Alternative techniques for beam halo measurements

In future high intensity, high energy accelerators it must be ensured that particle losses are minimized, as activation of the vacuum chambers or other components makes maintenance and upgrade work time consuming and costly. It is imperative to have a clear understanding of the mechanisms that can lead to halo formation and to have the possibility to test available theoretical models with an adequate experimental setup. Measurements based on optical transition radiation (OTR) are a well-established technique for measurements of the transverse beam profile. However, in order to be suitable for halo measurements as well, the dynamic range of the final image acquisition system needs to be high, being able to cover at least five orders of magnitude in intensity changes. Here, the performance of a standard acquisition system as it is used in the CLIC test facility (CTF3) is compared to a step-by-step measurement with a small movable photo multiplier tube and an innovative camera system based on charge injection device (CID) technology. Special emphasis is given on a description of the characteristics of the latter system

Status of the HIE-ISOLDE project at CERN

The HIE-ISOLDE project represents a major upgrade of the ISOLDE nuclear facility with a mandate to significantly improve the quality and increase the intensity and energy of radioactive nuclear beams produced at CERN. The project will expand the experimental nuclear physics programme at ISOLDE by focusing on an upgrade of the existing Radioactive ion beam EXperiment (REX) linac with a 40 MV superconducting linac comprising thirty-two niobium-on-copper sputter-coated quarter-wave resonators housed in six cryomodules. The new linac will raise the energy of post-accelerated beams from 3 MeV/u to over 10 MeV/u. The upgrade will be staged to first deliver beam energies of 5.5 MeV/u using two high-$\beta$ cryomodules placed downstream of REX, before the energy variable section of the existing linac is replaced with two low-$\beta$ cryomodules and two additional high-$\beta$ cryomodules are installed to attain over 10 MeV/u with full energy variability above 0.45 MeV/u. An overview of the project including a status summary of the different R&D activities and the schedule will outlined.Comment: 7 pages, 12 figures, submitted to the Heavy Ion Accelerator Technology conference (HIAT) 2012, in Chicag

High dynamic range beam profile measurements

In future high intensity, high energy accelerators, beam loss has to be minimized to maximize performance and reduce activation of accelerator components. It is imperative to have a clear understanding of the mechanisms that can lead to halo formation and to have the possibility to test available theoretical models with an adequate experimental setup. Measurements based on optical transition radiation (OTR) provide an interesting opportunity for high resolution measurements of the transverse beam profile. In order to be applicable for measurements within the beam halo region, it is of utmost importance that a high dynamic range is covered by the image acquisition system. The existing camera system as it is installed in the CLIC Test Facility (CTF3) is compared to a step-by-step measurement with a photo multiplier tube (PMT) and measurements with a cooled charge injection device (CID) camera. The latter acquisition technique provides an innovative and highly flexible approach to high dynamic range measurements and is presented in some detail

A Large Scintillating Screen for the LHC Dump Line

The 7 TeV proton beam from the LHC ring is ejected through a long transfer line to beam dump blocks, approximately 100m downstream of the ejection septa, a series of dilution kicker magnets provide a sweeping deflection spreading the extracted beam over a 40 cm diameter area on the face of the beam dump cores. During normal operation, the quality of each dump event must be recorded and verified. The so-called âﾜPost-Mortemâ dataset will include information from the beam dumping system (logic signals, kicker pulsesâ¦) as well as from the beam diagnostics along the extraction lines. For this purpose, profile monitors in front of the dump blocks must be permanently available during machine operation. With more than 1014 protons stored in LHC, the energy deposited in the screen becomes an issue and thermalresistant materials have to be considered. In this paper, the design of this quite unusual device is presented. The different technical options considered for the choice of the screen material are discussed first. The complete layout of the installation is then described with a special emphasis on the mechanical design, the screen assembly and the choice of the radiation-hard camera used to observe the screen

Advanced Simulations of Optical Transition and Diraction Radiation

Charged particle beam diagnostics is a key task in modern and future accelerator installations. The diagnostic tools are practically the “eyes” of the operators. The precision and resolution of the diagnostic equipment are crucial to define the performance of the accelerator. Transition and diffraction radiation (TR and DR) are widely used for electron beam parameter monitoring. However, the precision and resolution of those devices are determined by how well the production, transport and detection of these radiation types are understood. This paper reports on simulations of TR and DR spatial-spectral characteristics using the physical optics propagation (POP) mode of the Zemax advanced optics simulation software. A good consistency with theory is demonstrated. Also, realistic optical system alignment issues are discussed

Recent Results on Energy Calibration at LEP

The determination of the centre-of-mass energy at the four experiments installed on the CERN Large Electron Positron (LEP) collider is one of the major ingredients in the Standard Model investigations being carried on in the context of the experimental programme. Several depolarising effects at beam energies beyond 60 GeV limit the application of the Resonant Depolarisation (RD) method, which provi des an energy uncertainty of about ±1 MeV at the Z0 resonance. Extrapolation techniques from magnetic field measurements are used to obtain beam energies in the W-pair region, aiming at a total energy error £15 MeV. Consistency checks over a large range of precisely calibrated energies are mandatory to contain systematic errors from extrapolation. Progress obtained in extending the polarisable ener gy range in the 1997 LEP Run and the preliminary extrapolation errors are reported

First Results of the EDELWEISS WIMP Search using a 320 g Heat-and-Ionization Ge Detector

The EDELWEISS collaboration has performed a direct search for WIMP dark matter using a 320 g heat-and-ionization cryogenic Ge detector operated in a low-background environment in the Laboratoire Souterrain de Modane. No nuclear recoils are observed in the fiducial volume in the 30-200 keV energy range during an effective exposure of 4.53 kg.days. Limits for the cross-section for the spin-independent interaction of WIMPs and nucleons are set in the framework of the Minimal Supersymmetric Standard Model (MSSM). The central value of the signal reported by the experiment DAMA is excluded at 90% CL.Comment: 14 pages, Latex, 4 figures. Submitted to Phys. Lett.

Instrumentation for Longitudinal Beam Gymnastics in FEL's and at the CLIC Test Facility 3

Built at CERN by an international collaboration, the CLIC Test Facility 3 (CTF3) aims at demonstrating the feasibility of a high luminosity 3 TeV e+-e- collider by the year 2010. One of the main issues to be demonstrated is the generation of a high average current (30 A) high frequency (12 GHz) bunched beam by means of RF manipulation. At the same time, Free Electron Lasers (FEL) are developed in several places all over the world with the aim of providing high brilliance photon sources. These machines rely on the production of high peak current electron bunches. The required performances put high demands on the diagnostic equipment and innovative longitudinal monitors have been developed during the past years. This paper gives an overview of the longitudinal instrumentation developed at ELETTRA and CTF3, where a special effort was made in order to implement at the same time non-intercepting devices for online monitoring, and destructive diagnostics which have the advantage of providing more detailed information