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DIFFRACTION RADIATION DEFOCUSING OF AN ELECTRON RING

Description: The influence upon axial stability in an electron ring of the diffraction radiation reaction force, generated by a ring moving in an acceleration column, is calculated theoretically. A stability criterion is obtained, and numerical examples show that the criterion is not an important constraint upon the choice of parameters or the operation of an electron ring accelerator.
Date: December 1, 1970
Creator: Keil, E.; Pellegrini, C & Sessler, A.M.
Partner: UNT Libraries Government Documents Department

IMPEDANCE BUDGET FOR CRAB CAVITY IN MEIC ELECTRON RING

Description: The Medium Energy Electron-Ion Collider (MEIC) at Jefferson Lab has been envisioned as a first stage high energy particle accelerator beyond the 12 GeV upgrade of CEBAF. The estimate of impedance budget is important from the view point of beam stability and matching with other accelerator components driving currents. The detailed study of impedance budget for electron ring has been performed by considering the current design parameters of the e-ring. A comprehensive picture of the calculations involved in this study has been illustrated in the paper.
Date: July 1, 2012
Creator: S. Ahmed, B. Yunn, G. Krafft
Partner: UNT Libraries Government Documents Department

AW ANALOG METHOD FOR MEASURING THE LONGITUDINAL COUPLING IMPEDANCE OF A RELATIVISTIC PARTICLE BEAM WITH ITS ENVIRONMNET

Description: The stability of a coasting beam against self-bunching (negative mass instability) may be expressed in terms of a beam coupling impedance. The impedance has contributions from self-fields, wall impedance, and curvature effects. This paper describes procedures for measuring the wall and curvature contributions to the coupling impedance by means of an analog in which the beam is replaced by a conductor propagating a TEM-like mode. Conditions are derived under which the measurements are valid, various measurement procedures are described and results of the application of the method to the compressor of an electron ring accelerator are reported.
Date: August 1, 1971
Creator: Faltens, A.; Hartvig, E.C.; Mohl, D. & Sessler, A.M.
Partner: UNT Libraries Government Documents Department

LOWER BOUNDS ON SELF-FOCUSING SO AS TO MAINTAIN RING INTEGRITY NEAR THE INITIATION OF ACCELERATION IN AN ELECTRON RING ACCELERATOR

Description: Relationships necessary for ring stability are derived between the self-focusing forces of an electron ring and the magnetic field gradient defocusing forces present near and just subsequent to the start of ring acceleration.
Date: April 16, 1970
Creator: Pellegrini, Claudio & Sessler, Andrew.
Partner: UNT Libraries Government Documents Department

THE ELECTRON-RING ACCELERATOR PROGRAM AT BERKELEY

Description: Early in 1968 a research group was set up at the Lawrence Radiation Laboratory to investigate the exciting new concept of accelerating ions by means of relativistic electron rings, which had been introduced and developed by Veksler, Sarantsev, and other workers at Dubna. The initial work of our group was reported at the first USSR National Conference on Particle Accelerators in 1968. In this report the author review the subsequent progress and the present program.
Date: October 1, 1970
Creator: Peterson, J.M.; Chupp, W.W.; Garren, A.A.; Keefe, D.; Lambertson, G.R.; Laslett, L.J. et al.
Partner: UNT Libraries Government Documents Department

DIFFRACTION RADIATION BY A LINE CHARGE MOVING PAST A COMB: A MODEL OF RADIATION LOSSES IN AN ELECTRON RING ACCELERATOR

Description: A calculation is given of the radiated energy loss from a charged rod which moves at constant speed past an infinite set of parallel semi-infinite conducting plates of infinitesimal thickness, with the rod taken parallel to and at a fixed distance from the plate edges. The problem is analyzed using the Wiener-Hopf technique, and the resulting formulas are evaluated analytically in the limits of high rod speed and low rod speed, and compared with numerical evaluation over the full range of speeds.
Date: April 23, 1970
Creator: Hazeltine, R.D.; Rosenbluth, M.N. & Sessler, A.M.
Partner: UNT Libraries Government Documents Department

SYNCHROTRON RADIATION AND RING FORMATION IN THE ELECTRON RING ACCELERATOR

Description: We discuss the possibility of using synchrotron radiation to form electron rings having a very high electric field to hold the ions inside the ring. The formulas describing bow the energy and the dimension of the ring change under the effect of synchrotron radiation are derived, and a numerical example is given.
Date: May 13, 1970
Creator: Pellegrini, C.
Partner: UNT Libraries Government Documents Department

