A measurement wafer apparatus for measuring radiation intensity and temperature comprising: a wafer assembly including one or more cavities; and a detector assembly, the detector assembly disposed within the one or more cavities of the wafer assembly, the detector assembly including one or more light sensors, wherein the one or more light sensors include one or more diode detectors, the detector assembly configured to perform a direct measurement of the intensity of ultraviolet light incident on at least one surface of the wafer assembly, the direct measurement comprising a measurement of the light intensity of ultraviolet light incident on at least one surface of the wafer assembly which does not involve an intermediate conversion of a light signal from a first wavelength to a second wavelength, wherein the detector assembly is further configured to determine a temperature of one or more portions of the wafer assembly based on one or more characteristics of the one or more light sensors upon measuring the intensity of the ultraviolet light incident on the at least one surface of the wafer assembly; wherein the one or more characteristics of the one or more light sensors comprise: an electrical characteristic of the one or more light sensors; wherein the electrical characteristic comprises: a forward voltage across the one or more light sensors measured at a known current; wherein the wafer assembly includes one or more openings at the at least one surface of the wafer assembly configured to pass ultraviolet light incident on the at least one surface of the wafer assembly to the one or more light sensors of the detector assembly. a wafer assembly including one or more cavities; and a detector assembly, the detector assembly disposed within the one or more cavities of the wafer assembly, the detector assembly including one or more light sensors, wherein the one or more light sensors include one or more diode detectors, the detector assembly configured to perform a direct measurement of the intensity of ultraviolet light incident on at least one surface of the wafer assembly, the direct measurement comprising a measurement of the light intensity of ultraviolet light incident on at least one surface of the wafer assembly which does not involve an intermediate conversion of a light signal from a first wavelength to a second wavelength, wherein the detector assembly is further configured to determine a temperature of one or more portions of the wafer assembly based on one or more characteristics of the one or more light sensors upon measuring the intensity of the ultraviolet light incident on the at least one surface of the wafer assembly; wherein the one or more characteristics of the one or more light sensors comprise: an electrical characteristic of the one or more light sensors; wherein the electrical characteristic comprises: a forward voltage across the one or more light sensors measured at a known current; wherein the wafer assembly includes one or more openings at the at least one surface of the wafer assembly configured to pass ultraviolet light incident on the at least one surface of the wafer assembly to the one or more light sensors of the detector assembly. an electrical characteristic of the one or more light sensors; wherein the electrical characteristic comprises: a forward voltage across the one or more light sensors measured at a known current; wherein the wafer assembly includes one or more openings at the at least one surface of the wafer assembly configured to pass ultraviolet light incident on the at least one surface of the wafer assembly to the one or more light sensors of the detector assembly. a forward voltage across the one or more light sensors measured at a known current; wherein the wafer assembly includes one or more openings at the at least one surface of the wafer assembly configured to pass ultraviolet light incident on the at least one surface of the wafer assembly to the one or more light sensors of the detector assembly.