1380b 50ns schemes

LBOC 25-Oct-2011 CERN Massimiliano Ferro-Luzzi 1

1380b 50ns schemes1380b 50ns schemes

Reminder: – 25ns satellite-main collisions, why ?

– summer test New results from October:

– LDM measurements

– ALICE satellite-main collisions in 50ns physics Prospects for a test thursday this week

– see also Steve Hancock's presentation LMC_101


The current "sat-main" 1380b schemeThe current "sat-main" 1380b scheme

The intermediate 12b batch is shifted by 25ns such as to collide in IP8 (not IP2)

SPS injection gap: 250ns instead of 225ns

No more space for keeping the pilot => overinject


Attempt in 12jul to 26jul Attempt in 12jul to 26jul

48b48b

264b264b

840b840b

1092b1092b

1380b N=1.051380b N=1.051380b1380bmain-sat IP2 collisionsmain-sat IP2 collisions

normal schemenormal scheme

was not conclusive (see LBOC 23 Aug 2011)

was not conclusive (see LBOC 23 Aug 2011)


Why bother ?Why bother ?

Benefits:– ALICE luminosity diluted over all 25 ns slots: perfect, minimize pile-up!

– More collisions in ATLAS (1%), CMS (1%) and LHCb (2%)

– SPS 250ns gap: "more relaxed operation" w.r.t. 225ns gaps

Prospects:– PS RF (Steve Hancock): potentially could control the 25ns satellite

intensity!

– Next year: could squeeze ALICE according to achievable population of 25ns satellites,

e.g. b*=1m would allow operating with current satellite populations

with 1-2% satellites could operate at 10m and tune lumi by separation

– Upgrade LHC: if choose 50ns and if 3 main-main collisions are too much (beam-beam limits ?), this trick would maybe allow upgrade operation with ATLAS / CMS / LHCb (5e34 vs 2e33 luminosities)

all small gains, but all realall small gains, but all real


Fill 2222 25ns satellite distributionFill 2222 25ns satellite distribution

first 50 minutesfirst 50 minutes last 50 minuteslast 50 minutes fill averagefill average

LDM, Enrico BravinLDM, Enrico Bravin

all central RF buckets of the nominal 25ns slots

After removing those more than 1 slot away from a main bunch (exact definition ?)


Fill 2220 25ns satellite distributionFill 2220 25ns satellite distribution LDM, Enrico BravinLDM, Enrico Bravin


25ns bucket population products25ns bucket population products

22192219

22222222 22202220

22182218


bucket_product to luminosity conversion

is approximately (for 0 separation):

L[i]=bucket_product[i]*3.4e26 Hz/cm2

assuming 100um beams

All 25ns slots, but cut at 0.01for filling the histograms

N1*N2*1e9N1tot*N2tot

All 25ns slots, but cut at 0.01for filling the histograms

N1*N2*1e9N1tot*N2tot



22172217

22152215 22102210

22162216




22082208 22042204



Summary from LDMSummary from LDM

All in all, the satellite populations are reasonably stable!

(never believe in your machine colleagues' pessimism...)

For the relevant satellites (those which collide with a main) Mean population: 1.3 - 2.0 x10-3 (I take the start of fill) RMS population: 0.6 - 1.2 x10-3 Mean population product: 0.4 - 1.0 RMS population product: 0.4 - 0.7


ALICE: Vertex timingALICE: Vertex timing

Fill 2216, main-main V0 vertex Fill 2222, main-sat V0 vertex

Lateral peaks due to background

From fill 2217 onward, ALICE has pure "sat-main" collisions (i.e. is asking, I suppose) for zero separationFrom fill 2217 onward, ALICE has pure "sat-main" collisions (i.e. is asking, I suppose) for zero separation

Paolo Martinengo & CoPaolo Martinengo & Co


ALICE: Timing correlationsALICE: Timing correlations

Fill 2216, main-main T0 vertex

Fill 2222, main-sat T0 vertex



ALICE: Vertex distribution in XY planeALICE: Vertex distribution in XY plane

Main-sat Main-Main



ALICE: Vertex distribution along ZALICE: Vertex distribution along Z Paolo Martinengo & CoPaolo Martinengo & Co

Main-sat Main-main

FWHM FWHM


Approximately expected total luminosityApproximately expected total luminosity

bucket_product to luminosity conversion

is approximately (for 0 separation):

L[i]=bucket_product[i]*3.4e26 Hz/cm2

assuming 100um beams.

Here I used for the approximaley

expected total luminosity:

L = L[i]_mean * L[i]_entries

2217 and beyond2217 and beyond

Get 0.5-0.9 1030 Hz/cm2

ALICE wish to have up to 2x1030 Hz/cm2


ALICE lumi from TIMBERALICE lumi from TIMBER

At start of fill, fair agreement with the approximately expected! But too small lumi head-on => no levelling possible

2217 and beyond

0.5-0.9 1030 Hz/cm2 ALICE operating lumi (levelled)ALICE operating lumi (levelled)

ALICE operating lumi (levelled)ALICE operating lumi (levelled)


What now ?What now ?

LMC 101 minutes:

"DECISION: LMC gave the green light for an artificial satellite-bunch trial in the LHC"

What would be desirable: Prepare PS and SPS enhanced 25ns satellite beams just before an injection of a

50ns fill– about 1-2% satellite fraction is OK (essentially, anything you want which is bigger than

0.2% and smaller than 5%...)

Inject into LHC– check with LDM in the LHC

– if OK, use for physics fill

Mike: "There might be a little cost in ATLAS/CMS peak lumi"

=> Fine for one fill, then we evaluate Shouldn't cost more than, say, about 2h of LHC beam time The window for this test is very narrow: Thursday morning to Friday morning, or

saturday morning to sunday afternoon

Would be nice to achieve this before end of the proton run!!

1380b 50ns schemes

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