Multielement systems of double slots in rectangular waveguide with partial dielectric filling
Resonance characteristics of narrow transversal slots, energetic and directional characteristics of an antenna array (AA) with single transversal slots and double ones cut in a rectangular waveguide, partially filled with dielectric are investigated. In the case of the single transversal slots and double transversal slots a dielectric layer is parallel to broad walls of the waveguide. It was shown the possibility to construct an AA with double transversal slots the pattern without diffraction lobes and high level of radiation power in the frequency band.
Physical properties of narrow slots in a rectangular waveguide with dielectric layer
Narrow slots cut in rectangular waveguides with dielectric layers parallel to the waveguide narrow or broad walls are considered. The theory elaborated by the authors for such slots is applied to numerical studying of their physical properties. The resonance properties and energetic parameters of the longitudinal and transversal slots are investigated in one-mode regime of the waveguide. The most interesting regularities caused by variation of the layers permittivity epsiv are discussed.
rPET detectors design and data processing
Small animal PET systems based on rotating planar detectors posses some interesting advantages for high sensitivity, high resolution imaging. We have designed the rPET detectors based on MLS crystals assembled on a 30times30 matrix optically coupled to a flat-panel PS-PMT. Weighted position readout circuits pre-process the 64 signals from the 8times8 anodes matrix, which are digitized using a charge-integrating converter. The amplification electronics, including the trigger output for coincidence detection, and the high voltage supply are integrated in a three PCBs stack that forms the base attached to the back of the PMT. The whole assembly is enclosed in a light tight, lead (Pb) shielded aluminum box. The detectors are mounted on a rotating gantry with more than 180 degrees rotation span. The digitized events are screened and histogramed, and a modified center of gravity algorithm removes from the position calculation those signals with poor signal to noise ratio. Apparent mean crystal size on the 511 keV field-flood images is 0.6 mm, mean peak-to-valley ratio is better than 8, and intrinsic resolution is 1.5 mm at the central row, with the energy window wide open. Sensitivity (CPS) for a pair of these detectors set in coincidence at 160 mm distance is 1%