Halo scraping and loss rates at collimators

F. BurkartF. Burkart R. Assmann, R. Bruce, M. R. Assmann, R. Bruce, M. Cauchi, D. Deboy, S. Cauchi, D. Deboy, S.

Redaelli, A. Rossi, G. Redaelli, A. Rossi, G. Valentino, D. WollmannValentino, D. Wollmann

Outline

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1. Introduction

2. Halo scraping measurements

3. Results of data analysis from measurements

4. Collimation losses during high-luminosity fills

5. Results of data analysis from physics fills

6. Conclusion

7. Future work

Why halo scraping?

• Understand population and repopulation speed of the beam halo at 3.5 TeV

→ extrapolate the results to 7 TeV

→ loss rates at collimators

→ minimum instantenious lifetime of the beams

• Calibrate BLM-signal at primary collimator [Gy/s] to a particle lossrate [p/s]

→ compare to losses seen in collimation region during high-luminosity runs

→ distinguish between hor.,ver. and skew losses

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Halo scraping procedure

• Move single jaw of a primary collimator into the beam halo

• with different step sizes (5 micron, 20 micron, 40 micron)

• at different intensities

• in different machine states (injection, collision)

- measure beam intensity (FBCT) → loss rate

- measure BLM-signals

• Most EoF-studies after physics → beam dumped by BLMs

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Usage of different step sizes

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10 μm step size

5 μm step size

BLM-responseScraping with TCP.D B1, running

sum: 1.3 s

6

C-BLM: 8.5E+11 p/Gy

D-BLM: 1.7E+12 p/Gy

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Signal in TCP.C-BLM dominatedby vertical losses

BLM-response for different running sums

Scraping with TCP.D B1

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1.3s: 8.5E+11 p/Gy

10.24ms: 3.4E+12 p/Gy Loss rate diluted in large running sums

Calibration factor Halo scraping

RS09 / RS06

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5/1/10 6/20/10 8/9/10 9/28/10 11/17/10 1/6/11 2/25/11 4/16/111.00E+11

6.00E+11

1.10E+12

1.60E+12

2.10E+12

2.60E+12

3.10E+12

3.60E+12

1,3s10,24ms

Date

calib

rati

on

fac

tor

[p/G

y]

Variation up to a factor 6.6 → to be understood → impact parameter → error in lossrate due to 1 Hz FBCT-signal

Overview of different scrapings

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ScrapingCollimator

BLM on TCP.C

calibration factor [p/Gy]

1,3serror points

28.05.10 TCP.D6L7.B1 1.9E+11 5.4E+09 4

25.08.10 TCP.D6R7.B2 8.6E+11 4.4E+10 27

04.04.11 TCP.D6L7.B1 1.7E+11 2.8E+10 5

04.04.11 TCP.D6R7.B2 1.3E+11 2.5E+10 6

variation up to a factor 6.6 → not understood

Collimation losses during high-luminosity fills – steady

state

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• Measure BLM signals [Gy/s] on Collimators (TCP.C)

• Measure Beam Intensity (FBCT) [p]

→ steady state lossrate [p/s] (dominated by losses at collimators)

→ calibration factor [p/Gy]

Losses with colliding beams Fill 1722, 336 bunches

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Courtesy D.Wollmann

IR7: ~87%

IR8: ~6%

IR3: ~2.5%IR1:

~1%

Linear scale!

