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MP3 meeting
Participants
Adriaan Rijllart
Andrea Musso
Andrzej SIEMKO
Antonio Perin
Arjan Verweij
Gianluigi Arduini
Giorgio D'Angelo
Jaromir Ludwin
Jean-Philippe Tock
Jim Strait
Karl Hubert Mess
Marco Zanetti
Markus Zerlauth
Mateusz Bednarek
Matteo Solfaroli Camillocci
Michele Modena
Mike Koratzinos
Nuria Catalan Lasheras
Rüdiger Schmidt
Sandrine Le Naour
Vittorio Remondino
Walter Venturini Delsolaro
Zinur Charifoulline
MP3 meeting 12 August 2009
Concerning the RB circuits, this means skipping the last step and reducing the top current for the PLI3 step.
J. Strait asked what margin we are taking with respect to 3.5 TeV equivalent
Ruediger said that the margin can be small as at these currents we don't expect any training
He added that the taking a big margin would be against the minimum risk approach adopted by the management.
Arjan said that, from the splice safety standpoint, there is a big difference between hardware commissioning and operations with beam, insofar in the second case we can expect quenches at any current, while in the first case quench should only occur at the training level.
Nuria asked what is the impact of the reduced top current on the resolution of the calorimetry
A. Perin said that the resolution would be reduced
K.H. Mess suggested to increase the flat top time to compensate for the loss of resolution
M. Koratzinos said that the gain would be small as the resolution is limited by other factors
Nuria said that considering these unknowns, we should do the calorimetry as a type test on the first sector and evaluate the usefulness of it
A. Rijllart suggested skipping the flat top at 5 kA and keeping only that at 6 kA, arguing that the point at zero can be used as well
Nuria said that the fitting function is a parabola, so at least 3 points are needed
Concerning the RB procedure Nuria observed that we have still a provoked quench in it
Walter said that the usefulness of it had been put in doubt already in the past
Andrzej said that originally such tests were meant as type tests to assess propagation times from magnet to magnet and the reaction of the cryogenics system
Marco said it might have something to do with the symmetric quench protection
Walter said that a symmetric quench would be very unlikely to be observed anyway
Andrzej agreed
Jim Strait said that the propagation times are one of the important factors of uncertainty in Arjan's calculations of the safe currents
He does not imply that the provoked quench should stay in the powering procedure, as long as this parameters are measured sometime
Andrzej said that the right moment for this test is PGC as the most critical propagation time is the one from dipole to quadrupole
A. Perin said that the propagation times strongly depend on the position of the quenching magnet in the cryogenic cell and on the behavior of quench valves
K. H. Mess recalled that in HERA the quench valves opened readily and the propagation times were of the order of 10 seconds, much shorter than in the LHC.
Nuria suggested that a study should be done to select the right magnets to quench for this purpose, and that this should be integrated into the PGC procedure
Action -> A. Perin
Ruediger said that Rob van Weelderen made a study and developed a model for quench propagation at the string LHC Project Report 468 and that this model could be re-used for LHC. He suggested that Rob should be invited for a talk on the subject.
It was also agreed that the "provoked quench" step in the RB procedure be dropped if the QPS people do not have any reasons to keep it Action -> Marco will check this point with Reiner and Knud
K. H. Mess reminded the issue of the "praying junctions" in the IPQ
Nuria recalled that the experimental conditions under which the fatigue tests had been done were not fully representative of the reality in the tunnel
Andrzej suggested that MP3 recommands to set up a new experiment
There was general agreement on the proposal
Concerning the upcoming powering tests Ruediger suggested to keep in mind that for the circuits which will be commissioned up to 5 TeV, care should be taken not to take risks above 3.5 equivalent, in particular when requesting to repeat tests after training quenches.
Gianluigi said that the HCC is thinking to ask for one dedicated week at the end of the run to sort out performance issues
Andrzej said that this has to be done in any case before the next shutdown
The SPS cycle is clearly visible in the noise pattern of the voltage record
Answering to a question by Zinur, Mateusz precised that the integration time for one point is 100 ms
K. H. Mess asked why the SPS interference is not simply windowed out
Nuria said that the idea had been to study the noise in order to compare with the Megger results
Zinur asked if the current was measured
Mateusz: yes within a few ppm
Ruediger asked if there were any Keithley measurements around 20 K that could be used to get the RRR
Nuria said there is a limited set of data, which could nevertheless be used
Conclusion of the discussion: the next step will be to carry out a detailed comparison of the two sets of measurements (Megger and Keithley)
Action-> Mateusz and Mike
The plan is in Nuria's public folder
No snubber capacitor will be installed for the 3.5 TeV run.
There is still a discussion on the correct sequence of ELQA steps and nQPS connection.
Walter asked whether, without snubber capacitors, we are relying on the dynamic threshold increase to prevent massive quanch heater firing due to the travelling waves that develop upon switch opening
If this is the case, what is the reliability of the system?
Ruediger said this is as reliable as many other systems we have in the machine
He suggested to ask Jens Steckert to give us a presentation on this subject
Action->Walter
Andrzej said he had read in the minutes of LMC a proposal to suppress the global busbar detector
He does not agree with this proposal: he argued that the new QPS does not cover all stretches of bus, for example that it leaves out the connection cryostat and the bus near to the DFBA
He requested that a demostration be made and presented to MP3 that the global busbar detector can really be suppressed
Action -> Nuria will find a speaker for one of the next meetings
Walter asked whether somebody had any news about the tests of silent killers in FRESCA.
