262 research outputs found

    Popper's Experiment and Superluminal Communication

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    We comment on Tabesh Qureshi, "Understanding Popper's Experiment," AJP 73, 541 (June 2005), in particular on the implications of its section IV. We show, in the situation envisaged by Popper, that analysis solely with conventional non-relativistic quantum mechanics suffices to exclude the possibility of superluminal communication.Comment: Submitted to American Journal of Physic

    Beam dynamics issues of high-luminosity asymmetric collider rings

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    High-Intensity Effects in the Longitudinal Motion of Stored Particle Beams

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    Hadron cancer therapy complex employing non-scaling FFAG accelerator and fixed field gantry design

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    Non-scaling FFAG rings for cancer hadron therapy offer reduced physical aperture and large dynamic aperture as compared with scaling FFAGs. The variation of tune with energy implies the crossing of resonances during acceleration. Our design avoids intrinsic resonances, although imperfection resonances must be, and can be, crossed. We consider a system of three non-scaling FFAG rings for cancer therapy with 250 MeV protons and 400 MeV/u carbon ions. Hadrons are accelerated in a common RFQ and linear accelerator, and injected into the FFAG rings at .. .. . H+/C6+ ions are accelerated in the two smaller/larger rings to 31 and 250 MeV/68.8 and 400 MeV/u kinetic energy, respectively. The lattices consist of doublet cells with a straight section for RF cavities. The gantry with triplet cells accepts the whole required momentum range at fixed field. This unique design uses either high temperature super-conductors or super-conducting magnets reducing gantry size and weight. Elements with variable field at beginning and at end set the extracted beam at the correct position for a range of energies

    Hadron cancer therapy complex using nonscaling fixed field alternating gradient accelerator and gantry design

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    Nonscaling fixed field alternating gradient (FFAG) rings for cancer hadron therapy offer reduced physical aperture and large dynamic aperture as compared to scaling FFAGs. The variation of tune with energy implies the crossing of resonances during acceleration. Our design avoids intrinsic resonances, although imperfection resonances must be crossed. We consider a system of three nonscaling FFAG rings for cancer therapy with 250 MeV protons and 400   MeV/u carbon ions. Hadrons are accelerated in a common radio frequency quadrupole and linear accelerator, and injected into the FFAG rings at v/c=0.1294. H^{+}/C^{6+} ions are accelerated in the two smaller/larger rings to 31 and 250  MeV/68.8 and 400   MeV/u kinetic energy, respectively. The lattices consist of doublet cells with a straight section for rf cavities. The gantry with triplet cells accepts the whole required momentum range at fixed field. This unique design uses either high-temperature superconductors or superconducting magnets reducing gantry magnet size and weight. Elements with a variable field at the beginning and at the end set the extracted beam at the correct position for a range of energies

    BEAM-SURROUNDING INTERACTIONS AND THE STABILITY OF RELATIVISTIC PARTICLE BEAMS

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    In accord with recent custom, the organizing committee for this conference has scheduled this review paper on beam instabilities. In view of the various review papers which already exist and the fact that the fundamentals of the subject have even been treated in a textbook, I thought this paper might best be devoted to a limited part of the rather large field of beam instabilities. Thus, I have selected only an aspect of the general subject, but an aspect which has during the last years been very much at the center of activity, and will--if my judgment is correct--be even more so in the years to come. I wish to concentrate, here, on the interaction of a relativistic particle beam with itself which is a result of the coupling of the beam with its surroundings. Before approaching this topic, a few remarks on the existing review papers are in order. A comprehensive treatment of beam instabilities may be found in Ref. 1, where, also, the reader will find some 48 references to the original literature. In Refs. 2 and 3, the General subject is approached from other points of view. Reference 4 is concerned with some special topics, but treats them in depth; and the text of Ref. 5 closely follows the original papers
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