A STUDY ON THE CHOICE OF PARAMETERS FOR A HIGH ENERGY ELECTRON RING ACCELERATOR

Description: The production of high energy (multi-GeV) proton beams by an electron ring accelerator is considered. Both the final energy and intensity of the proton beam depend on the choice of parameters for the electron ring. Possible sets of parameters, consistent with all the known requirements of ring stability, and which optimize the energy and (or) the intensity of the proton beam, are presented.
Date: June 26, 1970
Creator: Bovet, C. & Pellegrini, C.
Partner: UNT Libraries Government Documents Department

Investigations of the Dynamics of Space Charged Dominated Beams

Description: We propose to perform investigations of the dynamics of space charge dominated beams. These investigations will support present activities such as the electron ring project at the University of Maryland as well as provide an improved basis for future accelerator designs. Computer simulations will provide the primary research element with improved code development being an integral part of the activities during the first period. We believe that one of the code development projects provides a unique strategy for the inclusion of longitudinal dynamics, and that this concept should provide a computationally rapid research tool.
Date: August 1, 2002
Creator: York, Richard C.
Partner: UNT Libraries Government Documents Department

TRANSVERSE TWO-STREAM INSTABILITY IN THE PRESENCE OF STRONG SPECIES-SPECIES AND IMAGE FORCES

Description: The theory of coherent transverse oscillations of two particle species is extended to include strong species-species and image forces. It is shown that in general the species-species force can considerably alter the instability threshold. Conversely, it is shown that the limit on the performance of an electron ring accelerator imposed by the requirement of stable ion electron oscillations, is not significantly improved by the inclusion of images.
Date: September 1, 1972
Creator: Laslett, L.J.; Sessler, A.M. & Mohl, D.
Partner: UNT Libraries Government Documents Department

COLLECTIVE PHENOMENA IN ACCELERATORS

Description: Recent years have witnessed the development of accelerators of ever-larger current, both peak and average, as well as a proliferation of storage rings of ever-greater luminosity. Consequently, there is considerable interest in and growing concern with, the phenomena which limit beam currents and beam densities, namely, the collective modes of behavior of relativistic particle beams. Furthermore, it has been demonstrated that the collective behavior can be controlled, at least to some extent, turned to good advantage, and employed for collective acceleration in devices such as the electron ring accelerator. Quite naturally then, almost every accelerator conference during the last five years has had a review paper on collective effects, while at the same time the number of original papers in this area now exceeds many hundreds. And thus I am faced with the dilemma of being unable to give a comprehensive and complete review (such a review, incidentally, would be most valuable; in my judgment the time is ripe for a comprehensive monograph on the subject.), and yet finding it difficult, in a brief review, to be comprehensible, balanced, and yet fresh. I have resolved the dilemma by firstly supplying sufficient references as to allow the interested reader to readily approach and efficiently attack the literature. Secondly, I take a few steps away from the details and the realities of the field and with the advantage of the broader view so gained, describe the basic many-body physics underlying the subject. Thirdly, I present a few examples of collective behavior, in part to make the general remarks concrete, but in large measure in order to illustrate the beauty of this kind of physics. Finally, I make some remarks on methods for control of undesirable collective behavior, and on the present state of understanding of the field.
Date: September 1, 1972
Creator: Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department

ON THE PERFORMANCE CHARACTERISTICS OF ELECTRON RING ACCELERATORS

Description: On the basis of our present understanding of the physical phenomena involved in an electron ring accelerator (ERA), a theoretical study is made of the performance which might be expected for an ERA. Rigorous upper bounds are obtained on the rate of energy gain, from which it is shown that, in order to prevent azimuthal instability, parameters must be selected such that (for reasonable fields, injector properties, etc., but with no safety factors) the proton energy gain is less than 80 MeV/m. Numerical examples and approximate formulas are given for the properties of rings satisfying the stability conditions for both azimuthal oscillations and ion-electron oscillations. It is found that for reasonable fields and injector properties, but without safety factors, the useable proton energy gain is less than 45 MeV/m.
Date: September 1, 1972
Creator: Mohl, D.; Laslett, L.J. & Sessler, A.M.
Partner: UNT Libraries Government Documents Department

