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MPP meeting
MPP meeting (18 Jun 2008)
Present: Boris Bellesia; Juan Casas-Cubillos; Maria Casas Lino; Nuria Catalan Lasheras; Giorgio D'Angelo; Sandor Feher; Robert Henry Flora; Karl Hubert Mess; Michele Modena; Antonio Perin; Mirko Pojer; Vittorio Remondino; Carlos Fernandez Robles; Stephan Russenschuck; Roberto Saban; Rudiger Scmidt, Pierre Strubin; Jean-Philippe Tock; Rob van Weelderen; Antonio Vergara Fernandez; Arjan Verweij; Louis Walckiers; Rob Wolf; Markus Zerlauth.
Chaired by: R. Wolf
ElQA issues and sector 2-3. G. D'Angelo
In sector 2-3, everything but DFBMB/C and Q6R2 and DFBX has passed ElQA at cold. No critical non-conformities. Worth mentioning the problems with the instrumentation in the proximity equipment and some non conformities during DOC tests in dipole correctors. They have all been solved.
In sectors 2-3 and 8-1 the level becomes unstable when overfilling and shows oscillations in phase with the vapor fraction. In sector 7-8 the level suddenly drops to zero every 2-3 days in most of the stand-alone cryostats. Taconis oscillations are suspected. There seems to be a correlation of the susceptibility of the system with tilt and slope in the tunnel.
The configuration of the level housing volume makes the level reading extremely sensitive to vapor pressure (~86 mm/mbar). A static heat load 0,3 W will corresponds to about 10 mm of systematic bias in the reading. Pressure variations from any source will directly translate into changes in level reading. The geometry of the cold capillary and the lack of mechanical support may lead to presence of liquid in the capillary which will block the gage. The magnet fill line is positioned near the magnet vapor exit which is in turn joined to the cold capillary. This increases the exposure to liquid droplets that will invalidate the level reading.
In the short term, it is proposed to set the maximum level to be controlled below the liquid fill point. In the long term, the cold vapor exhaust capillary should be changed for a larger diameter from 2 mm to 8 mm inner diameter and low points should be eliminated. Increasing the liquid fill point of the cold mass could also be envisaged.
J.Ph. Tock informed that this intervention is feasible in the tunnel but may have a large impact as warm vacuum has also to be disconnected.
As the level reading is not reliable, MPP needs to look at the consequences for the magnet if the coils/splices/bus-bars are not in liquid. The minimum controlled level that is not dangerous for the machine should be re-evaluated. At the same time the reading could be filtered for spikes.
J. Casas Cubillos reported that in the Q5R8 cryostat the pressure in the cold mass is higher than in line D when opening the warm by-pass. This had never been observed before and is under investigation. It is proposed to overfill the cold mass and check the outlet temperature. Cryogenic operation may be disturbed.
M. Zerlauth is preparing an ECR for the D3, D4. This includes the change of the DCCT in the power converter. A similar ECR will be needed for the inner triplet quadrupoles but the DCCT required in this case is longer to develop.
The magnets will not be tested up to this currents during this phase of hardware commissioning.
M. Bednarek and J. Ludwin showed the results of measurements done at 3 kA (see slides). When the quench detection compares the voltage between the poles of the same aperture the signal is flat and the voltage threshold is not attained. If the signals from each aperture are recalculated and compared, a spike at 70mV is made evident. The peak seems to be an artifact coming from the protection system algorithm. Additional voltage pulse test did not show signs of short circuit inside the magnet.
A. Verweij reported that both apertures seem to behave differently. This was already observed in SM18. A model assuming different contact resistance for the cable used in both apertures seems to match the observed voltages. Indeed the cables used for the apertures manufacturing showed a large spread at the beginning of cable production.
It is evident that there is no risk for the magnet. It is recommend to change the threshold to 250mV for this particular magnet and repeat the test at 7kA and then go on with the normal program. (Discussions after the meeting conclude that changing the threshold involves a non negligible work that can not be done immediately. As no discharge is foreseen in the remaining program, it was decide to go ahead with powering to nominal.)
R. Wolf showed data from SM18 tests where a large negative b3 was measured in one of the apertures. It does not however have the sign that it should if it was caused by a large contact resistance.
3 July 2008
Nuria Catalan Lasheras
Present: Boris Bellesia; Juan Casas-Cubillos; Maria Casas Lino; Nuria Catalan Lasheras; Giorgio D'Angelo; Sandor Feher; Robert Henry Flora; Karl Hubert Mess; Michele Modena; Antonio Perin; Mirko Pojer; Vittorio Remondino; Carlos Fernandez Robles; Stephan Russenschuck; Roberto Saban; Rudiger Scmidt, Pierre Strubin; Jean-Philippe Tock; Rob van Weelderen; Antonio Vergara Fernandez; Arjan Verweij; Louis Walckiers; Rob Wolf; Markus Zerlauth.
