Carl Kenty

Production of 2537 Radiation and the Role of Metastable Atoms in an Argon‐Mercury Discharge

The average population of 63P1 mercury atoms is calculated from the measured 2537 output and resonance radiation diffusion theory. Average populations of 63P2, 0 are then found by comparing the absorptions of 5461, 4358, and 4047. Populations for a 0.42‐amp. discharge in 3.5‐mm argon of high purity plus Hg vapor at 42°C in a tube 1½ inches in diameter are for 63P2, 1, 0, respectively, 7.6×1011, 1.9×1011, and 3.5×1011 cm−3; these are ⅕, 1/20, and ⅕ of the corresponding Boltzmann populations, for the electron temperature of 11,100°K.Rates of collisions of the first and second kinds involving electrons (average concentration 2.1×1011 cm−3), and the 61S0 and 63P2, 1, 0 states are calculated using known excitation functions and detailed balancing. The results predict populations for 63P2, 1, 0 within 10 percent of those observed; they further predict that ⅔ of the observed 2537, ⅔ of the visible triplet, and ¾ of the 3650 group are produced stepwise via 63P. Quenching collisions involving argon are assumed neg...

Gas Temperatures and Elastic Losses in Low Pressure Mercury‐Argon Discharges

The increase ΔT in average gas temperature for ac and dc has been determined from measurements of the increase in pressure. A small McLeod gauge was used. Wall temperature was regulated. Corrections for end effects were made by comparing results for long and short tubes of 3.6 cm diameter. Assuming the radial variation of heat input to be parabolic, the temperature distribution was calculated using published values of heat conductivity K. From the results the heat input Pm per centimeter length was calculated. This value was compared with the elastic loss Pc computed from electron temperature Te and number of electrons Ne per centimeter column, taking into account the variation of mean free path with electron velocity. Good agreement was obtained for mercury pressures ranging from 1 to 25 microns, with the arc current 0.2–0.6 ampere and the argon filling pressure 3.5 mm (Hg).

On Convection Currents in High Pressure Mercury Arcs

Convection speeds in commercial high pressure Hg vapor lamps are measured by photographing on a moving film, the tracks of incandescent particles of CaO and MgO. A deep red filter and panchromatic film are used. The convection system is found to consist of a laminar flow of hot gas upward in the center and of cold gas downward near the walls. For the 400 watt lamp (p≅1 atmosphere, m = mass of Hg per cm of tube length = 11.5 mg cm−1) an upward speed of about 40 cm sec.−1 is found at the axis in the mid‐section of the lamp. The speed is somewhat greater near the bottom, this effect increasing with m. Speeds are found to increase somewhat less rapidly than in proportion to m as predicted. An approximate theory of these currents is presented, based largely on the work of Elenbaas, which accounts sufficiently well for the order of magnitude of the observed speeds. For similar discharges, speeds do not depend on the tube diameter but simply on m; for such discharges the watts lost by convection are proportional...

Clean‐Up and Pressure Effects in Low Pressure Mercury Vapor Discharges: A Reversible Electrical Clean‐Up of Mercury

Studies with the ionization gauge reveal that in a positive column discharge in Hg vapor at low pressure there occurs a type of reversible electrical clean‐up in which, under equilibrium conditions, a large and continuous exchange of Hg takes place between the space and the walls. The amount of Hg held temporarily in this way on the walls may be several times that in the gas phase. Thus if the current is suddenly stopped, the pressure may rise momentarily to several times its normal value; while if it is suddenly raised from a low value to a high one the lowering of the pressure may be so extreme as to cause surges across the arc or extinction of the arc (common occurrences during the starting of the Cooper Hewitt lamp). Evaporation from and condensation on free Hg surfaces, if these are at all limited in extent, are not rapid enough to prevent the effects. Electrophoretic and pressure effects are shown to be of great importance in these experiments. Thus in equilibrium, in a 2.1 cm tube, 1 m long, the pr...

DIFFUSE CONTINUA-EMITTING DISCHARGES IN THE RARE GASES WITH AND WITHOUT NITROGEN.

If a current the order of 1 mA is passed through 50–750 torr of a pure rare gas in a 10‐cm‐diam tube a diffuse discharge results filling the tube and emitting mainly a continuous spectrum, strong in the vacuum uv, weak in the near uv, visible and ir. The discharge is characterized by a very high voltage gradient and a substantially flat volt—ampere characteristic. The ion and electron concentration is 108−109 cm−3 and the electron energies are high. Energy losses are principally elastic and the ions and electrons reach the wall by ambipolar diffusion. The continuous spectra are of molecular origin. Continua from Xe, Kr, and Ar are whitish, that from Ne a light blue. In any of the above discharges if a critical current is exceeded the discharge goes to a filamentary form. The addition of 0.1% N2 to the pure rare gas has profound effects, lowering the gradient in Xe 18‐fold and bringing out the arc lines of Xe. New spectral structures are found at 3466 A, 3650 A, and at 1.3 μ which are believed to be due to...

Studies of Cataphoresis and Electrophoresis—Some New Effects

A study is made of the rate of transport of Hg in a uniform positive column in a mixture of a rare gas and Hg vapor. In one case, the phenomenon of retrograde cataphoresis is encountered, that of Xe+Hg at currents above 1 A, in which the Hg is carried to the anode end of the tube. In all other cases, the Hg is transported to the cathode end.A pulsating discharge is described in which the color changes from the red of Ne to the blue‐white of Hg and back again within a period of 1–2 sec. The boundary between the two colors travels along as a wave motion. This phenomenon is related to the properties of the tube walls and the nature of the ions striking them.When an ac discharge is passed through a cataphoretic mixture, the trace gas of lower ionizing potential is urged from the ends toward the center of the tube, e.g., Hg in Ar, Ne and Kr, but from the center to the ends in He+Hg. With a trace of Ar in He, the Ar is urged toward the center of the lamp. With Xe+Hg, the Hg may go either to the center or to the...

An Apparatus for Micro Gas Analysis

Gas samples of a few micron liters can be analyzed to within a few percent accuracy with the described system. Identification of components is made from condensation points, comparison readings of Pirani and McLeod gauges, and differences in speeds of flow. Condensation points at sub‐liquid nitrogen temperatures are had by evaporating liquid nitrogen at reduced pressures. Except for the removal of CO and H2 by ignition with O2, and O2 with a tungsten filament, chemical methods have been eliminated. Transfer of minute gas quantities is greatly facilitated by use of small mercury‐diffusion pumps.

Rugged Quartz Membrane Manometers of Small Volume

Fused quartz membrane manometers, used as null instruments, have been developed for measuring pressures of Hg, or other vapors (or gases) from a few centimeters of Hg to 50 atmospheres, with an accuracy of the order of 0.1 percent. The membranes are clear fused quartz disks, plane polished, 0.1 to 0.5 mm in thickness, and 0.5 cm to 2.5 cm in diameter. These are sealed onto fused quartz heads, either plane or slightly concave. In the first case, the motions of the diaphragms are magnified mechanically by a three‐legged rocker, the two outer legs of which rest on fixed bearings and the middle one of which rests on the diaphragm. The three legs being only slightly out of line, a high magnification (up to 6000) is obtained when a mirror and a long light path are used, or a pointer and a microscope are employed. In the second case, interference fringes set up between the diaphragm and the near‐by slightly concave quartz surface indicate the motions of the former. Volumes as small as 4 mm3 have been attained, a...