The LHC: what to expect
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The LHC: what to expect (in the first 2 years). * Machine Milestones and Components * LHC Commissioning (2007,2008) - 450 GeV Engineering Run Staged Approach * Commissioning Challenges. A. Drees. ALICE-US Collaboration Meeting, Oct. 6 2006. 4.3 km. Machine Milestones.

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The LHC: what to expect (in the first 2 years)

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The lhc what to expect in the first 2 years

The LHC: what to expect

(in the first 2 years)

  • * Machine Milestones and Components

  • * LHC Commissioning (2007,2008)

    • - 450 GeV Engineering Run

    • Staged Approach

  • * Commissioning Challenges

A. Drees

ALICE-US Collaboration Meeting, Oct. 6 2006


The lhc what to expect in the first 2 years

4.3 km


Machine milestones

Machine Milestones

  • cryo-magnet cold tests are on schedule to finish in 2006

  • magnet installation rate is now >/= 25/week

  • last magnet in the ring: Mar 07

  • interconnect rate allows vacuum closure in Aug 07

  • no collisions at higher energy possible in 2007

  • engineering run at 450 GeV

  • machine checkout scheduled Nov. 1 2007

  • engineering run scheduled to begin mid Nov. 2007


Machine components

Machine Components

8 octants

8 IRs

4 experiments

almost 10000 dipoles

  • almost 100 collimators

  • betatron & momentum cleaning in 2 IRs

  • RHIC: only 5 per Ring

two rings:

ring 1 (blue)

ring 2 (red)


Lhc naming conventions and locations

LHC Naming Conventions and Locations

  • 1232 main dipoles

  • 752 H,V-correctors

  • 2464 sextupole correctors

  • blue beam clockwise (ring1)

  • red beam counterclockwise (ring2)


Why a 450 gev engineering run

Why a 450 GeV Engineering Run?

  • chance to check-out the machine with beam and have a window to address problems

    • commission beam instrumentation (BI)

    • aperture, machine protection, controls …

    • collimators

  • could also do in MD

    • 1st part of ramp (to ~1.1 TeV)

  • limited magnet cycling needed to reset hysteresis

    • 1.2 TeV, 1900 A in main bends, 16% nom.

    • linear correctors to full current

    • higher order corrections (>b3) can be skipped

  • Full beam commissioning to 7 TeV will profit and go faster and more efficiently


The lhc what to expect in the first 2 years

LHC 450 GeV 1st commissioning and setup for collisions


Some parameters and assumptions for the 450 gev engineering run

Some Parameters and Assumptions for the 450 GeV Engineering Run

  • pilot bunch

    • single bunch, 3 1010 p/bunch

  • number of bunches:

    • max. of 156 (no crossing angle)

  • initial b*

    • planned 11 m, possibly 6 m in IR1 and IR5 (will require additional setup time for squeeze)

  • cross sections

    • inelastic xsec @450 GeV: 40 mb

    • W [email protected] GeV: 1nb

    • Z [email protected] GeV: 100 pb

  • assumed: 50% of daytime in physics

  • assumed: operational efficiency 60%


Expected performance 450 gev

Expected Performance 450 GeV

assume 50% machine availability


Staged plan overview

Stage I

IV

II

III

Install Phase II and MKB

Hardware commissioning

Machine checkout

Beam commissioning

75ns ops

25ns ops I

25ns ops II

43 bunch operation

?

No beam

Beam

Beam

  • Pilot physics run

    • First collisions

    • 43 bunches, no crossing angle, no squeeze, moderate intensities

    • Push performance (156 bunches, partial squeeze in 1 and 5, push intensity)

  • 75ns operation

    • Establish multi-bunch operation, moderate intensities

    • Relaxed machine parameters (squeeze and crossing angle)

    • Push squeeze and crossing angle

  • 25ns operation I

    • Nominal crossing angle

    • Push squeeze

    • Increase intensity to 50% nominal

  • 25ns operation II

    • Push towards nominal performance

Staged Plan Overview


The lhc what to expect in the first 2 years

17


The lhc what to expect in the first 2 years

1 month min.


