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Why do BLMs need to know the Quench Levels?

Why do BLMs need to know the Quench Levels?. Measurement principle BLM design consideration Loss locations Response time, dynamic range (quench level vs loss duration or vs energy) Detector locations Particle shower development. Measurement Principle.

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Why do BLMs need to know the Quench Levels?

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  1. Why do BLMs need to know the Quench Levels? • Measurement principle • BLM design consideration • Loss locations • Response time, dynamic range (quench level vs loss duration or vs energy) • Detector locations • Particle shower development Why do BLMs need to know the Quench Levels, B.Dehning

  2. Measurement Principle • Detection of shower particles outside the cryostat to determine the coil temperature increase due to particle losses =>comparison with thresholds => beam dump if exceeded • Relation between loss rate and temperature increasequench levels:(J.B. Jeanneret et al., LHC Project Report 44) • Relation between loss rate and particle flux outside the cryostatfluence:(A. Arauzo Garzia et al., LHC Project Note 238, see:http://ab-div-bdi-bl-blm.web.cern.ch) Why do BLMs need to know the Quench Levels, B.Dehning

  3. Loss Levels and Required Accuracy Specification: Accurately known quench levels will increase operational efficiency Why do BLMs need to know the Quench Levels, B.Dehning

  4. Simulation Results on Longitudinal Proton Loss Distribution Tracking of tertiary halo particles, E.B. Holzer and V. Kain (end of 2003), complete aperture model (DS and arc right of IR7), (halo particles simulated by R. Assmann), ideal alignment. Longitudinal losses strongly peaked at the beginning of the quadrupoles, bin width = 1 m (dipoles not shown). Why do BLMs need to know the Quench Levels, B.Dehning

  5. Location of Proton Losses along the LHC Q11 Q8 Q7 p lost / p on primary collimator Dispersion suppressor and beginning of arc right of IR7, z [m] Why do BLMs need to know the Quench Levels, B.Dehning

  6. Change of Aperture at Quadrupoles Tertiary halo tracking => proton loss location (talk G. Robert-Demolaize)=> location of highest energy density in coil Why do BLMs need to know the Quench Levels, B.Dehning

  7. LHC Bending Magnet Quench Levels, LHC Project Report 44 38 mJ/cm3 = 5 mJ/g 5 mW/cm3 = 0.6 mW/g 0.8 mJ/cm3 = 0.09 mJ/g, (RHIC=2 mJ/g, Tevatron=0.5mJ/g) (RHIC = 8 mW/g, Tevatron = 8mW/g) Why do BLMs need to know the Quench Levels, B.Dehning

  8. Approximation of Quench Levels • Dump level tables are loaded in a non volatile RAM • Any curve approximation possible • Loss durations • Energy dependence Relative error kept < 20 % Why do BLMs need to know the Quench Levels, B.Dehning

  9. Quench Levels and Energy Dependence Fast decrease of quench levels between 0.45 to 2 TeV Why do BLMs need to know the Quench Levels, B.Dehning

  10. SEM Quench level and observation range 450 GeV 7 TeV Damage levels Ionisation chamber 1 turn Arc 2.5 ms Operational Range of BLMs Dynamic Arc: 108 Why do BLMs need to know the Quench Levels, B.Dehning

  11. Loss location BLM position BLM locations in the arcs – longitudinal • 3 loss locations simulated: shower development in the cryostat, GEANT 3. • The positions of the BLMs are chosen to: • minimize crosstalk • reduce difference between inside and outside loss • difference with and without MDCO. Why do BLMs need to know the Quench Levels, B.Dehning

  12. Shower Development in Dispersion Suppressor Magnets • Shower maximum: 1m after impact location • Shower width: FWHM  0.5m Why do BLMs need to know the Quench Levels, B.Dehning

  13. Beam and Magnetic Field Directions • 4 combinations of beam directions and magnetic fields. • 3 loss locations: inside and outside of beam screen and top of beam screen (bottom is about the same as top). Why do BLMs need to know the Quench Levels, B.Dehning

  14. Shower Development in Dispersion Suppressor Magnets • Angles theta (angle to the x-axis) and phi of charged particles at detector location: mostly in horizontal plane and with an angle of 45 degrees to the x-axis. Why do BLMs need to know the Quench Levels, B.Dehning

  15. BLM position BLM position Loss location Loss location Shower Development in Arc Magnets • Different corrector magnet layouts simplified to two cases (with and without MDCO in front of the dipole magnet). • Dependence on energy studied: Factor of 10 to 25 in signal for a 7 TeV proton compared to a 450 GeV proton. 10-4 MIPs/ p cm2 Why do BLMs need to know the Quench Levels, B.Dehning

  16. Location of Detectors Installation with a small support and straps or cables on the cryostats Chamber (89 mm) + fixation (8 mm) just fits between the cryostat and the transport space (2 mm space left). Why do BLMs need to know the Quench Levels, B.Dehning

  17. Detector Signal Chain Threshold Comparator: Losses integrated in 12 time intervals to approximate quench level curve. Why do BLMs need to know the Quench Levels, B.Dehning

  18. Subjects to be Studied? 3700 monitors need threshold values (11 time slots and 30 energy slots) • Loss locations and their variations • Quench levels as function of time and energy for the different magnet types • Transient loss values • Quench levels between few ms to 10 s (heat flow in magnet) • Steady state values (heat flow) • Identification of error margins Why do BLMs need to know the Quench Levels, B.Dehning

  19. Beam Loss Display Why do BLMs need to know the Quench Levels, B.Dehning

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