Summary notes of the
forty-sixth meeting of the LHC Commissioning Working Group
Tuesday June 3rd, 14:00
CCC conference room 874/1-011
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.
Status and plans for Machine Protection commissioning (Jorg)