  The scintillation efficiency (quenching factor) of fluorine and calcium
nuclei recoiling in a CaF-2(Eu) crystal was measured in an energy region
relevant to dark matter searches. The recoiling nuclei were obtained via the
19-F(n,n') and 40-Ca(n,n') reactions, where the neutron beam was provided via
the d(d,n)3-He reaction. The quenching factor of F and Ca nuclei in the
CaF-2(Eu) crystal was found to be 11 ~ 20 %, and 9 ~ 23 % relative to the
electron equivalent energy for 53 ~ 192 keV and 25 ~ 91 keV recoil energies,
respectively, and the energy dependence was observed. The quenching factor we
measured here is a little larger than that of previous studies, which may
depend on the Eu doping concentration of the crystal.
