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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


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


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


Description: We have investigated the preequilibrium kinetics of the L-isoleucine activation reaction catalyzed by Ile-tRNA synthetase in the presence of a fluorescent reporter group, 2-p-toluidinylnaphthalene-6-sulfonate, using the stopped-flow technique. It is found that of all the reactants involved, L-isoleucine binds slowest to the enzyme, apparently in a two-step process. The kinetics of the reaction are invariant in the presence of co-reactants, whereas the kinetics for ATP are drastically changed in the presence of Mg{sup 2+} ions. The formation of enzyme bound L-isoleucyl {approx} AMP is conveniently followed at dilute concentrations. The value for the rate constant of formation was determined to be 135 sec{sup -1} and of the reverse process to be 670 sec{sup -1} at pH 8.0 25 C. These values are considerably higher than the rate constant 15 sec{sup -1} of the dissociation reaction for L-isoleucine. The value of the kinetically defined equilibrium constant between the ternary Michaelis-Menten complex and the ternary enzyme-product complex indicates that, at equilibrium, the Michaelis-Menten complex is favored. The effect of temperature has been determined, and a tentative interpretation of the thermodynamic parameters is offered. The zero standard enthalpy and positive entropy for binding of L-isoleucine is consistent with hydrophobic interactions, whereas the enzyme-ligand complexes for ATP and pyrophosphate might be stabilized by hydrogen-bonds and ion-ion interactions. The equilibrium constant of formation of the ternary enzyme-product complex from the Michaelis-Menten complex does not increase significantly with temperature. The types of kinetic pathways have been restricted to the alternative of a random mechanism or an ordered sequential mechanism in which L-iso-leucine binds first. We believe that the mechanism is random.
Date: May 1, 1972
Creator: Holler, E. & Calvin, Melvin
Partner: UNT Libraries Government Documents Department


Description: The increasing availability of short lived gamma and positron emitting isotopes, coupled with the importance of dynamical studies and better imaging, has generated the need for an improved {gamma}-ray camera. The authors discuss a new type of {gamma}-ray camera which makes use of electron avalanches in liquid xenon. A configuration currently under development is shown in Figure 1. The successful operation of a liquid xenon proportional counter was recently reported. The liquid xenon camera promises better spatial resolution and higher counting rate than the existing NaI(Tl) scintillation camera. The spatial resolution for {gamma} rays is in principle limited only by the range of photoelectrons in liquid xenon, which is < 0.2 mm for energies < 1 MeV. A counting rate of 10{sup 6} C/s or more appears possible. As a result of the better resolution and high counting rate capability, the definition of the picture is improved. In addition, the high counting rate capability makes possible dynamic studies which were previously unfeasible. Although they expect the energy resolution with liquid xenon to be superior to that of NaI, the preliminary measurements show 17% FWHM for 279 keV {gamma}'s. Improvements are expected by using better geometry and smoother wire.
Date: February 1, 1972
Creator: Zaklad, Haim.; Derenzo, Stephen E.; Muller, Richard A.; Smadja,Gerard.; Smits, Robert G. & Alvarez, Luis W.
Partner: UNT Libraries Government Documents Department


Description: The authors describe several types of small liquid xenon-filled chambers, each optimized for a particular property such as a real-time spatial resolution of {+-} 15 {mu}, a time resolution of {+-} 10{sup -7} sec, or a pulse height of 10{sup -12} coulomb. Larger chambers combining all these properties will be of great value at NAL energies, and they describe some of the techniques necessary for their construction.
Date: September 1, 1972
Creator: Derenzo, S.E.; Flagg, R.; Louie, S.G.; Mariam, F.G.; Mast, T.S.; Schwemin, A.J. et al.
Partner: UNT Libraries Government Documents Department


Description: A prototype liquid xenon {gamma}-camera has been constructed and preliminary results obtained. The sensitive volume is 7 c x 7 cm in area and 1.5 cm thick. Orthogonal coordinates for each interacting {gamma}-ray are provided by 24 anode wires 5 {micro} in diameter spaced 2.8 mm apart and 24 cathode strips.
Date: December 1, 1972
Creator: Zaklad, Haim; Derenzo, Stephen E.; Muller, Richard A. & Smits,Robert G.
Partner: UNT Libraries Government Documents Department


Description: Previous work on generalizations of the ABFST multiperipheral model is extended to allow for vector meson exchange. The intercept of the Pomeranchon pole, the magnitude of asymptotic total cross sections and off-shell corrections to them are calculated.
Date: September 1, 1972
Creator: Avalos, Daniel R. & Sorensen, Cristian.
Partner: UNT Libraries Government Documents Department

Energy Spectra of Fragments from Silver and Uranium Bombarded with5.0 GeV Protons

Description: In this third paper in a series in which the characteristics of nuclear fragments produced in the interaction of 5 GeV protons with Ag and U targets were studied by means of dE/dx-E measurements with semiconductor detector telescopes new information was obtained on the energy spectra of light fragments. One set of measurements on fragments from a Ag target involved the use of a two-element telescope incorporating a {Delta}E detector as thin as 16 {micro}m. A new algorithm for processing the {Delta}E and E data to extract particle identification was developed and the resulting particle spectra showed superior resolution for the elements from Li(Z = 3) to S (Z = 16). Segments of the energy spectra of each of these elements were measured at 20{sup o} and, for many of them, also at 45{sup o}, 90{sup o}, 135{sup o} and 160{sup o} to the beam direction. By use of 3-element telescopes and absorbers the high energy part of the energy spectrum for isotopes of He, Li, Be, B, and C ejected from Ag and U targets was measured at 20{sup o}. The measurements extended beyond 300 MeV for {sup 6}Li and {sup 7}Li and to 400 MeV for {sup 7}Be. A distinct high-energy component was found in these cases. The suitability of nuclear evaporation as a description of the emission of the low-energy fragments was tested with two simple theoretical models, one specifying isotropic fragment emission from a moving nucleus at a fixed nuclear temperature and one specifying isotropic fragment emission from a set of moving nuclei with a Maxwellian distribution of excitation energies and forward momenta. The second could describe rather well all the 90{sup o} data, provided a Coulomb barrier 0.4 that of the classical tangent spheres barrier was used. However, the measured intensity in the forward direction ...
Date: August 1, 1972
Creator: Korteling, Ralph G.; Toren, C.R. & Hyde, Earl K.
Partner: UNT Libraries Government Documents Department