Preliminary Characterization of the O4+ Beam in Linac 3

The new GTS-LHC ECR ion source was installed in 2005. An oxygen 4+ beam was delivered to LEIR both for injection line (June 2005) and for the ring commissioning (September to December 2005). During these runs, studies were made of the beam transport in the Linac and towards LEIR. Some of the most significant results concerning the Linac are presented in this report. From 2006 the ECR source and the Linac3 delivered a lead beam for the LEIR commissioning, leaving some questions open for the oxygen beam transport. This report serves as a summary of the status of the investigations on the oxygen beam

New beam for the CERN fixed target heavy ion programme

The physicists of the CERN heavy ion community (SPS fixed target physics) have requested lighter ions than the traditional lead ions, to scale their results and to check their theories. Studies have been carried out to investigate the behaviour of the ECR4 for the production of an indium beam. Stability problems and the low melting point of indium required some modifications to the oven power control system which will also benefit normal lead ion production. Present results of the source behaviour and the ion beam characteristics will be presented

Towards An H−H^{-} RF Source for Future CERN Accelerator Projectss

An increase of beam intensity and brightness is essential for future upgrades of existing CERN proton accelerator facilities. A first step can be an injection of H- ions from a new higher energy H- linear accelerator called Linac4 into the Proton Synchrotron Booster (PSB. A second step could be the complete replacement of the PSB by a highpower linear accelerator, called SPL, injecting directly into the Proton Synchrotron (PS. Both injection scenarios require a high performance, high reliability negative hydrogen ion source. This paper will present the challenging source requirements and the two approaches to fulfil them

Options for upgrading the intensity of the CERN lead pre-injector ion source

CERN's heavy ion pre-injector has been in service since 1994, providing lead ions for fixed target collisions at 177 GeV per nucleon in the SPS. In the LHC era, heavy ion collisions require an increase in the beam brightness, compared to the present injector system of Linac 3, Proton Synchrotron Booster and the Proton Synchrotron. Stacking and cooling ions in a Low Energy Ion Ring should find the largest part of this increase. However, further improvements can be envisaged by upgrading the pre-injector and source. The performance and limitations of the present source and Linac 3 will be discussed, and options for increasing the source brightness will be presented. These options consist of upgrades of the ECR Source to higher frequencies, or its replacement with a Laser Ion Source

Studies on ECR4 for the CERN ion programme

The CERN heavy ion community, and some other high energy physics experiments, are starting to demand other ions, both heavy and light, in addition to the traditional lead ions. Studies of the behaviour of the afterglow for different operation modes of the ECR4 at CERN have been continued to try to understand the differences between pulsed afterglow and continuous operation, and their effect on ion yield and beam reproducibility. The progress in adapting the source and ion beam characteristics to meet the new demands will be presented, as will new information on voltage holding problems in the extraction

Effect of a Biased Probe on the Afterglow Operation of an ECR4 Ion Source

Various experiments have been performed on a 14.5 GHz ECR4 in order to improve the ion yield. The source runs in pulsed afterglow mode, and provides currents ~120 emA of Pb27+ to the CERN Heavy Ion Facility on an operational basis. In the search for higher beam intensities, the effects of a pulsed biased disk on axis at the injection side were investigated with different pulse timing and voltage settings. No proof for absolute higher intensities was seen for any of these modifications. However, the yield from a poorly tuned/low-performing source could be improved and the extracted pulse was less noisy with bias voltage applied. The fast response on the bias implies that increases/decreases are not due to ionisation processes. A good tune for high yield of high charge states during the afterglow coincides with a high plasma potential

Ion-stimulated gas desorption yields and their dependence on the surface preparation of stainless steel

Ion-induced gas desorption yields were investigated for 4.2 MeV/u lead ions incident on 316 LN stainless steel surfaces. Focussed on a possible application for the Low Energy Ion Ring (LEIR) vacuum system, the influence of surface treatments like chemical etching, electropolishing and gold-coating on the desorption yields was studied with accelerator-type vacuum chambers. The surface composition of similar prepared samples was investigated with X-ray Photoemission Spectroscopy (XPS). Desorption yields for H2, CH4, CO, Ar and CO2, which are of fundamental interest for LEIR and future accelerator applications, are reported as a function of impact angle, ion dose and charge state (+27, +53) of the lead ion beam

Universally diverging Grueneisen parameter and the magnetocaloric effect close to quantum critical points

At a generic quantum critical point, the thermal expansion $\alpha$ is more singular than the specific heat $c_p$. Consequently, the "Gr\"uneisen ratio'', \GE=\alpha/c_p, diverges. When scaling applies, \GE \sim T^{-1/(\nu z)} at the critical pressure $p=p_c$, providing a means to measure the scaling dimension of the most relevant operator that pressure couples to; in the alternative limit $T\to0$ and $p \ne p_c$, \GE \sim \frac{1}{p-p_c} with a prefactor that is, up to the molar volume, a simple {\it universal} combination of critical exponents. For a magnetic-field driven transition, similar relations hold for the magnetocaloric effect $(1/T)\partial T/\partial H|_S$. Finally, we determine the corrections to scaling in a class of metallic quantum critical points.Comment: 4 pages, 1 figure; general discussion on how the Grueneisen exponent measures the scaling dimension of the most relevant operator at any QCP is expande

Operation of the GTS-LHC Source for the Hadron Injector at CERN

The GTS-LHC ion source, designed and build by CEA Grenoble, was installed and commissioned at CERN in 2005. Since than the source has delivered oxygen and lead ion beams (O4+ and Pb27+ from the source, Pb54+ from the linac) for the commissioning of the Low Energy Ion Ring (LEIR). Results of this operation and attempts to improve the source performance and reliability, and the linac performance will be presented in this paper