Summary Notes of the Sixth Meeting of Sub Working Group on the Commissioning of the Machine Protection System,
Wednesday 9th May 2007

 

 

Present: Bernd Dehning, Verena Kain, Blanca Perea Solano, Laurette Ponce, Bruno Puccio, Stefano Redaelli, Rudiger Schmidt, Benjamin Todd, Jan Uythoven, Markus Zerlauth

 

CC: Ralph Assmann, Roger Bailey, Reyes Alemany Fernandez, Brennan Goddard, Magali Gruwe, Eva Barbara Holzer, Mike Lamont, Alick Macpherson, Walter Venturini, Jorg Wenninger

 

 

1. Comments on the minutes

There were no specific comments on the minutes of the previous meeting or on the procedures published.

 

2. MPS aspects of the Commissioning Procedures of the BLM system

Laurette presented the MPS aspects of the commissioning of the Beam Loss Monitoring System. An overview of the system was given together with a list of the systems the BLMs interface to:

  1. the collimators (trigger for collimator acquisition),
  2. the SIS (for threshold comparison): it needs to be defined WHEN this check will be made and what you do when a discrepancy is found (not inject / dump the beam if present),
  3. the BI timing system for triggering PM and XPOC,
  4. the general timing signal to obtain the beam energy information,
  5. the BIS connected via 2 CIBUs per octant. One octant for the BLMs is from mid arc to mid arc,
  6. the LBDS: direct hardwired monitors – not connected via the BIS. Fixed threshold, remotely readable.

 

Before each fill an internal test of the LBDS system is made; the user permit will be false if this tests fails.

 

The Individual System Tests are summarised on slide 8. It was discussed how often the radioactive source test should be repeated, about 3 months are needed for a full check of the machine. It seems to make sense to only check again when work has been going on in a specific area of the machine, except for the direct BLMs to the LBDS which should be checked every year. The only risk is a wrong cabling, as being disconnected is automatically detected. The SIL level tests mentioned are to be done before every fill.

 

The sensitivity of the magnets to a quench need to be validated with beam; this concerns the machine uptime and not the machine protection (unless one assumes that if we got the quench level really wrong, we might have a similar mistake with the damage level). Beam tests will also show if the predicted relative values between the different BLMs are correct.

 

During the cold check-out the interface with the sequencer should be tested, like including the task that an electronics check is made before every fill and the threshold values agree with the data base values. There is a hardware timer, which will automatically perform these tests when there is no beam. During the cold check-out it should be verified that if the data base threshold settings don’t agree with the actual settings a beam dump request is generated.

 

Tests with beam were briefly described: provoke a beam dump with lowered thresholds; at least one test per octant should be made. The effect of the masking of an interlock should also be tested. The PM facility should be used to measure the delay between the detection of a ‘beam loss’ and the moment that the beam is dumped. The ‘timing’ of the BLMs needs to be synchronised with the other systems. The timing for the PM is a general issue to be checked across all systems. It was proposed to discuss this in the LHCCWG. The tests of the interface between BLM and BIC also remain to be defined in more detail (dependence on beam / no beam conditions).

 

The necessity and some details of provoking a quench during the sector test and / or with circulating beam was discussed. Details of the tests remain to be defined. A single turn loss test was considered to be very important as it is a more direct measurement than for a steady state loss. It remains to be discussed if the direct BLM to the LBDS needs to be tested with beam (with reduced threshold?).

 

The procedure to disable a BLM monitor when required needs to be defined in detail. It also needs to be determined how many BLMs one would allow to be disabled. It also needs to be defined which monitors will be maskable.

3. Next Meeting

In the next meeting (20th June) the commissioning procedures of the WIC and the Injection System will be discussed.

Jan Uythoven, 29/05/07.