The Metamorphosis by K. (12)

In the last issue of the Bulletin we reported on the first run of the new NA62 experiment. In this issue, we go behind the scenes to take a look at the production of the experiment's new kaon beam.


The start of the K12 beam line as seen during the installation of the shielding.

10-2, 10-3, 10-4, 10-5, 10-6 mbar… send in the protons! Since Thursday 1 November, the P42 beam line of the SPS has once again been sending protons to the beryllium target to produce the K12 kaon beam line eagerly awaited by the NA62 collaboration. This was no trivial matter!

The first step was to clear the decks by dismantling the entire H10 beam line and NA60 experiment, as well as most of the NA48 experiment - representing some 1000 tonnes of equipment in total! Next came the complete renovation of the infrastructure, which dated back to 1979. The operation called on the expertise of virtually all branches of the EN and GS departments, as well as the Radiation Protection group: from those responsible for the electrical system to those in charge of the overhead travelling cranes, the cooling water distribution system, the ventilation, the control systems, the safety systems and the radiation control system. Civil engineers also had to be called in to remove some 75,000 tonnes of earth to make room for the construction of a new beam dump.

Once the preparatory work was complete, the new K12 beam line with its magnets, collimators, diagnostics system* and a crucial vacuum line could start to be installed. As Lau Gatignon, project leader for the K12 beam, explains: "The study of the decay of kaons produced by the K12 beam requires a very high-grade vacuum (10-6 mbar) over an exceptionally large volume (500 m3). This meant the need for recourse to large cryogenic pumps."

On the surface, the old control room was also completely transformed: "We moved the walls and changed the electrical distribution system and the air conditioning," adds François Butin, project engineer for the NA62 experimental area (ECN3). "After a final new lick of paint, we're now all set for the exciting years of research ahead!"

Thanks to meticulous planning and flawless alignment, the new K12 beam line was commissioned very quickly. On Thursday 1 November, protons were focussed on the 2 mm diameter beryllium target after only a few hours, and by the following day all the NA62 detectors were receiving a high-quality beam, ready for the experiment to start to be calibrated.

François and Lau conclude with the following words of thanks: "We would like to extend our warmest appreciation to all the technical teams from the BE, EN, GS and TE departments, who did a remarkable job, as well as to the groups from the PH department with whom we collaborated very closely."

* The diagnostics system consists of stations for monitoring and evaluating all the beam parameters.

by CERN Bulletin