2,673 research outputs found
Development of Rebunching Cavities at IAP
A focus of work at IAP has been the development and optimization of spiral
loaded cavities since the 1970s [A. Schempp et al, NIM 135, 409 (1976)]. These
cavities feature a high efficiency, a compact design and a big variety of
possible fields of application. They find use both as bunchers and post
accelerators to vary the final energy of the beam. In comparison to other
available designs, the advantage of these structures lies in their small size.
Furthermore they can easily be tuned to the required resonance frequency by
varying the length of the spiral. Due to the small size of the cavities the
required budget can also be kept low. Here, two slightly different types of
spiral loaded cavities, which were built for the REX-ISOLDE project at CERN and
the intensity upgrade program at GSI are being discussed.Comment: 4 pages, 9 figures PRST-AB special LINAC 2000 edition with additional
information in comparison to the 3 pages LINAC paper physics/000708
Efficiency of tunable band-gap structures for single-photon emission
The efficiency of recently proposed single-photon emitting sources based on
tunable planar band-gap structures is examined. The analysis is based on the
study of the total and ``radiative'' decay rates, the expectation value of
emitted radiation energy and its collimating cone. It is shown that the scheme
operating in the frequency range near the defect resonance of a defect band-gap
structure is more efficient than the one operating near the band edge of a
perfect band-gap structure.Comment: 9 pages, 7 figure
Collider design issues based on proton-driven plasma wakefield acceleration
Recent simulations have shown that a high-energy proton bunch can excite
strong plasma wakefields and accelerate a bunch of electrons to the energy
frontier in a single stage of acceleration. It therefore paves the way towards
a compact future collider design using the proton beams from existing
high-energy proton machines, e.g. Tevatron or the LHC. This paper addresses
some key issues in designing a compact electron-positron linear collider and an
electron-proton collider based on existing CERN accelerator infrastructure
An collider based on proton-driven plasma wakefield acceleration
Recent simulations have shown that a high-energy proton bunch can excite
strong plasma wakefields and accelerate a bunch of electrons to the energy
frontier in a single stage of acceleration. This scheme could lead to a future
collider using the LHC for the proton beam and a compact electron
accelerator of length 170 m, producing electrons of energy up to 100 GeV. The
parameters of such a collider are discussed as well as conceptual layouts
within the CERN accelerator complex. The physics of plasma wakefield
acceleration will also be introduced, with the AWAKE experiment, a proof of
principle demonstration of proton-driven plasma wakefield acceleration, briefly
reviewed, as well as the physics possibilities of such an collider.Comment: 6 pages, 2 figures, to appear in the proceedings of the DIS 2014
Workshop, 28 April - 2 May, Warsaw, Polan
RF Characterization of Superconducting Samples
At CERN a compact Quadrupole Resonator has been re-commissioned for the RF characterization of superconducting materials at 400 MHz. In addition the resonator can also be excited at multiple integers of this frequency. Besides Rs it enables determination of the maximum RF magnetic field, the thermal conductivity and the penetration depth of the attached samples, at different temperatures. The features of the resonator will be compared with those of similar RF devices and first results will be presented
Solar Magnetic Tracking. I. Software Comparison and Recommended Practices
Feature tracking and recognition are increasingly common tools for data
analysis, but are typically implemented on an ad-hoc basis by individual
research groups, limiting the usefulness of derived results when selection
effects and algorithmic differences are not controlled. Specific results that
are affected include the solar magnetic turnover time, the distributions of
sizes, strengths, and lifetimes of magnetic features, and the physics of both
small scale flux emergence and the small-scale dynamo. In this paper, we
present the results of a detailed comparison between four tracking codes
applied to a single set of data from SOHO/MDI, describe the interplay between
desired tracking behavior and parameterization of tracking algorithms, and make
recommendations for feature selection and tracking practice in future work.Comment: In press for Astrophys. J. 200
Low Power Measurements on a Finger Drift Tube Linac
The efficiency of RFQs decreases at particle energies higher than a few MeV/u and thus typically DTL structures are used in this energy region. However, the rf field in the gap always has a defocusing influence on the beam. In order to compensate this effect, fingers with quadrupole symmetry were added to the drift tubes, the focusing fingers do not need an additional power source or feed through. Beam dynamics have been studied with the code RFQSIM. Detailed analysis of the field distribution was done and the geometry of the finger array has been optimized with respect to beam dynamics. A prototype cavity with finger drift tubes was built and low power measurements were done. In this contribution, the results of the rf simulation with Microwave Studio are compared to bead perturbation measurements and the focusing effect on the beam is discussed
Investigations of OTR screen surfaces and shapes
Optical transition radiation (OTR) has proven to be a flexible and effective tool for measuring a wide range of beam parameters, in particular the beam divergence and the transverse beam profile. It is today an established and widely used diagnostic method providing linear real-time measurements. Measurements in the CLIC Test Facility (CTF3) showed that the performance of the present profile monitors is limited by the optical acceptance of the imaging system. In this paper, two methods to improve the systems' performance are presented and results from measurements are shown. First, the influence of the surface quality of the OTR screen itself is addressed. Several possible screen materials have been tested to which different surface treatment techniques were applied. Results from the measured optical characteristics are given. Second, a parabolic-shaped screen support was investigated with the aim of providing an initial focusing of the emitted radiation and thus to reduce the problem of aperture limitation
Extension of the Measurement Capabilities of the Quadrupole Resonator
The Quadrupole Resonator, designed to measure the surface resistance of
superconducting samples at 400 MHz has been refurbished. The accuracy of its
RF-DC compensation measurement technique is tested by an independent method. It
is shown that the device enables also measurements at 800 and 1200 MHz and is
capable to probe the critical RF magnetic field. The electric and magnetic
field configuration of the Quadrupole Resonator are dependent on the excited
mode. It is shown how this can be used to distinguish between electric and
magnetic losses.Comment: 6 pages, g figure
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