Pierce Type Research Articles

Theory of a low magnetic field gyrotron (gyromagnetron)

The stability of a relativistic electron layer inside a magnetron waveguide is examined. The dispersion relationship for the cyclotron maser/negative mass instability in this "gyromagnetron" device is derived, using a Pierce type analysis. The coupling constant e between the electron beam and the waveguide circuit is computed. Based on a study of ~, we design a proof-ofprinciple experiment for a gyromagnetron amplifier which operates at the sixth cyclotron harmonic, thereby reducing the magnetic field requirement by a factor of six. The operating beam voltage is relatively low. The problem of mode competition is examined, but is found to be not serious. The design procedure is described.

Two electron guns with adjustable beam compression and perveance

Abstract Two electron guns have been designed by computer simulation, in order to produce high density electron beams focused by a superconducting solenoid. A spherical impregnated tungsten cathode is used in a high perveance Pierce type gun, whereas a Rogowski type gun of low perveance may be operated with a directly heated tantalum strip. By variation of the Wehnelt electrode bias both guns are adjustable in the compression—perveance relation with tolerable deterioration of the beam quality.

Method of Active Charge and Current Neutralization of Intense Ion Beams for ICF

Intense ion beam neutralization by sufficiently cold, co-moving and co-injected electrons is crucial to Light Ion and important to Heavy Ion Inertial Confinement Fusion (ICF) drivers for the ballistically focused propagation onto ~ 5 mm radius targets located some 10 m downstream. Methods of generating the beam neutralization electrons with required properties are given in the context of a Light Ion Fusion Experiment (LIFE) designed accelerator. Recently derived envelope equations for neutralized and ballistically focused intense ion beams are applied to the LIFE geometry in which 10 MeV He+ multiple beamlets coalesce and undergo 45:1 radial compression while beam pulses experience a 20:1 axial compression in the propagation range of 10 m. For these representative conditions, the theoretical analysis produces a requirement of the initial electron temperature neutralizing the ions as Teo ≤ 35 eV where also the initial ion temperature T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">io</sub> is correlated. Both active and auto <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> -neutralization methods are examined and found to produce initial electron temperatures consistent with the requirement of the envelope equation for both radial and axial adiabatic beam pulse compressions. The stability of neutralized beam propagation is also examined concerning the Pierce type electrostatic instability and for the case of LIFE beams it is found to have insignificant effect. A scaled experimental setup is presented which can serve to perform near term tests on the ballistically focused propagation of neutralized light ion beams.

Spectral and dosimetric characteristics of soft X rays for studies in radiobiology.

A DEMOUNTABLE x-ray generator has been developed to investigate the radiobiological effects of soft x rays (1). This generator (Fig. 1) is capable of operating with high D.C. currents at relatively low potentials (e.g., up to 500 MA at 6 kV). I t consists of a Pierce type electron gun (2) and a water-cooled target. The use of the gun permits a large current even at an 11.5-cm target-cathode spacing. This large spacing is required to prevent deposition on the target of a significant amount of tungsten evaporated from the filamentary cathode. Such a deposit would change the target from the selected material to tungsten. The target is constructed from a hollow copper cylinder of square cross section. Each face of the cylinder forms one target and the target material is applied to the copper by vacuum evaporation. The design permits the use of each of the four different target materials without disturbing the vacuum. A thin composite window formed by a beryllium foil and a Mylar film isolates the high vacuum ...

Magnetic compression of axially symmetric Brillouin-focused electron beams

A study has been made of high-current density Brillouin-focused electron beams formed with magnetic compression. Analysis of the problem was by numerical calculation of electron trajectories using a digital computer. Electrostatic field data were measured using a resistance network analog. The effect of the magnetic field was calculated as an equivalent potential. An experimental system based on the results of the analysis was designed and tested. A Müller-type electron gun was found to provide a more uniform current density than a corresponding Pierce type. Experimental results were in close agreement with design objectives. For an area magnetic compression of 10 to 1, a focused beam approaching ideal Brillouin flow was achieved.

An analysis of thermal and space-charge spreading of electron beams from Guns of the pierce type

An existing technique for analyzing the spreading of an electron beam in a drift space is extended to be valid for regions with an arbitrary variation of potential. Equations enabling the complete profile of the beam to be computed are presented.

Untersuchungen für ein FFAG-elektronensynchrotron vom radialsektortyp (endenergie um 150 MeV): III. Injektion

For a FFAG accelerator of the radial sector type with an end energy of 150 MeV the radius of injection and the radial aperture of the magnets are evaluated and the limitation at injection due to Liouville's theorem, space charge and tolerable energy spread are considered. Injection below and above transition energy is discussed. The maximum space charge limited current for injection at 200 keV is 2.5 A. The repetition rate is limited to 50 or 100 cps (the last value holds when divided accelerating electrodes are used). The resulting mean output current is 2.5 μA or 5 μA and can be raised by a factor of five when storage and accumulation of particles at a medium energy is employed. Injection above transition energy (about 5 MeV) makes possible a repetition rate of 200 to 300 cps. The mean output current is then about 40 μA. A Pierce type injector for a pulse voltage of 200 kV and a pulse current up to 10 A has been constructed and investigated. The pulse current is space charge limited. The energy spread of the injected beam is smaller than ±0.5%, the stability of the pulse voltage is better than ±0.5%, the stability of the mean output current is ±1%.

