1

Joint BLM Threshold and LHC Collimation Working Group

meeting

2014 August 25

Francesco Cerutti, Anton Lechner, Eleftherios

Skordis

for the team

COLLIMATOR LOADAND BLM RESPONSE

proton interaction distribution in the collimators

by Roderik Bruce et al. (collimation team)

2014 August 25 F. Cerutti CWG#179 2

DIFFERENT SENSITIVITY [I]

PRIMARY COLLIMATORS (IR7, B1) 3.5 TeV

halo plane

BLMresponse

protoncatcher

BLM_TCP.D BLM_TCP.C BLM_TCP.B

horizontal TCP.C 0.01 1 2.53

vertical TCP.D 0.58 1.80 2.13

normalized to 4.58 10-12 Gy/p i.e. the BLM_TCP.C response to a 3.5 TeV proton caught in the

TCP.C6.5 TeV

BLM_TCP.C

1.38

dependence on jaw orientation

dominant cross talk

energy dependence

2014 August 25 F. Cerutti CWG#179 3

DIFFERENT SENSITIVITY [II]

TERTIARY COLLIMATORS (IR5, B1) 3.5 TeV

halo plane

BLMresponse

protoncatcher

BLM_TCTH BLM_TCTV

horizontal TCTH 6.27 1.21

horizontal TCTV 0.43 3.23

normalized to 4.58 10-12 Gy/p i.e. the BLM_TCP.C response to a 3.5 TeV proton caught in the

TCP.C7 TeV

BLM_TCTH BLM_TCTV

18.1 4.68

0.71 13.9

dependence on jaw material

dependence on jaw orientation

cross talk, even backwards

energy dependence

2014 August 25 F. Cerutti CWG#179 4

REFERENCE AND BENCHMARKING

E. Skordis’ presentation at the CWG #160 on May

6, 2013

2014 August 25 F. Cerutti CWG#179 5

LOSS DEPTH IN THE TCTs

TCT

V

TCT

H

TCTH

TCT

V

shifted by

5mm

3.5 TeV2011

7 TeVHL-LHC

shifted by 7.5mm

2014 August 25 F. Cerutti CWG#179 6

VARIATION OF THE TCT BLM RESPONSE [I]

TERTIARY COLLIMATORS (IR5, B1) 3.5 TeV

halo plane

BLMresponse

protoncatcher

BLM_TCTH BLM_TCTV

vertical TCTH 6.73 1.47

vertical TCTV 0.53 3.08

normalized to 4.58 10-12 Gy/p i.e. the BLM_TCP.C response to a 3.5 TeV proton caught in the

TCP.C7 TeV

BLM_TCTH BLM_TCTV

19.1 6.10

0.60 15.3

2014 August 25 F. Cerutti CWG#179 7

TERTIARY COLLIMATORS (IR1, B1) 3.5 TeV

halo plane

BLMresponse

protoncatcher

BLM_TCTH BLM_TCTV

vertical TCTH 7.21 1.14

vertical TCTV 0.40 3.25

normalized to 4.58 10-12 Gy/p i.e. the BLM_TCP.C response to a 3.5 TeV proton caught in the

TCP.C

VARIATION OF THE TCT BLM RESPONSE [II]

2014 August 25 F. Cerutti CWG#179 8

TERTIARY COLLIMATORS (IR1, B1) 3.5 TeV

halo plane

BLMresponse

protoncatcher

BLM_TCTH BLM_TCTV

horizontal TCTH 6.90 1.07

horizontal TCTV 0.41 3.31

normalized to 4.58 10-12 Gy/p i.e. the BLM_TCP.C response to a 3.5 TeV proton caught in the

TCP.C

VARIATION OF THE TCT BLM RESPONSE [III]

2014 August 25 F. Cerutti CWG#179 9

LOAD ON THE TCT JAWS

TCTH: 2.14 + 2.58 10-7 J per caught

protonTCTV: 3.22 + 1.82 10-7 J per caught

proton

7 TeVHL-LHC

2014 August 25 F. Cerutti CWG#179 10

LOAD ON THE TCP JAWS3.5 TeV

TCPC: 1.05 10-8 J (in the whole collimator) per caught proton

TCPB: 3.9 10-8 J (in the whole collimator) per proton caught in

the TCPC

[F. Cerutti’s presentation at the CWG #108 on Nov 9,

2009]

here (multiple) ionizing passages of halo

protons before interaction not considered

2014 August 25 F. Cerutti CWG#179 11

THE GLOBAL VIEW: IR7 LSSTCP

TCSG

TCLA

1MW @ 4 TeV

2014 August 25 F. Cerutti CWG#179 12

CONCLUSIONS

Number of protons lost in a collimator and signal of the respective BLM are not

connected by an universal constant. Strong dependence on jaw material, orientation

and relative BLM position as well as very important cross talk.

Response matrices (per lost proton) were calculated for primary and tertiary

collimators, considering different beam energies and machine configurations. Looking

at TCTs, the various spatial distributions of losses in the collimator jaws, varying from

one collimator to another and as a function of the halo plane and of optics and

collimator settings, with averages values of the order of mm, do not affect significantly

the BLM response. Collimator settings may significantly change the number of losses

on a collimator and consequently scale up the respective BLM signal, without changing

the response matrix. Before writing numbers in stone, a systematic revision is

advisable (e.g. to uniform assumptions on jaw density).

Assessment of collimator load limits can be improved based on joint simulations

including the thermomechanical stage.

Physics debris collimator thresholds are a special case, not touched here.

2014 August 25 F. Cerutti CWG#179 13