Effects of external magnetic filter on behaviors of fast primary electrons in a volume negative ion source.
The relationship between enhancement of hydrogen negative ion H(-), volume production, and behaviors of fast primary electrons is studied theoretically. Trajectories of fast primary electrons are calculated, including collisional effects with hydrogen molecules. Active region of fast electrons depends strongly on the field intensity of the magnetic filter (MF), B(MF), and filament position. Therefore, spatial distributions of ionization and vibrational excitation collision points are also affected with changing B(MF). Although number of vibrational excitation collision points is much smaller than that of ionization collision points due to different mean free path, the relative intensity is varied by changing energy of fast electrons. According to the results and discussions including transport of produced vibrationally excited molecules, for enhancement of H(-) production, it is desired that fast electrons should approach the MF position and move into the downstream region as deep as possible without destruction of H(-) ions. To realize these conditions, good combination between filament position and the intensity of the MF should be required.
Negative ion rich plasmas in continuous and pulsed wave modes in a minimum-B magnetic field
Generation of hydrogen negative ion rich plasmas is investigated in continuous wave (CW) and pulse modulated (PM) wave modes of 2.45 GHz in a minimum-B magnetic field. The waves are launched directly into the plasma device and utilize wave particle resonances for high density plasma generation. In CW operation, the chamber is divided into two sections, namely, the source and downstream region, separated by a transverse magnetic field that allows only cold electrons (∼1 eV) into the downstream region helpful for the generation of negative ions. The H− density is measured by the second derivative beat method and is compared with the values obtained from a steady state model and the extracted current density. In the pulsed mode, temporal filtering generates negative ion rich plasmas in the afterglow phase. The H− density in the afterglow is estimated using saturation current ratio method and the results are compared with a time dependent model using particle balance equations. The essential idea in both the ...
High-Speed Infrared Radiometers*
The paper describes high-speed infrared radiometers utilizing thermistor infrared detectors. Instruments with 4- and 8-in. diam Cassegrain mirror optics are described. The method of operation and the calibration of these radiometers is discussed.The radiometers are uniformly sensitive from 0.7 to 35 μ. They have a response time of 16 msec and a sensitivity of the order of 10−10 w/cm−2 corresponding to a blackbody temperature differential of 0.01°C.The radiometers are used for quantitative measurements of infrared radiation and remote temperature determinations.