  We report on frequency tripling of high energy, high repetition rate ns
pulses from a cryogenically gas cooled multi-slab Yb:YAG laser system
Bivoj/DiPOLE, using a type-I phase matched LBO crystal for second harmonic
generation and type-II phase matched LBO crystal for sum frequency generation.
We achieved conversion to 343 nm with stable energy of 50 J at repetition rate
of 10 Hz and conversion efficiency of 53%.
