Why do blms need to know the quench levels
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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
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


Measurement principle
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


Loss levels and required accuracy
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


Simulation results on longitudinal proton loss distribution
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


Location of proton losses along the lhc
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


Change of aperture at quadrupoles
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


Lhc bending magnet quench levels lhc project report 44
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


Approximation of quench levels
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


Quench levels and energy dependence
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


Operational range of blms

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


Blm locations in the arcs longitudinal

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


Shower development in dispersion suppressor magnets
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


Beam and magnetic field directions
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


Shower development in dispersion suppressor magnets1
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


Shower development in arc magnets

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


Location of detectors
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


Detector signal chain
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


Subjects to be studied
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


Beam loss display
Beam Loss Display

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


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