Values for the maximum Josephson critical current ( / : -) and distortion of the dependence of the critical current (I,) on magnetic field applied parallel to the plane of t h e tunnel junction (HI,) are calculated for different configurations of Abrikosov vortices in a wide range of their concentration. An experimental procedure is developed to trap both misaligned dipole vortices and monopole vortices in the NbiAlOJNb Josephson tunnel junction for study of their influence on the/,(Hll) curves and the value of/?. The results of the theoretical calculations agree well with the experimental data.

We report on experimental results about Josephson junctions for radiation detection with an annular geometry. The observed suppression of the critical Josephson current and the presence of one single resonance step in the current–voltage characteristic, as predicted by the theory, strongly support the idea that this geometry could be very convenient for radiation detection. The results were obtained when one single magnetic fluxon was trapped in the central hole, and they represent the first experimental confirmation of the theoretical predictions in the case of annular junctions with finite ring width.

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