Study of cleaning performance with ATS optics for post LS1

Daniele Mirarchi, BE-ABP-HSS Meeting

1

Study of cleaning performance with ATS optics for post LS1

Daniele Mirarchi, Stefano Redaelli, R. Bruce

On behalf of the LHC Collimation Team

Special thanks to S. Fartoukh for the useful discussions and help on optics modifications

15/5/14


2

Introduction

15/5/14

Possibility to implement the ATS optics at the post LS1 LHC restart

Study of its influence on cleaning performance of the collimation system are required

Complete loss map simulations made for various machine and system configurations:

Optics versions:- Nominal (NOM)- ATS

Collimators settings:- mm_kept- sigma_kept

Simulations made for each combination of them, for both planes and both beams at 6.5TeV

Comparative studies between these 16 cases are shown in the next


3

mm_kept settings sigma_kept settings

Configurations

15/5/14

Collimation layout:

same settings in mm as in the 2012 IR7-TCP same settings as in mm_kept,Nominal retraction in sigma for the rest

Key optics settings:

Crossing scheme values in MADX (V.5.02.00) modified each time in order to get always the same crossing angles.

IP PX [μrad] PY [μrad]

1 0 145

2 0 170

5 145 0

8 -250 0


4

“Observables”

15/5/14

Main parameters for comparative studies of optics influence on collimation performance:

Average value of losses density in the limiting regions of the whole LHC

Integrated losses in the limiting regions of the whole LHC

Average value of losses: calculated on a sub-set of bins, in which a reasonable number of primary protons are lost (to take low the statistical error, i.e. 1p in 1bin has 100% of error)

Various “threshold” were probed to identify how it effects the average value.

Final threshold chosen in order to have a reasonable statistical error (<30%) and a number of bin on which make sense to perform an average and a standard deviation (min 20bins)

Integrated losses: are given by the sum of all primary protons lost in “interesting” losses distributions


5

Beam 1

7/2/14

ATS vs NOM, H plane

NOMINAL OPTICS

ATS OPTICS

Whole LHC, horizontal plane, mm_kept collimator settings

!!!

Comments on H planeNew dangerous peak losses appeared just after IP8!

Due to the dispersion mismatch induced by the crossing scheme!Same peaks are seen in HL-LHC simulations, but they are cured by IR7 CRYO-Collimators

Stephane gave me a very nice tool to insert “a fake phase kick” between cells 78 and 81

Produced a NOM thin opt. with IP8 β*=3m: no significant changes seen in high of those peaks

no significant changes seen in high of those peaks

After many tests, the only phase shift would cure those peaks bringing them to NOM values would be π

This would imply ~7degree per cell, which is unfeasible as Stephane told me.

Many tricks tried with Stephane Fartoukh to decrease those dangerous dispersive peaks after IP8: Only difference between the two optics: IP8 β*=3m in ATS, while β*=10m in NOM

Tried to rematch IR7-ATS with IR7-NOM values of Dx and DPx at first TCP (TCP.D6L7.B1)

Summary H planeIR7

ZOOMNOMINAL OPTICS ATS OPTICS

Config. Average losses Integrated losses

Q8-9 Q10-11 Q10(8) B-T 16 T18 Q8-9 Q10-11 Q10(8) B-T 16 T18

mm+ ATS

2.1e-5 1.5e-5 2.5e-5 1.7e-5 6.7e-6 6.4e-4 3.3e-4 1.8e-5 3.7e-5 5.8e-6

mm+ NOM

1.5e-5 1.4e-5 - - - 4.1e-4 3.4e-4 - - -

sigma+ ATS

1.8e-5 1.3e-5 9.9e-6 7.1e-6 6.3e-6 5.2e-4 2.7e-4 1.6e-5 3.0e-5 4.1e-6

sigma+ NOM

1.3e-5 1.1e-5 - - - 3.1e-4 2.7e-4 - - -

Q8-9Q10-11 Q8-9

Q10-11

ZOOM ofdangerous peaks in IR8

Q10BC16-QT16

QT18

“Visual” summary H planePrevious summary table in histograms

mm_kept settings, average losses mm_kept settings, integrated losses

sigma_kept settings, average losses sigma_kept settings, integrated losses

ATS/

NO

M

ATS/

NO

M

ATS/

NO

M

ATS/

NO

M

“Visual” summary H planeBin by bin ratio: mm+ATS/mm+NOM (not significative for comparisons, just to give you the feeling)

Ratio only for losses on collimators (important for possible damages) IR7

ATS vs NOM, V plane

NOMINAL OPTICS

ATS OPTICS


!!!

