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

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

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 Florian Burkart 3

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 Florian Burkart 4

Usage of different step sizes 10 μm step size 5 μm step size Florian Burkart 5

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 Florian Burkart 6

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 Florian Burkart 7

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 Florian Burkart 8

Overview of different scrapings Collimator BLM on TCP.C calibration factor [p/Gy] 1,3s error 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 1.7E+11 2.8E+10 5 1.3E+11 2.5E+10 6 variation up to a factor 6.6 → not understood Florian Burkart 9

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] Florian Burkart 10

Losses with colliding beams Fill 1722, 336 bunches IR7: ~87% Linear scale! IR8: ~6% IR3: ~2.5% IR1: ~1% Courtesy D.Wollmann Florian Burkart 11

Beam Intensity versus time Fill 1749, B1 Intensity [p] 7.6*10^13 7.1*10^13 Time [s] 14 h Florian Burkart 12

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 Florian Burkart 13

BLM-signal versus time Fill 1749, B1 BLM-signal [Gy/s] 0.0006 0.0001 Time [s] 14 h Florian Burkart 14

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) Florian Burkart 15

Minimum Lifetime RS09 (1.3 s) 624 b, 768 b Florian Burkart 16

Comparison Min.Lifetime B1 RS09, RS06 Min. Lifetime for multiturn losses → RS06 Florian Burkart 17

Comparison Min.Lifetime B2 RS09, RS06 Florian Burkart 18

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 Florian Burkart 19

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 Florian Burkart 20

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) Florian Burkart 21

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 Florian Burkart 22

Thank you for your attention! END Thank you for your attention! Florian Burkart 23