[en] This session was the first of the two sessions dealing with future projects and the associated studies. Starting with descriptions of the plans and needs of the LHCb and ALICE experiments which are less extensively documented than those of ATLAS and CMS, it addressed the plans for the High Luminosity LHC and for the upgrade of the injectors, both for protons and other ions. (author)

[en] The 2011 LHC run is reviewed from the experiments' perspective. The LHC achievements directly related to physics production are summarized. This includes high luminosity p-p and Pb-Pb running, special activities (such as intermediate energy p-p physics, 90 m optics, luminosity calibrations) and other experiments (for example satellite-main bunch collisions in IP2, 25 ns stable beams tests, etc.). (author)

[en] During this workshop on LHC performance, operation of the machine in 2012, activities during the first long shutdown LS1 aiming at preparing for operation at 7 TeV per beam and substantial long term upgrades of both the injector chain and the LHC have been discussed. After a session dedicated to observations and lessons from the run 2011, strategies for the run 2012 have been discussed in order to optimize the machine performance and, in particular, the maximum and integrated luminosity provided to the main experiments. Two session were dedicated to the preparation of the first long shutdown (LS1) followed by a session aiming at optimizing the performance to be expected after this first shutdown. The last two session of the workshop were dedicated to substantial upgrades of the injector complex and the LHC aiming at increasing the integrated luminosity to 250 inverse femto-barn per year after implementation in a second long shutdown. Improvements of the injector complex comprise increased injection energies in the PS Booster and the PS, an upgrade of the SPS vacuum chamber to alleviate limitations due to electron cloud build up and many more upgrades required for the generation of beams with higher brightness and smaller emittances than possible with the present machines. Plans for the LHC comprise an upgrade of the interaction regions to allow for a smaller beta*, crab cavities for luminosity levelling and, upgrades of the collimation and other systems

[en] The minimal duration for LS1 is 20 months, meaning the time from physics to physics will be about 2 years. The actual start of LS1 is set for the 17. November 2012, which will allow the Liquid Helium emptying from the machine before Christmas. However, delivery dates for certain components are on the critical path of the experiments, which will allow the first beams for beam commissioning not before September 2014. Depending on the results of mid-2012 physics, the start date of LS1 will be reviewed. The actual plan for injectors is in line with the LHC plan, but the risk of running injectors for two years has to be assessed. The analysis of resources is progressing well throughout the complex (collaborations and internal mobility) and is being done according to priorities. Certain activities have already been postponed to LS2, and new requests will be carefully analyzed, as well as open issues

[en] In 2011, the LHC had an excellent year, with delivered luminosity for proton-proton running at 3.5 TeV per beam well in excess of the target of 1 fb^-1 set prior to the 2011 run. Indeed, with both record totals for delivered luminosities in both proton-proton and lead-lead running, several special optics runs and a vigorous machine development program, 2011 exceeded all expectations in terms of machine performance. Stable beam availability of about 32 %, which corresponds to a Hubner factor of 0.22 and 0.24 for proton and Ions runs respectively. While fault tracking was not fully complete, successful mitigations against downtime due to radiation induced single event upsets, have already been observed, and further improvements are expected in 2012. This should help reduce the number of non-programmed beam dumps in 2012

[en] The experience from the past LHC proton run has provided plenty of information and can be used to define possible scenarios for the 2012 physics run. The key parameters such as β* and crossing angle will be reviewed assuming a 4 TeV beam energy and considering options for 25 ns and 50 ns. Possible scenarios for the high-beta optics configuration during the 2012 run will be presented. (author)

[en] Insertion quadrupoles with large aperture and high gradient are required to upgrade the luminosity of the Large Hadron Collider (LHC). The US LHC Accelerator Research Program (LARP) is a collaboration of US DOE National Laboratories aiming at demonstrating the feasibility of Nb₃Sn magnet technology for this application. Several series of magnets with increasing performance and complexity have been fabricated, with particular emphasis on addressing length scale-up issues. Program results and future directions are discussed. (author)

[en] The fourth session of the 2012 LHC Performance Workshop included the following topics: -) beam Energy (it was decided to step back in energy from 4 TeV to 3.5 TeV in case of excessive number of quenches), -) optics options, -) collimation settings and performance, -) performance reach in the LHC for 2012, -) MD plans in 2012, and -) Ions in 2012

[en] The 2011 LHC run is reviewed from the experiments' perspective. Cooperation between machine and experiments was again very constructive. The LHC produced pp physics collisions at √s = 7 TeV with a peak luminosity reaching about 3.6*10³³ cm^-2s^-1 and delivering more integrated luminosity than expected (∼ 5.7 fb^-1 in IP1 and IP5, 1.2 fb^-1 in IP8). Thanks to this excellent LHC performance, ATLAS and CMS came close to discover or exclude the SM Higgs boson, while increasing further the pressure on supersymmetric models. LHCb was able to set unprecedented limits on the branching ratio of B_s → μμ and to observe an intriguing CP violating asymmetry in charm decay. An intermediate energy pp run was successfully carried out to complement the heavy ion physics data. Furthermore, an impressive 16-fold increase in peak and integrated luminosity with Pb beams was realized (4.5*10²⁶ cm^-2s^-1 and about 160 μb^-1 per IP). ALICE, ATLAS and CMS produced a wealth of new heavy ion physics results that will sharpen the understanding of the quark-gluon plasma. A first TOTEM measurement of the total pp cross section was realized and more diffractive physics results obtained with Roman Pots (TOTEM and ALFA/ATLAS). Luminosity calibration measurements with van der Meer scans and beam-gas imaging were further improved, to the point that cross sections could be measured with about 2% accuracy

[en] The improvements done to the RF parameters and hardware in 2011 are reviewed. Then the upgrades planned for 2012 are presented: further reduction of capture losses with the longitudinal damper, batch by batch blow-up at injection and modification of the controlled blow-up to preserve bunch profile. Operation at higher energy is readily possible with the present RF power, and does not degrade longitudinal stability thanks to the controlled longitudinal emittance growth during the ramp. For operation with higher beam current, the observations in 2011 indicate that there is no single bunch instability issue with up to 3*10¹¹ p per bunch. With the large gain of the RF feedback and One-Turn feedback, the cavity impedance at the fundamental will not be a limitation for ultimate intensity (1.7*10¹¹ p per bunch) with 25 ns spacing. The klystron power (300 kW RF at saturation) is sufficient for 25 ns operation with nominal intensity (2808 bunches per beam, 1.1*10¹¹ p per bunch). An RF road-map for going beyond will be outlined: it calls for an upgrade of the LLRF only and should allow for operation with ultimate beam intensity (25 ns spacing, 2808 bunches, 1.7*10¹¹ p per bunch) after Long Shutdown one. (authors)