Minutes of the HL-LHC WP2 Task 2.4
1st (EVO) meeting on Wednesday 11/04/2012 (10:30-12:30 max, 6/R-018)
Task 2.4 members: Alexey Burov (AB), Alessandro Drago (AD), Alessandro Gallo (AG), Andrea Mostacci (AM), Alessandro Vivoli (AV), Benoit Salvant (BS), Bruno Spataro (BrunoS), David Alesini (DA), Deepa Angal-kalinin (DAK), Elias Metral (EM), Elena Shaposhnikova (ES), Fabio Marcellini (FM), Fritz Caspers (FC), Frank Zimmermann (FZ), Giovanni Rumolo (GR), Hugo Alistair Day (HD), John Jowett (JJ), Luigi Palumbo (LP), Mauro Migliorati (MM), Michel Martini (MichelM), Mikhail Zobov (MZ), Nicolas Mounet (NM), Oliver Boine-Frankenheim (OBF), Olga Zagorodnova (OZ), Rainer Wanzenberg (RW), Uwe Niedermayer (UN), Wolfgang Hofle (WH).
Present/Excused: AB, AD, AG, AM, AV, BS, BrunoS, DA, DAK, EM, ES, FM, FC, FZ, GR, HD, JJ, LP, MM, MichelM, MZ, NM, OBF, OZ, RW, UN, WH.
- ES could not joined as she had another meeting where she needed to give a talk.
- AV could not join, will have little time to work on IBS but confirmed his interest (with MichelM in particular, using the SIRE code).
- OBF could not join.
1) Link to the Task 2.4 web page where all the info should be (maintained by EM) => Should always be the source of all information and therefore the most up to date: https://espace.cern.ch/HiLumi/WP2/task4/SitePages/Home.aspx. EM reviewed briefly all the information stored in the web page. Don't hesitate for any comment / suggestion etc
- FC mentioned that he proposed in the past the double-ridge option for a Crab Cavity.
2) Discussion about the WBS = Work Breakdown Structure (EM)
- See EM's talk
given at the 3rd HiLumi WP2 Task Leaders meeting:
https://espace.cern.ch/HiLumi/WP2/task4/Shared%20Documents/Talks/3rdWP2TaskLeadersMeeting_EM_29-03-12.pdf. Comments
were made during
the meeting or by emais (see below):
- OBF:
- TU Darmstadt involvement can only be rather marginal (as for the moment no agreement has been signed) and only 1 PhD student (UN) could help us on impedance studies (beam pipes, collimators, etc.). OBF could help on instabilities (ecloud, space charge effects) and IBS. The 2nd potential PHD student, Paul Gorgen, will work on beam-beam mitigation (his PhD work is a GSI/BNL collaboration on transverse BTFs for bunches with beam-beam and space charge). It was finally decided to remove him from the list as he will not work for this Task 2.4.
- Possible collaboration set-up still needs to be discussed => See Action 1 below.
-
MM:
- Possible collaboration set-up still needs to be discussed => See Action 1 below.
- In the past AM
worked on the longitudinal impedance of the LHC beam screen. The transverse part
still needs to be done and this is what is planned for the moment. To be done in
particular in contact with FC
who also worked on this subject in the past.
- RW:
- The DESY contribution to the calculation of the impedance of the beam pipes in the experiments is fine as they already worked on this subject in the past. Could also help with RF fingers studies as they had some problems also in the past => RW will review this DESY experience with RF fingers and heating in the future.
- JJ:
- Although the sub-task for IBS says only 2.4.3 (IBS): Estimate the Intra Beam Scattering (IBS) growth rates for the different beam parameters and optics, emittance growth is not the only effect of IBS. We should also estimate debunching losses due to IBS, for example. The various parties could contribute to predictions based on different calculation methods or simulations. One obvious way to organize things would be to define optics and parameter sets of interest for injection and physics configurations and compare results of the various approaches. If predictions are significantly different then there may need to be some discussion to understand why. JJ and Michaela Schaumann possible contributions:
1) Straightforward growth rate calculations as functions of all the parameters (with MAD for instance).
2) For more details the CTE (Collider Time Evolution) program could be used. It simulates IBS emittance growth taking account of non-gaussian longitudinal distributions, intensity loss from debunching, luminosity burn-off, radiation damping and other effects. CTE offers a few alternative IBS calculations. It has already been bench-marked against RHIC and LHC (previous work with Roderik Bruce et al, Tom Mertens, etc.) and is currently used to compare with LHC fill data (both for protons and lead ions).
