Summary notes of the forty-sixth meeting of the LHC Commissioning Working Group

 

Tuesday June 3rd, 14:00

CCC conference room 874/1-011

Persons present

 

Minutes of the Previous Meeting and Matters Arising

There were no comments on the minutes of the 45th meeting.

 

LHC Status (Roger)

Roger summarized the LHC status. Four sectors were at 2 K temperature, or thereabout, some just having recovered from power cuts. The other sectors were being cooled down. The last one  was Sector 4-5, where for the moment only the QRL was being cooled down in order to investigate a possible leak. Roger presented the planning schedule from 26 May which had been prepared by Katy Foraz. Except for Sector 4-5 the hardware commissioning seemed to be fully in line with this schedule. The whole machine should be cold by the middle of July. Hardware commissioning should then be completed 3 or 4 weeks later. Roger listed a few more details on each individual sector, e.g. Sector 56 was cold and had been commissioned for 5 TeV. A dipole training campaign in this sector had gone up to 6.5 TeV so far. Sector 78 was cold and being commissioned to 5 TeV.

 

Jean-Jacques commented that the commissioning of Sector 4-5 was a few weeks behind schedule, as had earlier been emphasized by Olivier Brunner, and that there was a possible conflict between BI and RF commissioning activities, which needed to be resolved.

 

Integration Tests continued (Mike)

Mike discussed the plan for integration and roll-out tests for the coming couple of months. These tests included software testing from CCC using controls infrastructure and software, and would involve the timing system, RF, collimation, beam instrumentation. One point which had come up recently was the roll-out and commissioning of the machine protection system, of which Jorg would now take charge. Mike mentioned that all the ongoing activities would smoothly lead into the machine protection commissioning, the partial checkout, and the full machine checkout.

 

“PGC+” would be the extension of PGC (the powering of groups of circuits), involving settings generation, the sorting out of the optics, and also the actual settings of collimators and kickers. Expanded, more flexible sequences would allow tests of ramp variations, including energy and optics changes, and of squeeze variation, as well as of all knobs and bumps (separation, angle, Q. Q’,..) – their generation, proper trimming, etc.

 

Roger asked whether the PGC already done was a subset of this planned activity. Mike confirmed that this was the case, clarifying that so far only injection, ramping and squeezing had been tested, but nothing else, e.g. there had been no trims yet.

 

One goal was to deploy and check every part of the FIDEL magnet description obtained from Luca and his team: transfer functions, harmonic errors, decay correction, and snapback correction.

 

Oliver asked how we would check the field model for the 5 TeV cycle, and whether we could just scale from the 7-TeV fields. Walter commented that no magnet measurements from 5 TeV were available at the moment. Mike remarked that the parameters in the FideL model could be adjusted to represent the 5 TeV situation. Oliver rephrased his question if there was no crosscheck planned against a real measurement. Stephane wished a clarification of the meaning of “transfer function”, and whether this term referred only to a linear slope, or would also contain saturation effects etc.  Mike reassured him that saturation and similar effects were included. Stephane then asked if the correct magnet lengths were taken into account. Walter remarked that the measurements provided the integrated fields. Stephane cautioned that the ABP optics models were normally quoting K and not KL values. Walter and Stephane concluded that we should work with integrated transfer functions, in order to avoid possible mistakes.

 

The PGC+ would comprise full cycle tests of all available circuits and devices, including RF and collimators (highlighted in red), establish near-perfect control of the power converters and test the trims. Ralph suggested that the collimators better be shown in green color, instead of red.

 

A physics/experiments dry run would qualify luminosity acquisition and displays, luminosity optimization, luminosity scans, experiment instrumentation, interlocks, experimental magnets and their compensation. Reyes was driving this activity.

 

A table summarized how particular hardware tests were covered by the different dry runs and rol-out activities. Collimators would be included in PGC when available. Andy commented on the availability of the rf systems and possible delays. Mike explained that the goal was to prepare and test devices as early as possible. As an illustration he flashed the cavity controller parameter space that had been established by Andy and Delphine.

 

Mike then recalled the generic objectives for various hardware items. A web site is available with a detailed list of software tests for the different systems:                    

http://lhc-commissioning.web.cern.ch/lhc-commissioning/dry-runs/systems/software-tests.htm

Mike also mentioned that there had been a review on Monday.

 

The phase following PGC+ was “PGC++”: an extended test of two cold sectors, naturally leading into the injection test; the PGC++ test would encompass machine protection, LHCb, nominal cycle, injection, and instrumentation. A detailed timing schedule showed how we were to move into this extended test mode during the next two months’ time. Mike added that various dry runs would continue, for the LBDS, etc, as also shown in the schedule.

