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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. - PowerPoint PPT Presentation
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03.03.2005Why do BLMs need to know the Quench Levels, B.Dehning
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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
03.03.2005Why do BLMs need to know the Quench Levels, B.Dehning
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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)
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Loss Levels and Required Accuracy
Relative loss levels
450 GeV 7 TeV
Damage to components
320/5tran./slow
1000/25 tran./slo
w
Quench level 1 1
Beam dump threshold for quench prevention
0.3 0.3/0.4 tran./slo
w
Warning 0.1 0.1/0.25tran./slow
Absolute precision (calibration)
< factor 2 initially: < factor 5
Relative precision for quench prevention
< 25%
Specification:
Accurately known quench levels will increase operational efficiency
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Simulation Results on Longitudinal Proton Loss Distribution
Longitudinal losses strongly peaked at the beginning of the quadrupoles, bin width = 1 m (dipoles not shown).
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.
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-0.00001
0.00004
0.00009
0.00014
0.00019
100 150 200 250 300 350 400 450 500
Losses
Dipoles
Quadrupoles
Other (no magnet)
Location of Proton Losses along the LHC
Q7Q8
Q11
p lo
st /
p o
n pr
imar
y co
llim
ator
Dispersion suppressor and beginning of arc right of IR7, z [m]
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Change of Aperture at QuadrupolesApperture Diameter in front of Arc Qadrupole
35
3739
41
43
4547
49
278 278.5 279 279.5
distance from last collimator [m]
[m
m]
horizontal
vertical
Apperture Diameter after Arc Qadrupole
35
40
45
50
285.5 286 286.5 287
distance from last collimator [m]
[mm
]
horizontal
vertical
Tertiary halo tracking => proton loss location (talk G. Robert-Demolaize)=> location of highest energy density in coil
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LHC Bending Magnet Quench Levels, LHC Project Report 44
Quench energy density in SC coil
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
0.01 0.1 1 10 100 1000 10000 100000
loss duration [ms]
J/cm
3
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
Gy
Quench Energy [J/cm3] 7 Tev
Quench Energy [J/cm3] 450GeVdummy
Quench power in SC coil
1.00E-03
1.00E-02
1.00E-01
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
0.01 0.1 1 10 100 1000 10000 100000
loss duration [ms]W
/cm
3
Quench Power[W/cm3] 7 TevQuench Power[W/cm3] 450 GeV
0.8 mJ/cm3 = 0.09 mJ/g, (RHIC=2 mJ/g, Tevatron=0.5mJ/g)
38 mJ/cm3 = 5 mJ/g 5 mW/cm3 = 0.6 mW/g
(RHIC = 8 mW/g, Tevatron = 8mW/g)
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Approximation of Quench Levels
Dump level tables are loaded in a non volatile RAM Any curve approximation possible
Loss durations Energy dependence
Avarage approximation
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0.01 0.1 1 10 100 1000 10000 100000 1000000
loss duration [ms]
Arc
cha
mbe
r cu
rren
t (1
litr
e) [
A]
7 TeV high 450 GeV lowApproximation Approximation
1.E-05
1.E-04
1 10 100
Relative error kept < 20 %
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Quench Levels and Energy Dependence
Fast decrease of quench levels between 0.45 to 2 TeV
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Operational Range of BLMs
DynamicArc: 108
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E+09
1.E+10
1.E+11
1.E+12
1.E+13
1.E+14
1.E+15
1.E+16
1.E+17
1.E+18
1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06
duration of loss [ms]
qu
en
ch
le
ve
ls [
pro
ton
/s]
Quench level and observation range
450 GeV
7 TeV
Damage levels
Arc
2.5 ms
Ionisation chamber
1 turn
SEM
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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 positionLoss location
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Shower Development in Dispersion Suppressor Magnets
120.PROX
0
20
40
60
80
100
120
9000 10000 11000 12000 13000 14000z cm
10-4
ch./p
/cm
2
210.PROX
0
25
50
75
100
125
150
175
200
9000 10000 11000 12000 13000 14000z cm
10-4
ch./p
/cm
2
MBB MBB MQML
MCBCB
MBB
MCS MCSMCS
MBAMCDO
MBB MBB MQML
MCBCB
MBB
MCS MCSMCS
MBAMCDO
Q10
Q10
beam1
beam2
loss@ 11448cm
loss@ 11448cm
left detector signal
right detector signal
shower maximum @ 11560cm
shower maximum @ 11360cm
• Shower maximum: 1m after impact
location• Shower width: FWHM 0.5m
x
y
z
MQML
right detector
left
det
ecto
r
D
F
beam1
iron yoke
coppercoils
vacuum vessel
beam2
shrinking cylinder
(0,0,0) x
y z
phi
Cross-section of the quadrupole MQML in Q10
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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).
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Shower Development in Dispersion Suppressor Magnets
phi
z (cm)
phi
phimean = 10.59º
region of shower maximum
Phi-distribution of particles exiting the vacuum-vessel
theta
Theta-distribution of particles in the detector
• 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.
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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 M
IPs/
p c
m2
BLM position
BLM position
Loss locationLoss location
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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).
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Detector Signal Chain
Threshold Comparator: Losses integrated in 12 time intervals to approximate quench level curve.
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Subjects to be Studied?
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
3700 monitors need threshold values (11 time slots and 30 energy slots)
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Beam Loss Display
0
0.2
0.4
0.6
0.8
1
1.2
Mea
sure
d / T
hres
hold
Det
ecto
r 1
Det
ecto
r 2
Det
ecto
r 3
Det
ecto
r 4
Det
ecto
r 5
Det
ecto
r 6
. . .
Det
ecto
r40
00
R1
R2
R3
R4
R5
R6
War
ning
Dum
p
Inte
grat
ion
Tim
e In
terv
als