832 research outputs found
Vapor feeding of liquid metal cathodes
Modified liquid metal cathode apparatus permits vapor feeding in the diffuse-spot pattern mode. Vapor-fed cathode has advantages over liquid-fed systems
High-temperature LM cathode ion thrusters Quarterly progress report, 5 May - 4 Aug. 1968
Design and operation of high temperature liquid mercury cathode ion thruster
High-temperature LM cathode ion thrusters Quarterly progress report, 5 Feb. - 4 May 1968
Poiseuille flow measurements for high temperature liquid metal cathode ion thruster
High-temperature liquid-mercury cathodes for ion thrusters Quarterly progress report, 1 Dec. 1966 - 28 Feb. 1967
High temperature liquid mercury cathodes for ion thrusters - thermal design analysi
Liquid mercury cathode electron bombardment ion thrusters Summary report, 1 Aug. 1964 - 31 Oct. 1966
Life tests of liquid mercury cathodes for electron bombardment ion thruster
High-temperature LM cathodes for ion thrusters Summary report, 1 Jun. 1966 - 31 Jul. 1967
Performance of liquid metal cathodes in electron bombardment thrusto
Microwave study of quantum n-disk scattering
We describe a wave-mechanical implementation of classically chaotic n-disk
scattering based on thin 2-D microwave cavities. Two, three, and four-disk
scattering are investigated in detail. The experiments, which are able to probe
the stationary Green's function of the system, yield both frequencies and
widths of the low-lying quantum resonances. The observed spectra are found to
be in good agreement with calculations based on semiclassical periodic orbit
theory. Wave-vector autocorrelation functions are analyzed for various
scattering geometries, the small wave-vector behavior allowing one to extract
the escape rate from the quantum repeller. Quantitative agreement is found with
the value predicted from classical scattering theory. For intermediate
energies, non-universal oscillations are detected in the autocorrelation
function, reflecting the presence of periodic orbits.Comment: 13 pages, 8 eps figures include
Quantum fingerprints of classical Ruelle-Pollicot resonances
N-disk microwave billiards, which are representative of open quantum systems,
are studied experimentally. The transmission spectrum yields the quantum
resonances which are consistent with semiclassical calculations. The spectral
autocorrelation of the quantum spectrum is shown to be determined by the
classical Ruelle-Pollicot resonances, arising from the complex eigenvalues of
the Perron-Frobenius operator. This work establishes a fundamental connection
between quantum and classical correlations in open systems.Comment: 6 pages, 2 eps figures included, submitted to PR
Shuffling cards, factoring numbers, and the quantum baker's map
It is pointed out that an exactly solvable permutation operator, viewed as
the quantization of cyclic shifts, is useful in constructing a basis in which
to study the quantum baker's map, a paradigm system of quantum chaos. In the
basis of this operator the eigenfunctions of the quantum baker's map are
compressed by factors of around five or more. We show explicitly its connection
to an operator that is closely related to the usual quantum baker's map. This
permutation operator has interesting connections to the art of shuffling cards
as well as to the quantum factoring algorithm of Shor via the quantum order
finding one. Hence we point out that this well-known quantum algorithm makes
crucial use of a quantum chaotic operator, or at least one that is close to the
quantization of the left-shift, a closeness that we also explore
quantitatively.Comment: 12 pgs. Substantially elaborated version, including a new route to
the quantum bakers map. To appear in J. Phys.
Three disks in a row: A two-dimensional scattering analog of the double-well problem
We investigate the scattering off three nonoverlapping disks equidistantly
spaced along a line in the two-dimensional plane with the radii of the outer
disks equal and the radius of the inner disk varied. This system is a
two-dimensional scattering analog to the double-well-potential (bound state)
problem in one dimension. In both systems the symmetry splittings between
symmetric and antisymmetric states or resonances, respectively, have to be
traced back to tunneling effects, as semiclassically the geometrical periodic
orbits have no contact with the vertical symmetry axis. We construct the
leading semiclassical ``creeping'' orbits that are responsible for the symmetry
splitting of the resonances in this system. The collinear three-disk-system is
not only one of the simplest but also one of the most effective systems for
detecting creeping phenomena. While in symmetrically placed n-disk systems
creeping corrections affect the subleading resonances, they here alone
determine the symmetry splitting of the 3-disk resonances in the semiclassical
calculation. It should therefore be considered as a paradigm for the study of
creeping effects. PACS numbers: 03.65.Sq, 03.20.+i, 05.45.+bComment: replaced with published version (minor misprints corrected and
references updated); 23 pages, LaTeX plus 8 Postscript figures, uses
epsfig.sty, espf.sty, and epsf.te
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