Knowledge Bank

A spectrometer which scans a wavelength band of 0.6 microns in 30 microseconds and is useful from 2 to 6 microns is described. The instrument can be synchronized with a pulsed source with a minimum triggering delay of 15 microseconds. Using this instrument data have been obtained of the absolute spectral radiation intensity of air, nitrogen, neon, and argon heated by reflected shocks in shock tubes to equilibrium temperatures in the range of 6000 to $10,000\circ K$. In this temperature regime an important source of continuum radiation in these gases is neutral Bremsstrahlung caused by the inelastic scattering of electrons from neutral atoms and molecules. The instrument is basically an Ebert spectrometer equipped with an indium antimonide detector at the exit slit, an aluminum scanning mirror placed 2 inches before the exit slit, and a wavelength calibration signal generator. The scanning mirror, which is supported on pivots inside a helical coil, deflects the spectrum through an angle of approximately 90 degrees onto the exit slit. When a capacitor is discharged through the coil, the resulting magnetic field spins the aluminum mirror causing the spectrum to move across the exit slit. The wavelength calibration signal generator produces a series of electrical pulses as the scanning mirror turns, permitting wavelength calibration when the pulses are displayed below the spectrometer signal on a dual beam oscilloscope. The unique features of the spectrometer are described. The calibration, use, and typical data are also presented. This work was supported jointly by Advanced Research Projects Agency monitored by the Army Missile Command, United States Army under Contract DA-01-021-AMC-1200(Z) (part of Project DEFENDER), and Headquarters, Air Force Special Weapons Center, Air Force Systems Command, United States Air Force under Contract AF 29(601)-7055 (Project No. 5710).