Magnetic Shielding With High-Tc (YBa2Cu3O7-δ)1-xAgx Superconducting Tubes

We present typical results of experiments carried out in (YBaCuO)1-xAgx tubular samples, for different values of the silver concentration x, having in mind the possible use of this material as a magnetic shield. We measured the times governing the dynamics of magnetic flux penetration, on a microsecond time-scale, and tried to correlate them with d.c. measurements of the resistivity and the critical transport current density, using a simple theoretical model based on the flux-flow régime

Flux propagation in tubular high-Tc ceramics

We present an experimental and theoretical study of the dynamics of low-field penetration in tubular YBaCuO ceramics when an axial magnetic field is suddenly applied. The main characteristics times of the phenomenon are calculated assuming a flux-flow process through the Josephson medium. The theoretical predictions are in good agreement with the experimental results at 77K. © 1994

Use of a neural network to exploit light division in a triangular scintillating crystal

This work presents a novel way of exploiting light division in a scintillating crystal to localise the point of interaction using a neural network. Because sensitivity at the centre of a positron tomograph would be significantly increased for a spherical geometry compared to a cylinder with the same area of detection, we explored the possibility of developing a position-sensitive triangular block detector that might be used ultimately as an element of a spherical shell. With 3 PMTs coupled on each side of a triangular BaF2 crystal of about 8 cm2 × 1 cm, we obtain spatial resolutions less than 4 mm FWHM over the whole surface of the triangle and energy resolutions of about 14 FWHM for 662 keV impinging photons. Experimental measurements are compared with Monte Carlo simulations and prospects for different configurations are discussed

Expansión de fases normales creadas por láser en películas superconductoras de alta temperatura critica

IP 1103-05-249-96ARTICULO(S) EN REVISTA: Dynamics of fast flux penetrationin high-t superconductors / H. Castro, L.;Rinderer, E. Holguin, J.F. Loude.-- En: Physica C. -- No.281(1997); p. 293-302. -- Estudio teorico sobre la;velocidad de propagacion de dos fases normales creadas porradicacion laser en peliculas delgadas;superconductoras de alta temperatuta critica / J. Leon, E.Holguin, J.F. Loude. -- En: Revista Colombiana de;Fisica. -- Vol. 32, no. 1 (2000); p. 122-124. -- Caracterizacionde peliculas delgadas por trasformada rapida;de fourier / J. Leon, E. Holguin, C.M. Torres. En: RevistaColombiana de Fisica. -- Vol. 29, no. 2 (1997); p.;147-150. -- Mediciones de densidad de corriente critica bajo laaccion deun campo magnetico externo y calculo;de la magnetizacion estatica en ceramicas superconductorasdealta temperatura critica / H. Castro, E.;Holguin, J.F. Loude. En: Revista Colombiana de Fisica. --Vol.29, no. 2 (1997); p. 243-246. -- Contribucion;al estudio teorico del flux-flow en superconductores convencionalesobservados por medio de la magneto-optica /;J. Leon, E. Holguin. -- Vol. 30, no. 1 (1998); p. 157-160.--Dinamica delestado mixto a dos dimensiones en;superconductores convencionales / C. Villaquiran, J. Leon,E,Holguin. --En: Revista Colombiana de Fisica. --;Vol. 31, no. 2 (1999); p. 255-258

Development of new mixed Lux(RE3+)1-xAP:Ce scintillators (RE3+ =Y3+ or Gd3+): Comparison with other Ce-doped or intrinsic scintillation crystals

This paper presents the development of new Ce-doped, fast and high effective-Z mixed Lux(RE3+)1-xAP:Ce crystals. These crystals have been grown by the Czochralski method and good results have been obtained with x = 0.1, 0.2 and 0.3 for Y3+ ions. Relative light yields measured for the Lux(RE3+)1-xAP:Ce crystals are 40% to 75% higher than for BGO and are comparable to the light yield of YAP:Ce crystal. Measured energy resolutions at 662 keV range over 8% to 15.3% FWHM and are close to the energy resolution obtained with a YAP:Ce. Thermally stimulated luminescence (TSL) measurements above room temperature have also been performed: in accordance with the expected effect of trap states on scintillation efficiency, an anticorrelation between TSL intensity and light yield is found

Development of an optimized LSO/LuYAP phoswich detector head for the Lausanne ClearPET demonstrator

This paper describes the LSO/LuYAP phoswich detector head developed for the ClearPET small animal PET scanner demonstrator that is under construction in Lausanne within the Crystal Clear Collaboration. The detector head consists of a dual layer of 8/spl times/8 LSO and LuYAP crystal arrays coupled to a multi-anode photomultiplier tube (Hamamatsu R7600-M64). Equalistion of the LSO/LuYAP light collection is obtained through partial attenuation of the LSO scintillation light using a thin aluminum deposit of 20-35 nm on LSO and appropriate temperature regulation of the phoswich head between 30/spl deg/C to 60/spl deg/C. At 511keV, typical FWHM energy resolutions of the pixels of a phoswich head amounts to (28/spl plusmn/2)% for LSO and (25/spl plusmn/2)% for LuYAP. The LSO versus LuYAP crystal identification efficiency is better than 98%. Six detector modules have been mounted on a rotating gantry. Axial and tangential spatial resolutions were measured up to 4 cm from the scanner axis and compared to Monte Carlo simulations using GATE. FWHM spatial resolution ranges from 1.3 mm on axis to 2.6 mm at 4 cm from the axis