Summary notes of the LCU meeting on 26/01/2010
Present: CA, OB, HB, RC, OD, SF, MG, WH, BH, JJ, EL, YL, JM, AR, FS, RT, GV, SW
Report from meetings
Trip report from Fermilab Workshop -> FS (slides)
RA and FS went two days to Fermilab to discuss the possible use of the TEVATRON for machine studies before the final shutdown end of 2011.
Proposals from FNAL (to improve the understanding of the machine before
shutdown), BNL (e-lens), CERN (test that are not considered suitable for the
LHC).
A number of ideas have already been collected. Further ideas are encouraged.
It will be probably not possible to ask for hardware changes in view of these
tests.
The planning will proceed in further iterations.
A revised list of proposals should be prepared by April and Fermilab will officialy
submit these proposals by July 2010.
The complete set of information can be found at the Workshop site.
News on the LHC online model and data analysis -> CA (slides)
CA reported about applications of the online model in the recent LHC run.
One application was to calculate coupling correction knobs.
CA also used the online model to study the effects of the measured alignment errors.
This, however, should be combined with the use of measured closed orbit.
CA also presented the analysis of the data taken during aperture measurements in the LHC.
The main aim is to quantify the available aperture and compare with the nominal
estimates. Furthermore, one aims at evaluating a measured n1, which is crucial for the collimation
setting up. The aperture in the LHC was measured systematically with circulating
beams, by means of 7-8 sigma bump amplitude at injection, and then increased until losses were observed.
Various phases were scanned in order to provide the minimum aperture over the
whole ring (H/V and Beam 1/2). Data analysis is still in progress. It is planned to perform in future also measurements of the off-momentum aperture.
Latest revisions of nominal 7 TeV IR8 optics -> EL (slides)
EL reported that the settings of the crossing and
separation bumps for the nominal squeeze of IR8 are referring to 5 TeV. This led
to a revision of the parameters in view of translating everything to 7 TeV and
simplifying the sequence of changes. In addition, the observed limitation of the
MCBX to 350 A was folded into the new bumps. The proposal consists of keeping
the separation constant to 2 mm from injection to the first point of the squeeze
and it is then reduced to 0.5 mm. Similarly, the crossing angle is kept constant
to 170 murad up to the end of pre-squeeze and it is then increased to 235 murad
and kept constant during the squeeze. The transition between the end of
pre-squeeze and the beginning of the squeeze is not at all smooth and could
induce some problems. It is worth mentioning that the number of MCBX used is now
4 in order to decrease the strength/magnet and remain within the limit found
during the hardware commissionig.
SF proposes to simplify further the operation by keeping the
separation constant to 2 mm from injection to squeeze (down to 2 m of beta*). In
order to fulfill the initial assumption that half of the strength of the MCBX
was devoted to misalignment correction, a different sharing between the strength
for the crossing/separation bump that the one presented should be used. Another
iteration will be made.
AOB
None
Last update: 26-January-10
MG & HB
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