WP2: Performance and Beam Dynamics

Following the project re-baselining in summer 2016, the layout and optics of the high luminosity insertion regions were reviewed and the performance re-evaluated. This has led to a small but visible reduction in performance, reducing the margins available for the achievement of the nominal and ultimate luminosity targets. Optimization of the machine settings is being pursued in collaboration with various HL-LHC work packages to recover some of the pre-existent margins relying on improved operational procedures (e.g. crossing angle variation) and tighter collimator settings presently being tested in the LHC.

WP3: Magnets

The triplet program went through a significant milestone at the beginning of the year, with the successful test of a 4-m-long coil in the mirror configuration in the US. This is the new world record in length for a Nb3Sn coil for particle accelerators. The left-hand side of Figure 1 shows the training performance of the magnet on the test bench. In spring, the second short model of the triplet was tested, reaching nominal current but failing to attain ultimate current (needed for 7.56 TeV operation). A coil will be replaced and a new test is planned for autumn 2017. A third short magnet is ready to be tested in June 2017.

In KEK (Japan), the first short model of D1 magnet reached in 2016 nominal field, but failed to attain ultimate. A second assembly with higher pre-stress reached ultimate current with a comfortable margin at the beginning of 2017. In LASA-INFN (Italy), the second type of the corrector magnet (octupole) was successfully tested in spring 2017. INFN recently signed the first collaboration agreement for the construction of the whole series of HL LHC high order correctors. In CIEMAT (Spain) the first mechanical test of the orbit corrector was successful and the laboratory is ready for the first winding tests. In INFN-Genoa, the contract for the construction of the short model of D2 magnet was attributed to industry. At CERN, the winding of the first CCT corrector for the D2 correctors was completed and the test is foreseen for summer 2017. Regarding the QUACO project, planning to construct two large Q4 aperture prototypes went through the initial phase of conceptual design and started the engineering in three European companies.

WP4: Crab Cavities

A major milestone towards the crab crossing of the HL-LHC beams was achieved in late February. Crab cavities are essential elements of the HL-LHC to fully exploit the inner triplet upgrade by maximizing the overlap of the two beams at the collision points. The crab cavities give each individual bunch a time-dependent transverse kick in the plane perpendicular to their motion to achieve the maximum overlap. Constructed from very high-purity niobium sheets, the HL-LHC crab cavities will operate at 2K to reach their nominal performance of 3.4 million volts of transverse voltage.

In late February, the two superconducting crab cavities manufactured at CERN underwent RF tests at the SM18 facility (Figure 2).

The cavities reached a maximum transverse voltage of 5 MV and 4.8 MV respectively, surpassing the nominal performance by a significant margin (Figure 3). By the end of 2017, the two crab cavities will be cryostated and installed in the Super Proton Synchrotron (SPS) to undergo the first ever tests with proton beams. Some 16 cavities (eight near ATLAS and eight near CMS) are required for the HL-LHC project.

WP15: Integration and Layout

The HL integration has progressed on three fronts in parallel:

• The preparation of the detailed integration for the equipment to be installed in LS2 (11T and new connection cryostat, TCLD, TANB, TDIS…). Various reviews of the installation of all the elements required to have each of this new equipment operational in the LHC machine, are ongoing. This activity covers vacuum, powering, cabling, electronics, cooling, survey and maintainability. The new installation locations for sensitive equipment are defined, taking into account the radiation to electronics requirement. The target is to complete the process before the end of 2017.
• The in-depth revision of the service routing in the new civil engineering complex that will be built at Point 1 and Point 5. The aim is to provide sound and efficient routing of electrical, cooling and cryogenic services among the various buildings, and to efficiently route them to the shaft providing access to the underground.
• The preparation of the layout drawings and related installation documentation (drawings and models) for the various parts of the machine that will be modified during LS2.