IMPURITY PHOTOI0mZATION THEORY OF PRECURSORS

An extension of Wetzel* s theory is proposed to explain electron precursor phenomena in pressure driven shock tubes. The theory is based on the assumption, which hae been experimentally verified, that radiation from the hot gas behind the shock front is responsible for the precursor effect. A point radiator, located at the shock front and moving with the shock velocity, is assumed. It is shown that this radiator can be idt?lized by a black body. The precursor electron density is derived from a one-step photbionization of the impurities present in the driven gas. As an application of the theory, precursor profiles are calculated for an H2 impurity. The partial pressure of H2 is . varied from 2 to 75|aHg. The temperature behind the shock is assumed to be 11, 000 K. This research was supported undsr Contract Nonr 839(38) for PROJECT DEFENDER, and the Advanced Research Projects Agency under Order No, 529 through the Office of Nav»! Research. Assistant Professor of Aerospace Engineering iStafc Research Fellow TABLE OF CONTENTS Section ii Pafif