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The ability to fully characterize a probe antenna using a near-field range is demonstrated subject to the conditions that two identical probes are available and that the E sub y field components are symmetric about the ky = O axis. A completely general three antenna approach, requiring no such assumptions, appears feasible. Some questions with respect to uniqueness of solution of the three antenna approach remain. Experimental results indicate that at wide angles (approx 77 deg), considerably below the apparent geometric limit, the planar near-field approach suffers a notable loss of accuracy. Improvements in both hardware and software techniques to increase the data handling ability of the near-field facility are described. (Author)

During the month of August 1974, a series of experiments was conducted at the ARPA Maui Optical Station (AMOS) on Mt. Haleakala, Maui, Hawaii. The objectives were to quantify astronomical seeing conditions, and to determine if the seeing quality has been degraded by the presence of the site structures. Instruments used were an acoustic sounder (to probe the altitudes of 100 to 1000 ft), finewire microthermal probes (to measure local turbulence in and around the domes) and a Hartmann sensor (to provide integrated strengths of turbulence for the entire atmosphere). According to fine-wire probe data, local turbulence can be on occasion a significant factor in degrading seeing. These sensors noted some thermal contamination from one of the domes which was in a nearly operational configuration. The acoustic sounder indicated that the strengths of turbulence in 100 to 1000 ft altitude are not sufficient to degrade seeing. Finally, the Hartmann device recorded significantly more degradation than was seen by either of the other two probes. It is speculated that there is significant turbulence at high altitude temperature inversions such as at the tropopause.

A large amplitude rf pump signal is applied to a wire antenna in a magnetic field free plasma. When the pump frequency (omega sub 0) corresponds to twice the sheath-plasma resonance frequency (omega sub r), and the pump amplitude exceeds a threshold value, spontaneous excitation of the signal at (omega sub r) = (omega sub 0)/2 is observed. The process is explained as a periodic variation of the sheath thickness causing the sheath-plasma resonance to become parametrically unstable. The rf field pressure can induce density relaxation oscillations near the ion plasma frequency which are observed to modulate the instability spectrum strongly.

Refractive-index fluctuations which affect optical propagation depend mostly on microthermal variations. Fine wire probes are sufficient to measure microtemperature so long as we have ready access to the propagation medium. A complete sensor unit currently in use includes the probe, a Wheatstone bridge and amplifier circuit, and a mechanical support assembly. In providing complete details on how to construct such a unit, we concentrated on a design developed in-house which we know to be effective. The unit is found to have a frequency range better than 0.01 to 100 Hz and responds to minimum temperature fluctuations of 0.015C. Of special importance is the low construction cost of only about $200., Sponsored in part by DARPA.

Work has continued in three general directions: condensed phase experiments, emission studies of SiN and N2(+), and plasma analysis. Improvements in apparatus allowed measurement of free carrier mobilities in solid and liquid argon and krypton. As a preliminary to the study of scattering processes, using laser beams, in liquids and van der Waal's solids, equipment and techniques were developed, which allowed observation of Raman and Brillouin scattering in CS2 and benzene liquids. Charge transfer processes in the benzeneiodine complex are being studied at low temperatures using absorption methods. The study has continued of flowing gas systems where the initiating energy source is an electrical discharge. The addition of volatile silicon compounds to active nitrogen has yielded new information on the electronic states of SiN. In a study of N2(+), a detailed perturbation calculation on the mutual interaction between the v = 1 level of the B(2)& state and the v = 11 level of the A(2)pi state were completed. Populations of vibrational and electronic states of N2(+) excited in a helium afterglow were obtained over a large pressure range., See also AD610094.

The impedance of an antenna probe surrounded by ionospheric plasma is examined. A review of several physical plasma parameters, research techniques, some past experimental results, and various theories is presented. A need is shown for further theoretical sophistication. The theory develops the impedance of an electrically short, cylindrical antenna probe immersed in a warm, lossy, compressible, magneto-ionic, electron fluid. The results are examined and compared to previous work and are applied to several ionospheric experiments. Experimental results as interpreted by the theory are examined and the usefulness of the theory is thus demonstrated. In particular, the theory is shown to be of value in determining electron density, temperature, and collision frequency from RF probe measurements.

