Plans for lumi delivery in 2009-2010 LHC runBeam cmg meeting26-May-2009 CERNMassimiliano Ferro-Luzzi...

Plans for lumi delivery in 2009-2010 LHC run Beam cmg meeting 26-May-2009 CERN Massimiliano Ferro-Luzzi 1

Plans for lumi delivery in 2009-2010 Plans for lumi delivery in 2009-2010 LHC runLHC run

What limitations can we expect ? How do we go from 1e28 to 1e32 ? How could the run look like ?

After discussions with

Ralph Assmann, Roger Bailey,

Helmut Burkhardt, Werner Herr,

Mike Lamont, Jorg Wenninger ,

and with the experiments.

My apologies for dropping lumi units cm-2 s-1


1st LHC Performance Workshop in Chamonix (feb 09)1st LHC Performance Workshop in Chamonix (feb 09)

Message from the LHC experiments:Message from the LHC experiments: Typically, with 50-100 pb-1 good data at 10-8 TeV many new limits

set on hypothetical particles (some more stringent than Tevatron), or even discoveries possible!

With 200-300 pb-1 g.d. at 10-8 TeV start competing with Tevatron for Higgs masses around 160 GeV

With 1 fb-1 g.d. at 10 TeV find Higgs if around 160 GeV mass

The higher the energy, the faster it goes...

Note: below ~20-40 pb-1 g.d. at 10-8 TeV, or at any lower energy, one would probably start talking about an "engineering run"

(can still be very useful, but perhaps not in terms of immediate physics results)


Outcome of First LHC Performance WorkshopOutcome of First LHC Performance Workshop

Held on 2-6 February 2009 in Chamonix

“Many issues were tackled in Chamonix this week, and important recommendations made. Under a proposal submitted to CERN management, we will have physics data in late 2009, and there is a strong recommendation to run the LHC through the winter and on to autumn 2010 until we have substantial quantities of data for the experiments. With this change to the schedule, our goal for the LHC’s first running period is an integrated luminosity of more than 200 pb-1 operating at 5 TeV per beam, sufficient for the first new physics measurements to be made. This, I believe, is the best possible scenario for the LHC and for particle physics.”

Rolf Heuer, CERN DG, 6 feb. 2009

Target: 300 pb-1 of good data at 10 TeV center of mass

Ion run at the end


What do we need ?What do we need ?

Assume an overall “efficiency factor”

Then, in order to reach few 100 pb-1 in a run of less than 10 months,

we need a luminosity L0 of order ~ 1e32

The main parameters are (assume is fixed to 5330)

kb = number of bunches

N = bunch population

* = focusing at IP

f kb N2 L0 = –––––––– F

4 N*

∫Trun L(t) dt

–––––––––– = 0.1 ... 0.2 L0 Trun


How do we get to 300 pbHow do we get to 300 pb-1-1: input from LHC expts...: input from LHC expts...... on lumi strategy

ATLAS and CMSATLAS and CMS: highest possible lumi, even if average number of inelastic interactions of = 7 (which we very probably never exceed in 2010)

ALICEALICE: a couple of different running modes with typically very low lumi (1e28 to 1e30) and low pile-up per crossing ( ~ 0.1 or smaller), for example

– kb=2-4, N~4e10, *=10m (largest possible bunch spacing)

– kb=72, N~1e10, *=2m (bunch spacing > 100ns, "trains" spaced as much as possible)

LHCbLHCb: “low lumi” ~ few e32 => as much as ATLAS and CMS for this run, but keep pile-up at reasonable level (nominally ~ 1, but may try working with higher pile-up)

TOTEM and LHCfTOTEM and LHCf: special short runs (typically of order few days)


Others, Others, en-vrac,en-vrac, possibly possibly incomplete incomplete ... ... some work ahead for the LPCsome work ahead for the LPC

All experiments:– explore 25 ns spill-over effects, prepare the road

– luminosity measurements (vdMeer, beam-gas, ...) cross-section normalisations

ALICE – collision spacing > 100ns whenever possible Pixel readout = 4 clock cycles

– reversed dipole polarity systematics

LHCb: – largest possible beam (at same luminosity) tranvserse vtx separation

– polarity reversal systematics

– fixed value of magnet (no ramp) save our spectrometer

– inclined crossing (only possible at large *) tame the "bad" polarity

– leveled luminosity (* adjustment during run) optimize integrated lumi

TOTEM/ALFA:– intermediate * , large * fwd physics program

LHCf– crossing angle increase acceptance


How do we get to 300 pbHow do we get to 300 pb-1 -1 : input from LHC: input from LHC

Main limitations may come from (as I understood it):

Collimation cleaning efficiency vs quench level => mostly limits total intensity I = kb N

– see Kassandralph's talk at LMC #6

Aperture limitations at the innner triplets

– will limit * : *min ~ 1/

– gets worse with external crossing angle

Beam-beam effects => limit on N– head-on are always there (independent of * and )

– long-range appear with small bunch spacing (absent for > ~500ns spacing) => see Werner Herr's talk at Chamonix: start with one bunch train per quadrant

(full long range effects), then add trains.

