Seminarium Fizyki Jądra Atomowego

Ultracold neutrons (UCN) form a tiny low-energy fraction in the Maxwellian spectrum of thermal neutrons in moderators of nuclear reactors and spallation sources. Their energy is extremely small (~10^-7 eV), their velocity equals a few meters per second only, and their effective temperature is as low as ~1 mK. The specific feature of UCN consists in their nearly total elastic reflection from the nuclear-optical potential of many materials at any incidence angle; therefore they could be stored in closed traps for extended period of time, thus used for extremely sensitive measurements in fundamental particle physics. We will focus on recent advances in the field, consisting in observation of the centrifugal quantum states of neutrons, providing, when combined with the observation of the gravitationally bound quantum states of neutrons, the first demonstration of the weak equivalence principle for an object in a quantum state. Also we will present state-of-the-art in gravitationally bound quantum states of neutrons and a new spectrometer GRANIT constructed for precision studied of the gravitationally bound quantum states of neutrons and for other applications in particle physics, quantum optics, and in surface studies.