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MPP meeting
MPP meeting (23 May 2008)
Present: Juan Casas-Cubillos; Nuria Catalan Lasheras; Vincent Chareyre; Sandor Feher; Robert Henry Flora; Ramon Folch; Thiesen Hugues; Karl Hubert Mess; Antonio Perin; Mirko Pojer; Vittorio Remondino; Andrzej SIEMKO; Pierre Strubin; Rob Wolf Chaired by: Dr. Siemko, Andrzej
General Information
Sector 8-1 is undergoing ElQA tests and will soon be released for powering.
DFB levels in sector 8-1
A. Perin reports that level gauge commissioning started last week for the DFBs.
Early this week boil-off tests were done.
The observed behaviour was normal, and data analysis is ongoing.
The DFB is already released for ELQA, and it is expected to be released for powering on Monday
DFBX: the heaters, needed to allow filling with LHe, are installed. One of the two level gauges is not operational. The controls will have to be switched to the other one. This is already possible as both are calibrated.
The level gauge in D2L1 is not working properly and is under investigation.
Rest of stand alone (Q5.L1, Q6.L1 and Q6.R8): the level gauges work, boil-off tests are ongoing or being analyzed. These 3 magnets should be released by Monday. It is expected that all the standalone magnets of sector 8-1 will be released by Wednesday.
It is finally agreed that tests with the instrumentation will be done at 1.7 kV. Qualification of the electronics and cables alone will be done at 1.9 kV.
K.-H. Mess recommended also to look at the corrector circuits, as the transmission though them should be faster.
A. Siemko: problem of Q5.R8. K.H. Mess summarizes the facts: at any current level, we observe 22 microOhm in all three branches of the circuit. This corrensponds to about 1 m of busbar in the normal state, for the expected range of RRR. The resistance is localised between the bottom of the leads and the magnet. The corrector circuits were measured again on Wednesday evening, observing the evolution of the voltage seen by the power converter for a long time, but this measurement was not conclusive as it is dominated by the warm cable resistance and by the associated noise. S. Feher reminds that at 700 A we observe a runaway (busbar quench) in the quadrupole circuits. It is recalled that these busbars are cryostable at low current. A team composed by A. Perin, V. Parma, J-Ph. Tock, S. Feher, K.-H. Mess, and A. Siemko will look into this. The first action could be to empty the DFBM and fill it again, the working hypothesis is that this is a cooling issue, as the cable worked before and was not touched during the intervention.
A.Siemko: the issue of MB quench heater in sector 7-8 is closed. It will be presented in the next meeting. In summary: the circuits is reconfigured with two LF heaters in parallel. The solution was already validated in SM18, although only at 4.5 K, and simulations have also been made. The other aperture will keep the standard configuration. The faulty heater will be disconnected at the magnet level. M Pojer points our that the insulation may be damaged. A.Siemko answers that we will apply a special procedure during start-up. HV tests will be repeated after the first important powering (7 and 9kA, and after any quench in the cell.
A.Siemko: reminds the request of ABP to increase the current in Q1/Q2/Q3 D3/D4. S. Feher will profit from the presence of US collaborators in WAMSDO to have a statement.
W. Venturini: 600 A correctors systematically quenching during FPA current discharges. The PO team has rejected a few PNO.d3 tests having observed the wrong time constant of the current discharge. Some magnets quench in this situation, due to the high dB/dt and dissipation in the parallel resistors. This is not optimal as it stresses the magnets unnecessarily. Also, it creates EMC issues. There is indeed no reason to discharge these circuits so fast, the limit should be set only in consideration of the protection of busbars. However changing the time constants is not possible for the time being. It is clear that these quenches are not a reason to fail PNO.d3 and PNO.a1 tests
A. Siemko comments that from the next meetings we will start to discuss the results of the analysis team. Ezio and Arjan will start with the dipole performance
A.Siemko reminds that most specificity documens for 8-1 are urgently needed. Action: editors
N.Catalan: we have not yet quenched the RB with RQF/RQD powered, which is the real situation. M. Pojer answers, it will be part of PGC test, but will not be done next week. Next meeting, Wednesday 4th of June
Present: Juan Casas-Cubillos; Nuria Catalan Lasheras; Vincent Chareyre; Sandor Feher; Robert Henry Flora; Ramon Folch; Thiesen Hugues; Karl Hubert Mess; Antonio Perin; Mirko Pojer; Vittorio Remondino; Andrzej SIEMKO; Pierre Strubin; Rob Wolf Chaired by: Dr. Siemko, Andrzej
General Information
Sector 8-1 is undergoing ElQA tests and will soon be released for powering.DFB levels in sector 8-1
A. Perin reports that level gauge commissioning started last week for the DFBs.
Early this week boil-off tests were done.
The observed behaviour was normal, and data analysis is ongoing.
The DFB is already released for ELQA, and it is expected to be released for powering on Monday DFBX: the heaters, needed to allow filling with LHe, are installed. One of the two level gauges is not operational. The controls will have to be switched to the other one. This is already possible as both are calibrated.
