Continuous channel electron multiplier operated in the pulse saturated mode.
Continuous channel electron multiplier operated in pulse saturated mode, noting space charge limiting as major cause of gain saturation
SATURATION↗
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Results for “SPACE CHARGE”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Semiconductor research
Structure preparation for study of space charge limited current of electrons in silicon
ELECTRON FLUX↗
Guidance and control research
Cesium vapor heat conduction in thermionic energy converters, space charge distribution in neutral plasma, and titanium oxide thin films
THERMIONIC CONVERTER↗
Active control of spacecraft potentials at geosynchronous orbit
Tests have been conducted concerning the active control of the potentials of the geosynchronous satellites ATS-5 and ATS-6. The ATS-5 tests show that a simple electron emitter can be used to reduce the magnitude of the potential of a spacecraft which has been charged negatively by the environment. The ATS-6 ion thruster had also a pronounced effect on the potential barrier. In this case, the flux of high-energy primary ions and of low-charge exchange ions produces a space-charge neutralization effect which the electron gun alone cannot achieve.
Goldstein, R.↗
Simultaneous holographic and photocurrent studies of the photorefractive effect in LiTaO3 and LiNbO3
In reduced LiNbO3:Mn both the photorefractive sensitivity and the simultaneously measured photocurrent result from drift with a polarization-dependent effective 'internal field' of about 6 kV/cm. In reduced undoped LiTaO3 the observed difference in applied fields of the minimum photorefractive sensitivity and zero photocurrent imply charge transport is by a mechanism that cannot be completely described by diffusion and drift in an electric field. The direct measurement of the harmonic content of phase gratings written in several LiNbO3 and LiTaO3 crystals shows termination of charge-transport results from the space-charge field of the hologram.
Spinhirne, J. M.↗
Plasma double-layers produced by ponderomotive force
Non-linear rectification of the RF electric fields excited in a convectively amplifying electron beam-plasma interaction results in a dc electric field, and a corresponding ponderomotive force acting on the charged particles to produce a space-charge separation, i.e. a type of plasma double-layer. This paper analyses the effect, taking into account plasma electron temperature and electron-neutral collisions. To measure such double-layers, an electron beam probe constitutes a convenient non-perturbing diagnostic technique, but great care is required in its calibration. An analysis is presented taking into account significant non-linear effects which had been neglected in previous work. The paper concludes with some preliminary experimental results illustrating the use of the technique in a beam-plasma interaction for which a weak double-layer electric field is predicted.
Levine, J. S.↗
Analysis of intense, undriven electron beams with significant self-field forces.
Nonaccelerated electron beam envelope trajectory equation reformulated and solved allowing for finite emittance, space charge and self- magnetostatic forces
TRAJECTORY ANALYSIS↗
Airplane testing of solar cells
Space charge flow configurations suitable for use in ion guns
ION SOURCE↗
A higher order paraxial ray theory.
Higher order paraxial ray method to obtain space-charge limited axial symmetry flow solutions in electrostatic systems
FLOW EQUATION↗
Vapor-filled thermionic converters final report
Cesium vapor diode thermionic converter - electrode surface properties, space charge neutralization, plasma studies on arc drop
SURFACE PROPERTY↗
Design guidelines for assessing and controlling spacecraft charging effects
The need for uniform criteria, or guidelines, to be used in all phases of spacecraft design is discussed. Guidelines were developed for the control of absolute and differential charging of spacecraft surfaces by the lower energy space charged particle environment. Interior charging due to higher energy particles is not considered. A guide to good design practices for assessing and controlling charging effects is presented. Uniform design practices for all space vehicles are outlined.
Purvis, C. K.↗
Design guidelines for assessing and controlling spacecraft charging effects
The need for uniform criteria, or guidelines, to be used in all phases of spacecraft design is discussed. Guidelines were developed for the control of absolute and differential charging of spacecraft surfaces by the lower energy space charged particle environment. Interior charging due to higher energy particles is not considered. A guide to good design practices for assessing and controlling charging effects is presented. Uniform design practices for all space vehicles are outlined.
