Peak irradiance

UV Irradiance is the radiant power arriving at a surface per unit area. The most commonly used unit of irradiance is W/cm. It varies with lamp output power, efficiency, the focus of its reflector system, and its distance to the surface. The intense peak of focused power directly under the lamp is referred to as peak irradiance. Although not a defined term, intensity is occasionally used to refer to irradiance. Irradiance... 

Lamp System Bulb Type Bulb Diameter, mm Peak Irradiance, W/cm (UVA)... 

Xenon lamps are available mainly as tubular and point source bulbs. The radiation produced by this type of lamps is not particularly rich at wavelengths below 400 nm, and therefore their applications are somewhat limited. However, it is possible to pulse xenon lamps, which enables them to achieve high peak irradiances. Commercially available pulsed xenon lamps are available with emissions in the UV and visible spectral range. Alternating the gas fill can produce output rich in UV. 

Some self-contained instruments are designed for on-line measurements in UV curing units to determine the integral UV dose delivered to the material being cured, peak irradiance, and irradiance/temperature profiles. The quantities and units of measurements have been established based on lUPAC s recommendation of 1996. These are listed in Table 9.3. 

Peak irradiance The intense peak of focused power under a lamp, the maximum point of the irradiance profile. The unit of measurement... 

Small stream invertebrates have also been noted to respond negatively to UVR in nature. Blackfly larvae appear to exhibit a diurnal emigration, or migration out of UV-exposed stream channels, during periods of peak irradiance but return to UV-exposed regions as irradiance levels decrease [45]. In streams that were experimentally shielded from UVR exposure, however, larvae remained in the stream channels throughout the day. Larvae were allowed to move... 

FIGURE 2. Schematic illustration of the dependencies of gross photosynthesis (Ag), cost(C) and net photosynthesis ( ) on ax C increases linearly with Pmax> while the increase of with PmnY is convex. reaves the plateau when the light saturation point of photosynthesis gets to the peak irradiance. The maximum An is realised when the difference between and C is maximal. 

The absorptive and refractive contributions to the Z-scan profile are coupled. However, when the aperture is removed (5 = 1) the Z-scan transmittance is no longer influenced by the beam distortion (refractive component) but is a function of only the nonlinear absorption. For a temporally Gaussian pulse and ji ol < 1, the open-aperture transmittance is expressed in terms of the peak irradiance as [15]... 

The CA Z-scan curves taken for solutions (see Figure 22.21a) are typical for a material with a negative nonlinear refractive index. The nonlinear absorption was too small to be detected here because the observation of absorptive nonlinearities generally requires nearly excitonic resonance in CdS NP solutions [75,76]. The Kerr (or nonlinear refractive) index, 2, was calculated to be approximately -2x 10 m W at a peak irradiance of 320 MW cm for... 

Weatherabilities of flexible PVC sheets were compared by exposing samples in a fluorescent light apparatus for UV exposure (ASTM G 154) for up to 5000 hours. Light source was either a UVB (nominal peak irradiance at 313 nm) bulb or a UVA bulb (nominal peak irradiance at 340 nm). Light source irradiance at 313 nm was 0.7 watts/m /nm and at 340 nm was 1.55 watts/m /nm. Operating cycle was 6 hours dry at 70°C and 6 hours wet at 50°C. 

The robot program was then fine-tuned to achieve uniform peak irradiance on an automotive door panel moving at a line speed of 12FPM. Once uniform peak irradiance was established, robot variables were tuned to achieve equal UV dose. Power output of the lamp was kept constant for all testing. The unit is capable of producing 500W/in at full power. 

The accompanying figure below shows the process of fine mning the light path for consistent peak irradiance during one of the earliest line trials. The total time to tune the system so that peak irradiance is kept within a narrow range is estimated to be less than one hour. 

Online data collection using the 3DCURE unit was successful in allowing the team to rapidly develop paths that yielded uniform peak irradiance and energy density. Several improvements to the data collection system are being implemented to make higher speed data collection easier. 

The radiometric data indicates that sufficient peak irradiance and dose can be achieved with the line speed (12 FPM) and robot arm speed (600 mm/sec) that were used during the trials to affect proper cure of commercial formulations. (Based on baseline cure data provided by coating formulators). This opens the doors to steps 5 and 6 of the roadmap that will involve curing of various formulations at production cycle times. 

Figure 11. Data gathered during validation trials. The first procedure is to obtain uniform peak irradiance.

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