Photoelectron yields of fast and slow decay components corresponding to 220 nm and 300 nm emissions in BaF

2

luminescence have been measured respectively. By means of the fast decay component of 220 nm emission

a BaF

2

detector with both high time resolution and high counting rate has been developed. Application of our BaF

2

detector to positron annihilation lifetime spectrometer to replace the plastic crystal scintillation counter improves the time resolution from FWHM=270 ps to FWHM=19.0 ps or increase the counting rate by ten times.Laval et al. discovered that there is a fast decay component with the lifetime of 0.6 ns at the wavelength 220 nm in BaF

2

luminescence in addition to the slow decay component with the lifetime of about 600 ns at the wavelength 300 nm. The time resolution of the BaF

2

crystal obtained by means of the fast decay component can be compared with that of the plastic scintillation crystal NE111. On the other side

the BaF

2

crystal

containing heavy element Ba

has the ability to effectively gamma-rays

and so

the BaF

2

detector has high detection efficiency.