Rarely, in the press of day-to-day scientific work, is there a quiet moment to stand back and survey our part of the geophysical landscape These quadrennial reviews, it seems to me, are the ideal place in which to do so But too often we have had a deadening recitation of details rather than a lively forum I could not write that kind of review

Atmospheric radiation: 1975–1983

A method to determine the spectral irradiance of a radiation source in the vacuum ultraviolet through the use of recently developed spectral-radiance standards is described. The method has been applied between 138 and 310 nm, and the spectral irradiances of several different light sources have been measured on an absolute scale with estimated uncertainties less than 10%.

Vacuum-ultraviolet spectral-irradiance calibrations: method and applications

In this work, we study a cascaded arc in argon that is used as a broadband light source for spectroscopic applications. In this arc, the arc channel is geometrically constricted. A numerical model is used to investigate the plasma parameters and light output of the arc. It is found that constricting leads to a higher electron density in the constricted area, which strongly enhances the local broadband emission of the plasma. A parameter study, in which the current is varied, is performed. The simulated arc voltages are compared with measured arc voltages, and excellent agreement is found. Furthermore, it is found that the emissivity increases strongly for increasing current, making the current a suitable control parameter to control the light output of the arc.

https://iopscience.iop.org/article/10.1088/0963-0252/15/4/033/pdf

Modelling of a pinched cascaded arc light source using argon

To realize a novel vacuum-atmosphere interface that does not require a large differential pumping system, a robust cascade arc discharge source called a plasma window is constructed and tested for long-term operation. By modifying a test plasma with a direct current discharge, a vacuum interface with a high gas pressure ratio of 1/407 between the discharge and expansion sections is demonstrated for currents as high as 20 A. No significant damage to the electrodes is observed during the operation. Analysis of the visible emission spectra reveals that a stationary, stable argon plasma having a temperature of 1 eV and a density of 1.5 × 1016 cm−3 is generated in the plasma channel.

Development of a cascade arc discharge source for an atmosphere-vacuum interface device.

We develop two cascade arc plasma sources for application to plasma windows for virtual vacuum interfaces. For windowless vacuum–atmosphere separation, a compact arc discharge source having a channel diameter of 3 mm is fabricated, and an atmospheric Ar thermal plasma is generated. For an alternative differential pumping system, separating low- and high-pressure vacuum chambers, a larger arc device with an 8-mm diameter is also constructed, producing a high-density He plasma. The performances of the two cascade arcs as plasma windows are investigated. The 3-mm arc discharge generates a steep pressure gradient of Ar 100 kPa–100 Pa through the discharge channel, while the 8-mm discharge apparatus isolates the high-pressure side at 7 kPa from the lower pressure of 54 Pa. Emission spectroscopy of visible and vacuum UV radiation reveals the characteristics of the Ar and He plasmas. Spectral analysis yields a plasma temperature of around 1 eV in both discharges. Stark broadenings of the H-β and Ar I lines give an electron density of 6.5 × 1016 cm−3 for Ar 60 A with a gas flow rate of 1.0 l/min and 4.7 × 1013 cm−3 under a He 100-A and 0.45-l/min condition.

High-density cascade arc plasma sources for application to plasma windows for virtual vacuum interfaces

A VUV calibration facility is described By means of this equipment, measurement of the responsivity of radiation detectors in the spectral range from 90 nm to 250 nm is possible The measuring method makes use of a wall-stabilized Ar-cascade arc as a standard radiator, and by measuring the spectral transmittance of the optical arrangement, the monochromatic radiant flux, which reaches the detector or the detector system, can be given The spectrum of the Ar arc in particular is investigated in the lambda < 125-nm spectral range

Calibration of radiation detectors in the VUV using a wall-stabilized Ar-cascade arc

The work described in this paper covers an intercomparison of absolute irradiance calibration methods applied at the U.S. National Bureau of Standards (NBS), the SRC Appleton Laboratory, Astrophysics Research Division (ARD), the Max-Planck-Institut fuer Extraterrestrische Physik (MPE), and the Physikalisch-Technische Bundesanstalt (PTB). This was done by determining the MPE and PTB quantum efficiencies of two different calibrated transfer standards developed by the NBS and ARD. The comparison shows that the calibrations agreed within the estimated bounds of uncertainty and also suggests that the uncertainty in the measured electron temperature required in the argon arc source technique may be less than was estimated.

H. Kaase

Papers

Calibration of radiation detectors in the VUV using a wall-stabilized Ar-cascade arc

Intercomparison of radiometric irradiance scales in the 90-250-nm wavelength range.