Configuration for the 2018 lead-lead run

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The data in this table has been compiled in collaboration with the HI machine experts (especially Michaela Schaumann helped to fill this table with interesting contents). This document is work in progress and will be updated whenever needed or useful.


General remarks

LHC configuration

General beam properties
Beam energy 6.37 ZTeV (8.16 TeV cms)
Ion beam intensity 2.0 x 108  
Ion beam emittance 1.3 - 1.5 µm  
Ion beam bunch length 0.09m depends on the blow up which will be set
RF voltage 14MeV  
β beating 5% temporary result from optics measurements
Peak lumi per bunch head-on 1.38 x 1025cm-2s-1 Initial lumi at IP1/5 with ß*=0.5m
β* 0.5m  
Half crossing angle 160µrad  
Geometric Factor 0.75  
Peak lumi estimate 7.4 x 1027cm-2s-1 Assuming 728 collisions and no levelling
β* 0.5m  
Leveling 1 x 1027cm-2s-1  
Geometric Factor 0.95  
Peak lumi estimate 9.1 x 1027cm-2s-1 Assuming 704 colliding bunches. Theoretical peak lumi if ALICE would not be leveled.
External crossing angle +137 µrad  
Internal crossing angle -77 µrad  
Total half crossing angle 60 µrad  
Magnet polarity + / + Dipole polarity flipped at half way (the same time as switch to 75 ns spacing)
IP8 (LHCb)
β* 1.5m  
Geometric Factor 0.7  
Peak lumi estimate 1.7 x 1027cm-2s-1 Assuming 528 colliding bunches and no levelling.
Dipole polarity positive  
External half crossing angle -180µrad  
Internal half crossing angle -138µrad  
Half crossing angle -318µrad  

VdM scans

The VdM scans need to be done in the 100ns configuration. They will be done with regular physics optics and using a physics filling scheme.

Even though the experiments slightly prefer to have the scans of ATLAS and CMS in the same fill it has been decided to have separated fills for the scans in CMS and ATLAS so that the proabability of a dump during the programme is smaller. ATLAS and CMS would like to have the Length Scale calibration in the same fill as the other scans. (It serves to increase the time between the first scans and the verification scans to increase the lever arm for changes of the beam parameters with time). The levelling in the other experiments has to be switched off during the scans of the programs. Since ALICE can not make use of data beyond 1e27 the lumi will be adjusted to a lower level to have some safety margin in case of lumi drifts during the scan of ATLAS or CMS. Between the various scans of the programme the lumi can be re-adjusted in ALICE. ATLAS and CMS will be separated to a low luminosity (1/4 of the head on lumi) during the scan of the other experiment in order to limit the burn off for the scanning experiment. A special filling scheme for the two fills will be used: this scheme disentangles completely the collisions in IP1/5 and IP 2/8 (i.e. a bunch which collides in IP1/5 will not collide in IP2/8 and vice versa). Like this ALICE and LHCb "can do what they want" during the scan of ATLAS and CMS and the fills should turn into productive luminosity fills for them. The proposed filling schme is:


The number of collisions in LHCb has been limited to 126 in order not to come too close to dump or quench thresholds (?in Q10?).


LHCb will perform a VdM scan during the intensity ramp up. The scan will be performed in the 2nd 250b ramp up fill (filling scheme below). The programme will last for approximately 4 hours.

ALICE will perform a scan during a dedicated fill with 100ns. Since the beams cannot be brought head-on in ALICE with full intensity (quench/dump) the fill will be started as a regular physics fill, and shortly before the levelling in ALICE stops all experiments are separated and ALICE performs the scan. The filling scheme is the normal 100ns production scheme.

Filling schemes

MKI flat-top validated for ~5.3µs. From this the following AGKs can be assumed:

100ns: 12 injections : 5.25 µs : 2100 buckets : optimal AGK : 32321
75ns :  14 injections : 4.05 µs : 1620 buckets : optimal AGK : 32801 (Longer injections are not considered even though possible from MKI length)

The 75ns AGK is compatible with 9 100ns batches (36bpi). It has been decided to use the 75ns AGK (32801) also for the 100ns period in order not to loose time for a change of the AGK in the middle of the run. 

Scheme Remarks
100_150ns_60Pb_40_40_40_20bpi_3inj.csv Ramp up 1st step  : 2 hours SB
100_150ns_256Pb_240_240_35_24bpi_12inj.csv Ramp up 2nd step : 2 fills with at least 6 hours SB
100_150ns_480Pb_456_456_53_24bpi_20inj.csv Ramp up 3rd step  : 2 fills with at least 6 hours SB : first fill
100_150ns_480Pb_456_456_53_36bpi_16inj.csv Ramp up 3rd step  : 2 fills with at least 6 hours SB : second fill
100_150ns_648Pb_624_624_48_36bpi_19inj.csv Considered good 100ns schemes with AGK optimised for 75ns (32801)
100_150ns_648Pb_620_619_52_36bpi_20inj.csv Considered good 100ns schemes with AGK optimised for 75ns (32801) and a Single Batch of 4b at the start of the scheme (can be used as "probe bunch")
75ns_735b_735_714_476_42bpi_19inj_800ns_bs150ns (in LPC editor) Considered a good 75ns scheme


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