Specification and Design of Solar Ultraviolet Simulators**From the Department of Medical Physics, Temple University Medical School, Philadelphia, Pennsylvania 19140.

Abstract

Vol. 53,No. 3 Peiated in U.S.A.Ultraviolet light (UV) causes most light induced skin reactions. Since the strongest source of UV in the normal environment is sunlight, an artificial source intended to elicit various normal and pathologic photoresponses should have a spectrum like that of the UV from the sun. It is the purpose of this paper to present the considerations required for the design of an ultraviolet solar simulator and to compare the measured performance of a completed instrument with design goals.Several types of light sources have been used in skin studies (1). Cold quartz mercury lamps have been of the most limited utility due to the preponderance of energy at 254 nm, a wavelength not naturally found (Fig. 1). Hot quartz mercury lamps and Kromayer lamps have a much higher proportion of energy at the 297, 303, 313, and 365 nm mercury spectral lines and have been used widely (Fig. 2). The ab-senee of a significant amount of energy between 313 and 365 nm limits the applicability of this light in reproducing photodcrmatitis (2-4). Carbon arc lamps employing appropriate rod material emit significant amounts of UV over the entire solar range (Fig. 3). In spite of superior spectral characteristics their use has been limited because of gaseous waste products which require adequate venting, and the maintenance problems resulting from consumable electrodes. The Westinghouse FS Sunlamp, a fluorescent light with a phosphor that peaks at 313 nm, readily causes sunburn but has negligible energy above 340 nm. The "black light" fluorescent lamp has a phosphor whose output peaks at 350 nm but falls off rapidly below this (Fig. 4). Its low intensity prevents its use in eliciting light induced dermatoscs. Xenon short arc lamps have been used since their availability in the early 1950's (5).They have a UV continuum like the sun, output is uniform over long periods, and there are not the maintenance problems of carbon arcs (Fig. 5). Xenon arcs have more of a heat problem than carbon arcs, for strong spectral lines exist in the near infrared.For completeness, the Vortex Stabilized Radiation Source and the Fluid Transpiration Arc should be mentioned. Each has abundant UV energy but the cost of these sources and their ancillary equipment is excessive (6). 192A light source which simulates the ultraviolet part of the solar spectrum, but at a much higher intensity, has been developed.t The source consists of a 150 watt xenon lamp, collecting optics, spectral shaping components, and a refocussing lens.The output spectrum has 70% of its enargy at wavelengths below 400 nm and resembles the spectrum of daylight ultraviolet for a 70° sun elevation. The intensity over a 1 cm diameter uniform spot is about 10 times that of daylight ultraviolet. At other focal positions, stronger intensities over smaller uniform areas and weaker intensities over larger uniform areas are found, all with the same spectrum. For uniform areas with less than 1 cm diameter the intensity can exceed the heat erythema threshold for multiple doses.Operation ...

Development of high intensity narrow-band lamps and studies of the irradiation effect on human skin. Irradiation with high intensity lamps

“…This might be due to the TR radiation alone or possibly to a combined UV-JR effect. Berger (2) has given values of 600-1 000 mW/cm' as the A<'fa Dermatovener (Srock/10/111) 55 pain threshold for his solar simulator in the long wave UV. Thesc values are higher than ours and, togcther with our results, thcy may indicate an in teresting area-size dependence typical of pain sensa tion where the cooling of the skin by heat conduc tion and convection of intercellular fluid may be im portant.…”