LHC BLM threshold modification reports

MPP Working Group on BLM thresholds

2010:

 

Date Title Author  
2010-07-17 Proposal on Threshold Corrections for RC Filters E.B. Holzer MPP
2010-07-28 Impact of the RC filters on BLM thresholds M. Sapinski WG meeting 1
2010-08-13 UFOs which triggered a dump and PM A. Nordt MPP
2010-08-18 BLM Thresholds on Superconducting Magnets M. Sapinski WG meeting 2
2010-09-03 QP3 code quench thresholds for the MB A. Verweij MPP
2010-09-03 Threshold Model Comparison M. Sapinski MPP
2010-10-25 New MQ threshold proposal for 2010 M. Sapinski WG meeting 4
2010-10-29 Quench test with wire scanner planning M. Sapinski WG meeting 5
2010-11-26 Quench thresholds for the MB and MQ using the code QP3 A. Verweij WG meeting 6
2010-11-26 Warm Magnet thresholds and threshold definitions E.B. Holzer WG meeting 6

 

Meeting Minutes

6th Meeting

2010-11-26   

The update on the warm magnet thresholds were presented in detail and new results from Arjan's model. The warm magnet thresholds will stay unchanged for 2011 start-up. Cold magnet thresholds will be adapted empirically (taking into account UFOs and other measured losses and wire scanner and quench tests.

5th Meeting

2010-10-29    Arjan, Bernd, Ruediger, Jorg, Mariusz, Chiara, Eduardo, Barbara

  1. Planning for wire scanner threshold test (Mariusz) foreseen for November 1st or 2nd: dedicated ramp, 150 bunches at 3.5 TeV, beam 2 (to avoid high losses at IP6), thresholds up to and including RS7 set to 23 Gy/s on 9 monitors (on 6 more monitors, MF set to 1).

4th Meeting

2010-10-25    Arjan, Ruediger, Jorg, Mariusz, Ralph, Stefano, Annika, Chiara, Eduardo, Barbara

  1. No new cold magnet master thresholds will be deployed in 2010. New thresholds using Arjan's model will be deployed for 2011 start-up.

  2. Ruediger will call for a mini-workshop on allowed limits of lost protons/m/s with Collimator, MPP and BLM people.

  3. Temporary thresholds to be prepared for quench tests with wire scanner --> proposal by Mariusz

3rd Meeting

2010-08-27    Arjan, Ruediger, Jorg, Jan, Annika, Chiara, Eduardo, Barbara

 

  1. Installation work technical stop 30.8. - 1.9. in order of priority:

    1. IP3 non conformities investigations; improve HV cabling (loop)
    2. Change position of diamond detectors. Location to be clarified. Ask permission from RP before drilling!
        DCUM before 30.8.2010 DCUM after 30.8.2010
      left IP7    
      right IP7    
    3. Install new IC with filter at same position as BLMEI.04L6.B2I10_TCSG.4L6.B2 and BLMEI.04R6.B1E10_TCSG.4R6.B1; introduce them in the DB with new expert names
  2. To be able to distinguish monitors with filters in Online display and Post Mortem Application:
    1. long term solution: propagate information about filters from MTF/Layout DB to LSA DB
    2. short term solution: read info from a local file, holding monitor names and multiplication factors (for each RS). Show filter monitors in one separate color. Add an option to multiply the signal and the threshold with the correction factor. --> check with Christos
  3. Change the steady state allowed loss rate in the calculations of the warm magnet (including septa) thresholds (temporary solution till new simulations are available). Increase threshold on long RS by a factor of 9. --> check with Mariusz (Delio Duarte Ramos, Alessandro Bertarelli) --> implementation: Eduardo (timescale 1-2 weeks)
      number of protons in 40us current
    number of protons in 89s    		 new
    number of protons in  89s
    450 GeV 1E12 1E12 1E11 protons/second
    7 TeV 1E10 1E10 1E9 protons/second

2nd Meeting

2010-08-18      Arjan, Ruediger, Annika, Chiara, Mariusz, Barbara

  1. In order to scale to diamond signals: 1 Gy/s measured in the BLM IC (ionization chamber) corresponds to XXX charged particles passing through the chamber? --> Barbara

  2. Time constants used in the cold magnet threshold calculations (from note 44), are according the Arjan very conservative, and the model rather unphysical.  Arjan will work with Mariusz on a more physical model for threshold calculation. Mariusz will deploy the new thresholds for the magnet(s) which see wire scanner losses for testing. On all other cold magnets we will stay with the existing model and time constants till the December technical stop (when we will most likely update with new thresholds). Up to then the applied thresholds can be increased by using the MF (monitor factor). Note 44 time constants were:

 

450 GeV

7 TeV

t_helium

44ms

8ms

t_metal

~6ms

~3ms

  1. FLUKA simulations of dust particles (M. Brugger, F. Cerutti, A. Ferrari, V. Vlachoudis, “FLUKA Estimations Concerning Obstacles in the LHC Magnets,” CERN-AB-Note-2007-018 ATB (2007)) should be compared to GEANT4 simulations of wire scans. (Additional question: Is there a significant difference in longitudinal loss pattern between beam hitting the aperture and material meeting the beam in the middle of the aperture?) --> Mariusz (simulations: Stella)

  2. BLM threshold quenchino test with nQPS and temperature measurements: Arjan pointed out that the 600A corrector magnets might quench earlier that the MB and MQ, because they have no helium inside the coil. (This statement is most likely not true for the 4.5K LSS magnets, because superfluidity is lost and He has less influence on cooling).  On the other hand the current in these magnets can be wet independently from the beam energy. We should include changing the corrector currents in the quenchino tests. --> Bernd:

  • Update test procedure to include changing corrector currents

  • Present test to MP3 for approval.

  1. Define threshold test creating losses with WS:

    • Can the nQPS system be adapted for quenchino measurements at the LSS magnets as well? Temperature measurements? --> Rudiger

    • Deploy new thresholds (see point 2 above)

    • Define test conditions

    • Can the WS movement be slowed down in order to slowly increase the losses till a quenchino occurs?

    • In case a wire breaks, what is the consequence?

    • Include changing corrector currents in the test procedure.

1st Meeting

2010-07-28      Brennan, Chiara, Wolfgang, Annika, Eduardo, Mariusz, Bernd, Barbara

 

The simulations of the delays were not conclusive - to be re-visited in the future.

Thresholds to be updated in order of priority:

1) TCTVB for injection and over-injection. 450 GeV thresholds to be increased by a factor of 10, all other energies not to be changed. Mariusz will calculate and set the new thresholds by 2010/07/30. --> task finished 2010/08/02 see LHC-BLM-ECR-0012

2) RC filter monitors injection region, cold magnets. Person to calculate and update and time for update to be defined. We will continue using the 'simple' exponential correction for the time being. --> task finished 2010/08/06 see LHC-BLM-ECR-0011

3) Warm magnets including septa. GEANT 4 simulation to be finished by Mariusz. Date to be defined.

 

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