Leir: towards the Nominal Lead Ion Beam

The Low Energy Ion Ring (LEIR) is a central piece for LHC ion operation at CERN, transforming long Linac3 pulses into high density bunches needed for LHC. The first phase of LEIR commissioning successfully attained its goal of providing the so-called “early ion beam” (one bunch of 2.25 10 Lead ions) needed for the first LHC ion runs with reduced luminosity. Studies in view of generating the beam needed for nominal ion operation (2 bunches of 4.5 10 ions in LEIR) were carried out in parallel with the setting-up of the early beam in the accelerators further downstream in the LHC injector chain. The main characteristics of the machine using a new state of the art electron cooler are discussed together with the latest results. INTRODUCTION The LHC [1,2], presently in construction at CERN will, in addition to proton operation, provide Pb ion collisions. The ion accelerator chain existing before the LHC era was by far not sufficient to provide the ion beams needed. The most fundamental upgrade of this ion accelerator chain [3-5] was the addition of the Low Energy Ion Ring. The role of this small accumulator ring, equipped with a new state-of-the-art electron cooler (built by BINPNovosibirsk), is to convert several (200 μs) long Linac pulses into short high brilliance bunches needed for LHC ion operation. Since nominal LHC ion operation is very demanding for both the LHC and the injector chain, first LHC ion operation will take place with a lower luminosity and less bunches using the so-called “early scheme” [3-5]. During the LEIR commissioning [6-9], the beam for this early scheme has been produced and transported to the PS injection region. The goal of the first LEIR operation run during last fall was to send the early beam to the PS to commission it[10], and to explore the way to the nominal beam in LEIR.