This final report describes a program to develop an instrument capable of measuring electron density in the 50 to 160 kilometer altitude region and capable of surviving a 60,000 'G' shock encountered during launch from a cannon. This report is in two parts: The first describes various techniques and instruments capable of measuring electron density in this altitude region. The second section describes the design techniques as well as flight results from these probes. Both dc and ac Langmuir probes were chosen as the best instruments for fulfilling the system requirements.

Techniques for ground-testing of ion engines are reviewed. Procedures for the neutralization of ion beams and the results of experiments measuring the space charge and current neutrality achieved are presented. Results of experiments with the window probe and a new probe for the measurement of beam potential are also presented. Results achieved with the methods described in the first Technical Documentary Report are discussed; more recently developed methods and their results are also reviewed.

Samples of 5.56mm bullets, copper coated and lead cored, representing two production lots (lots A and B), were analyzed. The purpose of the analysis was to ascertain metallurgical properties and characteristics of each lot which relate to quality and possibly to method of manufacture. The testing procedures included chemical, metallographical, electron micro-probe and hardness analyses. The results indicated that the electroplating quality of Lot B was superior to that of Lot A, especially with respect to adhesion and strength of coating. The electroplating techniques used in the manufacture of each lot were different as evidenced by Lot A having one continuous layer of copper and Lot B having a banded structure of three distinct layers of copper. Although the lead-antimony substrates of each lot were very similar chemically, it was demonstrated from the relative differences in hardness and hardness patterns that bullets of Lot B underwent more work-hardening than those of Lot A.

The author discusses an interesting problem in contemporary astronautics - the problem of using AES and spacecraft for meteorological and hydrological research, surveys of natural resources on a planetary scale, and for geological, topographical, terrain and other types of photography over large areas., Edited trans. of Novoe v Zhizni, Nauke, Tekhnike. Seriya Kosmonavtika, Astronomiya (USSR) n52 p1-48 1971, by Dean F. W. Koolbeck.

An experimental program to demonstrate the feasibility of combining a coaxial probe monopulse organ pipe scanner with a wide angle two-dimensional constrained lens is described. The antenna system which was built and tested to prove this feasibility operates in the 5250 mcs to 5750 mcs range. It produces a half power beamwidth of 2 degrees in azimuth by 4 degrees in elevation which can be scanned =36 degrees from broadside in the azimuth plane. Variations of the measured radiation characteristics with frequency and angle of scan are summarized in graphical form. Design data and typical monopulse sum and difference patterns are presented. The test results show that such a lens- scanner antenna system is practicable for wide angle scanning in one plane.

The feasibility of using a nonintercepting electron beam probe for obtaining the properties of linear electron beams as used in microwave tubes has been demonstrated. The nonintercepting probe employs the technique of injecting an atomic, molecular, or ionic beam normal to the electron beam and the determination of the electron beam properties from the photon emissions resulting from the interactions of the two beams. The use of this technique for analyzing crossed-field beams should be feasible because the density of crossed- field beams is about two orders of magnitude greater than that of the linear beam that has been studied. The major problem anticipated in the analysis of crossed-field beams is in the instrumentation of a crossed-field device. Through the use of miniaturized probing beam generators and fiber optics it is anticipated that this instrumentation problem will be solved.

Previous experiments on the rf impedance between two probes immersed in a plasma, and on the incremental dc characteristics of an rf modulated probe, have suggested that resonance effects occur at the local electron plasma frequency, omega sub p, and can be interpreted to obtain a direct measurement of electron density, free from many of the errors to which conventional Langmuir probe techniques are prone. A simplified model which gives predictions agreeing well with experiment is presented. This model is developed and applied to several different probe geometries of interest in ionospheric and space studies. Additional rf techniques are suggested which may prove superior to incremental dc observations for measurement and data coding for transmission to terrestrial stations. An assessment is made of the various regions of applicability of the resonance probe in space, and it is concluded that a detailed theory of the effects of magnetic field on the resonance is required to increase its usefulness for ionospheric probing.

In the report, different measuring devices, transmitting and receiving antennas (direction-finder antennas) for the VLF region are discussed. The measurements of propagation in inhomogeneous rock are mainly concentrated to the determination of the direction of the field vector at the point of reception. The problem near field - far field of a VLF dipole is also discussed. In order to determine the electrical parameters of rock, comprehensive measurements were conducted in solid rock and in rock samples, furthermore the frequency dependence of sigma and epsilon was studied. The influence of the gallery configuration on the result of a sigma-measurement was studied in detail. The theoretical part mainly deals with the problems of excitation of a VLF wave in rock, giving a detailed comparison between electrical and magnetic dipoles.

