Initial ionization rates in shock-heated Argon, Krypton, and Xenon

The rate of ionization behind strong shock waves in argon, krypton, and xenon, is observed by a transverse microwave probe, over a range of electron densities low enough that atom-atom inelastic collisions are the rate-determining mechanism. Shocks of Mach number 7.0 to 10.0 propagate down a 2-in. sq. aluminum shock tube into ambient gases at pressures of 3.0 to 17.0 mm. Hg., heating them abruptly to atomic temperatures of 5500°K to 9600°K. The subsequent relaxation toward ionization equilibrium is examined in its early stages by the reflection, transmission, and phase shifts of a 24.0 Gc/sec (1.25 cm) transverse microwave beam propagating between two rectangular horns abreast a glass test section. The data yield effective activation energies of 11.9 ± 0.5 eV for argon, 10.4 ± 0.5 eV for krypton, and 8.6 ± 0.5 eV for xenon. These coincide, within experimental error, with the first excitation potentials, rather than the ionization potentials of the gases, indicating that in this range ionization proceeds via a two-step process involving the first excited electronic states of which the excitation step is rate controlling

Response of electrostatic probes to ionized gas flows in a shock tube

In his excellent analysis of electrical measurements in shock tube flows, Hollyer(1) has demonstrated certain pitfalls in the application of conventional Langmuir probe techniques to the evaluation of charge densities in the moving stream of hot gas confined within the tube walls. The purpose of this note is to describe somewhat similar experiments which illustrate other eccentricities in probe behavior under these conditions

Acceptance and Motivational Impact of the Organic Certification System

In recent years the institutional framework of the organic certification system has step by step become a more formal and state run system. Our research shows that al-though the majority of the farmers accept the system, they are not convinced of its cost-benefit relationship. Farmers prefer a more association- and advice-oriented control of the organic certification process

Exploratory electromagnetic thruster research, phase 3, 23 June - 23 December 1969

Performance evaluation of MPD arc jets operating in quasi-steady mode

Recent advances in MPD thruster research at Princeton

A summary of last years anode, plasma, and cathode findings is presented. A summary of this years activities and findings is also presented. A brief discussion of previous and current understanding is given and covers the following topics: existence of microinstabilities; the scaling of Va with the Hall parameter; the scaling of anomalous resistivity with the Hall parameter; the relation between anomalous resistivity and the anode drop; the presence of turbulence in the anode region; numerical simulation with anomalous transport; the use of magnets to decrease dissipation; performance testing with the new anode; the mechanisms behind the ionization sink; and lithiated cathode research

Investigation of pulsed quasi-steady MPD arc jets

Evaluation of magnetohydrodynamic arc thrusters operating in quasi-steady mode with electrode vapor as propellan

The cathode region of a quasi-steady magnetoplasmadynamic arcjet, supplement 8

Electric and magnetic field measurements in cathode region of quasi-steady magnetoplasmadynamic arcje

Significance of the Sm-Nd isotopic systematics of the Akilia Association

Samarium-Neodymium analyses were carried out on fourteen samples of basic to ultrabasic metavolcanics from several enclaves of the Amitsoq gneisses (T = to or approximately 3,700 Ma). Field observations suggest that all the analyzed rocks belong to the pre-Amitsoq Akilia Association. Consequently, a minimum age of 3,700 Ma is postulated for the emplacement of their protoliths. When all the data points are put together in a conventional isochron diagram, no clear isochron relationship can be discerned. However, the points seem to fall within a band broadly corresponding to an age of 3,600 Ma. The isotopic results are difficult to interpret satisfactorily. Two contrasting interpretations are offered and summarized: (1) data scatter as a result of open system behavior; and (2) data scatter due to a melange of data sets defining two distinct isochrons

Pulsed Electromagnetic Gas Acceleration Eighth Semiannual Progress Report, 1 Jan. - 30 Jun. 1966

Pulsed electromagnetic gas acceleratio