LHC 2009 - 2010 potential luminosity performance

LHC 2009 - 2010 luminosity performance - estimate for 3.5 TeV - no move to higher energy

A path to the total integrated luminosity quoted at Chamonix 2009 while keeping the total intensity to a reasonable level. Necessarily approximate. Preliminary.

Step	Comment	Turn around time	Max number bunches	Protons/Bunch	% nom. intensity	Min beta*	Peak Luminosity cm^-2s^-1	Integrated Luminosity per month	events/X
1	Beam commissioning							First collisions
2	Pilot physics, partial squeeze, gentle increase in bunch intensity, avaialbility low	Long	43	3 x 10¹⁰		4 m	8.6 x 10²⁹	100 - 200 nb^-1
3		5	43	5 x 10¹⁰		4 m	2.4 x 10³⁰	~ 1 pb^-1
4		5	156	5 x 10¹⁰	2.5	2 m	1.7 x 10³¹	~9 pb^-1
5a	No crossing angle - could at this stage push intensity see 5b	5	156	7 x 10¹⁰	3.4	2 m	3.4 x 10³¹	~18 pb^-1	0.8
7	No crossing angle.	5	156	7 x 10¹⁰	3.4	2 m	4.9 x 10³¹	~26 pb^-1
8	50 ns - nominal crossing angle - aperture restricts squeezing further - note limited complement of bunches.	5	144	7 x 10¹⁰	3.1	2 m	4.4 x 10³¹	~23 pb^-1
9	50 ns	5	288	7 x 10¹⁰	6.2	2 m	8.8 x 10³¹	~46 pb^-1
10	50 ns*	5	432	7 x 10¹⁰	9.4	2 m	1.3 x 10³²	~69 pb^-1
(11)	50 ns*	5	432	9 x 10¹⁰	11.5*	2 m	2.1 x 10³²	~110 pb^-1

LHCb equivalent

Assuming:

8 hour fill length throughout - it could be longer, but given the possibility of lost fills, system un-reliability etc. 8 hours is probably optimistic.
20 hours luminosity lifetime - with the intensities above it should be longer but given vacuum, the learning process etc. it won't be optimum.
30 day months. Availability gives time available for physics including normal turn arounds. Rest of time in machine development, access, recovery etc.
40% machine availability assume - time for turn around and physics/total.
Constant availability assumed throughout, thus the total can be scaled as needed.
Nominal crossing angle assumed for 50 ns.
Total intensity limited to around 12% of nominal (see * below).
No squeeze beyond 2 m. with 156 bunches, crossing angle off - conservative - to avoid the operational difficulties which start to come in with squeezing beyond 2 m..

* Working with these intensities implies impeccable performance of the machine protection system, and a fully commissioned collimation system capable of highly efficient beam cleaning,. This is going to take time and must not be rushed.

Massi Ferro-Luzzi has made some similar estimates (see for example http://indico.cern.ch/conferenceDisplay.py?confId=57607 and here) in which he is slightly more optimistic regarding beta* and bunch intensity in the 156 bunch phase. Here we err on the cautious side (1 metre will not necessarily be straightforward, there might be machine protection, injection and ramping issues with higher bunch currents, and there is the issue of pile-up in the experiments (1e11 at 1 metre at 5 TeV buys approx. 7 inelastic per crossing)).

For beam losses, it would be reasonable to take around 10% of the first year figures quoted in "Estimates of Annual Protons Doses in the LHC" where 25 ns running and a peak luminosity of 10³³ cm^-2s^-1 is assumed.

Mike Lamont August 2009