THE EMMA LATTICE DESIGN

Description: EMMA is a 10 to 20 MeV electron ring designed to test our understanding of beam dynamics in a relativistic linear non-scaling fixed field alternating gradient accelerator (FFAG). This paper describes the design of the EMMA lattice. We begin with a summary of the experimental goals that impact the lattice design, and then outline what motivated the choice for the basic lattice parameters, such as the type of cells, the number of cells, and the RF frequency. We next list the different configurations that we wish to operate the machine in so as to accomplish our experimental goals. Finally, we enumerate the detailed lattice parameters, showing how these parameters result from the various lattice configurations.
Date: June 25, 2007
Creator: BERG,J.S.; RUGGIERO, A.; MACHIDA, S. & KOSCIELNIAK, S.
Partner: UNT Libraries Government Documents Department

MEASUREMENT AND SIMULATION OF SOURCE-GENERATED HALOS IN THE UNIVERSITY OF MARYLAND ELECTRON RING (UMER)

Description: One of the areas of fundamental beam physics that have served as the rationale for recent research on UMER is the study of the generation and evolution of beam halos. Recent experiments and simulations have identified imperfections in the source geometry, particularly in the region near the emitter edge, as a significant potential source of halo particles. The edge-generated halo particles, both in the experiments and the simulations are found to pass through the center of the beam a short distance downstream of the anode plane. Understanding the detailed evolution of these particle orbits is therefore important to designing any aperture to remove the beam halo.
Date: June 18, 2007
Creator: Haber, I.; Haber, I.; Bernal, S.; Kishek, R.A.; O'Shea, P.G.; Papadopoulos, C. et al.
Partner: UNT Libraries Government Documents Department

THE ELECTRON-RING ACCELERATOR PROGRAM AT LRL

Description: A progress report is presented on the activities at LRL in connection with electron-ring accelerators. A two-stage compressor unit (employing only low-intensity beams) has been built, and operated with a 4-MeV 100-mA linac as an injector. Electron rings have been formed and compressed from 20 cm radius to 7 cm radius. A three-stage compression unit has been constructed and is now under test with the high intensity (200 A) 3.3-MeV beam of the Astron injector. The apparatus is described. Design work on a magnetic expansion unit is reported.
Date: October 1, 1968
Creator: Allison Jr., R.W.; Avery, R.T.; Baker, W.R.; Chupp, W.W.; Hartwig, E.C.; Hernandez, H.P. et al.
Partner: UNT Libraries Government Documents Department

PHYSICS WITH AND PHYSICS OF COLLIDING ELECTRON BEAMS

Description: When particle physics is a closed subject which has been condensed into a text book, the material will surely be organized by concepts and not according to what fact was learned on what accelerator. But short of that day facilities must be designed, planned, and developed, and experiments must be executed on one of a number of available accelerators; and a very necessary point of view is to ask what physics can be done with one facility, in contrast to another. It is in this spirit that, in this note, we look at electron colliding beam devices. In the first section we discuss the physics that can be done with colliding electron beams. After some general remarks we review the experiments already performed, and then turn to experiments planned for the future. The physics that can be done with any accelerator is a strong function of the physics of the accelerator. Every reader of this Journal knows what determines the energy of an accelerator, but the physics that determines the beam intensity, quality, and pulse length is perhaps not so well known. In fact, we plan to devote a future Comment to the physics that limits the performance of conventional accelerators. In the second section of this note, we discuss the physics of colliding electron ring devices. Even more so than in conventional accelerators, the performance of colliding-beam devices is dominated by the physics of the machine, and hence our lengthy second section. But we trust it will be interesting, for the physics is subtle and there is beauty in it.
Date: November 18, 1969
Creator: Pellegrini, Claudio & Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department