 

Gianluigi asked about an intervention on the cryo-electronics intended at point 8, by which sensitive equipment should be moved out of a radiation area. Roger responded that this action had originally been foreseen to happen parasitically with an intervention on Q5. Since the Q5 problem had been resolved in the meantime, it was unclear whether the work on the cryo-electronics would still be done, but it might possibly happen in July. The topic could be brought up at the ICC the following Friday. This type of intervention would require a project decision.

 

Commissioning of Beam Instrumentation (Jean-Jacques)

Jean-Jacques summarized the discussions and results of a meeting with all BI commissioners on the instrument commissioning held about a week earlier. His summary included a reminder of the BI dashboard, the working conditions, the state of the common chapters, and what was coming next.

 

Jean-Jacques re-introduced the “dashboard” which featured many columns and links for each LHC beam instrument, guiding through its commissioning phases. The phases were classified in three different domains: BI hardware domain, BI software domain, and finally the AB/CO/OP commissioners’ domain. The color described the state of each of an instrument’s commissioning phases: Orange: HWC not finished; blue: HW finished OK; red: in progress; yellow: functionality ready to be tested by commissioners (leading to a switch to green); grey – functionality not foreseen.

 

Jean-Jacques presented the list of BI and external people involved per instrument, as well as their responsibilities. He planned to identify one person responsible for giving the green light, in cases where several names were shown.

 

Turning to the general working conditions, Jean-Jacques reviewed the different ways of triggering of BI front-end acquisitions, namely via central timing events, injection pre-pulses, general machine events, dedicated events like BLM captures or BWS triggers, or in continuous loops when no specific synchronization is required. For systems with turn or bunch resolution, events were forwarded by the LHC fast timing system BOB, which was already configured and capable to fulfill this role. For certain systems the beam energy must be known as well. It is transmitted through the global machine timing (GMT).

 

To test the various BI systems, and others as well, a test sequence of events had regularly been played. This sequence simulated a series of fills (i.e. injections and dumps at different energy) covering a full day. During each simulated fill, in addition to the standard injections, start/stop ramp, and beam dump events, also BI capture events were sent every 20 sec. The energy information too was transmitted through the timing. The same sequence could also be used for beam dump reliability tests. Unfortunately this sequence was no longer available at the time of this LHCCWG meeting, and would be restored only after the repair of the diluter kickers, foreseen for week 23. The kickers were part of the energy transmission loop. In the mean time, a simple interim event sequence ran capture events of interest (no PM events) on a regular basis at a fixed energy of 7648 GeV.

 

Jean-Jacques explained that BI retransmitted events through BST to guarantee turn-by-turn synchronization of acquisitions of BPMs etc. Events above zero on his slide no. 10 represented capture events. The tool described was available for commissioners to check the instrument status.

 

Jean-Jacques now reviewed in more detail the individual dashboard columns belonging to the commissioner domain, namely: XPOC (fast/systematic beam dump check), PM (Post Mortem Service), SetMan (Settign Management), RBAC (Role Based Access control), Logging, FixDisp (Fixed Displays and video transmissions), and OPGUI (OPerational Graphical User Interfaces).

 

For XPOC the feedback & OK would come from Verena and for PM from Markus Zerlauth. For SetMan, a tool‘extended acquire settings’ proposed by Greg would cover the needs. For every BI observable an LHC ‘HW’ group would be created, and the observable archives would be managed with the above tool. Some commissioners would participate in this archiving activity. Concerning RBAC, extensions were needed, which were to be finalized by CO. They were expected to be operational not earlier than at the end of June. The BI plans for RBAC are documented in EDMS. Reyes was taking care of RBAC issues for OP. Jean-Jacques insisted that non RBAC-aware applications would lose connection with RBAC-aware FESA servers. At the beginning of July a test would be made and the mode swapped to RBAC, in order to see what still ran.

 

Jean-Jacques pointed out that for the moment there was no RBAC server. If the other applications were shown not to comply with the RBAC policy, BI would not make the effort.

 

Concerning logging, Jean-Jacques announced that BLM logging was already ongoing. During this week, discussions, definitions and implementations would start for the logging efforts with BRANA, BRANB, BWS, BSRA, and BSRTS.

 

Mike asked for the status of BRAN. Jean-Jacques answered that all details could be found on the BI wiki page, e.g. wiki status information for the BRANA. The BRANB was ready for startup. On the other hand, for BRANA (to be installed in IP1 & 5) Jean-Jacques was confident that these monitors would not be ready for startup. As a temporary solution for 2008, BI was adding scintillators and photomultipliers. In this way at least some acquisitions would be possible. The physical status was that 2 of 4 systems of BRANA had been declared “operational”, but the electronics was not yet available. A 3rd BRANA would be repaired at CERN. No date was known for the arrival of 4th one. Part of the needed electronics work had not started yet. Oliver mentioned that a discussion with LARP was planned in the immediate future. He recalled that LARP had recently promised that the BRANA monitors would be ready, and had approved the corresponding funding. Helmut remarked that data from the experiments would be available, including signals from the zero-degree calorimeters. These signals could provide more information, and they were already included in data exchange between machine and experiments (DIP). Jean-Jacques added that later a simple swap was possible from the temporary detectors to the real BRANA when available.

