Hollow Cathode Gas Discharge Research Articles

Hyperfine structure and isotope shift measurements on spin-forbidden transitions of atomic gadolinium

We present the first measurements of the [Xe]4f75d16s6p$\;^{11}{F_J}$11FJ excited state hyperfine coefficients and isotope shifts of spin-forbidden transitions of atomic gadolinium (Gd) at 726 and 743 nm in a hollow cathode gas discharge. In addition, we performed a King Plot analysis to determine specific mass shift and field shift constants for these lines. Moreover, we observed King Plot nonlinearity for the 743 nm transition, which is an effect recently proposed to aid in searches for hypothetical new light bosons. Spectroscopic results obtained from this study will facilitate the development of more efficient isotope separation techniques, enable narrowband laser cooling of Gd for novel dipolar physics investigations, and foster technological advances in high precision atomic clocks and quantum enhanced metrology.

High-Power Compact <inline-formula> <tex-math notation="LaTeX">$P$ </tex-math></inline-formula>-Band UHF Oscillator Based on Hollow Cathode Discharge

This paper describes a novel high-power ultra high frequency oscillator based on hollow cathode gas discharge. The oscillator generates the pulses with a carrier frequency of 380 MHz, power of 390 kW, and pulse duration of 450 ns. The oscillator has been tested in a pulsed-periodical regime with a pulse repetition rate of 2.5 kHz. The lifetime of the oscillator is 10 7 pulses. The oscillator has been tested for operation into radiating three-element array of dipole antennas. These tests showed the oscillator and antenna array compliance.

High-current electron beam in a hollow-cathode gas discharge at elevated pressures (∼100 Torr)

A discharge with plasma filling a flat-bottom cavity of depth δ in the cathode, partly closed by a dielectric plate with a hole (determining the aperture of the discharge between the cavity bottom and the anode), has been studied. In a discharge cell of type 1 with δ = 0.5 mm and a hole diameter of 22 mm, a pulsed electron beam was obtained with a duration of t EB = 700 ns and a beam current j EB approximately 10 times greater than that (j AD) of the equivalent anomalous discharge (at fixed discharge voltage U and gas pressure p He = 3.5 Torr). An electric field with the direction opposite to the field of applied voltage appeared at the cathode that was related to a space charge formed at the cathode plasma boundary, which could not follow a rapid drop of voltage across the discharge gap. In a discharge cell of type 2 with δ = 0.5 mm and a narrow slit (S = 0.1 × 5 cm2) in the dielectric plate, a pulsed electron beam was obtained with a duration of t EB = 2 ns and a beam current of j EB = 0.7 kA/cm2 (j EB/j AD = 1.5) at U = 4.2 kV and p He = 50 Torr.

Transport properties of ground-state aluminium atoms in hollow cathode gas discharge plasma

For investigation of Al atoms transport properties a pulse-periodic longitudinal hollow cathode gas discharge in cylindrical geometry is used. The cathode represents a 20 cm in length and 1.8 cm in inner diameter hollow aluminium cylinder. During the discharge Al atoms are sputtered from the wall into the cathode volume, while in the afterglow phase their concentration decreases due to diffusive losses back to the wall surface. The diffusive loss rates at different buffer gas pressures are measured by using a double-channel time-resolved optical absorption technique with gated photon counting. By relating the experimental loss rates with a diffusion model based on the experimental geometry and a boundary condition of the third kind, the diffusion coefficient of ground-state Al atoms in argon, as well as the reflection coefficient of these atoms from the cathode surface are obtained. The experimental value for the diffusion coefficient at 313 K temperature and 133 Pa argon pressure is D0 = 160 ± 30 cm2s−1. The reflection coefficient was found to be in the range: 0.2 < ρ < 0.82. The result for the diffusion coefficient is compared with theoretical results based on 12-6 Lenard-Jones and rigid-sphere inter-atomic interaction model.

Diffusion of Sputtered Ground-State Tungsten Atoms in Krypton

The work is dedicated to investigations of the diffusive transport of sputtered ground-state tungsten atoms in buffer gas krypton at ambient temperatures. For sputtering of the metal, a pulse-periodic longitudinal hollow cathode gas discharge in cylindrical geometry is used. The cathode represents a 20 cm in length and 2.6 cm in diameter hollow copper cylinder, the inner surface of which is coated with a thin tungsten layer. During the discharge W atoms are sputtered from that layer into the cathode volume, while in the afterglow phase their density decreases due to diffusive losses back to the surface. The diffusive loss rates are measured by using a time-resolved double-channel optical absorption technique. By relating the experimental loss rates with a diffusion model based on the experimental geometry and a boundary condition of the third kind, the following value for the diffusion coefficient of W atoms in krypton is obtained: D0 = 130+40−30 cm2s−1 at 133 Pa buffer gas pressure and 315 K temperature. The reflection coefficient of these atoms at the cathode surface is obtained within the range 0 ⩽ ρ ⩽ 0.8. The experimental results for the diffusion coefficient are compared with theoretical calculations based on model interaction potentials.

High-power pulsed high-frequency generator based on the hollow-cathode discharge

We describe a high-power high-frequency generator based on the hollow-cathode gas discharge. In the frequency range from 10 to 30 MHz, the output-signal power of this simple device with a cold cathode reaches 1 MW. The duration of the high-frequency pulse ranges from 0.4 to 1 µs.

A high-power, high-frequency pulse generator based on a hollow-cathode discharge

A high-power high-frequency generator based on a hollow-cathode gas discharge is described. This simple device, equipped with a cold cathode, produces high-frequency pulses with up to 200-kW of power in a frequency band of 20–60 MHz. The duration of the high-frequency pulses varies from 0.5 to 1.5 μs.

Studies of Diffusion Losses in Gaseous Media Using a Boundary Condition of the Third Kind

The application of two approaches for the simultaneous measurement of diffusion and reflection coefficients of particles in gaseous media is carried out using one and the same data set. Both approaches are based on the analysis of the effective lifetimes of particles measured under different experimental conditions and implement a boundary condition of the third kind. The experimental data used are those of Mg atoms diffusing in neon and argon. These were obtained by a pulsed afterglow technique using a hollow cathode gas discharge. The results obtained after processing the data by the two methods are found to show good agreement.

Energy analysis of electron beams from perforated-mesh hollow-cathode gas discharge guns

The operating characteristics of perforated-mesh hollow-cathode gas discharge electron guns (hc guns) have been investigated paying particular attention to the energy spectrum of the electrons forming the beam. While it was found impractical to attempt a complete systematic study, sufficient quantitative data was obtained to apparently confirm certain findings made by Boring and Stauffer in 1963 relating to the potential of the plasma within the cathode. Further observations made visually help towards a more complete understanding of the operation of the gun.There are similarities between the spectra produced by this gun and those produced by the hollow-anode (ha) gun. The most obvious difference is that electrons from the hc gun lie within one of two distinct energy ranges, both of which are often present, while in the case of the two-electrode ha gun only one range is present. Of these two energy groups one is associated with the full cathode to anode potential difference while the other seems to be the result of acceleration from the internal cathode plasma potential to anode potential.It has been found that similar, but not identical, spectra can be obtained from an ha gun modified to include a third electrode at a potential near that of the cathode. This also indicates that the electrons from the hc gun are produced at two different sites and that the mechanism which is necessary for the production of electrons in the ha gun also operates in the hc gun.