PRELIMINARY EVALUATION OF NEW UV/VUV RADIOMETRIC STANDARDS

THERE ARE ONLY A FEW RADIOMETRIC STANDARDS AVAILABLE IN THE 115-350 NM WAVELENGTH REGION. AMONG THEM ARE THE ARGON MINI-ARC AND THE DEUTERIUM LAMP. BOTH LAMPS PROVIDE STABLE SOURCES OF UV/VUV RADIATION, AND CAN BE CALIBRATED BOTH IN RADIANCE AND IRRADIANCE. HOWEVER, EACH HAS DISADVANTAGES THAT LIMIT ITS USEFULNESS AS A BENCHTOP OR SPACE-QUALIFIED STANDARD. ONE POSSIBLE ALTERNATIVE SECONDARY RADIOMETRIC STANDARD FOR THE UV/VUV IS THE RF-EXCITED ELECTRODELESS DISCHARGE LAMP. THESE LAMPS ARE SMALL, HAVE LOW INPUT POWER REQUIREMENTS, HAVE A LONG LIFETIME, AND HAVE BEEN ADAPTED FOR SPACEFLIGHT. BY VARYING THE RARE GAS FILL PRESSURE (FROM A FEW TORR TO TENS OF TORR) EITHER CONTINUUM RADIATION OR SPECTRALLY PURE LINE RADIATION CAN BE GENERATED IN THE UV AND VUV. PRELIMINARY MEASUREMENTS ON A KRYPTON VUV CONTINUUM LAMP INDICATE THAT THE LAMPS ARE LONG-LIVED AND STABLE ENOUGH TO BE CONSIDERED AS POSSIBLE RADIOMETRIC STANDARDS. THE OBJECTIVE FOR THE PHASE 1 EFFORT IS THE EVALUATION OF A FEW RF-EXCITED LAMPS IN TERMS OF THEIR SUITABILITY AS SECONDARY UV/VUV RADIOMETRIC STANDARDS. BY CHARACTERIZING A FEW KEY SOURCE PARAMETERS, ONE CAN DETERMINE WHETHER FURTHER CONSIDERATION OF THESE SOURCES IS WARRANTED.