Flyby infrared absorption measurements in Martian atmosphere for determination of profiles of carbon dioxide, particulate matter and water vapor

Zeolite trap of migrating photon radiated by metastable argon atoms from sputter ion pump to ion collector

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation A. E. Barrington, R. F. K. Herzog, G. O. Sauermann; Helium Memory Effects Observed with Tandem Mass Spectrometer. J. Vac. Sci. Technol. 1 March 1965; 2 (2): 89–90. https://doi.org/10.1116/1.1492406 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAVS: Science & Technology of Materials Interfaces and ProcessingJournal of Vacuum Science and Technology Search Advanced Search |Citation Search

The strongly coupled multicavity synchrotron system proposed for the 6-bev Cambridge Electron Accelerator operates at 475 Mc and, because of its large size, presents complex problems of assembly and tuning. To achieve a better understanding of the characteristics of the system, a scaled model operating at 9000 Mc was constructed. The work was undertaken in two stages; first a simple single-cavity ring was studied and later a more complicated double-cavity ring. An account is given of the design of cavities and waveguide links of variable electrical length, and instrumentation devised for various measurements is described. This is followed by experimental data which were in good agreement with theoretical predictions. Recommendations arising from the model study for the assembly and tuning of the 475-Mc system are put forward.

A squaring unit based on the Hall effect is used to give an a.c. output, the amplitude of which is proportional to the square of an input current. The input impedance is low, so that the unit may conveniently be fed from a shunt. The output is amplified in a tuned amplifier, and fed through a rectifying circuit to an integrating instrument such as a fluxmeter, so that a direct reading of ∫i2.dt is obtained. A modification is suggested to enable ∫ei dt to be measured, giving the arc energy in a circuit breaker or fuse. Thus, direct and immediate readings of these integrals can be obtained, and the need to apply timeconsuming graphical techniques to records of the appropriate current or voltage waveforms is avoided. The accuracy is shown to be better than 2%.

Contains an entry for each author and coauthor included in this issue of the publication.

The Faraday effect in a straight rectangular waveguide, a section of which is completely filled with a ferrite material subjected to an axial magnetic field, has been described by Du Pré, who states that, owing to the presence of a medium of dielectric constant and permeability greater than those of air, modes other than the usual TE10 mode may be propagated in the ferrite-filled section. In particular, the TE01 mode whose electric vector is perpendicular to the narrow dimension of the guide may be supported. If, owing to Faraday rotation, the TE10 mode is converted to the TE01, mode, propagation cannot take place beyond the ferrite-filled section. Experimentally this was confirmed by Du Pré who observed minimum of transmitted power for 90 degree rotation. Similar results were obtained in this laboratory with a straight rectangular guide loaded with a cylindrical ferrite specimen the ends of which were tapered for matching purposes as shown in Fig. 1(a). For a given axial magnetic field the reduction of transmitted power was Iargest with the specimen in the center of the guide, but, as might have been expected, no nonreciprocal effects were observed. A twisted rectangular waveguide section, however, loaded with the same specimen, exhibited nonreciprocal characteristics. In the experiment the sampIe was mounted centrally midway between the flanges of a 90 degree commercial 0.4x 0.9 inch twist and an axial magnetic field was applied as shown in Fig. 1(b).

Following a brief review of existing refiectometer methods for the measurement of Q-factors of microwave cavities, a simplified system is described in which the complexity and cost of components are reduced appreciably. Values of Q-factors, from 200 to 4 000, measured in this way are in good agreement with those obtained with established techniques. Because the local oscillator is tuned manually, a frequency range wider than that obtainable with electronic tuning may be covered.

The behaviour of wires fused by means of a high-frequency discharge yielding peak-current densities of 100-200 kA/mm2 is investigated. From records of electrical transients it is estimated that complete melting does not occur prior to break-up. The nature of the arc discharge following break-up is shown to depend on the length and the material of the wires when exploded in air, but independent of these when exploded in vacuum. As a consequence of these experiments, results obtained by earlier investigators are examined critically.

A novel method of heating thermionic cathodes in transverse electric and magnetic fields is described. Hydrogen at an accurately controlled pressure is admitted into the vacuum envelope from a hybride replenisher (consisting of an indirectly heated nickel pellet coated with a suspension of zirconium hydride). Following the initiation of a low-pressure gas discharge in the interelectrode space, the cathode is heated by positive ion bombardment until it reaches the temperature required for thermionic electron emission. The hydrogen is then reabsorbed by the replenisher and high-vacuum conditions are restored, while the cathode is maintained hot by electron back-bombardment alone. Following a section dealing with physical phenomena, practical applications of the method are discussed, such as the processing and starting of oxide-coated as well as high-temperature magnetron cathodes.