Examination of Levitation of Thin Non-Magnetic Conductor by AC Electoromagnet Type Electro Dynamic Suspension
Because transportation by magnetic levitation has the advantage of not contacting, it has various good points. Conventional studies of electro dynamic suspension (EDS) are aimed on the large-scale applications, and use the non magnetic conductor of 1mm or more in thickness. However, in theoretical, it is possible that the thinner non magnetic conductor of less than 1mm in thickness levitate, using higher frequency or larger magnetomotive force. Therefore, applications to a smaller levitation model can be expected. In this paper, the relation between lift force and the temperature rise in the conductor is examined from the numerical analysis, when we consider a smaller levitation model. Skin effect and electromagnetic force between gaps are taken into account. These results are verified by experiments.
Levitation Characteristics of Magnetically Suspended Vehicles Utilizing Continuous Conductive Sheets
In a magnetically levitated railway system with superconducting vehicular magnetic coil, short-circuiting ground coil, and a loop-type track, the magnetic field produced by ground coils is not uniform and therefore the lift force fluctuates as the train moves and the magnetic flux of the superconducting magnet fluctuates with time. The sheet-type track consists of continuous conductive sheets of aluminum or copper. The levitation characteristics of the sheet-type track have been analyzed so far by directly solving Maxwell's equation or by replacing the sheet current by an image current. In these analyses, it has usually been assumed that the sheet is infinitely or semiinfinitely wide. Until now, the levitation characteristics of a sheet-type track with finite width have been analyzed little. An analysis is given in which a ground sheet with finite width is replaced by a number of conductors with square cross section arranged in the running direction. Self- and mutual inductances of the conductors are taken into account in calculating the levitation characteristics. Calculated levitation characteristics of the sheet-type track are compared with those of the loop-type track.
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%