Overview presentation LTC July 2006 LHC initial commissioning - draft project note - includes consideration of 450 GeV run
| Phase | ||
| 1 | Injection & First turn | As for 7 TeV. Ring 2; Ring1. Commission injection, thread beam around first turn, commission relevant beam instrumentation. |
| 2 | Circulating beam | As for 7 TeV. Ring2; Ring 1. Capture, adjustment of key beam parameters |
| 3 | 450 GeV - Preliminary system commissioning | |
| 4a/4b | 450 GeV - Detailed measurement program | Increase current, commission machine protection, transverse damper, measure aperture, optics. |
| 5a | 450 GeV - two beams | Pilots → higher intensity. Separation bumps, BLMs, crosstalk |
| 5b | Prepare 450 GeV collisions | Collide pilots. Unsqueezed. |
| Collisions | Experiments on. Increase to 43 on 43 | |
| Calibration run | Intertwined physics and further commissioning of squeeze, raising bunch intensity, increasing the number of bunches |
| Phase [both beams] | Beam Time [days] | |
| 1 | Injection and first turn | 4 |
| 2 | Establish Circulating beam | 3 |
| 3 | 450 GeV - initial | 4 |
| 4a | 450 GeV - consolidation | 1-2 |
| 4b | 450 GeV - system commissioning | 2-3 |
| 5a | 2 beam operation | 1 |
| 5b | Collisions | 1-2 |
| TOTAL | 16 days |
Given an operational efficiency of 60%, this gives an elapsed time of about 26 days. That is, 26 days after first taking beam down TI8 into the LHC. we would have hoped to have established collisions at 450 GeV.
Initial collisions will be performed with pilot++ beam (single bunch, 3 10^10 protons/bunch). After this the number of bunches and intensity will be increased. The number of bunches to a maximum of 156 (no crossing angle), and the bunch intensity to 10^10 protons per bunch (optimistic).
Initial beta* is planned to be 11 m. in IRs 1 & 5 with the possible use of beta* = 6 m. optics if things look OK.
Performance table below represent a possible, and I repeat optimistic, evolution. The plan is to interleaf luminosity production with extended periods of machine development.
| No of bunches | 1 | 4 | 43 | 43 | 156 | 156 |
| Particles/bunch 10^10 | 4 | 4 | 2 | 4 | 4 | 10 |
| Beam Intensity | 4 10^10 | 16 10^10 | 8.6 10^11 | 1.7 10^12 | 6.2 10^12 | 1.6 10^13 |
| fraction of nom beam intensity | 0.0001 | 0.0005 | 0.003 | 0.005 | 0.02 | 0.05 |
| beta* [m] | 11 | 11 | 11 | 11 | 11 | 11 |
| Luminosity [cm^-2 s^-1] | 1.7 10^27 | 6.6 10^27 | 1.8 10^28 | 7.2 10^28 | 2.5 10^29 | 3 10^30 |
| Beam size at IP [microns] | 293 | 293 | 293 | 293 | 293 | 293 |
| RMS Bunch Length - nominal [cm] | 11.24 | 11.24 | 11.24 | 11.24 | 11.24 | 11.24 |
| event rate [kHz]* | 0.07 | 0.27 | 0.7 | 2.9 | 10.4 | 65 |
* Assuming 450GeV inelastic cross section 40mb
It seems that we will have no problem to raise the voltage after all injections to 16 MV for the store at 450 GeV. This could improve the beam lifetime. The associated increase in dp/p is from (2sigma) 0.88E-3 to ~1.1E-3 (if we have the 1 eVs emittance; it might be lower), which shouldn't be a problem generally. (Trevor Linnecar)
The increase of dp/p, basically the bucket half height increased to sqrt(2)*10 ^(-3) for a voltage of 16 MV instead of 8 MV, will mainly affect the arc aperture where n1 will be reduced by 0.8 in the QFs and a bit less in QD's (both due to the nominal H-dispersion and the V and H spurious dispersion). In the triplet, with only spurious dispersion, the loss will be only dn1=0.2 (re-increasing beta* by 6% will easily solve this if needed). To summarise the first bottom-neck will be a priori the arcs and Ralf will possibly have to close further his collimator: with the magnets we try to stick to n1=7 at QF and 6.7 at QD and generally Ralf works with n1=6 so all his margin will be left!.. or we will have to reduce our margin for CO from 4 to 3 mm which is a non sens for commissionning phase. Other potential issue is loss of DA for particle with large synchrotonic excursion but my feeling is this shall be minor provided Q' and Q'' (not so high with the proposed squeezed optics) is more or less correctly adjusted. (Stephane Fartoukh)
Last updated: 3/8/2006 ML