A New Method of Complex Dielectric Permittivity Determination
The article proposes a new method of complex dielectric permittivity determination based on the use of surface wave resonator. This method is applied to fluorocarbon polymer-4, yttrium stabilized-zirconium and sapphire at frequency band 6-70 GHz.
Irradiation of HTS Josephson junctions with the surface wave resonator
The new type of surface wave resonator (SWR) consists of HTS film on a dielectric substrate is developed. A possibility of optimal coupling between the electromagnetic field of the SWR and the HTS Josephson junction array is shown; The topologies for embedding the bicrystal HTS Josephson junctions in the SWR are developed. These topology ensure the junction synchronization, that can be used for creation voltage standards, microwave detectors and Josephson generators and so on; The microwave properties of the SWR with HTS Josephson junction arrays (up to 450 junctions) and nonlinear elements based on Shottky-barrier diodes have been investigated. For the array with 450 HTS Josephson junctions the voltage sequence with 10 mV step has been obtained, sensitivity of the detector based on this array is 0.1 A/W with dynamic range 10/sup 2/ dB; The Josephson generation with microwave power at several nW for the SWR with bicrystal HTS JJs is detected. There were two groups of junctions. These groups are formed at the time of fabrication due to imperfection of HTS junction fabrication technology.
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%