Development of an adiabatic field rotation system to measure spin polarization of unstable nuclei

Highlights: • An adabatic field rotation system has been developed for efficient β-NMR experiments. • The system enables to measure spin polarization separately from β-NMR measurements. • A magnetic field of 300 mT produced with Nd can be adiabatically inverted in 150 ms. • The system performance was investigated with spin-polarized 20F. -- Abstract: A system for the spin-polarization measurement of unstable nuclei has been developed, in which the alternation of nuclear spins takes place by adiabatically rotating a holding magnetic field for the preservation of spin polarization, without applying a resonant oscillating magnetic field for NMR. The performance of the system was studied with spin-polarized 20F (Iπ = 2+,T1/2 = 11.163 s) produced in the 19F(d→,p)20→F reaction at E/A = 7 MeV at the RIKEN RIBF facility. In the measurement, the magnitude of 20F spin polarization |P(20F)|=1.6(2)% was successfully observed with the new system