Intensity Of He Research Articles

Sounding rocket observation of helium 304- and 584-A glow

The altitude distribution of the extreme ultraviolet emissions of neutral helium (He 584 A) and singly ionized helium (He+ 304 A) was measured by aluminum and bismuth thin-film photon counters aboard an exospheric sounding rocket flown from Uchinoura, Japan, on September 19, 1970, 2030 JST. On ascent the He 584-A intensity increased from 40 to 100 R between 250 to 720 km and then decreased gradually to 30 R at 1600 km. On the downleg the intensity remained nearly constant at 5 R between 1400 and 600 km and then decreased gradually to about 2 R at 440 km. The excitation mechanism of the He 584-A glow is ascribed to resonance fluorescence of atmospheric helium by solar 584-A radiation. The observed distribution is consistent with a diffusive equilibrium distribution of helium at a thermopause temperature of 1180±50°K and having a base-line value of density of (1.2±0.2)×106 atoms/cm3 at 720 km. The intensity of He+ 304-A glow decreased from 12 to 4 R on ascent from 420 to 1200 km and then remained almost steady at 1.5±0.5 R through the same altitude range on descent. The absolute intensity of the 304-A flow was at least 2.5 times greater than expected from resonance fluorescence by ionospheric helium ions of solar 304-A radiation. Evidence for the presence of extraterrestrial helium glow is discussed.

Spectrographic Measurements of a Pulsed Arc

A Kerr cell shutter has been used with a photographic spectrograph to do time-resolved studies of an arc discharge in 2.5 Torr of helium with air impurity. The arc had a peak current of 40 kA and a period of 40 μsec. Temperatures were obtained from line intensity ratios of NII, NIII, OII, CII, CIII, and electron densities from Stark broadening measurements. Plasma temperatures were found to reach a peak in the first few μsec and decline thereafter. For an unconfined arc, Ne declined in time, whereas for a confined arc (tube diam 8–13 mm) the initial temperature was higher (as much as 3.8 eV), and its decline was accompanied by an increase in Ne (from 1017 to 1018 cm−3) due to wall erosion. The intensity of He I 5876 was anomalously low at first. This is interpreted as a temperature deficiency in neutral helium which decreases as time goes on, reaching equilibrium in some 30 μsec.

Measurement of Recombination-Rate Coefficient ofHe++

The rate of recombination of doubly ionized helium in the afterglow of a $C$ stellarator discharge is deduced from measured light intensities of He II and He I, emitted by recombining ${\mathrm{He}}^{++}$ and ${\mathrm{He}}^{+}$. The electron temperature and the ${\mathrm{He}}^{++}$ and ${\mathrm{He}}^{+}$ and electron densities are determined from the Saha equations for the highly excited states and the condition of charge neutrality. The electron density is also measured directly with a 4-mm microwave interferometer. The rate of recombination of ${\mathrm{He}}^{+}$ is found to be in good agreement with previous measurements, at temperatures 0.25 eV. At higher temperatures, where ${\mathrm{He}}^{+}$ and ${\mathrm{He}}^{++}$ are both present, the recombination rate is found to follow a ${Z}^{3}$ relationship. The measurements appear to be in quite good agreement with the calculations of Bates, Kingston, and McWhirter over the entire range of measurement.

Determination of Temperature in a Toroidal Theta Pinch Discharge with an Image Converter Camera

With an image converter camera, developed at the Instituut voor Plasma-Fysica, streak pictures have been made of toroidal θ-pinch discharges in helium at pressures ranging from 0.01 to 0.06 torr. The discharges are produced by a capacitor bank of 2.5 kJ. From the pictures the acceleration of the outward drifting plasma column and the drift time (1 to 2 μs) have been measured. From these quantities the mean plasma temperature after the compression has been determined. The temperature depends on the pressure and varies from about 5 x 105°K at 0.01 torr to 105°K at 0.06 torr. These results are compared with temperatures calculated from the irreversible heating during the compression. From spectroscopical measurements of the intensities of He II λ = 4686 Å and He I λ = 5015 Å the electron temperature is estimated and the assumption of complete ionization is checked.

A Note on the Intensities of he i in P Cygni

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Note on the Intensities of He I in P Cygni Schwede, Harold F. Abstract The total areas for absorption and emission of λ4388 and λ4472 of the He I spectra of P Cygni are given from measurements of eight plates. The ratio of the averages of λ4472_abs/λ4388_abs=1.1 while λ4472_em/λ4388_em=9.8. Publication: The Astrophysical Journal Pub Date: June 1933 DOI: 10.1086/143480 Bibcode: 1933ApJ....77..348S full text sources ADS |