Beam losses through the cycle G. Papotti, A. Gorzawski, M. - - PowerPoint PPT Presentation

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Beam losses through the cycle G. Papotti, A. Gorzawski, M. - - PowerPoint PPT Presentation

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LHC Beam Operation workshop - Evian 2012 Beam losses through the cycle G. Papotti, A. Gorzawski, M. Hostettler, R. Schmidt outline motivation 2011 vs 2012, PM browser module beam losses per beam mode capture, ramp, flat top,

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SLIDE 1

Beam losses through the cycle

  • G. Papotti,
  • A. Gorzawski, M. Hostettler, R. Schmidt

LHC Beam Operation workshop - Evian 2012

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SLIDE 2
  • utline
  • motivation

– 2011 vs 2012, PM browser module

  • beam losses per beam mode

– capture, ramp, flat top, squeeze, …

  • all 2012 fills until end of November

– thanks to A. Gorzawski for a lot of data, analysis and plots

  • some information on bunch-by-bunch differences

– appetizers on instabilities – bunch-by-bunch losses in stable beams and burn off

  • disclaimer:

– give only overview of the year, no details on fill to fill differences – injection not treated

19 Dec 2012 giulia.papotti@cern.ch 2

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SLIDE 3

at the SPS

  • SPS page 1 and Larger

– e.g. LHC3, 72 bunches

19 Dec 2012 3 giulia.papotti@cern.ch

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SLIDE 4

at the LHC

  • (inject)
  • ramp

– 0.45 TeV to 0.5 TeV – 0.5 TeV to 4 TeV

  • flat top
  • squeeze
  • adjust
  • stable beams

19 Dec 2012 4 giulia.papotti@cern.ch

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SLIDE 5

before stable beams

19 Dec 2012 5 giulia.papotti@cern.ch

  • zoom from injection to

end of adjust

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SLIDE 6

before stable beams

  • zoom from injection to

end of adjust

  • same for a fill in 2011

19 Dec 2012 6 giulia.papotti@cern.ch

  • 2011: used to have ~100%

transmission to stable beams

  • 2012: <100%
  • … so look into the reasons

2011 ¡ 2012 ¡

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SLIDE 7

PM Beam Power Loss Module

19 Dec 2012 giulia.papotti@cern.ch 7

  • statistical analysis over many fills
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SLIDE 8

PM Beam Power Loss Module

  • statistical analysis over many fills
  • peak power loss per mode

– based on sliding window (e.g. 5s, 20s, 80s)

19 Dec 2012 giulia.papotti@cern.ch 8

P = n2 − n1 t2 − t1 E1e11p@ 4TeV

2 ¡ 1 ¡

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SLIDE 9

2011 vs 2012 statistics

  • 2012 transmission:

– beam 1: ~96.2% – beam 2: ~95.3%

19 Dec 2012 9 giulia.papotti@cern.ch

  • 2011 transmission: ~99.4%

– from end of injection to start of stable beams

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SLIDE 10

Losses per beam mode

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SLIDE 11

capture losses (.45->.5 TeV)

  • generally b1 worse than b2
  • first energy matching improved the situation

– second not so much

  • got generally worse ~after MD3

– enhanced satellites? (Q20? batch-by-batch blow-up was often off) energy ¡matching ¡

19 Dec 2012 11 giulia.papotti@cern.ch

MD3 ¡

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SLIDE 12

ramp (.5->4 TeV)

  • non-negligible losses
  • transmission improved towards the end of the run

– when had the higher losses at capture? – Q20 and smaller emittances?

19 Dec 2012 12 giulia.papotti@cern.ch

TS3 ¡

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SLIDE 13

ramp (.45 -> 4 TeV)

  • max power loss during ramp
  • highest losses either at the start or at the end

– ramp function: 770s long

  • beam 1, higher loss spikes

19 Dec 2012 13 giulia.papotti@cern.ch

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SLIDE 14

ramp (.45 -> 4 TeV)

  • plots for longer window (now 80s, was 20s)
  • highest loss mostly at the end of the ramp function
  • very similar peak loss values for beam 1 and beam 2

19 Dec 2012 14 giulia.papotti@cern.ch

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SLIDE 15

flat top

  • few minutes long: manual tune trims and squeeze loading
  • negligible losses, generally b2 worse lifetime

– slightly worsened after octupole polarity change

MO ¡polarity ¡change ¡

19 Dec 2012 15 giulia.papotti@cern.ch

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SLIDE 16

squeeze

  • generally b2 worse than b1,

throughout the year

  • both beams got worse after

MO polarity change

  • max power loss

– very reproducible for beam 1, but at different times – at precise times for beam 2 MO ¡polarity ¡change ¡

19 Dec 2012 16 giulia.papotti@cern.ch 930s (sq. function = 925s long) 820s (β*~0.8-0.7m) 420s (β*~3m)

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SLIDE 17

adjust

  • split collision beam process

made the difference

– very reproducible losses and max power loss

split ¡coll ¡beam ¡process ¡

19 Dec 2012 17 giulia.papotti@cern.ch

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SLIDE 18

first 5 mins in stable beams

  • b1 generally worse

– shift crews used to say: “b2 loses earlier in cycle, b1 loses at start of stable beams” split ¡coll ¡beam ¡process ¡