The main problem scheduled for the year by the team working on VLF problems was the explanation and elimination of discrepancies between the results of theoretical calculations and experimental measurements that still existed. For this purpose all factors influencing the propagation of VLF waves were studied theoretically and the experimental methods of measurement were further developed. The improvement of all apparatus used so far as well as the expansion of measurements over much greater distances at which clear effects are to be expected according to theoretical considerations, are of special importance. Measurements were conducted in German and Dutch mines to explain the effect of different geological bodies on wave propagation; furthermore, a number of conductivity measurements were made., Legibility of this document is in part unsatisfactory. Reproduction has been made from best available copy.

The fabrication of the apparatus required for the formation of a high density plasma is in progress. The instrumentation for the investigation of the properties of high density plasmas has been partially tested. For the formation of the high density plasma, a bank of capacitors is discharged through a one turn coil. Measurements of the magnetic field strength, uniformity and variation in time have been made. Testing of microwave equipment is proceeding and indicates that there is greater than 2% ionization in the plasma. Photomultiplier observations of the visible light emitted by the plasma have not yet shown satisfactory agreement between any two photomultiplier tubes. Spectroscopic investigations are also in progress. A laser is under construction for use as a diagnostic tool in very high density plasmas.

The design of an experiment is given which employs an inverted coaxial diode geometry to investigate absorption of electromagnetic radiation below and above the plasma frequency. Data obtained when a pure electron stream is introduced into the system are analyzed, but cannot be completely explained. Difficulties encountered in introducing and ionizing a real gas are discussed. The results of an investigation concerning the form of the electron distribution function in such an experimental arrangement are reported. Finally, the process of free-free absorption is discussed, and expressions are given for the absorption coefficient in the presence of ions and neutral atoms or molecules. These are shown to be essentially equivalent to the results of the usual Lorentzian theory., Sponsored in part by DARPA.

Electron energy distribution measurements were determined in an RF excited plasma and are feasible if the plasma is excited by a cylindrical coil fed push-pull from a balanced power source and if probe measurements are made along the axis of the coil. As far as is known, the measurements made during this investigation are the first energy measurements made in an RF plasma. The basic theory of plasma generation and general probe theory were reviewed; Medicus' spherical probe theory was used in making the determinations. Experimental equipment was designed and built and suggestions for improvement were made. The results indicated that in the argon RF plasma of this investigation, the energy distribution is markedly non-Maxwellian., Master's thesis.

This program consists of a study of plasma oscillations with the objective of determining and explaining the mechanism for the growth of instabilities and oscillations in a gaseous discharge, with particular emphasis on the action of sheaths and wave interactions with particles in the discharge. The effect of parameters such as geometric shapes and boundaries, magnetic field, pressure and velocity distributions will be taken into account.

The flow field of a compressible plasma over a biased body is discussed with special emphasis on the electrical characteristics. The governing equations in various asymptotic regions are investigated. A stagnation point probe theory, because of its great practical interest, is given in detail. An analytic current-voltage characteristic is obtained for this case under the assumption of a very thin electrical sheath., Sponsored in part by DARPA.

A method is presented for producing a dense plasma in a resonant cavity with microwave energy. The plasma is contained in a quartz tube lying along the axis of a resonant cavity that is excited near the TE111 coaxial-mode resonance with 10-microsec pulses of up to 800 kw of peak power in the 10-cm band. The plasma serves as a center conductor for the coaxial mode, shifting the mode resonance near the exciting frequency. The initial transient in the plasma electron density occurs very rapidly, and the system appears to reach a steady state in less than 10-microsec. A second microwave system excites the cavity in the TE011 coaxial mode, which is used as a low-level probe to measure the properties of the plasma. A perturbation formula is developed that can be used to calculate the perturbing effects of the dense plasma. This formula is used to develop methods of calculating the electron density and collision frequency of the plasma by measurements of the detuning of the cavity mode. Plasma electron densities of over 10 to the 14th power per cc are measured when over 80 kw of peak power are dissipated in the discharge. Studies are also presented of helium discharges and of light generated by the discharges.

