For my new set-up, I have used a photomultiplier tube (PMT). The PMT also makes use of the photoelectric effect, except it is far more sensitive than a photodetector. The set-up is a box with the blue filter on top. The crystal sits on the filter, and the laser shines on the crystal.
In order to make full-use of the sensitivity of the PMT, the apparatus had to be shielded. Thus far, the PMT has shown pretty conclusively that F+-centers have been created from x-ray irradiation. The irradiated crystal consistently at least doubles the intensity of the light striking the PMT. Evidence also suggests that the "unirradiated" crystal also has F+-centers but more sparsely than the other.
I plan to continue by testing the irradiation dose-rate with the measured intensity. I also intend to try to find a more stable laser as the laser-pointer is not designed for such extended use.