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

Die numerische Auswertung von Kleinwinkelstreukurven

Aus dem Streubild der Kleinwinkelstreuung kann im Allgemeinen, die die Streuvertei-lung erzeugende Struktur nicht eindeutig rekonstruiert werden. Die Ursache dafür wird erörtert und die damit verbundenen Einschränkungen bei der rechnerischen Auswertung der Streukurven an Beispielen veranschaulicht. Dies geschieht an Streukurven, die mit bekannten Größenverteilungen berechnet wurden. Weiterhin wird untersucht, welche Fit- Ansätze sich zur Auswertung der Kleinwinkelstreuexperimente am besten eignen. Als Fit- Ansätze wurden Reihenentwicklungen nach Trigonometrischen- und Polynomfunkti-onen und eine theoretisch motivierte Funktion verwendet. Neben dem entscheidenden Vergleich mit der Streukurve der Ausgangsfunktion werden die Ergebnisse auch den Rechnungen gegenübergestellt, die mit der weit verbreiteten Glatter- Methode erzielt werden

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

Negative thermal expansion in the plateau state of a magnetically-frustrated spinel

We report on negative thermal expansion (NTE) in the high-field, half-magnetization plateau phase of the frustrated magnetic insulator CdCr2O4. Using dilatometry, we precisely map the phase diagram at fields of up to 30T, and identify a strong NTE associated with the collinear half-magnetization plateau for B > 27T. The resulting phase diagram is compared with a microscopic theory for spin-lattice coupling, and the origin of the NTE is identified as a large negative change in magnetization with temperature, coming from a nearly-localised band of spin excitations in the plateau phase. These results provide useful guidelines for the discovery of new NTE materials.Comment: 6 pages, 2 figure

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

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

Black Hole Photon Rings Beyond General Relativity

We investigate whether photon ring observations in black hole imaging are able to distinguish between the Kerr black hole in general relativity and alternative black holes that deviate from Kerr. Certain aspects of photon rings have been argued to be robust observables in Very-Long-Baseline Interferometry (VLBI) black hole observations which carry imprints of the underlying spacetime. The photon ring shape, as well as its Lyapunov exponent (which encodes the narrowing of successive photon subrings), are detailed probes of the underlying geometry; measurements thereof have been argued to provide a strong null test of general relativity and the Kerr metric. However, a more complicated question is whether such observations of the photon ring properties can distinguish between Kerr and alternative black holes. We provide a first answer to this question by calculating photon rings of the Johannsen, Rasheed-Larsen, and Manko-Novikov black holes. We find that large deviations from Kerr and large observer inclinations are needed to obtain measurable differences in the photon ring shape. In other words, the Kerr photon ring shape appears to be the universal shape even for deviating black holes at low inclinations. On the other hand, the Lyapunov exponent shows more marked variations for deviations from the Kerr metric. Our analysis lays out the groundwork to determine deviations from the Kerr spacetime in photon rings that are potentially detectable by future observing missions.Comment: 31 pages + appendices; 20 figure

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