A 243 nm source is developed based on a Cr:LiSAF laser operating at 25 Hz. The Cr:LiSAF laser is operated at 972 nm and is frequency quadruped in two successive second harmonic generation stages to 243 nm. An innovative multi-crystal design is implemented in each of the second harmonic generation stages. In this way the total crystal length required to efficiently convert temporally long pulses with low peak powers is maintained while broadening the effective spectral acceptance of the nonlinear interaction. Using six BBO (beta-barium borate) crystals in series an effective spectral gain bandwidth that exceeds by as much as 5 times the spectral bandwidth of a single crystal of equivalent length is achieved. The resulting 243 nm source is shown to have a spectral bandwidth of 140 pm (fwhm) and a temporal pulse length of 167 nsec (fwhm).