Yearly beam losses in past and future operation

Yearly beam losses in past and future operation

Mike LamontBelen Maria Salvachua Ferrando

Very much an invitation to do some more work!

4-June-12 LHC Annual Doses 2

Loss Mechanisms

• Transverse– Beam gas– Collisions – Halo productions:

• Nonlinearities, long range beam-beam, electron cloud, IBS

• Longitudinal– Touschek, RF noise, IBS

Particles can be:• Scattered directly out of aperture• Particle pushed to large betatron or momentum amplitude

– lost on physical or dynamic aperture• Emittance growth

– slow push to large betatron or momentum amplitudes

Many, many moons ago – attempted to cross product loss mechanisms against the nominal cycle


Nominal cycle

0

14000

-3000 -2000 -1000 0 1000 2000 3000

Time [s]

MB

cur

rent

0

1

2

3

4

5

6

7

8

9

B [T

]

RAMP DOWNSTART RAMP

PHYSICS

PREPAREPHYSICS

BEAM DUMP

PREINJECTIONPLATEAU

INJECTION

T0 Tinj

SQUEEZE

PHYSICS

Ramp down 18 MinsPre-I njection Plateau 15 Mins

I njection 15 MinsRamp 28 Mins

Squeeze 5 MinsPrepare Physics 10 Mins

Physics 10 - 20 Hrs

I t2

I et

I t

LHC Annual Doses 44-June-12

RADWG-RADMON LHC Beam Loss Rates 5

Nominal cycle – WHEN• Injection

– Losses at injection: injection oscillations, RF capture– Big beams, lower dynamic aperture, full buckets, un-captured beam, long range beam-

beam, crossing angles, persistent current decay– Won’t be pretty. 10 hours lifetime will be good.

• Start ramp– Un-captured beam: lost immediately (~5% total)– Snapback: chromaticity, tunes all over the place

• Ramp– Things should calm down, assume 10 hour lifetime

• Squeeze– Tunes, chromaticity, collimator, TCDQ adjustments – expect some lifetime dips

• Collide– Beam finding, background optimisation

• Physics– Collisions, beam-gas, halo production– Synchrotron radiation damping will help against IBS, noise


Operational Cycle

Phase Loss Destination

Injection 2% transverse IR7 collimators, TDI

1% longitudinal IR3 collimators

Injection plateau 20 minutes - 10 hour lifetime IR7 collimators mainly

Start ramp – out of bucket flash

5% beam IR3 collimators

Start ramp - snapback 1 minute – 1 hour lifetime IR7 collimators

Ramp 20 minutes – 10 hr lifetime Ring, collimators

Squeeze 10 minutes – 1 hour lifetime2*10 s dips to 0.2 hr lifetime

IR7 collimators

Physics Detailed above Ring, insertions, IR3, IR7

Some old, rather pessimistic assumptions


Process Lifetime [hr] Emittance Growth [h] Destination

Residual gas - inelastic 129 - Ring Residual gas - elastic 459 - Ring/IR/Coll

Touschek 1250 - IR3 Collisions - inelastic 108* - Low IR/DS

Collisions – SD I 2697* - DS Collisions – SD II 674* - IR3 Collision - elastic 310 44 IR7

IBS transverse - 80 - IBS longitudinal - 61 -

Noise/beam-beam - 55 - SR - long - -13 -

SR - transverse - -26 -

Physics


Lifetime evolution in physics

yxgas

t

N

tb

yxgasgas eeNtN

21

211

1112

1211

0

Attempt to combined the various lifetime effects and proportion the losses to their destination

y = 3E+14e-0.0267x

R2 = 0.9956

1.5E+14

2.0E+14

2.5E+14

3.0E+14

3.5E+14

0 2 4 6 8 10 12 14 16 18 20

Time [hours]

Tota

l no.

parti

cles

Nominal single beam lifetime, fitting to exponential ≈ 37 hoursLuminosity lifetime~ 18 hours

LHC Annual Doses 9

Losses before physics

4-June-12

LHC Annual Doses 10

Losses in physics

4-June-12

beam loss in various locations, per fill for differing fill lengths. Nominal physics – one beam.


Old operations assumptions

• 200 days physics per year.

• 60% operational efficiency – Machine available for beam

• Fill lengths– Assume between 8 and 20 hours.

• Turnaround– Time between consecutive physics coasts – Absolute minimum turnaround time between physics coasts: ≈ 90 minutes. – Varied between three and ten hours.

New operational assumptions – not so much different


Totals Per Year

Fill Length [hours] 8 12 15 20TOTAL DUMPED - ONE BEAM 6.6 E+16 3.8 E+16 3.0 E+16 1.8 E+16

TOTAL INTO 2 IRS - ONE BEAM 5.0 E+15 4.4 E+15 4.4 E+15 3.5 E+15

TOTAL MAIN RING - BOTH BEAMS 6.5 E+15 5.7 E+15 5.6 E+15 4.4 E+15

TOTAL IR7 – BOTH BEAMS 3.7 E+16 2.8 E+16 2.6 E+16 1.9 E+16


Fill Length [hours] 8 12 15 20TOTAL DUMPED - ONE BEAM 8.8 E+16 5.0 E+16 3.9 E+16 2.3 E+16