J.Philippe Tock said there was a presentation scheduled in the LMC on the subject
Walter asked whether MP3 should not be informed
Ruediger said this is how it should happen
Action->Walter will ask Luca to present the experiment to the next MP3
General information
Nuria reported on the latest LMC meeting which was devoted to discuss the risks of running the LHC to a given energy, taking into account the knowledge of the splices and simulations of beam induced quenches in the busbars.Hardware Commissioning at 3.5 TeV equivalent (M.Zanetti)
Marco presented a proposal for adapting the powering procedures to the energy for the first LHC run. (see slides) .Concerning the RB circuits, this means skipping the last step and reducing the top current for the PLI3 step.
J. Strait asked what margin we are taking with respect to 3.5 TeV equivalent
Ruediger said that the margin can be small as at these currents we don't expect any training
He added that the taking a big margin would be against the minimum risk approach adopted by the management.
Arjan said that, from the splice safety standpoint, there is a big difference between hardware commissioning and operations with beam, insofar in the second case we can expect quenches at any current, while in the first case quench should only occur at the training level.
Nuria asked what is the impact of the reduced top current on the resolution of the calorimetry
A. Perin said that the resolution would be reduced
K.H. Mess suggested to increase the flat top time to compensate for the loss of resolution
M. Koratzinos said that the gain would be small as the resolution is limited by other factors
Nuria said that considering these unknowns, we should do the calorimetry as a type test on the first sector and evaluate the usefulness of it
A. Rijllart suggested skipping the flat top at 5 kA and keeping only that at 6 kA, arguing that the point at zero can be used as well
Nuria said that the fitting function is a parabola, so at least 3 points are needed
Concerning the RB procedure Nuria observed that we have still a provoked quench in it
Walter said that the usefulness of it had been put in doubt already in the past
Andrzej said that originally such tests were meant as type tests to assess propagation times from magnet to magnet and the reaction of the cryogenics system
Marco said it might have something to do with the symmetric quench protection
Walter said that a symmetric quench would be very unlikely to be observed anyway
Andrzej agreed
Jim Strait said that the propagation times are one of the important factors of uncertainty in Arjan's calculations of the safe currents
He does not imply that the provoked quench should stay in the powering procedure, as long as this parameters are measured sometime
Andrzej said that the right moment for this test is PGC as the most critical propagation time is the one from dipole to quadrupole
A. Perin said that the propagation times strongly depend on the position of the quenching magnet in the cryogenic cell and on the behavior of quench valves
K. H. Mess recalled that in HERA the quench valves opened readily and the propagation times were of the order of 10 seconds, much shorter than in the LHC.
Nuria suggested that a study should be done to select the right magnets to quench for this purpose, and that this should be integrated into the PGC procedure
Action -> A. Perin
Ruediger said that Rob van Weelderen made a study and developed a model for quench propagation at the string LHC Project Report 468 and that this model could be re-used for LHC. He suggested that Rob should be invited for a talk on the subject.
It was also agreed that the "provoked quench" step in the RB procedure be dropped if the QPS people do not have any reasons to keep it Action -> Marco will check this point with Reiner and Knud
K. H. Mess reminded the issue of the "praying junctions" in the IPQ
Nuria recalled that the experimental conditions under which the fatigue tests had been done were not fully representative of the reality in the tunnel
Andrzej suggested that MP3 recommands to set up a new experiment
There was general agreement on the proposal
Concerning the upcoming powering tests Ruediger suggested to keep in mind that for the circuits which will be commissioned up to 5 TeV, care should be taken not to take risks above 3.5 equivalent, in particular when requesting to repeat tests after training quenches.
Gianluigi said that the HCC is thinking to ask for one dedicated week at the end of the run to sort out performance issues
Andrzej said that this has to be done in any case before the next shutdown
Keithley mesurements of busbar resistances at 80 K (M. Bednarek)
Mateusz showed the measurement results and explained the evaluation of the measurement uncertainties. (see slides)The SPS cycle is clearly visible in the noise pattern of the voltage record
Answering to a question by Zinur, Mateusz precised that the integration time for one point is 100 ms
K. H. Mess asked why the SPS interference is not simply windowed out
Nuria said that the idea had been to study the noise in order to compare with the Megger results
Zinur asked if the current was measured
Mateusz: yes within a few ppm
Ruediger asked if there were any Keithley measurements around 20 K that could be used to get the RRR
Nuria said there is a limited set of data, which could nevertheless be used
Conclusion of the discussion: the next step will be to carry out a detailed comparison of the two sets of measurements (Megger and Keithley)
Action-> Mateusz and Mike
Shft plan (Nuria)
Nuria showed the latest version of the shift planThe plan is in Nuria's public folder
AOB
Ruediger showed the status of the energy extraction parameters : the time constants will be 50 s for the RB and 10 s for the RQF-RQD.No snubber capacitor will be installed for the 3.5 TeV run.
There is still a discussion on the correct sequence of ELQA steps and nQPS connection.
Walter asked whether, without snubber capacitors, we are relying on the dynamic threshold increase to prevent massive quanch heater firing due to the travelling waves that develop upon switch opening
If this is the case, what is the reliability of the system?
Ruediger said this is as reliable as many other systems we have in the machine
He suggested to ask Jens Steckert to give us a presentation on this subject
Action->Walter
Andrzej said he had read in the minutes of LMC a proposal to suppress the global busbar detector
He does not agree with this proposal: he argued that the new QPS does not cover all stretches of bus, for example that it leaves out the connection cryostat and the bus near to the DFBA
He requested that a demostration be made and presented to MP3 that the global busbar detector can really be suppressed
Action -> Nuria will find a speaker for one of the next meetings
Walter asked whether somebody had any news about the tests of silent killers in FRESCA.
J.Philippe Tock said there was a presentation scheduled in the LMC on the subject
Walter asked whether MP3 should not be informed
Ruediger said this is how it should happen
Action->Walter will ask Luca to present the experiment to the next MP3
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The agenda of this meeting is empty