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 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

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 increase quench levels: (J.B. Jeanneret et al., LHC Project Report 44) Relation between loss rate and particle flux outside the cryostat fluence: (A. Arauzo Garzia et al., LHC Project Note 238, see: http://ab-div-bdi-bl-blm.web.cern.ch) 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Loss Levels and Required Accuracy Relative loss levels 450 GeV 7 TeV Damage to components 320/5 tran./slow 1000/25 tran./slow Quench level 1 Beam dump threshold for quench prevention 0.3 0.3/0.4 tran./slow Warning 0.1 0.1/0.25 Specification: Absolute precision (calibration) < factor 2 initially: < factor 5 Relative precision for quench prevention < 25% Accurately known quench levels will increase operational efficiency 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

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). 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

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] 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Change of Aperture at Quadrupoles Tertiary halo tracking => proton loss location (talk G. Robert-Demolaize) => location of highest energy density in coil 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

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) 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

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 % 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Quench Levels and Energy Dependence Fast decrease of quench levels between 0.45 to 2 TeV 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Operational Range of BLMs Quench level and observation range 450 GeV 7 TeV Damage levels Arc 2.5 ms Ionisation chamber 1 turn SEM Dynamic Arc: 108 BLMS*: 3.2E13 protonen (nominal SPS injection) lost in about 10E-5 seconds. 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

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. BLM position Loss location 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Shower Development in Dispersion Suppressor Magnets Shower maximum: 1m after impact location Shower width: FWHM  0.5m 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

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). 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

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. 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Shower Development in Arc Magnets BLM position Loss location 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 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Why do BLMs need to know the Quench Levels, B.Dehning 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). 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Why do BLMs need to know the Quench Levels, B.Dehning Detector Signal Chain Threshold Comparator: Losses integrated in 12 time intervals to approximate quench level curve. 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Why do BLMs need to know the Quench Levels, B.Dehning 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 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning

Why do BLMs need to know the Quench Levels, B.Dehning Beam Loss Display 03.03.2005 Why do BLMs need to know the Quench Levels, B.Dehning