19 Dec 2012 18 giulia.papotti@cern.ch

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SLIDE 19

max power losses in 2011

  • generally factor 2-3

smaller than 2012

  • beam 1 generally

higher losses

  • no clear clustering

in time as in 2012

19 Dec 2012 19 giulia.papotti@cern.ch

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SLIDE 20

Bunch-by-bunch observations

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SLIDE 21

BBQ signal amplitude

  • hard to correlate to max power loss

– preliminary analysis, more time required

19 Dec 2012 giulia.papotti@cern.ch 21

  • 1. ¡TS2 ¡
  • 2. ¡MO ¡polarity ¡change ¡
  • 3. ¡split ¡coll ¡beam ¡process ¡

?. ¡Q’/MO ¡reducAon ¡incorporated ¡ in ¡collapse ¡funcAon ¡ 1 ¡ ? ¡ 2 ¡ ? ¡ 3 ¡ 3 ¡ 1 ¡

not ¡bunch-­‑by-­‑bunch! ¡

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SLIDE 22

500 1000 1500 2000 2500 3000 3500 2 2.5 3 3.5 4 Bunch number Lumi Emittance [um] 2500 2600 2700 2800 2900 3000 3100 3200 3300 3400 200 400 600 800 1000 Fill number Blownup bunch count

emittance from luminosity

  • count blown-up bunches in stable

beams

– emittance from luminosity

  • 1.65e11ppb, 2.5um -> 7.26e33Hz/cm2
  • 1.65e11ppb, 3um -> 6.25e33Hz/cm2

19 Dec 2012 22 giulia.papotti@cern.ch

MO ¡polarity ¡change ¡ Q20 ¡& ¡split ¡coll ¡beam ¡process ¡

  • not easy to correlate to

BBQ amplitudes

– more analysis required

  • M. ¡Hoste6ler, ¡LBOC, ¡20.11.2012 ¡
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SLIDE 23

Time in SB [h] Bunch Length [ns] Bunch length histogram evolution, Fill 3287 1 2 3 4 5 6 7 1.1 1.2 1.3 1.4 1.5

b1 bunch length histogram splitting

  • bunches with larger transverse

emittance get lower bunch length

– build up during stable beams in beam 1 – no visible effect on beam 2 – for fills with selective transverse emittance blow-up

  • results in two distinct families
  • M. ¡Hoste6ler, ¡LBOC, ¡20.11.2012 ¡

19 Dec 2012 23 giulia.papotti@cern.ch

Lumi Emittance [um] Bunch length [ns] Emittance vs. Length, 7h SB, Fill 3287 3 3.5 4 4.5 1.1 1.15 1.2 1.25 1.3 1.35 1.4 Time in SB [h] Emittance [um] Emittance histogram evolution, Fill 3287 1 2 3 4 5 6 7 2 2.5 3 3.5 4 4.5

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SLIDE 24

b1 loss structure in stable beams

  • first ~30 bunches of each SPS batch

in beam 1 lose up to 10% less in stable beams (SB)

– very reproducible, also there in 2011 – no correlation with number of long- range interactions – not visible on beam 2 (or smaller?)

  • cause not clear yet

19 Dec 2012 24 giulia.papotti@cern.ch

500 1000 1500 2000 2500 3000 3500 0.15 0.2 0.25 0.3 0.35 0.4 Beam 1 losses: Fill 3363, 10.0h SB Slot Number

  • Rel. Loss [1]

500 1000 1500 2000 2500 3000 3500 0.15 0.2 0.25 0.3 0.35 0.4 Beam 2 losses: Fill 3363, 10.0h SB Slot Number

  • Rel. Loss [1]

20 40 60 80 100 120 140 0.2 0.225 0.25 0.275 0.3 0.325 0.35 Bunch loss B1, Fill 3363 Offset in 144 bunch train Intensity loss in SB [1]

  • M. ¡Hoste6ler, ¡LBOC, ¡30.10.2012 ¡
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SLIDE 25

burn off

  • e.g. above plots for fill 3045 at 8 h of stable beams
  • residual loss has SPS batch structure

– after removing burn-off component from total losses (σproc = 101.8 mb) – particularly strong on b1

19 Dec 2012 25 giulia.papotti@cern.ch collisions ¡in ¡ IP ¡8 ¡15 ¡158 ¡

25 ¡ns ¡slot ¡

  • ffset ¡in ¡SPS ¡batch ¡

beam ¡1 ¡ beam ¡2 ¡

  • ffset ¡in ¡SPS ¡batch ¡
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SLIDE 26

conclusions

  • losses through cycle are non-negligible: transmission ~95%

– capture (degradation towards the end possibly related to enhanced satellites?) – ramp: ~1% towards the end – squeeze: peak losses at precise moments for beam 2 – adjust: split collision beam process improved the reproducibility – stable beams

  • observation of bunch length histogram splitting and correlation to

transverse emittance blow up

  • 144-bunch loss pattern to be understood

– stronger on beam 1

  • plenty more analysis possible
  • support fill-to-fill data analysis tool

– more useful than end-of-the-year overview!

19 Dec 2012 26 giulia.papotti@cern.ch

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SLIDE 27

integrated lumi comparison

  • for full picture on

performance, need to fold in availability

  • intensity increase did not

‘clearly’ pay off in terms

  • f integrated luminosity

19 Dec 2012 giulia.papotti@cern.ch 27

2500 2600 2700 2800 2900 3000 3100 3200 3300 3400 0.1 0.15 0.2 0.25 0.3 0.35 Losses in 8h of SB [1]

2500 2600 2700 2800 2900 3000 3100 3200 3300 3400 1.2 1.4 1.6 1.8 2 x 10

14

Intensity at start of SB [p] 2500 2600 2700 2800 2900 3000 3100 3200 3300 3400 3 4 5 6 7 x 10

7

  • Int. ATLAS Lumi, 8h SB [ub

1]