I came up with the following idea of a device: We have a short circuited type-2 (to allow more current) superconducting solenoid. A current is flowing through the solenoid, and it creates magnetic induction inside, B1. Inside the solenoid we place a piece of type-1 superconductor. B1<critical induction of the type-1 superconductor. When the type-1 superconductor cools down and starts superconducting, it expels the magnetic field from itself, and, therefore, reduces the inductance of the solenoid. Now the coil is superconducting, which means that the voltage drop in the wire is zero. That means that, as the inductance gets reduced, the current through the solenoid is increased. Since the current is increased, the magnetic induction, caused by the coil, also increases, to a value B2. If we arrange the parameters of the device so that B2>critical induction, then the piece of superconductor will lose it's superconductivity. Which means that the inductance of the solenoid is reduced to it's original value. The current decreases, and the induction of the solenoid goes back to B1<critical induction. We are back where we started. So the device will oscillate, changing the current through the solenoid. What do you think of it?