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874/1-011 (CERN)

874/1-011

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Andrzej SIEMKO (CERN AT-MTM)
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MPP meeting (30 Jul 2008)
Present: Boris Bellesia; Maria Paz Casas Lino; Juan Casas-Cubillos; Nuria Catalan Lasheras; Giorgio D'Angelo; Sandor Feher; Robert Henry Flora; Glyn Kirby; Sandrine Le Naour; Karl Hubert Mess; Michele Modena; Antonio Perin; Mirko Pojer; Rüdiger Schmidt; Andrzej SIEMKO; Pierre Strubin; Jean-Philippe Tock; Walter Venturini Delsolaro; Louis Walckiers; Rob Wolf Chaired by: Dr. SIEMKO, Andrzej

General information

Points 5 and 6 of the agenda were postponed. The commissioning of sectors 2-3 and 6-7 is almost finished. The time needed to commission a sector was about two and a half weeks. Remaining sectors: 1-2, 3-4 and 4-5 (recommissioning). The injection test in 2-3 is scheduled on the weekend of 8/9th August. The beam will be dumped on the collimators in LSS3. Q6.R2 is not yet commissioned, and is needed for the injection test. Injection in the complete machine will follow in September. MPP involvement in beam commissioning needs to be defined. In sector 1-2 the powering tests can start at the end of this week for the arc and next week for ML2 and XL2. The inner triplet in XR2 should be finished on Friday. One current lead of Q8.L6 was found to be not tight enough, it heated up to 80 degrees, and took some time to be detected. The temperature of the warm part of the CL is not interlocked. In the short term there is not much that can be done, except reinforcing the procedure already in place that foresees cheking of the lead temperatures before approving the last commissioning step of each circuit. There is a software tool, specified by Amalia, that can be used to ease the job. Also, the cryo operators can be asked to check the lead temperatures, as agreed between Andrzej and Serge. In the long term, a solution (a software interlock or an alarm, at least) should be pursued. (Action: ECR A. Ballarino)

Recommissioning of sector 4-5 change

A first proposal had been presented by Boris at the previous general MPP meeting. Nuria presented the summary of an ad hoc MPP meeting held on Wednesday 23 July to discuss Boris' draft. The oucome of that has been collected by Nuria in a document which is being circulated through the edms system (EDMS doc number 944733). The presentation triggered a few questions and comments. Concerning the dipole circuit, it was observed that a step at intermediate current is needed, to look for possible "unbalanced magnets" by means of "Zinur's tool". A. Siemko remarked that much more parallelism can be allowed, as the circuits have already been debugged

Status of Q6.R2.

Juan illustrated the problems with the level gauge of Q6.R2. As a consequence of the well known effects, the gauge reading can be up to 28% lower than the actual level in the magnet. This means that in the worst (or best, whichever is preferred) case, the level is underestimated by 28%. This seems to be confirmed by the outcome of the boiloff tests. Besides, stable regulation is achieved around 38% (read value). Regulating at higher values has a negative impact on the availability of the cryo_start. Giorgio showed the results of ELQA tests in SM18 and in the tunnel. Taking into account the outcome of the ELQA, showing that this magnet has excellent insulation; that the quench heaters circuits were already tested at high voltage in He gas in SM18; and that the maximum voltage during quench is estimated at about 400 V (A. Siemko); it is concluded that the magnet will be released for QPS IST and subsequent powering at the maximum stable level that is 38%.

Status of DFBs in sector 1-2 and 3-4.

Antonio showed a synoptic slide with the status of the DFBs. A couple of DFBs are still under work. The conclusion was however that there were no showstoppers for the moment.

Instrumentation in the 600 A current leads in the DFBXs

Sandor reminded that, contrary to standard cern praxis, these sensors are not doubled. By design, there is not enough space for two off-the-shelf PT100. The exchange of a faulty sensor is a time consuming operation due the difficult accessibiliy. This is not considered compatible with the anticipated levels of radioactivity in this area. Two solutions are envisaged: looking for smaller sensors that could be used to build a redundant system, or using the available QPS voltage signals and the PO DCCT output to get an on line measurement of the resistance of the lead. This can be used to regulate the valve. The first solution will be investigated by A. Perin, the second by the MEI group (Louis)
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