes, why?) => Done (see minutes of 78th meeting on 03-04-13).
- Action 10 (FC et al.): Real part of the longitudinal impedance at low frequency and in particular of the SPS vacuum chamber at 43 kHz (revolution frequency) => Done (see minutes of 78th meeting on 03-04-13).
- Action 11 (NM): Try and understand where the factor ~ 2-2.5 in the LHC transverse impedance measurements come from.
- Action 12 (impedance team): Follow-up of the proposal to use a dedicated beam-gas vertex detector in the LHC as a 3D bunch shape monitor to see if there could be some impedance issues.
- Action 13 (EM): Check with RalphS if with his new measurement method for LHC transverse instabilities he measures a shifted power spectrum (centered at the chromatic frequency, which would mean that the chromaticity could be measured at the time of the instability) or if this information is lost => Ralph Steinhagen informed.
- Action 13 (e-cloud team): Actions from the last CMAC (14-15/03/13: https://indico.cern.ch/conferenceDisplay.py?confId=235072):
- Investigate the possibility of installing electron cloud diagnostics in the LHC to enhance the understanding of the scrubbing process with 25 nsec bunch spacings, the operational state of the machine during collisions at 6.5 TeV, and the effects of future mitigation methods on the SEY. Compare with “PyECLOUD” code predictions.
- Perform additional simulations for 25 ns bunch spacing of the dedicated scrubbing process at 450 GeV and parasitic scrubbing at 6.5 TeV to predict the operational state of the LHC after a few months into the 2015 run looking for acceptable vacuum condition and cryogenic heat load.
- Investigate the possibility to operate the LHC at 6.5 TeV with a combination of trains with 50 nsec bunch spacing interleaved with trains with 25 nsec bunch spacing to allow particle physics to proceed while 25 nsec scrubbing continues.
- Investigate the possibility to use bunch spacing shorter than 25 ns to enhance the scrubbing efficiency i.e. the 5 + 20 ns bunch pattern used in the SPS.
- Action 14 (Beam-beam team): Is a minimum separation of 10 sigmas OK / enough for the new IR8 crossing schemes at injection? => Done (see minutes of 85th meeting on 26-06-13).
- Action 15 (Impedance team): Is the NC http://emetral.web.cern.ch/emetral/ICEsection/2013/2013-06-05/NC_IC-QQBI.29R5_5contactstripsProtrudingIntoAperture.png a pb and should we propose to repair it?
- Action 16 (Impedance team): 2 actions, in fact, related to TCTP collimator studies => i) Perform electromagnetic measurements and impedance simulations on 4E2 ferrite (model for the simulations: TCTP collimator) and ii) Confirm the RF losses on ferrite used as inputs for the thermal simulations (for the TCTP).
- Action 17 (NM): Study the dependence of impedance on octagonal Beam Screen aperture (in the framework of HL-LHC WP2) and report about the results on 01/07/2013 => Done (see https://indico.cern.ch/conferenceDisplay.py?confId=259525).
- Action 18 (FrankZ and GR): Study the dependence of e-cloud effects on octagonal Beam Screen aperture (in the framework of HL-LHC WP2) with counter-rotating beams => Deadline: end of summer, mid September.
- Action 19 (KL): Check the effect on transverse beam stability of the longitudinal beam distribution in bunch lengthening mode (and I would also suggest bunch shortening mode) with a possible 800 MHz HHRF system (in the framework of HL-LHC WP2) => Deadline: end of summer.
- Action 20 (BS): Scale the LHC beam-induced RF heating estimates to the HL-LHC parameters (using table in the PLC web page: https://espace.cern.ch/HiLumi/PLC/_layouts/xlviewer.aspx?id=/HiLumi/PLC/SiteAssets/Parameter%20Table.xlsx&Source=https%3A%2F%2Fespace%2Ecern%2Ech%2FHiLumi%2FPLC%2FSiteAssets%2FForms%2FAllItems%2Easpx&DefaultItemOpen=1) with the current LHC impedances to have a first idea (it will be then redone properly afterwards with the impedances for HL-LHC) => Deadline: end of Summer.
- Action 21 (Beam-Beam team): Study / show on an example case why 1 number (beam-beam separation in sigmas) is sometimes not enough to approve an optics.
- Action 22 (Impedance team): Check the power loss computation in the triplets (with the 2 counter-rotating beams) to be sure that our approach is ~ OK.
- Action 23 (NM): Check / follow-up of the impedance contribution to the luminosity measurememts.
- Action 24 (KL): Damping time in the SPS with ions (request from WolfgangH through GA)? => HEADTAIL simulations to be performed without an with space charge for the ions in the SPS (as done in the past for the PS).
- Action 25 ("instability and damper team"): Following a discussion with / request by F. Blas and following the recent work on the effect of a transverse damper on transverse coherent instabilities, can we give some recommendation on the necessary bandwidth needed to damp a transverse instability at a certain frequency? => Seems quite difficult question (depends on the type of instabilities, etc.) which we cannot answer now but which hopefully we will be able to discuss in the future => We should work in this direction.
- Action 26 ("instability team"): Answer to the idea / suggestion from Alexej Grudiev to try and increase transverse Landau damping in the LHC => Could an RF quadrupole be useful for this? This would introduce a linearly z-dependent transverse betatron tune (a nonlinear dependence could also be created by using higher frequency). For which kind of instabilities could this be useful? What are the required parameters to reach a transverse (incoherent) tune spread similar to the one from the Landau octupoles?
- Action 26 (Impedance team): Impedance estimates of the possible BBLR wire compensation scheme for the LHC, as a drawing seems to be now available (to be sent by RalphS).
- Action 27 (BB team): Do we have other observables than lifetime to check that the BBLR wire compensation scheme is working properly? Are these effects significant enough to ask BI to improve their diagnostics?
- Action 28 (Impedance team): Some problems found recently with the TCTP (more precisely with the vacuum firing of the steel plates that go along the collimator jaws, and also serve as screen of the ferrites, to absorb the emitted heat). The problem is probably related to the sandblasting procedure used to improve the emissivity. One possible solution to reduce deformations during the vacuum firing might be to cut them in 2/3 pieces and then assembled. This procedure risks however to leave some small transverse gaps, probably below 500micron. Do we see any potential issues if there are these gaps?
- Action 29 (All the team): Actions for the RLIUP workshop and HL-LHC WP2.
- Action 30 (all the team to think about): Possible effects of chromatic aberrations (chromatic beta-beating) on collective instabilities.
- Action 31 (NB): Next step for the LIU PS impedance studies => Simulate the TMCI at transition with the updated impedance model.
- Action 32 (EM): Finalize with ElenaB the detailed planning and deadlines for the PSB-LIU beam dynamics activities.
