High Power Couplers and Pushing the Limits of Superconductive Cavities

To appear in the ProceedingsAt present different linear accelerators (linac) projects share the application of the superconductive cavities technology. The effort on SC cavities has, in fact, pushed the cavities performances close to the theoretical field limits. A non-negligible part of this brilliant result is due to the attention paid to the integration of the cavities with their ancillaries and in particular with the interfaces. Among them a primary role is undoubtedly played by the power couplers. The importance of the integration of the power coupler in the cavity will be illustrated. A description of the different phases needed to ensure the required high performances will be given with particular attention to the technology associated with the RF windows and their multipactor suppressing coating

The ThomX Project

on behalf of the ThomX CollaborationInternational audienceThomX is a Compton source project in the range of the hard X rays (40 / 90 keV). The machine is composed of an injector Linac and a storage ring where an electron bunch collides with a laser pulse accumulated in a Fabry-Perot resonator. The final goal is to provide an X-rays average flux of 10^11/10^13 ph/s. The emitted flux will be characterized by a dedicated X-ray line. Different users are partners in the ThomX project, especially in the area of medical science and cultural heritage. Their main goal will be the transfer of all the experimental techniques developed on big synchrotron rings to these more compact and flexible machines. The project ThomX has recently been funded and will be located on the Orsay University campus. In this article the project and its associated scientific interest are presented

High Power Couplers for Linear Accelerators

online : http://cern.ch/AccelConf/l06/PAPERS/TH2001.PDFHigh power input couplers are a fundamental component of linear accelerating structures and, in particular, of superconducting structures. In fact, in this case, the power coupler's function is not only power transfer and vacuum separation but also includes the thermal transition and the integrity of the cavity cleanliness. A lot of activity has been recently carried out in the framework of different project on both CW (KEK and Cornell) and pulsed (SNS and TTF) power couplers. Special attention has been devoted during the design phase to take care of the thermo-mechanical and electromagnetic performances, the multipacting thresholds, the preparation procedures and, last but not least, the cost which in the case of high energy linacs is a critical issue. In this framework not only the design phase but also the conditioning of the couplers has stimulated different studies. Partial reviews of the existing designs and of the couplers characteristics will be presented taking into account the different challenges

Considerations on the Diffraction Limitations to the Spatial Resolution of Optical Transition Radiation

The interest in using optical transition radiation (OTR) in high energy (multiGeV) beam diagnostics has motivated theoretical and experimental investigations on the limitations brought by diffraction on the attainable resolution. This paper presents calculations of the diffraction effects in an optical set-up using OTR. The OTR diffraction pattern in a telescopic system is calculated taking into account the radial polarization of OTR. The obtained diffraction pattern is compared to the patterns obtained by other authors and the effects of different parameters on the shape and on the size of the OTR diffraction pattern are studied. The major role played by the radial polarization on the shape of the diffraction pattern is outlined. An alternative method to calculate the OTR diffraction pattern is also sketchedComment: Submitted to Particle Accelerator

Energy chirp measurements by means of an RF deflector: a case study the gamma beam source LINAC at ELI-NP

RF Deflector (RFD) based measurements are widely used in high–brightness electron LINAC around the world in order to measure the ultra–short electron bunch length. The RFD provides a vertical kick to the particles of the electron bunch according to their longitudinal positions. In this paper, a measurement technique for the bunch length and other bunch proprieties, based on the usage of an RFD, is proposed. The basic idea is to obtain information about the bunch length, energy chirp, and energy spread from vertical spot size measurements varying the RFD phase, because they add contributions on this quantity. The case study is the Gamma Beam System (GBS), the Compton Source being built in the Extreme Light Infrastructure–Nuclear Physics (ELI–NP) facility. The ELEctron Generation ANd Tracking (ELEGANT) code is used for tracking the particles from RFD to the measurement screen

Characterization of a nondestructive beam profile monitor using luminescent emission

The LHC (large hadron collider) [LHC study group: LHC. The large hadron collider conceptual design; CERN/AC/95-05] is the future p-p collider under construction at CERN, Geneva. Over a circumference of 26.7 km a set of cryogenic dipoles and rf cavities will store and accelerate proton and ion beams up to energies of the order of 7 TeV. Injection in LHC will be performed by the CERN complex of accelerators, starting from the source and passing through the linac, the four booster rings, the proton synchrotron (PS), and super proton synchrotron (SPS) accelerators. One of the main constraints on LHC performance is emittance preservation along the whole chain of CERN accelerators. The accepted relative normalized emittance blowup after filamentation is ±7%. To monitor the beam and the emittance blowup process, a study of different prototypes of nonintercepting beam profile monitors has been performed. In this context a monitor using the luminescent emission of gases excited by ultrarelativistic protons (450 GeV) was developed and tested in the SPS ring. The results of beam size measurements and their evolution as a function of the machine parameters are presented. The image quality and resolution attainable in the LHC case have been assessed. A first full characterization of the luminescence cross section, spectrum, decay time, and afterglow effect for an ultrarelativistic proton beam is provided. Some significant results are also provided for lead ion beams

On the non-paraxial modes of two-dimensional nearly concentric resonators

to be published in Applied OpticsA non-paraxial scalar diffraction integral is used to determine numerically the resonance modes of a two dimensional nearly concentric Fabry-Perot resonator. Numerical examples are provided and results are compared to those published by Laabs and Friberg [IEEE J. Quant. El., vol. 35, pp. 198-207, 1999]. Discrepancies are reported and further discussed on the basis of the difference between the solution space supported by the numerical method used in the present work and the one used by Laabs and Friberg

Effect of Beam Dynamics Processes in the Low Energy Ring ThomX

As part of the R\&D for the 50 MeV ThomX Compton source project, we have studied the effect of several beam dynamics processes on the evolution of the beam in the ring. The processes studied include among others Compton scattering, intrabeam scattering, coherent synchrotron radiation. We have performed extensive simulations of a full injection/extraction cycle (400000 turns). We show how each of these processes degrades the flux of photons produced and how a feedback system contributes to recovering most of the flux.Comment: Submitted to IPAC'14, WEPRO00