Collimator Year 1settings limitIntermediate (start of physics run): I < 2e13 p Tight (towards end of run ?) I < 5e13 p

Bunch spacing "easy" "challenging"and ext. angle * * > 500 ns , ext = 0 2m 1m> 500 ns , ext 0 3m 2m

Nmax = ??? 5e10 "easy" 9e10 "challenging" ???


Some special complications...Some special complications...

Special complication for IP8: one polarity is worse than the other– see LPN 419. I assume, roughly:

ext = 0 and bunch spacing > 500ns:

– like for IP1,5 (local bump is transparent to rest of machine)

ext 0 and bunch spacing = 50ns:

– "good" polarity: can reach essentially same * as in IP1,5

– "bad" polarity: would have to step back by +1m

ALICE special bunches: – how to deal with BPMs ?

dynamic range for high intensity bunches may not allow to measure the small intensity bunches ?

switch to low scale a few BPMs ?

– what spacing is possible for the special Alice bunches ? (150 ns ?)

– how many can be fit in ?


Optimum number of bunches for lumiOptimum number of bunches for lumi

Simple-mindedly: given a max intensity Imax and a max bunch charge Nmax, the number of

bunches for maximizing luminosity is

opt Imaxkb = ––––Nmax

For illustration:

At the beginning, we are likely to have optimum at ~200-400 bunches

(just beyond 156…)

Imax Nmax kbopt

2e13 p5e10 p 400

9e10 p 222

5e13 p5e10 p 1000

9e10 p 555


Fill schemes: no crossing angleFill schemes: no crossing angle

that's about the maximum number of "equidistant" bunches (minimum spacing driven by length of common pipe section ~120m)

delayed by 75ns

Start with 2x2– each IP gets 1 colliding pair and 1 non-colliding bunch/beam

Then move on with equidistant schemes: see LPN 323+415 start from a modified equidistant NxN scheme that gives N / 0 / N / ½N

collisions in IP1/2/5/8 and shift symmetrically from IP1 a number of bunches to make them collide in IP2 (no change for IP1 and 5, but less collisions for IP8)

43x43– 43 / 2 / 43 / 20 colliding pairs in IP1 / 2 / 5 / 8

156x156– 156 / 4 / 156 / 72


Fill schemes: with crossing angleFill schemes: with crossing angle

Move on to crossing angle schemes

Many possibilities:

75 ns, 50 ns, 25 ns spacing (100 ns ? 150 ns ? ...)

NB1: the short spacing introduces long-range encounters in the IR => reduced reach in bunch charge ?

NB2: the crossing angle reduces the aperture in triplet => reduced reach in * ?

=> We most probably lose lumi with these schemes for the same intensity as in156x156!! Will require higher intensity to recover same lumi as in 156x156


Fill schemes: with crossing angleFill schemes: with crossing angle

Why 50 ns instead of 25 ns or 75 ns ?

Allows to distribute lumi over 4 IPs in very flexible and optimal manner– Few colliding pairs in IP2 with “full” sequence at other three IPs

– Hence, avoid large defocusing or lateral displacement at IP2 (ALICE)

More favorable in terms of beam-beam effects:– Only 3 IPs give the full head-on collisions (instead of 4 for 25 and 75 ns)

– Required crossing angle almost independent of *

When reaching close to 50% nominal intensity and 100% nominal bunch charge (in 2011?), it should gives the highest possible luminosity (while waiting for phase 2 collimation system)

For details, see LHC Project Note 415 and W. Herr in Chamonix 2009


Overview table (preliminary)Overview table (preliminary)

24

1.5

2


900 GeV10 TeV

develop 50 ns, truncated

introduces crossing angle

short physics runs at 50 ns and go back to best luminosity (156x156) for mass lumi production

until 50ns breaks even (then stay at 50 ns)

try also 25 ns at the end

Physics run modesPhysics run modes

2x25e10

10-11m

2x25e10

10-11m2x2

5e1010-11m

2x25e10

10-11m2x2

5e102m

2x25e102m

43x435e102m

43x435e102m

156x1569e101m

156x1569e101m

156x1565e102m

156x1565e102m

toroids & solenoids ON*, spectr. dipoles OFF

toroids, solenoids & spectr. dipoles ON*

* expt magnet ON means at full nominal field ( as for 14 TeV)

50ns/4329e103m

50ns/4329e103m

“few shifts”

“more few shifts”

“few days”“more few days”

“few weeks”

“few months”


ProposalProposal

Write in a document the target parameters for the 2009-2010 run (as discussed in Chamonix and right after)

Why ?– needed by many people for: radiation estimations, bkg studies,

computing farm dimensioning, physics/trigger MC simulations Replace (new version of) EDMS document 931921v2

– https://edms.cern.ch/document/931921/2 Include summary table for physics conditions But also add paragraphs to explain the strategy:

– rough overview of requirements from experiments

– what are the expected limitations ?

