Marvin Swartz

Study of the X Rays Produced by a Vacuum Spark

The results of experiments on the x rays emitted by an energetic vacuum spark are presented. X-ray spectroscopic studies show, in addition to the characteristic x-ray lines of the electrode metal, lines originating from very high stages of ionization of the element. In particular, lines of the 1s2–1snp sequence in the helium-like spectra Ti xxi through Ni xxvii, and the 1s–2p transition in Fe xxvi, were observed. Pinhole photography and time-resolved studies of the total x-ray emission indicate that these highly ionized species originate in a small, hot region between the two electrodes, which is produced by a pinch in a plasma of evaporated anode metal.

Vacuum Ultraviolet Source

A low inductance three‐electrode spark source for the vacuum ultraviolet fed by a 20‐kV, 13‐μF capacitor is described. Its main feature is its ability to generate spectra of very high degrees of ionization. A 6‐kV spark produces spectra of CV and CVI as well as FeXVI, while a 17–18‐kV spark yields FeXVIII, AlXII, and AlXIII.

Diagnostic application of highly ionized iron lines in the XUV spectrum of a solar flare

Recent atomic data have been used to analyze a solar flare spectrum obtained with the Goddard Space Flight Centers grating spectrometer on the OSO-5 satellite. There exist in the wavelength region 90–200 Å strong lines from each of the ions Fe xviii-Fe xxiv. The Fe xxi lines can be used as an electron density diagnostic for the 107 K plasma. From our analysis of a particular flare, we find a steep positive slope in the emission measure between 106.5 and 107.2 K and an electron density of ∼4 × 1011 cm−3 at 107 K. We emphasise the need for high spectral and spatial resolution observations of solar flares in this wavelength region, which has to date been largely neglected.

Observations of n = 3 → n′ = 4 transitions in the Mg i and Si i sequences for elements chromium through zinc

Extreme ultraviolet spectra of 3p2-3p4d and 3p3d-3p4f transition arrays in twelve- and fourteen-electron ions, which differ by only a closed 3s2 subshell, are investigated in more detail than hitherto obtained for the elements chromium through zinc. The spectra were obtained with a two-meter vacuum spectrograph using a high-voltage spark source. Single- and multi-configuration calculations were carried out to compare predictions obtained for different model assumptions, and for the two different sequences.

Newly Identified Lines of Ni xviii, Cu xix, and Zn xx in the Na i Isoelectronic Sequence

Lines are reported belonging to Ni xviii, Cu xix, and Zn xx for the following transitions: 3s S2-4p P2°,   3p P2°-4s S2,   3p P2°-n1 d D2 (n1=4,5),         and         3d D2-n2f F2° (n2=4,5,6).Wavelengths, energies, and term values are given.

Measurements of an intensified CCD detector for the solar and heliospheric observatory

An engineering model intensified CCD detector for the SOHO Coronal Diagnostics Spectrometer has been built and tested at the NASA Goddard Space Flight Center. A windowless MCP intensifier tube converts EUV radiation (30 - 65 nm) into visible light, which is focused via a lens system onto a Tektronix 1024 X 1024 CCD. Tests have been made of this engineering model to determine the following characteristics: quantum efficiency, resolution, throughput, linearity, statistical variation, readout noise, scattering, and flat-field response. In almost all respects, the detector performed as expected. This detector has been delivered, and work is underway on the flight detector.

Observations of 3p 5 3d–3p 5 4f and 3p 6 3d–3p 5 3d4s transitions in iron, cobalt, nickel, and copper

Wavelengths of 3p53d–3p54f and 3p63d–3p53d4s transitions, in the range 60–120 A, have been remeasured in iron, cobalt, nickel, and copper. In the former array, some additional transitions of singlet type are tentatively identified. For the latter array the present wavelengths differ by about 0.04 A from values previously given in the literature for Nix.

Intensified CCD detector using the phosphor TPB

The Research Amplifying Imaging Detector consists of a microchannel plate image intensifier with a thin coating (3500-10,000 A) of the phosphor tetraphenyl-butadiene (TPB) on the entrance window to convert EUV radiation to visible, and coupled via a lens to a CCD detector. This design allows great flexibility in selecting the pixel size and field of view, with a simple mechanical design. The phosphor appears to be quite rugged, with no degradation having appeared during several months of testing both in and out of vacuum. Tests have been made at visible and EUV (304 A) wavelengths of the following performance aspects: EUV spectral sensitivity, spatial resolution (both of components and of the system as a whole), noise, linearity, and dynamic range. An improved detector for the Coronal Diagnostic Spectrometer experiment on the Solar Heliospheric Observatory satellite is being presently designed.