 

Massimiliano asked about the impact of the temporary monitors on the use of LHCf. Jean-Jacques responded that this would have to be discussed with Enrico Bravin. He did not see any impact. Helmut commented that the scintillator was a thin object and did not replace any other component. Massimiliano clarified that his question indeed concerned the material interference, and not the data processing.

 

As for fixed displays and video transmissions, these included alarms, BI video transmissions, and CO ‘standard’ fixed displays. The full list of video links illustrates that there is an exceptional treatment in the video treatment for certain devices, e.g. BTVDD and BSRT/BGI have dedicated links.

 

Concerning OPGUI, Jean-Jacques reported that BI was collecting all available information on BI instrument applications on the SW portal LIDS. Commissioners should consult this web site, and also the AB-BI LHC Technical Board Wiki pages, featuring all the instrumentation, with details on the interface, software link, navigator link, expert GUI links, software links, BI links etc.

 

Mike asked whether anyone could launch applications from this web site. Jean-Jacques replied that it was not accessible from outside CERN. He then pointed out an issue for the ABP colleagues, sitting mainly in Meyrin with non-configured/non-trusted machines. One possibility was to open a future BI terminal server cluster to ABP commissioners; this option was under discussion with CO. Jean-Jacques stressed that “the door would be closed” when RBAC was implemented.

 

Ralph suggested that the PC in his office should be correctly configured. Jean-Jacques described one difficulty, namely that the general network should not affect the technical network, and that Stefan Lueders and Pierre Charrue had reduced the list of trusted machines to zero. An alternative was to use terminal servers, where nothing could be installed. Operators would use the consoles instead. The goal was to provide a simple recipe for accessing a place where also expert applications can be found. Ralph expressed the hope to get a written summary of this procedure. 

 

Jean-Jacques pointed out that the web site provided information for all machines, not only the LHC. He showed one example of an instrument status. These pages were supposed to be maintained by the instrument commissioners after taking over. To support this commissioner activity, mini team mailing lists were set up, and an “issue tracking tool” was also made available.

 

John inquired whether after an MD one could still access data from BI instruments using a non-configured computer. Jean-Jacques reassured him that most of the BI GUIs could acquire and save. There also was a general tool, ROSALIE. So there were indeed two possibilities to access data depending on the purpose. For instance, correlations might better be done with ROSALIE. To do this from an ABP computer, one would need to log on to the terminal server. Mike asked where the data would be located. Jean-Jacques replied that after login one could see and access afs, Nice directories, and many other places. So it would be easy to copy data to another accessible place. Indeed there were many options; only the data space was quite limited.

 

John asked whether one could mount a disk with saved data on one’s own PC, which was possible with the standard repository (“LHC_data”) as pointed out by Mike.  SDDS is the standard data format. Jean-Jacques regretted that a tool was missing in CCC to save data in SDDS format, and that there was an unfortunate clash between ROSALIE and SDDS, for the moment without any technical solution. He emphasized however that there was no problem to access data after an experiment. He also pointed out that the terminal servers had much improved, thanks to an enormous effort in IT.

 

The discussion now returned to RBAC and security. In principle every group should be represented in the security committee. Gianluigi mentioned that Christian Carli was the ABP representative. Ralph asked about some RBAC issues for collimation. Jean-Jacques recalled that Alessandro Masi was representing the collimation in the RBAC committee. Roger recommended that Ralph directly contacts the RBAC people for his question. Jean-Jacques agreed that Ralph’s proactive approach would minimize side effects.

 

Ralph recalled a LEP example. Then, applying his example to LHC, he asked how one would access databases with one’s own programmes, i.e. he would like to bring, compile, and run self-written codes, underlining that we would need to define a path for such activities. Jean-Jacques answered that the RBAC team defined the general rules, and the equipment owners defined the access rights. Roger commented that this topic might require a dedicated meeting with all the people involved.

