A new Chemical Oxygen-Iodine Laser (COIL) has been developed and demonstrated at chlorine flow rates up to 1 gmol/s. The laser employs a cross flow jet oxygen generator operating with no diluent. The generator product flow enters the laser cavity at Mach 1 and is accelerated by mixing with 5 gmol/s, Mach 5 nitrogen diluent in an ejector nozzle array. The nitrogen also serves as the carrier for iodine. Vortex mixing is achieved through the use of mixing tabs at the nitrogen nozzle exit. Mixing approach design and analysis, including CFD analysis, led to the preferred nozzle configuration. The selected mixing enhancement design was tested in cold flow and the results are in good agreement with the CFD predictions. Good mixing was achieved within the desired cavity flow length of 20 cm and pressure recovery about 90 Torr was measured at the cavity exit. Finally, the design was incorporated into the laser and power extraction as high as 20 kw was measured at the best operating condition of 0.9 gmol/s. Stable resonator mode footprints showed desieable intensity profiles, which none of the sugar scoop profiles characteristic of the conventional COIL designs.
Active imaging techniques are described that have minimum transmitter aperture redundancy and maximum transmitter intermittency. The proposed techniques are variants of Fourier telescopy. These techniques largely overcome conventional signal limitations by encoding the image information in the time domain. The basic approach combines long-baseline interferometry with phase closure to obtain high resolution images with very low average transmitter power, by proper choice of phase closure strategy. Several strategies are discussed and simulation results are presented.
Since its first demonstration in 1976 the free-electron laser has evolved rapidly, producing coherent radiation over a spectral range extending from the millimeter to the ultraviolet. Recent establishment of user facilities is enabling its use as an investigative tool in a number of scientific disciplines. Its ability to generate tuneable, high power radiation over a wide range of wavelengths interests medical, industrial and military users. However, exploiting the many features of this intrinsically high power laser poses new challenges in optical resonator design. We review significant advances in optical resonators for free-electron lasers including the influence of this peculiar gain medium on resonator designs.