Non-invasive single-bunch matching and emittance monitor

On-line monitoring of beam quality for high brightness beams is only possible using non-invasive instruments. For matching measurements, very few such instruments are available. One candidate is a quadrupole pick-up. Therefore, a new type of quadrupole pick-up has been developed for the 26 GeV Proton Synchrotron (PS) at CERN, and a measurement system consisting of two such pick-ups is now installed in this accelerator. Using the information from these pick-ups, it is possible to determine both injection matching and emittance in the horizontal and vertical planes, for each bunch separately. This paper presents the measurement method and some of the results from the first year of use, as well as comparisons with other measurement methods.Comment: 10 pages, 10 figures; added figure, minor textual additions; To be resubmitted to Phys. Rev. ST-A

Mechanical behavior of a continuous fiber reinforced aluminum matrix composite subjected to transverse and thermal loading

The transverse properties of an aluminum alloy metal matrix composite reinforced by continuous alumina fibers were investigated. The composite is subjected to both mechanical and cyclic thermal loading. The results of an experimental program indicate that the shakedown concept of structural mechanics provides a means of describing the material behavior. When the loading conditions are within the shakedown region, the material finally responds in an elastic manner after initial plastic response, and for loading conditions outside the shakedown region, the material exhibits a rapid incremental plastic strain accumulation. The failure strain varies by an order of magnitude according to the operating conditions. Hence, for high mechanical and low thermal loading, the failure strains is small; for low mechanical and high thermal loading, the failure strain is large

Reduction of thermal stresses in continuous fiber reinforced metal matrix composites with interface layers

The potential of using an interface layer to reduce thermal stresses in the matrix of composites with a mismatch in coefficients of thermal expansion of fiber and matrix was investigated. It was found that compliant layers, with properties of readily available materials, do not have the potential to reduce thermal stresses significantly. However, interface layers with high coefficient of thermal expansion can compensate for the mismatch and reduce thermal stresses in the matrix significantly

The magnetic quadrupole pick-ups in the CERN PS

The idea of using non-linearities of beam position monitors to measure the second moment sx2 - sy2 of the transverse beam distribution is almost as old as the synchrotron. However, although a few successful experiments have been reported, the method has not become widely accepted. One reason for this has been that little or no effort was put into optimising the pick-ups that were used for the new purpose. In a standard beam position pick-up, the signal from the second moment is extremely weak and embedded in a strong common-mode background. Separating the signal from the background has therefore been a major stumbling block. Driven by the need for a non-destructive measurement of injection matching to preserve the small emittance of the LHC beam, a dedicated quadrupole pick-up has been developed for the CERN PS. The design employs magnetic coupling in a special pick-up geometry to remove the otherwise dominating background signal, thereby reducing the common-mode rejection requirements by about 60dB. Two pick-ups have been installed in the machine. When the data from these pick-ups is combined, it is possible to measure both the matching parameters and the emittance of each bunch in the injected beam. This paper gives an overview of the pick-up design, describes the methods used to analyse the data, and presents some measurement results, including comparisons with other instruments in the machine

Optimisation of a Magnetic Quadrupole Pick-up Structure using HFSS

A magnetic quadrupole pick­up has recently been designed for the CERN proton synchrotron. The design is based on a new idea, where the undesired common mode signal is suppressed by coupling to the radial component of the field. One design detail is a thin resistive layer between the beam and the actual pick­up structure. This layer serves to lower the longitudinal impedance, but also influences the coupling impedance of the pick­up. To optimise the design, a series of simulations of the pick­up structure have been performed using the HFSS program. The longitudinal impedance was determined by simulating the coaxial wire­method, and the pick­up coupling to the different field modes created by the ''beam'' was studied and optimised. In this paper, the simulations are presented together with some comparative measurements

Terrorism, Criminal Law and Politics : The Decline of the Political Offence Exception to Extradition

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A Non-Invasive Single-Bunch Matching and Emittance Monitor for the CERN PS Based on Quadrupole Pick-Ups

On-line monitoring of beam quality for high brightness beams is only possible using non-invasive instruments. For matching measurements, very few such instruments are available. Therefore, a new type of quadrupole pick-up, sensitive to the beam width, has been developed for the CERN PS. A measurement system consisting of two such pick-ups has been installed in the accelerator. Using the information from these pick-ups, it is possible to determine not only the injection matching in the two planes, but also the emittances. Both measurements use the periodicity of the circular machine to eliminate a number of systematic error sources, while the statistical error is reduced by using data from several turns. The analysis can be done on each bunch separately. This is required because of the PS filling scheme, where each injected bunch comes from a different Booster ring, and therefore can have different properties. After an overview of the measurement system, some of the first measurement results are presented along with a discussion on the measurement error