Volume 72, Issue 12, December 2001
Index of content:
Calculation of the spectral dependence of the radiance temperature of the high-stability tungsten strip lamp72(2001); http://dx.doi.org/10.1063/1.1416119View Description Hide Description
Tungsten strip lamps are calibrated at specific wavelengths. The calibration at one wavelength can be corrected to make it valid at another wavelength λ for calibrating a radiation thermometer that operates at λ. The correction can be obtained by a calculation based on either Wien’s or Planck’s radiation law with the knowledge of the spectral emissivity ε of the lamp filament and the spectral transmittance τ of the lamp window. Using published measurements of ε for tungsten and our measurement of τ for the window of a high-stability tungsten strip lamp, we develop analytical expressions for ε as a function of wavelength and temperature and for τ as a function of wavelength. These allow accurate calculations of the spectral dependence of the radiance temperature of such a lamp, from which the appropriate corrections can be made. Results are presented.
72(2001); http://dx.doi.org/10.1063/1.1416102View Description Hide Description
A simple accessory for bit error rate test instruments provides a means to monitor error rate audibly without watching a display so that the user may observe and make adjustments to equipment under test while hearing the effects of these adjustments. Normally inaudible narrow error pulses trigger a toggle flip-flop to provide a signal rich in audible components.
72(2001); http://dx.doi.org/10.1063/1.1416118View Description Hide Description
Recent advances in spot-welding technology such as high frequency direct currentinverter welders provide an improved and reproducible method to spot-weld difficult junctions. The importance of removing the oxide layers on metal surfaces, accurately delivering the weld pulse profile, and controlling the force applied to the materials during the welding process are discussed in the context of resistance spot-welding a molybdenum crystal to a tantalum loop and attaching a tungsten–rhenium thermocouple to the crystal.
72(2001); http://dx.doi.org/10.1063/1.1419217View Description Hide Description
We have developed an enhanced Littrow configuration extended cavitydiode laser (ECDL) that can be tuned without changing the direction of the output beam. The output of a conventional Littrow ECDL is reflected from a plane mirror fixed parallel to the tuning diffraction grating. Using a free-space Michelson wavemeter to measure the laser wavelength, we can tune the laser over a range greater than 10 nm without any alteration of alignment.