As the LHC's proton-ion run gets underway, I'd like to add my voice to those lauding the amazing success of this year’s proton-proton run. It has been truly spectacular, from the performance of the accelerator complex to the great wealth of results produced very quickly by the experiments, and the performance of our over-stressed computing infrastructure. I'd like to congratulate all involved. In this message, however, I'll be focusing on some other CERN machines. This is a diverse lab with a diverse programme of research, and there have been some significant milestones across the board over recent days.
On 25 October our new linear accelerator, Linac 4, accelerated beams up to its design energy of 160 MeV. This is a very significant milestone for the machine that will be the first step in the CERN accelerator chain after the next long shutdown, LS2. As a key component of the high luminosity LHC project, Linac 4 will replace Linac 2, which has been in operation since 1978 and has a beam energy of 50 MeV. Linac 4 will allow the beam brightness from the PS booster to be doubled, enabling not just higher luminosity for the LHC, but for all beam facilities at CERN. The next milestone for the new linac will be stripping the electrons from its negative hydrogen ions, leaving protons that will be passed on to the rest of the CERN accelerator chain.
Among the facilities poised to benefit is ELENA, a new ring that will take antiprotons from the AD and reduce their energy from 5.3 MeV to 100 keV. For most AD experiments, this job is currently done by passing the AD beam through foils, an approach that drastically reduces the amount of antiprotons that can be used by the experiments. ELENA will allow improvements by up to two orders of magnitude in terms of anti-proton acceptance of the experiments. The full ELENA ring is now installed, with the exception of its electron cooler. Although this is a vital component, the ring can already be tested with beam, and that’s scheduled to start during the week of 14 November using an independent ion source. Installation of the first experiment for ELENA, GBAR, is also proceeding well. The other experiments presently operating at AD will be connected to ELENA during the second long shutdown LS2.
I’d like to conclude where I began: with the LHC. After a great proton run, it is now time for the ions. The transition went smoothly, and first collisions were delivered to the experiments on 10 November, heralding a strong end to a fantastic year.