Beam Intensity versus time Fill 1749, B1

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Intensity [p]

14 h

Time [s]

7.6*10^13

7.1*10^13

Loss rate versus time Fill 1749, B1, running average

240sec

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14 h

Time [s]

Lossrate [p/s]

dN FBCT

dt

4*10^8

1*10^8

BLM-signal versus time Fill 1749, B1

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14 h

Time [s]

BLM-signal [Gy/s]

0.0001

0.0006

Calibration factors(stable beams)

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Average value B1: 2.2E+12 p/Gy B2: 1.54E+12 p/Gy Variation : 6,5 (B1), 3,4 (B2)

17421743174417451746174717481749175017511752175317541755175617571.00E+11

1.00E+12

1.00E+13

Beam1Beam2

fill number

ca

lib

rati

on

fa

cto

r [p

/Gy

]

Minimum Lifetime RS09 (1.3 s)

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17421743

17441745

17461747

17481749

17501751

17521753

17541755

17561757

0

10

20

30

40

50

60

70

Beam1Beam2

fill number

min

. li

feti

me

[h

]

• 624 b, 768 b

min=3h

=N FBCT

RBLM

Comparison Min.Lifetime B1 RS09, RS06

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17421743

17441745

17461747

17481749

17501751

17521753

17541755

17561757

0

5

10

15

20

25

fill number

min

. li

feti

me

[h

]

Min. Lifetime for multiturn losses → RS06

Comparison Min.Lifetime B2 RS09, RS06

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17421743174417451746174717481749175017511752175317541755175617570

10

20

30

40

50

60

70

RS06 Beam2RS09 Beam2

fill number

min

. li

feti

me

[h

]

Overview of physics fills RS09

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Fill numb

er

#bunch

e

calibration factor

B1 [p/Gy]

calibration factor

B2 [p/Gy]Peak loss B1 [p/s]

Peak loss B2 [p/s]

min lifetime B1 [h]

min lifetime B2 [h]

1743 624 3.2E+12 2.2E+12 3,28E+09

1,45E+09 6,50 14,40

1744 624 2.4E+12 1.3E+12 6,90E+09

1,02E+09 3,00 20,11

1748 624 1.8E+12 9.3E+11 2.26E09 1.73E+09 9,40 12,10

1749 624 3.0E+12 2.2E+12 7.1E+09 9.6E+08 3,00 21,20

1753 768 1.38E+12

1.52E+12 7.2E+09 9.5E+08 3,60 27,00

1755 768 1.9E+12 1.99E+12

1.49E+09 4.56E+9 18,40 58,90

1756 768 4.86E+11

6.29E+11 1.13E+9 1.6E+09 23,50 22,30

Overview of physics fills RS06

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Fill number

#bunche

calibration factor B1

[p/Gy]

calibration factor B2

[p/Gy]Peak loss B1 [p/s]

Peak loss B2 [p/s]

min lifetime B1 [h]

min lifetime B2 [h]

1743 624 2,40E+12 1,68E+12 6,80E+09 2,74E+09 3,12 7,361744 624 1,82E+12 9,40E+11 1,57E+10 1,70E+09 1,33 11,901748 624 1,27E+12 6,23E+11 3,30E+09 2,17E+09 6,40 9,601749 624 2,09E+12 1,51E+12 1,02E+10 1,65E+10 2,09 1,151753 768 7,80E+11 1,17E+12 1,39E+10 4,00E+09 1,90 6,271755 768 1,37E+12 1,47E+12 2,76E+09 1,14E+09 9,96 23,401756 768 6,42E+11 4,20E+11 1,70E+09 4,20E+09 15,30 6,20

Courtesy D.Wollmann

Conclusion

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Halo scrapings

• For vertical losses BLM at TCP.C shows highest signal

• More scraping experiments needed

• More usable data points per experiment → sufficient loss rate

• Variation of calibration factors (~ 6.6)

Physics fills

• Losses mainly appear at collimators (IR7: ~87%)

• Average calibration factor B1: 2.2E+12 p/Gy

• Average calibration factor B2: 1.54E+12 p/Gy

• Min. Lifetime B1 > 1.3 h (RS06)

• Min. Lifetime B2 > 1.15 h (RS06)

Future work

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• Analysis of other integration times

• Analysis of other BLM-signals e.g. TCHSV (physics fills data, scraping data)

• More scrapings with different step sizes → understand variation of calibration factor

• Scrapings with different optics (squeezed, collision)

• Measure repopulation speed

END

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Thank you for your attention!