LS1 Report: PS beams are back!

For the first time in over 15 months, there are beams back in the PS. Making their first tour of the accelerator today, 20 June, their injection marks the end of weeks of cold checkouts and hardware commissioning in the PS.


The CERN Control Centre (CCC) is back in business: people gather to restart the LHC injectors, today the PS.

Since hardware commissioning was wrapped up on 23 May, the Operations Group (BE-OP) has been conducting cold checkouts on the PS. This involves switching on all of the machine's systems, verifying that they respond to commands by OP and ensuring they are calibrated to beam timings. "These verifications were done, in part, during the hardware commissioning dry runs," says Rende Steerenberg, PS section leader. "But the cold checkouts are on a much larger scale, as we act as if there is beam in the whole machine. We placed a full load on the controls system, cooling, networks, etc. in order to setup the accelerator in the most realistic conditions possible, with the aim to identify remaining issues before injecting beam."

Although the beam made it into the PS right on schedule, teams were called on many occasions to conduct hardware interventions: fixing vacuum leaks, re-configure timing links, correcting magnet connections and, in one instance, replacing an entire magnet with a spare due to a water leak. "These types of hardware issues are typically found during hardware commissioning phase," says Steerenberg. "Any remaining issues are brought to light during the full operation of cold checkouts."

The PS heartbeat has been revived: powered by the POPS (Power for PS) system, which provides the precisely regulated current cycles to the PS main magnets, keeping the beam centred in the vacuum chamber during acceleration.

Thanks to the new-and-improved PS Complex Access Control and Safety System, the vast majority of these interventions could be carried out without affecting the upstream accelerator chain. "The PS tunnel also contains part of the Linac2 line leading to the PS Booster; this used to be problematic, as the Booster beam had to be shut off whenever access was needed in the PS," explains Steerenberg. "By dividing the PS tunnel into two access zones, around 75% of our interventions were carried out without any impact on the Booster. It was a simple solution, but one that gained the accelerator chain restart weeks of time."

With beams now in the machine, BE-OP has begun the beam commissioning tests. During this final phase, all of the beam diagnostics - from beam current to bunch spacing - have to be checked. These will be first verified with low intensity beams (some 1011 protons), then moving up to higher intensity levels (some 1012 protons) before 10 July. By that time, the PS must be ready to send beams to setup the downstream physics facilities in the East Area and nToF, where physics will start on 15 July.

The OP team would like to give a big thanks to all those involved in the LS1 work for the PS: "Their hard work has made it possible to have the accelerator working again after all the modifications made," concludes Steerenberg.

This morning, the PS injection kicker (green signal) sent the first proton bunch into the accelerator for thousands of turns. Beam position monitors see the bunch every time it completes one turn (purple signal - seven turns displayed in this image). It takes the beam 2.3 µs to travel the 628 metre circumference of the PS; this can be deduced using the purple signals.


Meanwhile, elsewhere...

On 18 June, the SMACC Project teams celebrated the closing of the last W bellow (no1695).

At the LHC, the teams have closed the last of the W bellows (see photo). The leak tests on the entire machine are also proceeding nicely, as are the pressure tests, which have just been completed in Sector 5-6 and are currently under way in Sector 7-8.

Meanwhile, Sector 6-7 has reached a temperature of 20 K. The teams are now preparing to carry out the CSCM (Copper Stabilizer Continuity Measurementtests.

In the SPS, the QDA magnet in Long Straight Section 1 (LSS1), which had had to be brought to the surface for repair, was re-installed a week ago. On 27 June, it will thus be possible to close access to the SPS ready for the start of equipment testing.


by Katarina Anthony & Anaïs Schaeffer