Varian Associates

About: Varian Associates is a based out in . It is known for research contribution in the topics: Beam (structure) & Wafer. The organization has 2160 authors who have published 2591 publications receiving 46002 citations.

Controlled susceptibility plugs

Abstract: It is desired to promote magnetic homogeneity of materials, including structural elements, present in the sensitive volume of a gyromagnetic analysis apparatus. Where the sample is rotated along an axis transverse to the field the requirement reduces to establishing axial homogeneity. Plugs which match the solvent magnetic susceptibility are employed to constrain a sample within the central region of an RF probe coil thereby appearing relatively invisible in the magnetic sense to the instrument. The susceptibility of materials can be tailored to achieve a desired value to suppress magnetic perturbation without introducing extraneous signals.

Microwave window having dielectric variations for tuning of resonances

Abstract: A high-power microwave window structure is disclosed. The window structure includes a hollow waveguide having a dielectric wave permeable gastight partition sealed thereacross to form the window assembly. The window structure is capable of being impedance matched to the waveguide structure to provide a relatively wide passband. In certain windows the passband can be as wide as the recommended bandwidth for the waveguide itself. Such window structures are plagued by ''''trapped'''' and ''''ghost'''' resonant modes which are excited into resonance by slight asymmetries in the window structure. At their resonant frequencies, these modes couple energy from the main propogating mode to produce an impedance mismatch and at high-power levels, overheating and failure of the window structure. Thus, operation at high-power levels is typically restricted to frequency ranges between a pair of such resonant modes. The frequency separation between the resonant modes is increased to provide broader band operation by selectively tuning the resonant frequencies of these modes by selectively varying the electrical path length through the window structure for one or more of these modes. For example, the window is made thicker near the periphery where one of the resonant modes has its most intense electric fields and made thinner near the center where another of the modes has its intense electric fields to tune one of the modes higher in frequency, while the other mode is being tuned lower in frequency. The mean thickness of the window is maintained approximately constant such as not to change appreciably the passband for the main propagating mode. Alternatively, the dielectric constant for various portions of the window can be changed for changing the electrical path length through the window as aforedescribed.