1. Halo scraping and loss rates at collimators
F. Burkart
R. Assmann, R. Bruce, M. Cauchi, D. Deboy, S. Redaelli, A. Rossi, G. Valentino, D. Wollmann 1

2. Outline 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
Florian Burkart 2

3. 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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4. 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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5. Usage of different step sizes
10 μm step size
5 μm step size
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6. C-BLM: 8.5E+11 p/Gy D-BLM: 1.7E+12 p/Gy
BLM-response
Scraping with TCP.D B1, running sum: 1.3 s
C-BLM: 8.5E+11 p/Gy
D-BLM: 1.7E+12 p/Gy
Signal in TCP.C-BLM dominated
by vertical losses
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7. BLM-response for different running sums
Scraping with TCP.D B1
1.3s: 8.5E+11 p/Gy
10.24ms: 3.4E+12 p/Gy
Loss rate diluted in large
running sums
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8. Calibration factor Halo scraping
RS09 / RS06
Variation up to a factor 6.6 → to be understood → impact parameter
→ error in lossrate due to 1 Hz FBCT-signal
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9. Overview of different scrapings
Collimator
BLM on TCP.C
calibration factor [p/Gy]
1,3s
error
points
TCP.D6L7.B1
1.9E+11
5.4E+09 4
TCP.D6R7.B2
8.6E+11
4.4E+10 27
1.7E+11
2.8E+10 5
1.3E+11
2.5E+10 6
variation up to a factor 6.6 → not understood
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10. Collimation losses during high-luminosity fills – steady state
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]
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11. Losses with colliding beams
Fill 1722, 336 bunches
IR7: ~87%
Linear scale!
IR8: ~6%
IR3: ~2.5%
IR1: ~1%
Courtesy D.Wollmann
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12. Beam Intensity versus time
Fill 1749, B1
Intensity [p]
7.6*10^13
7.1*10^13
Time [s]
14 h
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13. Fill 1749, B1, running average 240sec
Loss rate versus time
Fill 1749, B1, running average 240sec
Lossrate [p/s]
4*10^8
1*10^8
Time [s]
14 h
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14. BLM-signal versus time
Fill 1749, B1
BLM-signal [Gy/s]
0.0006
0.0001
Time [s]
14 h
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15. Calibration factors (stable beams)
Average value B1: 2.2E+12 p/Gy B2: 1.54E+12 p/Gy Variation : 6,5 (B1), 3,4 (B2)
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16. Minimum Lifetime RS09 (1.3 s)
624 b, 768 b
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17. Comparison Min.Lifetime B1 RS09, RS06
Min. Lifetime for multiturn losses → RS06
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18. Comparison Min.Lifetime B2 RS09, RS06
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19. Overview of physics fills RS09
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
3.2E+12
2.2E+12
3,28E+09
1,45E+09
6,50
14,40
1744
2.4E+12
1.3E+12
6,90E+09
1,02E+09
3,00
20,11
1748
1.8E+12
9.3E+11
2.26E09
1.73E+09
9,40
12,10
1749
3.0E+12
7.1E+09
9.6E+08
21,20
1753
768
1.38E+12
1.52E+12
7.2E+09
9.5E+08
3,60
27,00
1755
1.9E+12
1.99E+12
1.49E+09
4.56E+9
18,40
58,90
1756
4.86E+11
6.29E+11
1.13E+9
1.6E+09
23,50
22,30
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20. Overview of physics fills RS06
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
7,36
1744
1,82E+12
9,40E+11
1,57E+10
1,70E+09
1,33
11,90
1748
1,27E+12
6,23E+11
3,30E+09
2,17E+09
6,40
9,60
1749
2,09E+12
1,51E+12
1,02E+10
1,65E+10
2,09
1,15
1753
768
7,80E+11
1,17E+12
1,39E+10
4,00E+09
1,90
6,27
1755
1,37E+12
1,47E+12
2,76E+09
1,14E+09
9,96
23,40
1756
6,42E+11
4,20E+11
4,20E+09
15,30
6,20
Courtesy D.Wollmann
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21. Conclusion 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)
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22. Future work 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
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23. Thank you for your attention!
END
Thank you for your attention!
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