3) Another model can be used, based on systems of ordinary differential equations (ODEs) that can take account of different classes of bunches, differences between beams, luminosity burn-off, vacuum effects, radiation damping, etc. It doesn't presently predict debunching.
4) Later,
investigation of possible cooling schemes for LHC (but this is probably not
relevant for p-p).
- DAK:
- She is using other codes and it will be a good idea to start with some benchmarks. DAK is already in contact with JJ. MM and AV are also using another code called SIRE. I imagine OBF is also using another code => See Action 2 below.
- MZ:
- Frascati was not planning to participate in the design of the crab cavities (as shown in the slide 4), only in the 800 MHz second harmonic cavity => EM answered that the design of the Crab cavities is done by other people. In the past we gave some recommendations on the maximum allowed impedance (which we will have to review) and now that some prototypes are available, together with HOMs table (Rama Calaga will send them to me in the future, or we could even re-simulate them if we have the drawings), we should try and estimates the power loss and related instabilities. MZ accepted.
- MZ reminded us
that DAFNE has been equipped with ecloud clearing electrodes and 1st
(promising)
measurements have been done => Could be presented at some point.
- MZ (and team) would like to participate to some LHC MDs. Reminder: LHC schedule for 2012 where the LHC MDs blocks are shown in blue: https://espace.cern.ch/be-dep/BEDepartmentalDocuments/BE/LHC_Schedule_2012.pdf. The MD planning is discussed at the LSWG: https://espace.cern.ch/lhc-md/default.aspx. The 1st MD block is foreseen for end of next week (3 days, from Friday till Sunday, where in particular we will try and measure the longitudinal impedance). The 2nd MD block (of 5 days) is foreseen in June (from 20/06 to 24/06) => MZ should contact in particular NM (for transverse instabilities studies) and ES (for longitudinal instabilities studies), see Action 3 below.
- EM:
- We need some help for our LRFF (LHC RF Fingers) Task Force to simulate many equipments with RF fingers. RW will help us as they also had similar issues in the past at DESY (first by reviewing their experience). Someone else interested? We will try and make many bench impedance measurements (with wires) but we need many people to make simulations to benchmark the bench measurements (mainly of the real part of the longitudinal impedance, i.e. for the RF heating).
- FC:
- Some measurements have been done
in the past on pulsed BBLR (Beam-Beam Long Range) compensation. FC reminded us
that it is a kind of pick-up, it is resonant and it could be improved from the
impedance point of view.
- WH:
- Concerning the ADT (LHC
transverse damper/feedback), the effect of the noise on the emittance growth is
currently being followed up and some improvements might be needed for the
future. What will be needed in the future are the predicted instability
rise-times vs frequency (as was done in the past for the current LHC machine)
and in particular if we expect big contributions between ~ 10 MHz and ~ 20 MHz
where there is a roll-off the ADT gain. The use of the ADT with a slightly
negative chromaticity will be studied in some MDs and might require further
studies. At the end of this project, one should have some specifications to
decide on an upgrade of the ADT or not.
- Discussion with FZ after the meeting on ecloud activities for HL-LHC => Could be interesting to review what was already done in the past for HL-LHC, what is being done and what is the plan for the future.
3) Actions to be taken for the next meeting
- Action 1 (EM): Discuss with Stephane Fartoukh and Lucio Rossi to set up a collaboration (official papers + some funding) for those who didn't sign a FP7 agreement (with Brussels), i.e. OBF for GSI / TU Darmstadt and MM for La Sapienza => Already done by EM and more news from Lucio Rossi in few weeks.
- Action 2 (All the IBS contributors): Contact JJ to start the benchmarking between the different approaches (codes etc.) which will be used (see also the Task 2.4 web page where some info can be found about the beam parameters and optics to be used + discuss with Stephane Fartoukh). JJ and Michaella Schaumann will make a presentation at the 2nd EVO Task 2.4 meeting (currently foreseen on 30/05/2012).
- Action 3 (MZ): Contact NM (for transverse instabilities studies) and ES (for longitudinal instabilities studies) to plan their participation to future LHC MDs.
4) Miscellaneous
- The next (2nd) EVO meeting will take place on 30/05/2012 (i.e. the week after IPAC12) between 10:30 and 12:30 in room 6-R-018 (for people at CERN) => Agenda:
1) Some IBS studies for the current LHC, nominal LHC and HL-LHC and set-up of a benchmarking case with all the IBS contributors (Michaela Schaumann with JJ).
2) AOB.
- See preliminary agendas for the next meetings (with the EVO info for each meeting).
Minutes by E. Metral, 13/04/2012.