why do blms need to know the quench levels?

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

1/xx

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


2/xx

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)


3/xx

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


4/xx

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.


5/xx

-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]


6/xx

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


7/xx

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)


8/xx

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 %


9/xx

Quench Levels and Energy Dependence

Fast decrease of quench levels between 0.45 to 2 TeV


10/xx

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


11/xx

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


12/xx

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


13/xx

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).


14/xx

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.


15/xx

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


16/xx

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).


17/xx

Detector Signal Chain

Threshold Comparator: Losses integrated in 12 time intervals to approximate quench level curve.


18/xx

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)


19/xx

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

why do blms need to know the quench levels?

Documents

magnet quench levels

quench prevention0

dehningquench levels

dehningloss levels

loss rate

proton loss location

lhc project report

particle losses