AN ULTRAVIOLET-B VISIBLE/NEAR-INFRARED TRANSFER RADIOMETER/

One of the main problems of natural radiation measurements, especially for ultraviolet-B (UVB) radiation, is the calibration and quality con trol of the radiometers used. We have developed a simple radiometer wh ich allows the comparison of other radiometers, spectroradiometers and light sources. The filter radiometer consists of a Spectralon diffuse r, interference filters, a silicon photodiode and signal amplification . The peak wavelengths of the thirteen interference filters are distri buted between 301 nm and 1040 nm. The measurements of the UVB edge of the solar spectrum require very stable filters with a small half-width (FWHM). We used five special UVB filters with a FWHM of about 1 nm. T he transfer radiometer has a dynamic range of 10(8); its resolution is better than 1 part in 10(4) and the smallest detectable spectral irra diance is 1,2 x 10(-9) W . cm(-2). nm(-1) at 305,48 nm. Using this tra nsfer radiometer, we compared four different irradiation sources: two 1 kW FEL lamps (a PTB- and a NIST-based standard), one 200 W deuterium lamp (PTB-related standard) and the primary standard irradiation sour ce BESSY. It was found that the deviation between the four radiation s ources was in agreement with the standard deviation of each irradiatio n source.