Purvis, C. K.↗
A single collision model for electron-beam currents between plane electrodes.
Space-charge and potential distributions calculated for region between two plane electrodes of single collision model
ELECTRON COLLISION↗
Clear, Conductive, Transparent, Flexible Space Durable Composite Films for Electrostatic Charge Mitigation
Space environmentally durable polymeric films with low color and sufficient electrical conductivity to mitigate electrostatic charge (ESC) build-up have been under investigation as part of a materials development activity. These materials have potential applications on advanced spacecraft, particularly on large, deployable, ultra-light weight Gossamer spacecraft. The approach taken to impart sufficient electrical conductivity into the polymer film while maintaining flexibility is to use single wall carbon nanotubes (SWNTs) as conductive additives. Approaches investigated in our lab involved an in-situ polymerization method, addition of SWNTs to a polymer containing reactive end-groups, and spray coating of polymer surfaces. The work described herein is a summary of the current status of this project. Surface conductivities (measured as surface resistance) in the range sufficient for ESC mitigation were achieved with minimal effects on the physical, thermal, mechanical and optical properties of the films. Additionally, the electrical conductivity was not affected by harsh mechanical manipulation of the films. The chemistry and physical properties of these nanocomposites will be discussed.
Watson, Kent A.↗
Dielectrics for long term space exposure and spacecraft charging: A briefing
Charging of dielectrics is a bulk, not a surface property. Radiation driven charge stops within the bulk and is not quickly conducted to the surface. Very large electric fields develop in the bulk due to this stopped charge. At space radiation levels, it typically requires hours or days for the internal electric fields to reach steady state. The resulting electric fields are large enough to produce electrical failure within the insulator. This type failure is thought to produce nearly all electric discharge anomalies. Radiation also induces bond breakage, creates reactive radicals, displaces atoms and, in general, severely changes the chemistry of the solid state material. Electric fields can alter this process by reacting with charged species, driving them through the solid. Irradiated polymers often lose as much as a percent of their mass, or more, at exposures typical in space. Very different aging or contaminant emission can be induced by the stopped charge electric fields. These radiation effects are detailed.
Frederickson, A. R.↗
The effect of charged-particle environments on manned military space systems
Charged particle environment effect on manned military spacecraft systems - radiation effects
CHARGED PARTICLE↗
Langmuir probe theory and the problem of anisotropic collection
A more general understanding of Langmuir probe theory by going beyond particular coordinate systems as far as possible was studied. To delineate the role of initial velocities in the problem and to characterize the interaction between the velocity flow field and the electrostatic potential field both of which enter into the determination of particle trajectories are desired. The probe is supposed to be negatively charged throughout and the ensuing region of positive space charge about it differs fundamentally from the plasma region beyond in the sense that the former represents a region in which deterministic trajectories dominate while the lattice is a region dominated by statistical interactions largely controlled by the collisionless stationary Boltzmann equation. A general solution of this Boltzmann equation is given and its relationship to the problem of saturation current density in 3D is elucidated.
Kyrala, A.↗
Propagation of charge-neutral beams in space - Modifications when negative ions are present
Two-dimensional (three velocity component) electrostatic simulations are used to investigate the properties of a charge-neutral beam consisting of H(+), H(-), and electrons which will be used in the Beams on Rockets (BEAR) experiment to be launched in late 1987 or early 1988. For cross-field injection and beam densities much greater than the ambient plasma density, the beam splits into two approximately charge-neutral beams: a H(+)-e(-) beam that propagates down the field lines and a H(+)-H(-) beam that propagates at nearly the initial beam velocity on time scales less than the ion gyroperiod. Because of this splitting, space-charge oscillations are induced in the H(+)-H(-) component, which lead to its breakup. At lower beam densities, particularly when the beam electron density is less than about the density of the ambient plasma, the ambient plasma response reduces the space-charge fields as the beam splits and the space-charge oscillations are suppressed.
Winglee, R. M.↗