Stand-alone magnets level measurements in sector 8-1
Juan reported the situation of levels in the standalone magnets: in Q5.R8 there is no reading, it looks like the capillary is blocked. A warm bypass was installed yesterday and is not tested yet.The level gauge in D2L1 is not working properly and is under investigation.
Rest of stand alone (Q5.L1, Q6.L1 and Q6.R8): the level gauges work, boil-off tests are ongoing or being analyzed. These 3 magnets should be released by Monday. It is expected that all the standalone magnets of sector 8-1 will be released by Wednesday.
Status of ECR for temperature sensor electronics
Juan illustrates the proposal for an ECR concerning voltage ratings of this piece of equipement. The signal cables are qualified at 1.9kV. Electronic cards are also qualified in the lab at 1.9 kV. The weak point is at the level of the connectors that are not rated for high voltage. Juan's proposal is to continue to test the high voltage components at 1.9 kV, and to test the final assembly at a reduced voltage (below 1.6 kV). K. H. Mess remarks that this impacts the voltage rating of the whole LHC. The risks are of short circuits to the ground during quenches, and of loosing temperature sensors of the current leads. A. Siemko insists to keep the value at 1.7 kV, as it appears that problems occurred above 1.8 kV and there is no risk of damage if the magnet chain is disconnected, due to the low energy delivered by the measurement instrument. This will allow to spot weak components. P. Strubin points out that a consolidation will definetly be needed, but that this cannot be envisaged before the next shutdown. Therefore, for the time being, he suggests to focus on risk assessment and mitigation: define the consequences of reduced voltage ratings and the possible operational conducts that could improve the situation. K.H. Mess answers that recovering the design safety margin would imply decreasing considerably the energy of the machine.It is finally agreed that tests with the instrumentation will be done at 1.7 kV. Qualification of the electronics and cables alone will be done at 1.9 kV.
Matters arising
A. Siemko: anomalous fast propagation of dipole quenches. We have had four events with the one of today, which should exclude the theory of accidentally sinchronous training quenches. These are real quenches and not triggered by the QPS. Therefore we are looking for a mechanism of fast energy propagation from one magnet to the other, and we rule out hydraulics and acustics as too slow. Remains an electrical disturbance that we would not see because of the low time resolution of the signals we receive. To observe it we need scopes, or some other kind of faster acquisition. F. Caspers has found equipment already in the tunnel, wireless controlled. A. Siemko will look into it.K.-H. Mess recommended also to look at the corrector circuits, as the transmission though them should be faster.
A. Siemko: problem of Q5.R8. K.H. Mess summarizes the facts: at any current level, we observe 22 microOhm in all three branches of the circuit. This corrensponds to about 1 m of busbar in the normal state, for the expected range of RRR. The resistance is localised between the bottom of the leads and the magnet. The corrector circuits were measured again on Wednesday evening, observing the evolution of the voltage seen by the power converter for a long time, but this measurement was not conclusive as it is dominated by the warm cable resistance and by the associated noise. S. Feher reminds that at 700 A we observe a runaway (busbar quench) in the quadrupole circuits. It is recalled that these busbars are cryostable at low current. A team composed by A. Perin, V. Parma, J-Ph. Tock, S. Feher, K.-H. Mess, and A. Siemko will look into this. The first action could be to empty the DFBM and fill it again, the working hypothesis is that this is a cooling issue, as the cable worked before and was not touched during the intervention.
A.Siemko: the issue of MB quench heater in sector 7-8 is closed. It will be presented in the next meeting. In summary: the circuits is reconfigured with two LF heaters in parallel. The solution was already validated in SM18, although only at 4.5 K, and simulations have also been made. The other aperture will keep the standard configuration. The faulty heater will be disconnected at the magnet level. M Pojer points our that the insulation may be damaged. A.Siemko answers that we will apply a special procedure during start-up. HV tests will be repeated after the first important powering (7 and 9kA, and after any quench in the cell.
A.Siemko: reminds the request of ABP to increase the current in Q1/Q2/Q3 D3/D4. S. Feher will profit from the presence of US collaborators in WAMSDO to have a statement.
W. Venturini: 600 A correctors systematically quenching during FPA current discharges. The PO team has rejected a few PNO.d3 tests having observed the wrong time constant of the current discharge. Some magnets quench in this situation, due to the high dB/dt and dissipation in the parallel resistors. This is not optimal as it stresses the magnets unnecessarily. Also, it creates EMC issues. There is indeed no reason to discharge these circuits so fast, the limit should be set only in consideration of the protection of busbars. However changing the time constants is not possible for the time being. It is clear that these quenches are not a reason to fail PNO.d3 and PNO.a1 tests
A. Siemko comments that from the next meetings we will start to discuss the results of the analysis team. Ezio and Arjan will start with the dipole performance
A.Siemko reminds that most specificity documens for 8-1 are urgently needed. Action: editors
N.Catalan: we have not yet quenched the RB with RQF/RQD powered, which is the real situation. M. Pojer answers, it will be part of PGC test, but will not be done next week. Next meeting, Wednesday 4th of June
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