The lhc what to expect in the first 2 years

(stage 2)


The lhc what to expect in the first 2 years

design


Staged approach timeline

Staged Approach: Timeline


Staged commissioning plan for p@7tev

Stage I

II

III

Hardware commissioning

7TeV

Machine checkout

7TeV

Beam commissioning

7TeV

43 bunch operation

75ns ops

25ns ops I

Shutdown

No beam

Beam

III

Shutdown

Machine checkout

7TeV

Beam setup

25ns ops I

Install Phase II and MKB

Beam

No beam

Staged commissioning plan for [email protected]

2008

2009


Pilot physics

Sub-phase

Bunches

Bun. Int.

beta*

Luminosity

Time

Int lumi

first Collisions

1 x 1

2 x 1010

18 m

4 x 1027

12 hours

0.15 nb-1

repeat ramp - same conditions

-

-

-

-

2 days @ 50%

0.3  nb-1

multi-bunch at injection &

through ramp - collimation

-

-

-

-

2 days

-

physics

12 x 12

3 x 1010

18 m

1 x 1029

2 days @ 50%

8 nb-1

physics

43 x 43

3 x 1010

18 m

3.8 x 1029

2 days @ 50%

30  nb-1

commission squeeze – single

beam then two beams, IR1, IR5

-

-

-

-

2 days

-

measurements squeezed

-

-

-

-

2 day

-

physics

43 x 43

3 x 1010

10 m

7 x 1029

3 days - 6 hr t.a. - 70% eff.

75 nb-1

commission squeeze to 2m

collimation etc.

-

-

-

-

3 days

-

physics

43 x 43

3 x 1010

2 m

3.4 x 1030

3 days - 6 hr t.a. - 70% eff.

0.36 pb-1

commission 156 x 156

-

-

-

-

1 day

physics

156 x 156

2 x 1010

2 m

5.5 x 1030

2 days - 6 hr t.a. - 70% eff.

0.39 pb-1

physics

156 x 156

3 x 1010

2 m

1.2 x 1031

5 days - 5 hr t.a. - 70% eff.

2.3 pb-1

29 days total

Pilot physics


Breakdown of a normal year

~ 140-160 days for physics per year

Not forgetting ion and TOTEM operation

Leaves ~ 100-120 days for proton luminosity running

? Efficiency for physics 50% ?

~ 50 days ~ 1200 h ~ 4 106 s of proton luminosity running / year

Breakdown of a Normal Year of Operation

Breakdown of a normal year

7-8


I lhc commissioning

I-LHC Commissioning

  • I-LHC performance limited to 50% of nominal beam intensities due to collimation system inefficiency and Bound Free Pair Production (BFPP)

  • Charmonix:

    • Pb commissioning in SPS in spring 2007 (competing with high intensity protons)

    • 1st Pb operation in LHC end of 2008 after pp run (allow cool down!)

    • delays in the PS and SPS imply 1st Pb in LHC not before 2009

  • switching time pp-PbPb: somewhere between few days and 3 weeks

  • keep optical configuration for Pb close to proton operation to minimize switching time (RHIC: ~2 weeks)

  • earlier commissioning of ions is being discussed


Switching time for early ions

Switching Time for “early ions”

  • Pb ions have the same rigidity as protons

  • assume reasonable reproducibility, keep from p-run

    • injection

    • 1st turn

    • ramp

  • leave squeeze IR2 to similar b* as already used in IR1&5 (biggest item!)

    • don’t change magnetic optics

  • can keep RF capture and instrumentation setup as for p

  • use optimistic estimate (as used for p)

    • would give about 4 days (minimum)


Ions in the lhc

Ions in the LHC

  • Start with early ion scheme (62 bunches instead of 592, 7 107 ions per bunch)

  • Will have to

    • Set up RF capture

    • Commission essential instrumentation

    • Commission squeeze in IR2

    • Establish collisions

  • Could do (some of) this early on if injectors are ready (same optics as for p)

  • Ion runs could provide cool down of PS, SPS, LHC after proton operation

  • After early ion scheme run, increase number of bunches

  • Move to nominal when possible


Lhc critical tasks

LHC critical tasks

  • Machine Protection System (MPS)

    • LHC cannot operate without

    • depends on various other systems

  • collimation

    • early stages

    • phase II

    • ions

  • radiation protection (RP)

    • stage 1,2,3

    • nominal

  • Many more:

    • beam dumps

    • orbit control

    • beam instrumentation

    • gap cleaning

    • etc. etc.


