Processing and characterisation of long-length silver/bismuth-2223 tape for electric power applications
The potential of high temperature superconductivity (HTS) to raise efficiencies in electric power utilisation is dependent on the availability of HTS materials in a form which can be engineered into devices. This paper reviews a program of continuous process and product improvement which has enabled tape with lengths up to 1000 m and appropriate engineering properties to be reproducibly processed using the powder-in-tube technique. Underpinning this development of a large scale process capability, tape development on a small scale was necessary in the areas of innovative tape design, metal forming optimisation and heat treatment. In addition, techniques for the characterisation of long lengths of tape were developed. These techniques included the modelling of the effect of the self-field generated by the tape under test at 77 K to enable zero field Ic data to be determined.
Silver-sheathed Bi-2223 tapes: the state of the art
At present, rolled multifilamentary Bi-2223/Ag tapes exhibiting at 77 K are fabricated, making them the most favourable candidates for the fabrication of high-temperature superconductor (HTS) conductors for power applications. In this paper the fabrication process of long Bi-2223/Ag tapes by the powder-in-tube technique is presented and discussed with the aim of surveying the influence of some selected process parameters on the properties of final conductors. limitations in HTSs are discussed and some of the possible applications of Bi-2223/Ag or Bi-2212/Ag tapes are briefly presented.
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%