TOTAL INTO 2 IRS – ONE BEAM 1.2 E+16 9.8 E+15 9.6 E+15 7.5 E+15

TOTAL MAIN RING - BOTH BEAMS 9.5 E+15 8.0 E+15 7.7 E+15 6.0 E+15



NOMINAL

ULTIMATE

7 TeV equivalent

LHC Annual Doses 13

IN REALITYAnalysis: Belen Maria Salvachua Ferrando

4-June-12

LHC Annual Doses 14

Experience• We know have vast experience of ramping,

squeezing, colliding and stable beaming high intensity beams

4-June-12

Spacing No bunches Bunch intensity

Beam intensity

June 2012 50 ns 1380 1.5e11 2.07e14

Design 25 ns 2808 1.15e11 3.23e14

LHC Annual Doses 15

Take a recent fill• 2663

– Peak luminosity: 6.52e33 cm-2s-1

– Stable beams: 11 hours 20 minutes– Beam current: ~2.1e14 – Average bunch intensity: ~1.5e11

4-June-12


Injection - bct

Ramp

Squeeze


Injection – TCP losses B1

Injection – TCP losses B3


Ramp – TCP3 losses B1




Squeeze – TCP7 losses B2


Adjust – TCP7 losses B2

Stable beams – TCP7 losses B1

Stable beams – TCP7 losses B2


Stable beams – QXA losses B1

LHC Annual Doses 25

SO CAN ACCURATELY DETERMINE HOW MUCH IS LOST AND WHEN…

4-June-12

Total Integral: 180.02 Gy/sTotal time during RAMP 792.0 secBeam1: Total proton lost 1.15e+12Beam2: Total proton lost 2.17e+12

Total Integral: 263.8 Gy/sTotal time during SQUEEZE 1038.0 secBeam1: Total proton lost 0.78e12Beam2: Total proton lost 2.27e+12

Total Integral: 220.6 Gy/sTotal time during ADJUST 467.0 secBeam1: Total proton lost 1.07e+12Beam2: Total proton lost 1.67e+12

Total Integral: 1005849.1 Gy/sTotal time during STABLE 40839.0 secBeam1: Total proton lost 0.49e+14Beam2: Total proton lost 0.55e+14


Vast majority in IR7 with some at injection protection


• IR3 – out of bucket flash at start of ramp• Gentle “scraping” in IR7 at top of ramp as collimators move to tight• Clearly can change if we have problems…


• IR7!


• IR7!• Plus start of collisions…


protonsdebris


• Luminosity debris• Transverse emittance blow-up• Longitudinal losses• Minimal beam-gas

Lumi Beam-gas Coll Total

~87 ~300 ~500 ~60

IR1&5 Ring IR7

Fully quantifiable (with a little effort)

Single beam lifetimes [hours]

LHC Annual Doses 33

2663 loss summary

4-June-12

B1 B2 2004 estimate

Injection 3.1%

Ramp start .1% .15% 6.5%

Ramp top .2% .8%

Ramp total .58% 1.1% 3%

Squeeze .35% 1.1% 10%

Adjust .56% .84%

Stable beams 24% 27% 28%

Relatively straightforward to establish:• When• Where• How muchMine the past to predict the future…

LHC Annual Doses 34

Annual Number of Lost Protons at TCPs andPrediction for 2012

4-June-12

LHC Annual Doses 35

Detailed Look into Losses at TCPs DuringStable Beams in 2011 (BLM vs BCT)

4-June-12

LHC Annual Doses 36

NB: not yet approved

10 year plan

4-June-12

LS1

HL-LHC

PHYSICS AT 6.5/7 TeV

LS2

“ULTIMATE” PHYSICS

LS3

LHC Annual Doses 37

2012 – canonical (long) year

4-June-12

DaysMachine check-out 2Commissioning with beam 21Machine development 22Technical stops 20Scrubbing (25 ns) 3Technical stop recovery 6Initial intensity ramp-up ~21Proton running ~126Special runs ~8Ion setup 4Ion run 24

~150 days

LHC Annual Doses 38

Efficiency

4-June-12

2012

LHC Annual Doses 39

Potential performance LS1 to LS2

4-June-12

Beta*[cm]

IbSPS

EmitSPS

[um]

Peak Lumi[cm-2s-1]

~Pile-up

Int. Lumi[fb-1]

25 ns 50 1.2e11 2.8 1.2e34 28 32 25 ns

low emit 50 1.2e11 1.4 2.2e34 46 57

50 ns level 50 1.7e11 2.1

1.7e34level

0.9e34

76level40

40 – 50*

• 150 days proton physics• 5% beam loss, 10% emittance blow-up in LHC• 10 sigma separation• 70 mb visible cross-section• * different operational model - caveat

All numbers approximate!

LHC Annual Doses 40

Performance estimate LS2+• 7 TeV • 150 days of proton physics• Hübner Factor = 0.2 for 25 ns• Different OP model for 50 ns levelled

Beta*[cm]

Ib(SPS)

Emit(SPS)um

Peak Lumi[cm-2s-1] Pile-up

Int. Lumi[fb-1]

25 ns 50 1.6e11 2.3 2.5e34 56 ~65

50 ns 50 2.7e11 2.72.8e34level

0.9e34

125level

40~50

4-June-12

Neglecting low emittance optionAll numbers approximate!

LHC Annual Doses 41

Projection

4-June-12

• 25 ns• Low emittance option viable between LS1 & LS2• Usual warnings apply

LHC Annual Doses 42

Conclusions• Old estimates presented• The LHC is a lot cleaner than expected

(fortunately!)• Good handle on when, where and how much• Reasonable understanding of the mechanisms• Given past experience of losses and availability

should be possible to make realistic predictions for future operations based on appropriate scaling with total beam current and luminosity.

4-June-12

Yearly beam losses in past and future operation

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