Mps stored energy

Stored energy in MJ

Beam

450 GeV

7 TeV

single pilot 5×109

0

0.006

beam of 1012

0.07

1.1

43 bunches of 4×1010

0.12

1.9

156 bunches of 4×1010

0.45

7.0

936 bunches of 4×1010

2.70

42.0

2808 bunches of 4×1010

8.09

125.9

2808 bunches of 1.15×1010

23.27

362.0

~ stored energy of SPS, HERA, TEVATRON

MPS: Stored energy

  • Stored energy alone is not the whole story, the beam size is also important !

  • The failure mechanism plays also an important role for damages:

    Impact angle and time-constant


Mps damage test results

Shot

Intensity / p+

A

1.2×1012

B

2.4×1012

C

4.8×1012

D

7.2×1012

Based on those results we have adopted for the LHC a limit for safe beams @ 450 GeV of:

1012 protons with nominal emittance

limit for safe beams @ 7 TeV: 1010 p with nominal emittance

MPS: Damage test results

TT40 damage test presented by

V. Kain at Chamonix 2005:

  • Melting point of Copper reached for  2.5×1012 p [beam impact  to target surface].

  • Results agree with estimates based on FLUKA simulations.

A B D C


The lhc collimation challenge

The LHC Collimation Challenge

  • LHC Collimation System: hardware device designed to protect the ring elements from beam losses (without getting destroyed themselves!), the main features of such a system are:

  • Halo Cleaning: beam induced quenches of superconducting magnets are to be avoided => out of 2x105 protons lost at the collimators at 7 TeV, not more than 1 proton may escape and impact on any given meter of the LHC cold aperture

  • Protection: passive protection of the machine aperture against abnormal beam loss; beam loss monitors at the collimators detect unusually high loss rates and generate a beam abort trigger.

  • Problem: almost NOTHING survives the impact of the LHC full beam (including collimators). Even if there's no incident of full impact, collimators will be very radioactive => how to repair/replace anything?


The lhc type collimator

The LHC Type Collimator

Collimators are made of carbon to increase their chance of survival (but this will also decrease the collimation efficiency)

About 100 collimators in the LHC!!


Collimators commissioning scenarios

Bun-ches

Bunch Intensity

[1010 p]

Total Intensity

[1014 p]

Loss rate for =0.2 h

[p/s]

One pilot bunch

1

0.5

0.00005

6.9E+06

1

10

10.0

0.01000

1.4E+09

43 bunches

43

4.0

0.01700

2.4E+09

Scenario I: 156 bunches

156

4.0

0.06200

8.7E+09

Scenario II: 156 bunches

156

9.0

0.14000

2.0E+10

Scenario 75 ns

936

4.0

0.37000

5.2E+10

Scenario I: 25 ns

2808

4.0

1.10000

1.6E+11

Scenario II: 25 ns

2808

5.0

1.40000

2.0E+11

Nominal 25 ns

2808

11.5

3.20000

4.5E+11

Quench limit for continuous losses @ collimation:

450 GeV~ 2.2 × 1010 p/s

7 TeV~ 4.5 × 108 p/s

Collimators: Commissioning Scenarios

  • Official scenarios:

    • Intensity is an important parameter but not comprehensive!

  • Important:

    • Beam loss rate:Rloss≈ Itotal / Lower beam lifetime initially?!

    • Number of important failures:Bathtub curve: most failures initially. Redundancy more important for commissioning?

no nom. bunch


Rp quantities

RP Quantities

  • Prompt Radiation (during operation,Counting Rooms)

  • Induced Radioactivity

    • Residual Dose Rates (Maintenance)

    • Material Activation (Zonage, Waste)

  • Releases

    • Air Activation & Control => IR7

      (e.g., dose to critical groups)

    • Water Activation & Control(e.g., demineralised water circuit)


Rp intensities losses startup

RP: Intensities/Losses – Startup

Expected losses are an educated guesses, however are subject to related uncertainties with respect to loss patterns and the final numbers (and location) of lost particles.


Area classification beam off

Area Classification –Beam Off

STAGE 1

RELAXED

SITUATION

???

Controlled Areas

(Collimation, Triplets,…)

Supervised Areas:(Access galleries,…)

IR7 Stage 1


Summary

Summary

  • Many different scenarios and schedule options

    • 450 GeV Engineering run in 2007

    • Pilot Run in 2008

    • no ions scheduled before end of 2008 (2009 likely depending on injectors)

  • a lot of challenges

    • machine protection, radiation, collimation, machine parameters, …


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