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The latest from the LHC

On 26 August, the first two fully tested crates for the new quench protection system (QPS) were installed in Sector 1-2. These are the first of 436 crates that will be installed around the ring. The two crates include detectors for both the enhanced busbar protection and the symmetric quench protection (more details).

To test the crates before installation, a dedicated test bed has been created, capable of simulating all the conditions in the LHC, from a symmetric quench to an increase in busbar resistance. The teams are working two shifts a day, including weekends, to test the new crates. Two more test benches are also being built to increase the production rate. The whole task is on target for completion in mid October.

Another important new task for the QPS team is to try and speed up the energy extraction from the magnets. The quicker the energy can be extracted the lower the risk of dangerously high temperatures should a quench occur.

The time constant for the dipoles will be halved to about 50 seconds. The decision to run at 3.5 TeV, and therefore with lower current in the magnets, has in fact made this task relatively straightforward. By switching two of the three ‘dump’ resistors into a series circuit instead of having all three resistors in parallel, allows the energy to be converted to heat much faster. This modification is currently ongoing and takes only a few hours for each of the 16 extraction systems. In the quadrupole circuits the task is more complex. Reducing the time constant to the desired 10 seconds, from a previous 35 seconds, requires adding extra resistors.

Another advantage of the new QPS system is that it will allow accurate resistance measurements to be taken remotely. Over the past 3 months the QPS team has checked nearly 40 000 individual resistance measurements by hand, and in the process clocked up an impressive 500 km walking around the ring. A small testing device is currently being developed to automate this process using the new QPS system. This will save a huge amount of time and effort for the next rounds of interventions – for example when the LHC energy is increased.




In Sector 8-1 the flexible hose, which caused the helium leak into the insulation vacuum, has now been replaced and the sector is now being cooled down again.


Work to install the ‘pressure release springs’ is progressing well, with only one sector remaining - Sector 3-4.


In Sector 6-7 repairs are being made to fix the short-circuit to ground, which occurred in the dipole circuit on 20 August (see previous update).