Fluid mixing technique increases the gain and output power of carbon dioxide laser systems

High speed flowing gas system provides uniform mixing in short times compared to flow transit times and carbon dioxide vibrational relaxation times. This system minimizes the effects of surrounding surfaces and provides a uniformly high gain that is independent of dimensions transverse to the flow direction

Recombination rates and non-equilibrium electrical conductivity in a seeded plasma

Experimentally determined values of electrical conductivity and electron temperature have been measured in a non-equilibrium seeded plasma. These results are in good agreement over a wide range of parameters with values calculated from a two-temperature model of the plasma. There is no doubt that the two-temperature model is valid over a wide range of gas temperatures, seed concentrations, and current densities for the argon-potassium and helium-potassium plasmas. However, the model does not give an accurate description of the plasma when the current density is below about 0.4 amp/cm^2; in this range the omission of the influence of atom-atom excitation and the influence of non-equilibrium excited state populations may explain the discrepancy between experiment and theory. In addition, the electron-elecron-ion collisional recombination rate for potassium has been measured in the argon-potassium system. The range of electron temperatures investigated was between 1900° K to 3000° K with electron densities between 3X10^(13) and 4x10^(14)/cm^3. The measured values show a scatter of 60 per cent about theoretical values calculated from present recombination-rate theory employing the Gryzinski classical collision cross sections

Experiments Concerning Nonequilibrium Conductivity in a Seeded Plasma

Measurements of conductivity have been made in a plasma composed of argon seeded with potassium vapor. The gas temperature was 2000°K; the pressure, 1 atm; and the potassium concentration was between 0.22 and 0.80 mole-percent. Conductivity values, calculated from a two-temperature model in which the energy dependence of the cross sections and radiation losses from the plasma are taken into account, agree well with experimental values. Measured values of the plasma temperature appear to be about 10% less than predicted values. Relaxation times for the conductivity in response to a step function change in the electric field were proportional to (n_e0l/σ_0E^2) and were a few tens of microseconds for a field strength in the range 3 to 10 v/cm. The ionization rate appeared to be limited primarily by the heating rate for the plasma, and the short relaxation times suggest that ionization occurs by a multistep process. Analysis of conductivity and light intensity data obtained during the transient period indicates that the electron temperature approaches its final value during the first few microseconds

Molecular energy transfer by fluid mixing Progress report, 1 Jan. 1968 - 1 Jan. 1971

CW chemical laser development, N2-C02 electrically excited fluid mixing laser techniques, and gas dynamic mixing behind shock wave

The AGN Contribution to the Mid-IR Emission of Luminous Infrared Galaxies

We determine the contribution of AGN to the mid-IR emission of luminous infrared galaxies (LIRGs) at z>0.6 by measuring the mid-IR dust continuum slope of 20,039 mid-IR sources. The 24 micron sources are selected from a Spitzer/MIPS survey of the NOAO Deep Wide-Field Survey Bo\"otes field and have corresponding 8 micron data from the IRAC Shallow Survey. There is a clear bimodal distribution in the 24 micron to 8 micron flux ratio. The X-ray detected sources fall within the peak corresponding to a flat spectrum in nufnu, implying that it is populated by AGN-dominated LIRGs, whereas the peak corresponding to a higher 24 micron to 8 micron flux ratio is likely due to LIRGs whose infrared emission is powered by starbursts. The 24 micron emission is increasingly dominated by AGN at higher 24 micron flux densities (f_24): the AGN fraction of the z>0.6 sources increases from ~9% at f_24 ~ 0.35 mJy to 74+/-20% at f_24 ~ 3 mJy in good agreement with model predictions. Deep 24 micron, small area surveys, like GOODS, will be strongly dominated by starburst galaxies. AGN are responsible for ~ 3-7% of the total 24 micron background.Comment: 6 pages, accepted for publication in Ap

The Mid-IR and X-ray Selected QSO Luminosity Function

We present the J-band luminosity function of 1838 mid-infrared and X-ray selected AGNs in the redshift range 0<z<5.85. These luminosity functions are constructed by combining the deep multi-wavelength broad-band observations from the UV to the mid-IR of the NDWFS Bootes field with the X-ray observations of the XBootes survey and the spectroscopic observations of the same field by AGES. Our sample is primarily composed of IRAC-selected AGNs, targeted using modifications of the Stern et al.(2005) criteria, complemented by MIPS 24 microns and X-ray selected AGNs to alleviate the biases of IRAC mid-IR selection against z~4.5 quasars and AGNs faint with respect to their hosts. This sample provides an accurate link between low and high redshift AGN luminosity functions and does not suffer from the usual incompleteness of optical samples at z~3. We find that the space density of the brightest quasars strongly decreases from z=3 to z=0, while the space density of faint quasars is at least flat, and possibly increasing, over the same redshift range. At z>3 we observe a decrease in the space density of quasars of all brightnesses. We model the luminosity function by a double power-law and find that its evolution cannot be described by either pure luminosity or pure density evolution, but must be a combination of both. Our best-fit model has bright and faint power-law indices consistent with the low redshift measurements based on the 2QZ and 2SLAQ surveys and it generally agrees with the number of bright quasars predicted by other LFs at all redshifts. If we construct the QSO luminosity function using only the IRAC-selected AGNs, we find that the biases inherent to this selection method significantly modify the behavior of phi*(z) only for z<1 and have no significant impact upon the characteristic magnitude M*_J(z).Comment: Corrected minor typo in equations (4) and (6). Accepted for publication in The Astrophysical Journal. 56 pages + 6 tables + 16 figure

Ground and space-based study of two globular cluster CVs: M22 CV1 and M5 V101

As a class of compact binaries with large binding energy, cataclysmic variables formed through close encounters play an important role in the dynamical evolution of globular clusters. As part of a systematic search for CVs undergoing dwarf nova eruptions in globular clusters, our 2004 monitoring programme of M22 detected an outburst of the dwarf nova candidate CV1 during May. We implement the ISIS image subtraction routine to obtain a light curve for an outburst of CV1. We present the outburst light curve as well as HST/WFPC2 photometry in the V, U and near ultra-violet (nUV) bands and a Chandra/ACIS-S spectrum of the object. Our results confirm the DN nature of the outburst and the CV status of the object. We also present the results of a ground-based study of another globular cluster CV, M5 V101 - including quiescent medium-resolution WHT/ISIS spectroscopy in the B and R bands, displaying prominent Balmer and HeI emission, and R-band photometry.Comment: 12 pages, 11 figures. Accepted for publication in MNRA

Another Faint UV Object Associated with a Globular Cluster X-Ray Source: The Case of M92

The core of the metal poor Galactic Globular Cluster M92 (NGC 6341) has been observed with WFPC2 on the Hubble Space Telescope through visual, blue and mid-UV filters in a program devoted to study the evolved stellar population in a selected sample of Galactic Globular Clusters. In the UV $(m_{255}, m_{255}-U)$ color magnitude diagram we have discovered a faint `UV-dominant' object. This star lies within the error box of a Low Luminosity Globular Cluster X-ray source (LLGCX) recently found in the core of M92. The properties of the UV star discovered in M92 are very similar to those of other UV stars found in the core of some clusters (M13, 47 Tuc, M80, etc)---all of them are brighter in the UV than in the visible and are located in the vicinity of a LLGCX. We suggest that these stars are a new sub-class of cataclysmic variables.Comment: 21 pages, 4 figures. Astrophysical journal in pres