The CERN internal review of the HL-LHC Beam Dump System [BDS] took place on February 5^th and was chaired by Volker Mertens. It was to a large extent triggered by two observations from the LHC beam operation towards the end of Run2, which led to the recommendation of integrating two options of the HL-LHC project into the baseline:

• A new dilution kicker failure mode, that effectively eliminates three dilution kickers, was observed during the Run2 period and triggered the recommendation to install two additional horizontal dilution kicker magnets.
• Mechanical stress and resulting Nitrogen leaks in the main dump absorber block showed up during repeated high intensity dumps during the Run2 period and triggered the recommendation to upgrade the design of the entire dump core.

The initial worst case failure scenario for the BDS assumed the failure of two out of the six vertical and four horizontal dilution kickers. A new failure type of flashover failure with anti-phase showed that three dilution kickers can effectively fail simultaneously. The risk for this failure mode can be mitigated by installing two additional horizontal dilution kicker modules [previously not in the HL-LHC baseline]. The review strongly encouraged the project to integrate these two additional horizontal dilution kickers into its baseline and the project is currently pursuing this line with an in-kind contribution from Russia.

In August 2017, following a series of high intensity dumps, major Nitrogen leaks appeared at the dump block for Beam2 (UD62) and illustrated major vibration of the dump core that are directly proportional to the total beam intensity. The review underlined that increased vibrations could lead to increased leaks and need for intervening in the tunnel to repair the entire dump sector (18 meters). It also highlighted the risk of radioactive graphite dust (Be7) contamination and loss of the dump core integrity (Graphite powder was already found in the Nitrogen sector during 2016-2017 inspections). The review therefore also encouraged the project to replace the entire dump block with an upgraded design. Design studies are still ongoing, with the hope of finalizing the upgrade design by the end of 2020, but the project has already launched the process of securing the upgrade through an in-kind contribution from Russia. The full program of the review can be found here.

The international review in the HL-LHC Collimation System took place on February 11th and 12th and was chaired by Mike Seidel from PSI. Overall, the review gave the HL-LHC collimation system a positive evaluation and indicated the readiness to launch the series production. It also endorsed the recent decision to change the location of the 11T dispersion unit in IR7 from cell 8 to cell 9. However, in spite of the general positive evaluations, the review gave three recommendations that affect the HL-LHC baseline:

• The observation of overpopulated beam tails (5% beyond 3.5o) underlined again the need for an active beam halo control. The project is pursuing this recommendation through an in-kind contribution from Russia for the implementation of Hollow Electron Lenses.
• The installation of additional NEG cartridges to cope with the vacuum degradation from outgassing of the new collimator jaws.
• Larger than initially expected cost estimates for the Mo coated MoGr shows triggered the decision to reduce the number of collimator jaws by four units in order to stay within the allocated budget line (without risking a significant loss in machine performance).
• The review encouraged the collimation team to strengthen the case for new CuCD tertiary collimators and to study if these could be replaced by Tungsten collimators.
• The option of Crystal collimators should be further developed especially for ions but not be considered as a replacement for DS collimators. The project is pursuing this recommendation though an in-kind contribution from Russia for the implementation of the Crystal collimators.

The full program and closeout report of the review can be found here.

The international review of the Crab Cavity System took place from June 19^th to 21^st and was chaired by Akira Yamamoto from KEK. The review looked in particular at the international aspects of the Crab Cavity collaboration and production plan and the Crab Cavity tests in the SPS. Overall, the review gave the Crab Cavity System a positive evaluation. In particular, it encouraged the project to continue tests of the DQW Crab Cavity system in the SPS during the Run3 period and to pursue the installation and testing of the second Crab Cavity type, the RF Dipole design, in the SPS test facility.

The full program and closeout report of the review can be found here.