LS2 Report: All interconnections in the LHC have been closed

The DISMAC project is coming to an end: the last of the 1232 interconnections was closed in August and the cool-down of the machine will now begin.


LS2 Report: all interconnections in the LHC have been closed
On 3 August, the last of the 1232 interconnections was closed in sector 7-8 of the LHC, with Frédérick Bordry, Director for Accelerators and Technology at CERN, in attendance. (Image: CERN)

The DISMAC project (Diode Insulation and Superconducting MAgnets Consolidation), one of the main ongoing activities in the LHC since February 2019, is coming to an end, which also marks the end of LS2 in the accelerator. 22 of the main superconducting magnets (19 dipole magnets and three quadrupole magnets) have been replaced, and the electric insulation of the diodes of the 1232 dipole magnets in the accelerator has been consolidated. The final interconnection was closed on 3 August. This is the first time since February 2019 that all the interconnections have been simultaneously closed, the first one having been opened on 1 March 2019 in sector 7-8.

The final validation tests are currently underway: “Over 95% of the leak tests in the vacuum and helium circuits have taken place. Pressure tests have been carried out in five sectors, and the last tests will be completed in sector 6-7 at the end of October. Electric quality assurance tests (ELQA) at room temperature are also underway - these will be carried out again once the machine has been cooled down”, says Jean-Philippe Tock, leader of the DISMAC project.

The first LHC sector will begin cooling in October. One by one, the eight sectors of the LHC will be cooled from room temperature to the operating temperature of the LHC magnets: 1.9 K (-271.3°C). Between now and the end of the year, six out of the eight machine sectors will begin cooling.

Since the start of LS2, many activities have taken place in the LHC in parallel. Leaks and instrumentation faults that were detected during the second run and in tests carried out in LS2 have been fixed. “We’ve also made the most of the technical stop to install flowmeters, with the HL-LHC project in mind, in order to study the beam-induced heat loads”, Jean-Philippe Tock adds.

As far as the schedule is concerned, the COVID-19 pandemic will certainly have had an impact on the progress of activities in the LHC. “We are looking at a delay of around three months, which corresponds roughly to the amount of time spent in safe mode,” Jean-Philippe Tock explains. “We work in close collaboration with institutes in Pakistan, Poland, Greece and Spain on the DISMAC project, and the closure of the borders was not without its challenges.” It goes without saying that working procedures have also been adapted to comply with the health and safety rules laid down by the HSE unit: wearing masks, physical distancing, cleaning instruments and individual equipment... “Nothing has been left to chance in order to guarantee the safety of the teams,” Jean-Philippe Tock emphasises. “The teams remain motivated, enthusiastic and are especially determined following the restart of activites in the LHC tunnel.”

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