Electron plasma oscillations were investigated. The plasma was generated and controlled by an electron beam. The results of the investigation show that the character of the observable oscillations severely vary on the plasma boundaries.

A double microwave reflectometer probe was designed and developed for measuring the properties of dense plasmas. It was to measure the properties of plasmas having up to 10 to the 16th power electrons per cc and collision frequencies up to 10 to the 12th power per sec. The system and its theory of operation are discussed. Measurements of the effect of a magnetic field on the transmission and reflection characteristics of a plasma slab were made. The measured values of transmission-loss check well with those predicted from the measured plasma properties and linear theory while the reflection coefficient is a function of power level. A theoretical justification is given for this linear transmission-nonlinear reflection phenomenon. The curves of stagnation point N, Nu and shock stand-off distance given in the Interim Engineering Report #2 were extended to a 50 lb Trailblazer II payload. Design of the instrumentation for the forthcoming flight tests was begun., See also AD0267934.

The standard model of floating probes in plasmas is reviewed. It is shown that a maximum charge density exists for the application of this model. An explicit expression of voltage applied to the probes in terms of circuit current is obtained. When certain simplifying assumptions are used, this equation is reduced to the Langmuir single probe equation and the Johnson-Malter double probe equation. From measurements of probe current versus applied probe voltage, electron temperature at each respective probe can be determined. One example is given to illustrate the calculation.

A quartz chemical scavenger probe was developed to study local active species concentrations in a gas expanded from a converging-diverging nozzle glow discharge source. The probe samples a small central portion of the supersonic non-equilibrium jet. Results obtained with active N at one relatively low discharge power output are discussed. The sampled gas mixed and reacted inside the probe with one of the scavenger gases NO, NH3 or C2H4 at 18.8 mm Hg and an average temperature of 500 K. The NO light titration technique and the production of HCN from C2H4 set an upper and lower bound respectively for the atom concentration. The observed maximum amount of NO decomposition was 2.1 times as large as the NO light titration end point flow rate. This difference is far in excess of that observed in conventional discharge flow systems and is interpreted as being due to excited N2 molecules reacting with NO in a reaction slow compared to that between N-atoms and NO. The contribution of these molecules to the energy content of the jet was found to be at least comparable to that of the N-atoms. A new analytical technique for quantitative analysis of the undecomposed NO was developed. Decomposition of NH3 also showed the presence of excited molecules. The NO light titration technique can also be used for composition measurements of the total supersonic jet. (Author) AD-296 3989N4 +++Chemical scavenger probe determinations of atom and excited molecule concentrations in nonequilibrium supersonic streams of active nitrogen.

Experiments were conducted to study the problem of heating and stability of pulsed discharges. In order to have reproducible conditions and de fined geometry a predischarge representing a highly ionized plasma was used and described. Then, the basic equations for the heating process which were developed in our institute and the main features of a model which allows to apply them to a cylindrical discharge are summarized.

This report details the development of electromagnetic probes for S, X, and K-band insertion loss studies on supersonic flames and of associated automatic VSWR equipment. Evaluation of the life of the probes is set forth, along with information on flame-loading of probes and certain insertion loss data taken with a 1500-lb oxygen-alcohol and a 400-lb acid-aniline motor., The original document contains color images. All DTIC reproductions will be in black and white.

Construction details are given for experimental equipment designed to permit measurement of the self and mutual admittances, current distributions along the radiating elements, and far field radiation patterns of small antenna arrays. The antennas are formed by extending the longitudinally slotted inner conductor of a rigid coaxial line beyond a large groundplane while terminating the outer conductor on the ground plane. A small balanced loop probe can be moved along the slot to sample the tangential magnetic field near the conductor. Measurement errors due to the probe are discussed. The array under test can be rotated by means of a turntable which is described. Radiation patterns are measured by transmitting with the array under test and receiving with a corner reflector antenna mounted on the groundplane but in the far field of the array. Although designed for 663 Mcps the equipment will operate over a wide range of frequencies.

Electrostatic probes were used in various array configurations to examine the characteristics of the turbulent wake behind hypersonic spheres in a ballistic range facility. Convection velocities measured with 5-probe axial arrays were found to agree with the mean wake velocity measured by the sequential spark technique at the same Reynolds number. The r.m.s. fluctuation in the wake velocity measurements was used to infer turbulence intensity. Preliminary results on filtered convection velocity indicate some variation with eddy size. Time scales of the turbulence derived from the moving frame autocorrelation data of the axial array are presented together with space correlation data for 'electron density fluctuations.' (Author), Presented at AIAA Fluid and Plasma Dynamics Conference, Los Angeles, Calif., 24-26 Jun 68, Paper-68-689.