High Current Duoplasmatron Ion Source with Ferrite Permanent Magnets

A duoplasmatron ion source capable of producing about 12 mA of hydrogen ions has been constructed and tested. The source uses ferrite permanent magnets and a low voltage, Pierce type extraction lens system.

Design of a Mercury Vapor Target X-Ray Tube

A mercury vapor target x-ray tube has been constructed and utilized for bremsstrahlung studies. An electrically heated boiler at the bottom of the target chamber vaporizes mercury which is expanded through a nozzle to form the target. The mercury jet expands into a water-cooled condenser at the top of the target chamber and the liquid mercury is returned to the boiler. A Pierce type electron gun provides the bombarding beam which exits from the high vacuum beam-formation region through a 3-mm-diam aperture into the higher pressure target chamber. The radiation produced can be observed from ports in the target chamber wall. The apparatus is operable up to 30 kV with beam currents as high as 50 mA. The equivalent solid thickness of the target ranges up to 500 Å, which yields a photon intensity near the high frequency limit comparable to that from a solid target. Design and operational features of the device are discussed.

Electrostatic Focusing Systems for Intense Electron Beams

ABSTRACTThis paper describes the electrostatic systems for the focusing of intense electron beams, based on Pierce's principles. Analytical calculation of the shape of electrodes for the strip and cylindrical beams is carried out. Problem of focusing is discussed for beams of large length by means of a periodic electrostatic system composed of elementary Pierce's type lenses.

The KS-3 MeV Van de Graaf injector of the Frascattielectron synchrotron

Abstract The modifications apported to a standard 3 MeV Van de Graaff, used as injector for the 1100 MeV Frascati synchrotron, are reported. They concern the voltage stabilizer, a compensation circuit that takes care of the fast variations of the voltage at the belt frequency, and the Pierce type electron source. A few data concerning the synchrotron operation in the period Jan. 1–Aug. 31, 1960, are added. Finally it is shortly described the project of a storage ring for 250 MeV electrons and positrons which being built in Frascati.

Comment on a paper by D. E. Radley, “ The Theory of the Pierce Type Electron Gun ”

Comment on a paper by D. E. Radley, “ The Theory of the Pierce Type Electron Gun ”

"Two backward wave local oscillators"

The present paper describes the development of two low-power backward wave oscillator tubes covering the frequency range 7.6-12.4 kmc/sec, and 11.6-18.0 kmc/sec. The initial design of the tube geometry is based on a Pierce type analysis for the starting current and frequency, which includes the effects of space charge and circuit loss, as well as the effect of the dielectric loading of the support structure. After successful completion of the X-band tube, scaling was employed to arrive at the proper dimensions of the high frequency tube. These tubes employ unifilar helix circuits, hollow beams, modified Pierce type electron guns using impregnated cathodes. A sectioned air-cooled electromagnet package consuming approximately 200 watts provides for the necessary confining magnetic field, while permitting the use of waveguide coupling throughout. The total weight of the magnet and tube assembly is 7 pounds. A helix-to-waveguide match with a maximum VSWR of 2:1 was developed resulting in very smooth tuning and power output curves. Minimum power outputs in the X- and Ku-band tubes are approximately 50 and 25 milliwatts, respectively, and power variations in the frequency range are about 4:1. Ten such tubes in each range were built and the results are discussed in detail.

A Detailed Analysis of Beam Formation with Electron Guns of the Pierce Type

The theory of Cutler and Hines is extended in this paper to permit an analysis of beam-spreading in electron guns of high convergence. A lens correction for the finite size of the anode aperture is also included. The Culter and Hines theory was not applicable to cases where the effects of thermal velocities are large compared with those of space charge and it did not include a lens correction. Gun design charts are presented which include all of these effects. These charts may be conveniently used in choosing design parameters to produce a prescribed beam.

An Improved Apparatus for the Direct Measurement of the Absorption of Sound in Gases

Apparatus has been designed and built for measurements in absorptive gases such as carbon dioxide and nitrous oxide. Measurements are made of the sound pressure by a microphone as it is moved away from a piston source vibrating in a large baffle. The resulting pressure-distance curves are recorded photographically and yield the absorption coefficient, after a correction, owing to divergence, is made. The source is a magnetostrictive rod driven by an improved Pierce type oscillator. The range of frequencies covered is 22 to 112 kc. Reflections from the walls of the measuring chamber are reduced materially by specially designed glass baffles. A magnetic drive is employed to move the microphone, eliminating packing glands and providing a constant volume chamber for the measurements. A milliampere meter movement is used in the recorder, making possible comparatively rapid recordings. The microphone was built up from a single bender type Rochelle salt bimorph element. The apparatus has been used in measuring the absorption of sound in carbon dioxide and nitrous oxide.