Analysis and Tests of a Right Circular Cylinder in a Photon Environment

Abstract

An initial effort to test the predictive ability of certain SGEMP analytical tools has been completed, utilizing a simple 90 cm × 90 cm right circular cylinder as the test object. A set of pretest predictions were made for this object based on the expected PIMBS IA photon pulse characteristics, using strictly analytical tools, i.e., QUICKE2 for electron emission and the two dimensional code ABORC for surface current responses. The object was then tested in the photon environment generated in a large vacuum tank by the PIMBS IA source, and the responses measured. The reverse electron emission yield and approximate spectrum for the surface material used on the cylinder were also measured in a separate experiment, using a biased x-ray diode. This allows disagreement between analysis and experimental results to be separated into emission and particle motion components. Comparison of the predictions and experimental responses test the ability of the codes to predict the response of this very simple axisymmetric geometry in a low fluence (nonspace-charge-limited), low-frequency (nonresonant) regime. This is a very low strees test of the tools, particularly ABORC. The measured object responses averaged a factor of ~2.5 lower than the pre-test predictions based on a total predicted emission current of 3.5 amps (5.5 amps/m2). The biased diode results, scaled to the object emitting surface location, indicate a 0 bias total emission current of 1.7 amps (2.7 amps/m2). Scaling the predictions to this lower emission current brings the results into about 40 percent agreement.