– how do we plan to overcome them ?

– how much beam commissioning time expected for the various steps ?

– define "extreme" (but likely) case for background simulations


““Very draft schedule 2009-2010”Very draft schedule 2009-2010”

From first LHC Performance Workshop, Chamonix, feb. 2009 Baseline

– 1 month commissioning

– 10 month proton physics

– 1 month Lead Ions

– Shutdown – end September 2010

– Built in slip potential

see Mike Lamont in LMC_12c


Winter stop 2009-2010Winter stop 2009-2010

Unusual for CERN to run through winter Assessed cost at LHC Performance Workshop 2009 in Chamonix,

and decided to run through Technical consequences and modalities being assessed

– Main worry from accelerator sector is the manpower coverage (including burn-out risks)

– Expts: no need for shutdown, more than happy with a 2-3 days technical stop per month

Proposal made at LMC (see Mike at LMC_12c):– Stop LHC with beam ~19th December 2009

– Earliest restart ~ 4th January 2010

– Could possibly use weekends either end =>12 days stop

=> Some expts questioned whether not better to have no stop at all Difference in manpower investment and general impact for a no-

stop scenario and a 2-week stop (standby) scenario is being assessed (see LMC 14)


Regular (Planned) Technical Stops (from Mike's talk)Regular (Planned) Technical Stops (from Mike's talk)

Survey across machine and expts needs was done

=> Programmed technical stop 3 days including recovery and re-closure of ring

– QPS plus power converters, controls, R2E etc. Mon – Wed allowing weekday time for re-setup with beam Followed by one day set-up with beam and systematic checks of

machine protection system Clearly if major breakdowns occur at other times – advantage will be

taken. Injector maintenance in parallel is an option [Have not considered scheduling of MD…]


Very draft LHC schedule for 2009-2010Very draft LHC schedule for 2009-2010

First draft produced (Mike),

for discussion


TI8 test (6-7 June) TI8 test (6-7 June)

LHCb's main purpose: – time and space align of silicon detectors (VELO, TT and IT) and

– time align + tuning of Beam Conditions Monitor (BCM) + Beam Loss Scintillator (BSC)

good alignment is essential for tracking and triggering– remember: LHCb can't use cosmics for this...

requires special timing settings and special data analysis (not for free!), but proved to be very useful (2008 experience) => will give a good start in 2009 !

considered important enough by the collaboration to put a special request requiring almost full operation of the experiment

It's the red beam, beam2, anticlockwise beam, the wrong beam, etc.

BSCBCMupstr

BCMdwnstr

ITTT


TI8 test (6-7 June) ...continued...TI8 test (6-7 June) ...continued...

LHCb wish list: LHCb would like to take data on about 500 bunches of (optimally) 2e9 p/bch. This could

be any time from saturday morning to monday morning, including nights. LHCb control room will be fully manned for data-taking from saturday morning to monday morning.

Need:

– injection pre-pulse => ?? (Andy Butterworth ? JJ Gras ?)

– LHC clock for beam2 => OK (Sophie Baron, RF)

LHCb will acquire data parasitically during machine TI8 studies and therefore would like to know what will be the maximum intensity (per bunch) that will be used: now assuming 1e10 p/bch. => yes, confirmed by Brennan

LHCb would appreciate if beam shots are given to them on the TED during any unforeseen break of beam studies of > ~1/2 hour (and where beam can still be delivered on the TED).

LHCb would appreciate if the bunch (or injected train) intensity could be published on DIP. If multibunch operation is attempted, LHCb would be interested to take data as well,

parasitically. Lowest possible intensity per bunch would again allow best usage for LHCb (the higher the intensity the least number of devices can be turned on: 2e9 p/bch is optimal, 1e10/bch is still useful).


TI2 test (11-12 July)TI2 test (11-12 July)

ALICE: no particular request. will take data, but fully parasitically (means probably some minor requests

on the fly, to be fulfilled if that does not disturb too much the test).

LHCb: depending on outcome of June 6-7 test (in TI8), would perhaps be happy to

make use again of some beam in TI8 during the TI2 test, if not too disruptive for the test and for the work in adjacent sectors (s81, s78)

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