Measurements of D-region conductivity are of extreme importance in understanding the basic, normal atmospheric processes as well as for investigating special events associated with the D-region, i.e., auroral absorptions, polar cap absorptions (PCA) and sudden ionospheric disturbances (SID). This report discusses the theory and possibilities of adapting one type of conductivity probe, the Gerdien condenser for operation on sounding rockets at supersonic and subsonic velocities. Details are presented for two systems developed for making correlating measurements during simultaneous rocket flights. The first is designed for the Black Brant II rocket (supersonic flow); and the second, employing a parachute system, is designed for the Arcas rocket (subsonic flow)., Research supported in part by DASA.

Efforts concerned measuring microwave fields. At least four types of probes are required to probe the high intensity microwave fields and the ac companying plasmas. The disturbance of the plasma and the fields due to the volume displacement of the physical presence of the probe and stem, and due to the small amount of energy extraction necessary for the probe readings is unavoidable, but scattering due to the antenna-like configura tion of the probe stem can be minimized to be negligible. The stems which support the probes and which contain the transmission line connec tions should be as small as mechanical and elec trical designs will readily permit, and must be designed in a special way in order to minimize scattering of the microwaves. It is necessary to design a structure upon the surface of the probe ms which has a high wave impedance for the microwaves, compared to the impedance of space. This permits the currents excited in the probe stems by the microwaves to be held to a minimum so that their reradiation scattering will not interfere with the probe measurements or the general course of the experiment. Probes have so far been designed and tested which are essentially responsive to microwave magnetic field, microwave electric field, microwave power, as a function of wave direction, as in a directional coupler, and temperature of a small test object exposed to the microwave and to any plasma which may exist in its vicinity.

Classical (Langmuir) probe theory is reviewed and the conditions under which it is applicable to the re-entry physics problem identified. Some later developments in probe theory, which account for flow velocity in the free- molecular case, are presented. Measurements of current densities have been made with ion probes mounted flush in the walls of a pressure-driven shock tube; the results are interpreted using a one-dimensional, collision-dominated probe theory, allowing for the spatial nonuniformities in ion density. Correlation of the probe theory with a zero-order gas dynamic boundary layer theory is shown to lead to theoretical current estimates in fair agreement with the experimentally observed values. Some shock ionization precursor results in air are also presented. Finally, the results of some calibrations on probes that were flown on the RVIP and LORV programs are presented.

Hall measurements on thin films via a four-point probe method are described. Basic formulas are derived for an infinite sheet. Modifications of the infinite-sheet formula to correct for boundary conditions imposed by real, finite samples are discussed. Experimental evidence is presented which verifies the theory.

Laser Raman Scattering (LRS) has been investigated as a possible approach toward providing a nonperturbing flow calibration method for arc-heated wind tunnel facilities. Such a calibration is needed to evaluate the chemical and thermodynamic properties of the high temperature air flow which cannot be accurately determined using standard probe techniques. Theoretical calculations showed that the number densities and vibrational temperatures of nitrogen, oxygen, and nitric oxide could be obtained using the Raman spectroscopic method. Exploratory experimental LRS results obtained in the Air Force Flight Dynamics Laboratory 50-Megawatt Reentry Nose Tip (RENT) Facility showed that it is indeed feasible to apply LRS to arch-tunnel flow diagnostics.

Experimental spectra of Raman Scattering Stokes fundamental vibrational Q-branches for nitrogen and hydrogen in hydrogen-air flames have been fit to theoretically-calculated profiles in order to determine temperature. The temperature measured from a least square fit of the full nitrogen profile agreed to within about 1/2% of the value calculated from the ratio of the peak intensity of the first upper state band (i.e., 'hot' band) to that of the ground state band. Agreement with the temperature estimated from fine-wire thermocouple measurements was approximately 2%. Additional theoretical profile calculations are given from nitrogen and hydrogen over the wide range of temperatures., Prepared in cooperation with General Electric Corporate Research and Development, Schenectady, N.Y.

