Quantization of diamagnetic current in a superconducting ring with Josephson point contact

It is experimentally established, that the critical value of diamagnetic current excited by an external magnetic field in a superconducting ring (inductance approx 10-6 H) with a Nb-Nb clamping point contact, possessing the Josephson contact properties, is a strictly periodic function of field, despite the complex microstructure of the clamping contact. The reasons of the periodic dependence are discussed on the basis of the model of interference of diamagnetic current and quantum values of circulating current in the microinterferometer, formed by the clamping contact.