 

Changing subject, Stephane now made a general comment related to the fact that the commissioners needed to declare the readiness of an instrument. In practice they could check the display, applications, etc., but he stressed that what would be needed was a simulator to produce fake data. He had once written such programme for the HEADTAIL monitor. He asked whether there existed such simulators for the other instruments. Jean-Jacques replied no, there weren’t any, and that there was no time either to provide such a generator. However, there would be a tool that checked functionality and/or the calibration of the instrument in intervals without beam. Stephane commented that it was easy to write simple simulator. Jean-Jacques explained that the difficult part would be to implement it in the frontend software. Instead he proposed to consider possible experience and tests in other machines. He emphasized that BI and the commissioners could not produce such simulations while other much more important items were still missing.

 

Returning to an earlier BI commissioning discussion, Gianluigi brought up 2 points: the BPM sum signal, and the BLM calibration. Concerning the BPM sum signals, Jean-Jacques reported BI was in the process of producing the cards, but not all cards would be ready by the end of July. The cards would be installed after their receipt. Gianluigi proposed to install cards at every second BPM for example to cover the full machine. Jean-Jacques responded that he would discuss with Rhodri, and he mentioned possible problems with access. He would discuss with Lars for the software side. Paul pointed out that these BPM sum signals would be required only in case of serious problems according to an earlier statement by Rhodri. Jean-Jacques agreed that yes, indeed, this was the case. However, the last BPM measurements in TI8/TT40 were more encouraging than earlier data. In any case, replying to a question by Bernhard, he confirmed that the auto-triggering of the BPMs should give sufficient information for steering the beam and to find obstacles, since the BPMs show no signal without beam. The auto-triggering threshold for the pilot beam corresponds to 2e9 protons. Jean-Jacques elaborated that there were two fixed auto-triggering thresholds, for the pilot and the nominal beam, respectively. They cannot be changed. The only variable was the intensity of the pilot bunch. Jena-Pierre Koutchouk commented that it would be nice to also have the BPM sum signal.

 

Status of Commissioning Procedures (Roger, Commissioners, EICs)

The status of procedures was discussed around the table. The EDMS procedures for phases A.0 and A.1 had been released thanks to Magali.  For phase A.2, Gianluigi reported that Magali had found the time to implement changes only the day before the meeting. Magali and he would try to discuss with Andy to get information on signals and tools from RF. Phase A.3, handled by Verena, was still listed as “under approval” only because EDMS did not close by itself. Verena received a comment to take into account the detailed BI internal commissioning procedures in this document. However, the parts of the BI procedures relevant for beam commissioning must first be surveyed. Jean-Jacques asked whether the request was one for feedback or to include the BI procedures. Verena clarified that the specific request had been to make the BI and LHCCWG procedures coherent. BI was still working on the procedures. LHCCWG should make a request what was needed. Jean-Jacques gave his OK to close the A.3 procedures for now. For phase A.4, Massimo reported that availability checks were still to be done. He pointed out that there were several common issues with phase A.9.

 

Roger highlighted that the next three stages, A.5-A.7, were still without an associated responsible commissioner, which was a point presently under discussion. For phase A.5 Laurette had implemented all comments and changes. For phase, A.6 Walter had closed the approval. All comments were included except for one, which was being followed up.  For phase A.7, collisions at low energy, Helmut mentioned that there was no special effort at the moment. He would check the situation with Magali.

 

For the status of phase A.8, Mike commented that he would check with Reyes. For phase A.9, Frank reported that tools for beta beating and dispersion had just been successfully tested at the SPS by Rogelio Tomas’ team the day before the meeting.  A concern was the ac dipoles, which were not yet operational and which would be helpful to achieve the needed resolution of optics measurements as well as for aperture studies. A slower alternative is bumps. Yannis Papaphilippou already had a fresh look at the 7 TeV IR bumps. Collimation activities must still be followed up for this phase. Local coupling tools were expected to be ready in July. For phase A.10 Helmut will check with Reyes.

 

Verena asked whether the procedures should not also include the experience gained in recent dry runs. Roger replied that the procedures were not meant to be a watertight plan, but would serve as a guideline. Mike inquired about the agreement between the web site and the EDMS procedures. Verena answered that there was 100% agreement at the moment. Roger clarified that in case of doubt the web based version should always be the place most up to date.

 

Phase A.11 was released. Stephane mentioned as potential issues the triplet misalignments in some of the IRs, and the response to too high a coupling, e.g. a large roll angle of one of the triplet magnets.  There was also a need to discuss with Mike how to change the sequence, and our general strategy with regard to beta* knobs, feedforward and feedback from beam measurements.

 

Roger announced that it had been decided that Jorg Wenninger would take charge of machine protection commissioning. Jorg would make a presentation in one week’s time. In two weeks we would look at the wishes for TOTEM commissioning.

 

Next Meeting

Tuesday June 10th, 14:00

CCC conference room 874/1-011

Provisional agenda

 

Minutes of previous meeting

Matters arising

Status and plans for Machine Protection commissioning (Jorg)

AOB

 

 

 Reported by Frank