The Hall coefficient and conductivity have been measured during pile irradiation for a number of zone-refined p-type silicon crystals with initial resistivities of 1, 8, and 100 ohm-cm. The conductivity of zone-refined silicon shows much faster changes with irradiation than pulled silicon samples of equivalent resistivity. The 100-ohm-cm samples exhibit a monotonic nonlinear decrease of 1n sigma (conductivity) vs phi f (integrated fast flux), whereas the other samples with initial Fermi levels closer to the valence band have one or two regions of linear decrease in 1n sigma vs phi f before the nonlinear de crease region is observed. The Hall mobility for the 100-ohm-cm samples decreases and becomes negative as a result of the carrier density decreasing with irradiation. In the case of the 8-ohm-cm sample, the Hall mobility decreases with irradiation, whereas the 1-ohm-cm sample shows no change in Hall mobility with irradiation up to the maximum integrated flux used in the present experiment. The origins of the dependence of 1n sigma on phi f as well as the behavior of the Hall coefficient and Hall mobility with irradiation are discussed.

Two different probes were developed for measuring the electrical charge and velocity of a moving charged projectile. The probes were tested using 5/32-inchdiameter steel balls fired from a rifle at roughly 4500 feet per second. The projectiles were frictionally charged to from 50 to 100 micromicrocoulomb by passing through a 0.0003-inch-thick plastic sheet.

A small shielded loop antenna, to be used as a probe for indicating and measuring radiofrequency interference fields from electronic equipment, has been analyzed. The input impedance is similar to an equivalent shorted two wire, balanced, transmission line. Voltage induced by a field conforms, over the usable frequency range, to that calculated by equations applicable at low frequencies, but the output voltage varies because of the transmission line effect. A number of loop probe designs have been analyzed and found to have undesirable characteristic impedance discontinuities which make calculation of their characteristics almost impossible. A method of calibration, which uses another small shielded loop to establish a radiofrequency field of known characteristics, has been developed, and its accuracy and reliability are proved experimentally. A simplified loop probe design has been found to be the most satisfactory. Loop probes of the approximate dimensions of those analyzed have been shown to be usable for the desired application at frequencies below approximately 400 Mc only, both because of unsatisfactory response characteristics and because of difficulties of calibration at higher frequencies.

A method using electrical resistivity measurements to determine the in situ porosity of marine sediments was investigated in the designed, fabricated and tested. Formation Factor-porosity relationships determined in the laboratory for three clays (kaolinite, illite, and montmorillonite), Providence silt, four sands, and four marine sediments showed that porosity was predicted within plus or minus 2 percent. The Formation Factors ranged from 1.1 to 5.9 while porosity ranged from 26 to 93 recent. The particle size and distribution influenced the electrical resistivity of these sediments independent of porosity while particle shape did not., Report on Porosity determination by electrical meons.

Two portable, lightweight instruments, operating on the principle of comparing the fixed electromagnetic characteristics of a reference transformer with the variable ones of a measured transformer, were evaluated for ability to locate and identify reinforcing steel in reinforced concrete. Both instruments were tested for locating reinforcing rods, identifying rods up to 1 in. in diameter with a cover of 2 to a in., and determining thickness of concrete cover to an accuracy of 1/4 in.

By use of the continuum theory of mixtures, a theory is presented for elastic conductors. The ionic lattice and electronic gas as separate continua constitute the members of the mixture. Balance laws and jump conditions are given, and a set of properly invariant constitutive equations are obtained and linearized. The field equations are solved for a problem of electrostatic probe, namely, a charged spherical cavity in a solid plasma.

The impedance characteristics of a capacitive ionospheric rocket probe have been determined as a function of the electron density, collision frequency, and temperature. The physical model used in developing the theory incorporated both effects of the ion sheath which forms about the rocket body and the anisotropic nature of the surrounding magnetoionic medium. Results are obtained and numerically evaluated to show that the sheath makes a very significant contribution to the impedance characteristics.

An analytical and experimental investigation of plasma magnetrons with smooth-bore anodes is described. Secondary-emission yield of several materials is investigated and the region in which limiting anode currents are obtained is related to the operation of conventional magnetrons. Basic phenomena caused by Philips ion-gage discharge particles are described, with particular emphasis on the sheath region. The phenomena underlying the build-up of anode cur rent are elucidated.

Physics status solidi v2 n7 p157-159 1962.