Chaired by: R. Wolf
ElQA issues and sector 2-3. G. D'Angelo
In sector 2-3, everything but DFBMB/C and Q6R2 and DFBX has passed ElQA at cold. No critical non-conformities. Worth mentioning the problems with the instrumentation in the proximity equipment and some non conformities during DOC tests in dipole correctors. They have all been solved. Level gauges. R. van Weldeeren
R. van Weldeeren summarized the problems seen on level gages for the stand-alone magnets.In sectors 2-3 and 8-1 the level becomes unstable when overfilling and shows oscillations in phase with the vapor fraction. In sector 7-8 the level suddenly drops to zero every 2-3 days in most of the stand-alone cryostats. Taconis oscillations are suspected. There seems to be a correlation of the susceptibility of the system with tilt and slope in the tunnel.
The configuration of the level housing volume makes the level reading extremely sensitive to vapor pressure (~86 mm/mbar). A static heat load 0,3 W will corresponds to about 10 mm of systematic bias in the reading. Pressure variations from any source will directly translate into changes in level reading. The geometry of the cold capillary and the lack of mechanical support may lead to presence of liquid in the capillary which will block the gage. The magnet fill line is positioned near the magnet vapor exit which is in turn joined to the cold capillary. This increases the exposure to liquid droplets that will invalidate the level reading.
In the short term, it is proposed to set the maximum level to be controlled below the liquid fill point. In the long term, the cold vapor exhaust capillary should be changed for a larger diameter from 2 mm to 8 mm inner diameter and low points should be eliminated. Increasing the liquid fill point of the cold mass could also be envisaged.
J.Ph. Tock informed that this intervention is feasible in the tunnel but may have a large impact as warm vacuum has also to be disconnected.
As the level reading is not reliable, MPP needs to look at the consequences for the magnet if the coils/splices/bus-bars are not in liquid. The minimum controlled level that is not dangerous for the machine should be re-evaluated. At the same time the reading could be filtered for spikes.
J. Casas Cubillos reported that in the Q5R8 cryostat the pressure in the cold mass is higher than in line D when opening the warm by-pass. This had never been observed before and is under investigation. It is proposed to overfill the cold mass and check the outlet temperature. Cryogenic operation may be disturbed.
Curent levels for D3,D4 magnets. S. Feher.
The recommended maximum powering currents for Q1 and Q3 is 7180A (215 T/m) and for Q2 11960 A (215 T/m). This current levels were tested in Fermilab and KEK. For the separation dipoles D3 and D4 7100A is considered to be safe based on the BNL RHIC magnet experience. They may however experience training quenches as they were never powered to this current.M. Zerlauth is preparing an ECR for the D3, D4. This includes the change of the DCCT in the power converter. A similar ECR will be needed for the inner triplet quadrupoles but the DCCT required in this case is longer to develop.
The magnets will not be tested up to this currents during this phase of hardware commissioning.
Matters arising. MB30.R7 MB1007
During the PLI3.f1 test in RB.A78 (provoked quench at 7kA in magnet B19R7) of June 9th, the magnet MB30.R7 quenched almost simultaneously. On June 11th the same magnet quenched during the test PLI3.d2 (7 kA discharge requests). A fast differential voltage raise was observed during the fast discharge that may be the sign of an inter-turn short in one of the apertures. The QPS system detection is based on the comparison of both apertures in the same magnet. Scopes were connected to this magnet acquiring the signals of all voltage taps available.M. Bednarek and J. Ludwin showed the results of measurements done at 3 kA (see slides). When the quench detection compares the voltage between the poles of the same aperture the signal is flat and the voltage threshold is not attained. If the signals from each aperture are recalculated and compared, a spike at 70mV is made evident. The peak seems to be an artifact coming from the protection system algorithm. Additional voltage pulse test did not show signs of short circuit inside the magnet.
A. Verweij reported that both apertures seem to behave differently. This was already observed in SM18. A model assuming different contact resistance for the cable used in both apertures seems to match the observed voltages. Indeed the cables used for the apertures manufacturing showed a large spread at the beginning of cable production.
It is evident that there is no risk for the magnet. It is recommend to change the threshold to 250mV for this particular magnet and repeat the test at 7kA and then go on with the normal program. (Discussions after the meeting conclude that changing the threshold involves a non negligible work that can not be done immediately. As no discharge is foreseen in the remaining program, it was decide to go ahead with powering to nominal.)
R. Wolf showed data from SM18 tests where a large negative b3 was measured in one of the apertures. It does not however have the sign that it should if it was caused by a large contact resistance.
3 July 2008
Nuria Catalan Lasheras
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