The influence of paramagnetism and diamagnetism will significantly alter the vacuum toroidal magnetic field in spherical torus. Therefore, plasma parameters dependent upon B/sub T/ such as the ...q-profile and local /spl beta/ value need an independent measurement of B/sub T/(r,t). The multi-chord tangential far infrared interferometer/polarimeter (FIReTIP) system currently under development for National Spherical Torus Experiment (NSTX) will provide temporally and radially resolved toroidal field profile B/sub T/(r,t) and 2D electron density profile S(r,t) data. Two channel interferometer will be operational this year and full system will be ready by 2002.
Novel RF-MEMS extended tuning range varactors are being developed for incorporation in arrays of RF MEMS based true time delay lines for use in millimeter-wave Phased Antenna Array (PAA) systems. A ...frequency of 28 GHz (Ka-Band) has been selected for the activity since it is a frequency region of considerable commercial, scientific, and military interest as well as being sufficiently high to result in small size units. The design of the 28 GHz proof-of-principle RF MEMS varactor based true time delay line is presented together with the fabrication process and the initial measurement results.
A multichannel ultrashort pulse reflectometry (USPR) system has been upgraded to enhance the performance of simultaneously measuring electron density profiles and fluctuations on the sustained ...spheromak physics experiment device (SSPX). In addition to the use of a high power frequency multiplier in the transmitter subsystem, the optimization of filter bandwidths in the receiver subsystem results in significant improvement of the dynamic range and signal-to-noise ratios of the USPR signals, thereby dramatically reducing the number of "lost" signals. Details of the upgraded USPR system are described together with USPR profile and fluctuation data.
The Electron Spectrometer (ELS) instrument of the ASPERA-3 package on the Mars Express satellite has recorded photoelectron energy spectra up to apoapsis (
∼
10
,
000
km
altitude). The ...characteristic photoelectron shape of the spectrum is sometimes seen well above the ionosphere in the evening sector across a wide range of near-equatorial latitudes. Two numerical models are used to analyze the characteristics of these high-altitude photoelectrons. The first is a global, multi-species MHD code that produces a 3-D representation of the magnetic field and bulk plasma parameters around Mars. It is used here to examine the possibility of magnetic connectivity between the high-altitude flanks of the martian ionosheath and the subsolar ionosphere. It is shown that some field lines in this region are draped interplanetary magnetic lines while others are open field lines (connected to both the IMF and the crustal magnetic field sources). The second model is a kinetic electron transport model that calculates the electron velocity space distribution along a selected, non-uniform, magnetic field line. It is used here to simulate the high-altitude ELS measurements. It is shown that the photoelectrons are essentially confined to the source cone, as governed by magnetic field inhomogeneity along the field line. Reasonable agreement is shown between the data and the model results, and a method is demonstrated for inferring properties of the local and photoelectron source region magnetic field from the ELS measurements. Specifically, the number of sectors in which photoelectrons are measured is a function of the magnetic field intensity ratio and the field's angle with respect to the detector plane. In addition, the sector of the photoelectron flux peak is a function of the magnetic field azimuthal angle in the detector plane.
UCD Ka-Band Harmonic Peniotron Status Dressman, L.J.; McDermott, D.B.; Luhmann, N.C.
2006 IEEE International Vacuum Electronics Conference held Jointly with 2006 IEEE International Vacuum Electron Sources,
2006
Conference Proceeding
The UC Davis 34 GHz peniotron experiment is currently being prepared for test. The device is presently being operated in a "beamstick" configuration to characterize beam transmission and validate the ...magnetic design. Upon completion of this step the device is reconfigured as the intended second-harmonic oscillator and tested for power output and efficiency (predicted values are 125 kW and 47% respectively)
A user-friendly, time-saving computer-automated test system for quasi-optical overmoded waveguide frequency multiplier grid array research has been developed, utilizing the graphical programming ...software Labview and the standard interface GPIB (General Purpose Interface Bus). The system measures pulsed and CW power and efficiency by controlling an RF source, gathering data from oscilloscopes, and calculating input and output power levels and efficiencies utilizing calibration tables. The efficiencies and output powers for frequency tripler and doubler grid arrays have been tested. Experimental results of output power and efficiency versus input power for a frequency tripler grid array and efficiency versus frequency for a frequency doubler grid array are shown in this paper.
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