The efficiency of S20 multialkali photocathodes is a function of thickness, wavelength, polarization and angle of incidence of light into the cathode. Therefore no single set of conditions can maximize performance over the entire spectral range. Consequently, two prototype photocathodes have been made with a gradation in thickness so that during monochromatic analysis the optical beam can be addressed to different thickness regions at preferred angles of incidence. This potentially enables a spectrum to be recorded under optimal conditions at a single interaction event. Relative to normal commercial S20 photomultipliers the quantum efficiency (QE) has been significantly raised across the entire spectral range. The current data were primarily obtained between 450 and 800 nm and at 450 nm it resulted in values of at least 65% QE, which is the highest value ever cited at this wavelength. Signals at longer wavelengths, for example at 750 and 800 nm, were recorded with up to 20 and 10% QE, respectively. Once again these are new record values that match performance from multiple interactions in waveguide cathodes. The data from this new design of photocathode underline the potential for improvements in efficiency for non-normal incidence in graded thickness photocathodes and indicate that current S20 technology could be significantly enhanced. Alternative enhancement methods are mentioned, particularly for spectrally dispersed signals. The enhancements are compared with data for a standard high quality S20 photocathode.

Photodiagnosis and photodynamic therapy of non-melanoma skin cancers using delta-aminolevulinic acid/protoporphyrin IX (5-ALA/PpIX) give a combined application with broadest dissemination in the current clinical practice. The problems with using of lasers as light sources are the expenses associated with the operation of these types of installations. This is why we test the capability of cheaper sources -light-emitting diodes at 405 nm for fluorescence excitation of PpIX and 635 nm for photodynamic action initiation. A LED matrix is developed in our laboratory using two types of LEDs and a combined photodiagnosis/photodynamic theory device applicable for clinical practice is built. Geometrically matrix is formed in such way that power density at 635 nm is about 40 mW/cm 2 , which allow to reach treatment doses for a 15-20 min irradiation depending of the lesion size in the focus of the system. The therapeutic mode of system developed can be used also with some other photosensitizers from the porphyrins derivatives family.