Summary V planeIR7

ZOOMNOMINAL OPTICS ATS OPTICS


Q8-9 Q10-11 Q10(8) B-T 16 T18 Q8-9 Q10-11 Q10(8) B-T 16 T18

mm+ ATS

1.6e-5 1.4e-5 1.3e-5 1.4e-5 9.0e-6 4.9e-4 3.5e-4 2.7e-5 3.0e-5 1.0e-5

mm+ NOM

1.6e-5 1.4e-5 - - - 4.7e-4 4.0e-4 - - -

sigma+ ATS

1.6e-5 1.4e-5 8.7e-6 8.5e-6 6.1e-6 3.8e-4 2.9e-4 2.2e-5 2.2e-5 8.3e-6

sigma+ NOM

1.4e-5 1.2e-5 - - - 3.6e-4 2.3e-4 - - -

Q8-9Q10-11 Q8-9

Q10-11

ZOOM ofdangerous peaks in IR8

Q10BC16-QT16

QT18

“Visual” summary V planePrevious summary table in histograms



ATS/

NO

M

ATS/

NO

M

ATS/

NO

M

ATS/

NO

M


Ratio only for losses on collimators (important for possible damages) IR7


15

Beam 2

7/2/14


16

ATS vs NOM, H plane

15/5/14

NOMINAL OPTICS

ATS OPTICS


Summary H planeIR7-DS limiting location for the whole LHC, summary of expected losses on Q 8-9-10-11

(shown only plots for mm_kept settings, more conservative. Better performance are achieved with sigma_kept settings)

IR7ZOOM

NOMINAL OPTICS ATS OPTICS


Q8-9 Q10-11 Q8-9 Q10-11

mm_kept + ATS 2.2e-5 1.7e-5 6.0e-4 3.1e-4

mm_kept + NOM 2.1e-5 1.3e-5 6.8e-4 3.4e-4

sigma_kept + ATS 1.9e-5 1.4e-5 4.7e-4 2.4e-4

sigma_kept + NOM 1.8e-5 1.2e-5 5.5e-4 2.6e-4

Comparable performance are found, seems that with ATS slightly less and more concentrated losses

Q8-9Q10-11

Q8-9Q10-11

“Visual” summary H planePrevious summary table in histograms



ATS/

NO

M

ATS/

NO

M

ATS/

NO

M

ATS/

NO

M


Ratio only for losses on collimators (important for possible damages)

IR7

ATS vs NOM, V plane

NOMINAL OPTICS

ATS OPTICS

Whole LHC, vertical plane, mm_kept collimator settings

Summary V planeIR7-DS limiting location for the whole LHC, summary of expected losses on Q 8-9-10-11

(shown only plots for mm_kept settings, more conservative. Better performance are achieved with sigma_kept settings)

IR7ZOOM

NOMINAL OPTICS ATS OPTICS


Q8-9 Q10-11 Q8-9 Q10-11

mm_kept + ATS 1.6e-5 1.3e-5 5.1e-4 3.2e-4

mm_kept + NOM 1.9e-5 1.5e-5 5.5e-4 3.2e-4

sigma_kept + ATS 1.5e-5 1.3e-5 4.0e-4 2.6e-4

sigma_kept + NOM 1.5e-5 1.2e-5 4.3e-4 2.6e-4

Comparable performance are found

Q8-9Q10-11

Q8-9Q10-11

“Visual” summary V planePrevious summary table in histograms



ATS/

NO

M

ATS/

NO

M

ATS/

NO

M

ATS/

NO

M


Ratio only for losses on collimators (important for possible damages)

IR7

ConclusionMany configurations where probed to test the influence of ATS optics on the collimations system

performance, with different settings, in both planes, for both beams, at 6.5 TeV.Beam 1:

Horizontal plane: - averaged and integrated losses in the DS systematically higher with ATS opt. than with NOM

opt. Worst case: factor 1.4 in averaged losses, 1.7 in integrated losses - Presence of dangerous peaks in IP8, with a average losses comparable with the ones in the DS.

Vertical plane: - Comparable results are found, however ATS slightly worse than NOM- Presence of dangerous peaks in IP8, with a average losses comparable with the ones in the DS.

Beam 2: Horizontal plane:

- ATS worse than NOM with a factor 1.4 in terms of average losses, but slightly better in terms of integrated losses (factor 0.9)

Vertical plane: - Comparable results are found

Since the worse/comparable performance of the system with ATS w.r.t. NOM opt. further and more detailed studies are needed (i.e. coupled simulations with FLUKA to access the effects on collimators too)

Work is still on-going to try to mitigate dangerous spikes at IP8 (tried also to close more the TCT, but it’s not enought)

Documents

Study of cleaning performance with ATS optics for post LS1