CROSSING OF AN INCOHERENT INTEGRAL RESONANCE IN THE ELECTRON RING ACCELERATOR

Description: In one mode of operation of an electron ring accelerator (ERA), at the end of compression rings are slowly moved through the radial integral betatron resonance Q{sub r} = 1. Although the coherent radial oscillation frequency of the ring as a whole remains below unit, the oscillation frequencies of individual electron are (incoherently) caused to pass through the resonance because of the additional focusing from ions trapped in the ring. In this paper the effect of field errors on ring major and minor radii is evaluated--theoretically--for the cases in which the spread in the square of the electron oscillation frequency ({Delta}{sup 2}) is (a) much larger and (b) much smaller than the contribution to the square of the oscillation frequency from the ions ({Lambda}{sup 2}). It is shown that for the ERA, where case (b) applies, the increase in ring minor dimensions, for given field errors and rate of resonance crossing, is less than in case (a) by a factor of ({Delta}/{Lambda}){sup 2}. Numerical examples show that the degradation of ring quality in case (b) should, with suitable attention to the design and construction of the ERA apparatus, be acceptably small.
Date: January 26, 1970
Creator: Pellegrini, Claudio & Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department

Recent Observations on a Horizontal Instability in the DAFNE Positron Ring

Description: A strong horizontal instability limits the maximum positron current storable in the DAFNE Phi-Factory. A powerful feedback system makes it possible to store and put in collision more than 1300 mA of positron current in 105-109 bunches. Nevertheless, a much higher current (>2.4A) has been successfully stored in the twin electron ring. Measurements have been carried out to understand the positron current limit and to characterize the behavior of the horizontal instability at high current with different bunch patterns. Grow/damp turn-by-turn data obtained by turning off the horizontal feedback have been acquired and analyzed. Spectral analysis and growth rates of the instability are shown. In particular, the -1 mode has strong evidence and fast growth rate. Its growth rate behavior is analyzed at different beam currents and bunch patterns.
Date: January 20, 2006
Creator: Drago, A.; Zobov, M.; /Frascati; Teytelman, D. & /SLAC
Partner: UNT Libraries Government Documents Department

eRHIC ring-ring design with head-on beam-beam compensation

Description: The luminosity of the eRHIC ring-ring design is limited by the beam-beam effect exerted on the electron beam. Recent simulation studies have shown that the beam-beam limit can be increased by means of an electron lens that compensates the beam-beam effect experienced by the electron beam. This scheme requires proper design of the electron ring, providing the correct betatron phase advance between interaction point and electron lens. We review the performance of the eRHIC ring-ring version and discuss various parameter sets, based on different cooling schemes for the proton/ion beam.
Date: May 4, 2009
Creator: Montag,C.; Blaskiewicz, M.; Pozdeyev, E.; Fischer, W. & MacKay, W. W.
Partner: UNT Libraries Government Documents Department

A METHOD FOR STATIC-FIELD COMPRESSION IN AN ELECTRON-RING ACCELERATOR

Description: A review of methods for static-field compression of an electron ring is shown to suggest advantages for a method in which there is no axial acceleration or deceleration of the ring. In the method proposed here the static magnetic field itself is o such a character that the electrons are neither focused nor defocused in the axial direction. The integrity and movement of the ring through the compressor is controlled by a small traveling magnetic well. The feasibility of creating such a traveling well is discussed, and an example is presented of a current distribution capable of producing the static magnetic field of the compressor.
Date: February 20, 1969
Creator: Laslett, L.Jackson & Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department

EXPERIMENTS ON FORMING,COMPRESSING AND EXTRACTING ELECTRON RINGS FOR THE COLLECTIVE ACCELERATION OF IONS

Description: In experiments related to the development of the electron-ring accelerator, electrons were injected into a pulsed magnetic field to form rings that were then compressed radially to a small size. The injected beam had a current of about 150 A at an energy of 3.3 MeV with an energy spread of {+-} 0.1% and a pulse length duration of 20 nsec. At low intensity, an increase in the minor radius of the ring and a large loss of electrons was observed to occur during the compression cycle. At high intensity, cooperative phenomena that caused a large increase in the energy spread accompanied by particle loss were observed. Theoretical interpretation of these observations suggests that the primary source of electron loss and enlargement of the axial dimension was the crossing of single-particle resonances during compression in the presence of large magnetic field nonlinearities and perturbations. The cooperative phenomena are interpreted as resulting from a negative mass instability. Despite the large minor radius and small number of electrons, experiments on extracting the ring were performed; under acceleration the ring failed to retain its integrity because of inadequate self-focusing.
Date: October 1, 1970
Creator: Keefe, D.; Chupp, W.W.; Garren, A.A.; Lambertson, G.R.; Laslett, L.J.; Luccio, A.U. et al.
Partner: UNT Libraries Government Documents Department