LHC Report: Beams are back in the LHC
The LHC has shaken itself awake after the winter break, and, as the snow melts on the lower slopes, the temperature in the magnets has dropped to a chilly 1.9 K once more.
Following the cool-down, the last few weeks have seen an intense few tests of the magnets, power supplies and associated protection systems. These tests, referred to as hardware commissioning, have been completed in record time. At the same time the other accelerator systems have been put through the preparatory machine checkout.
In parallel, the injectors (LINAC2, Booster, PS and SPS) have also come out of the technical stop in order to prepare to deliver beam to the LHC very early in the season. Of particular note here was the remarkably seamless transition to POPS, the PS's new main power supply system.
All this work culminated in the LHC taking beam again for the first time in 2011 on Saturday, 19 February. The careful preparation paid off, with circulating beams being rapidly re-established. There then followed a programme of beam measurements and re-commissioning of the essential sub-systems such as RF, beam dumps, beam instrumentation, feedback systems, etc. Initial measurements show that the LHC is in good shape and magnetically little changed from last year.
Low intensity beams were taken back up to 3.5 TeV on Monday night and then through the squeeze. The squeeze reduces the beam size at the collision point inside the experiments and thus increases the collision rate. This year the beam sizes at the collision point are being pushed to lower values than those of 2010 and the first test of 2011 was very encouraging.
