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We report a measurement of the spin-flip probabilities for ultracold neutrons interacting with surfaces coated with nickel phosphorus. For 50~$mu$m thick nickel phosphorus coated on stainless steel, the spin-flip probability per bounce was found to be $beta_{rm NiP;on;SS} = (3.3^{+1.8}_{-5.6}) times 10^{-6}$. For 50~$mu$m thick nickel phosphorus coated on aluminum, the spin-flip probability per bounce was found to be $beta_{rm NiP;on;Al} = (3.6^{+2.1}_{-5.9}) times 10^{-6}$. For the copper guide used as reference, the spin flip probability per bounce was found to be $beta_{rm Cu} = (6.7^{+5.0}_{-2.5}) times 10^{-6}$. The results on the nickel phosphorus-coated surfaces may be interpreted as upper limits, yielding $beta_{rm NiP;on;SS} < 6.2 times 10^{-6}$ (90% C.L.) and $beta_{rm NiP;on;Al} < 7.0 times 10^{-6}$ (90% C.L.) for 50~$mu$m thick nickel phosphorus coated on stainless steel and 50~$mu$m thick nickel phosphorus coated on aluminum, respectively. Nickel phosphorus coated stainless steel or aluminum provides a solution when low-cost, mechanically robust, and non-depolarizing UCN guides with a high-Fermi-potential are needed.
Neutron lifetime is one of the most important physical constants which determines parameters of the weak interaction and predictions of primordial nucleosynthesis theory. There remains the unsolved problem of a 3.9{sigma} discrepancy between measurem
Ultracold neutrons provide a unique tool for the study of neutron properties. An overview is given of the ultracold neutron (UCN) source at PSI, which produces the highest UCN intensities to fundamental physics experiments by exploiting the high inte
We report the first measurement of angular correlation parameters in neutron $beta$-decay using polarized ultracold neutrons (UCN). We utilize UCN with energies below about 200 neV, which we guide and store for $sim 30$ s in a Cu decay volume. The $v
A clock comparison experiment, analyzing the ratio of spin precession frequencies of stored ultracold neutrons and $^{199}$Hg atoms is reported. %57 No daily variation of this ratio could be found, from which is set an upper limit on the Lorentz inva
We present a detailed report of a measurement of the neutron $beta$-asymmetry parameter $A_0$, the parity-violating angular correlation between the neutron spin and the decay electron momentum, performed with polarized ultracold neutrons (UCN). UCN w