Description
The Sun emits light in the 100-200 nm wavelength range, known as the vacuum ultraviolet (VUV). Whilst the Solar VUV is absorbed by atmosphere and thus not observed on the Earth's surface, it plays a significant role in physical processes in our Solar system. Molecular dissociation of oxygen by the Solar VUV results in the formation of ozone and photoionization of nitric oxide forms Earth’s ionospheric D-layer. The Solar VUV has also been observed to degrade Solar cells, polymers, coatings and various other optical elements. Photoemission-driven dust charging has been hypothesised to occur on the surfaces and atmospheres of various rocky bodies. During the Apollo missions, this charged dust was observed to be one of the major environmental hazards of the Lunar surface, damaging various mechanical, thermal, optical, and electrical systems. The development of space systems requires testing in high-fidelity simulations of the space environment, which in turn requires high-fidelity Solar VUV simulators to enable testing against a variety of radiation-driven phenomena.
Here, we demonstrate a Solar VUV simulator based on an inductively coupled, radiofrequency plasma. Several plasma source configurations are considered in terms of maximising the light output and efficiency of the source. The VUV emission from the source was quantified using a radiometrically calibrated spectrometer, and the spatial radiation distribution was mapped via a calibrated photodiode.
At the source output, fluxes as high as 50 mW/cm$^2$ were measured, at least 4 orders of magnitude greater than the flux at 1 AU in the same wavelength range. Given this high flux, this source will enable exposure testing of materials and technologies under simulated Solar VUV. This testing can be rapidly accelerated, allowing exposure to several years of equivalent VUV dose in only hours of laboratory time.
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