Title :
Phase characterization of gyrotron beams from intensity measurements using the moment method
Author :
Anderson, J.P. ; Shapiro, M.A. ; Temkin, R.J. ; Denison, D.R.
Author_Institution :
Plasma Sci. & Fusion Center, MIT, Cambridge, MA, USA
Abstract :
We present the formulation of the moment method applied to the determination of phase profiles of microwave beams from known amplitudes. While traditional approaches to this problem employ an iterative error-reduction algorithm, the moment method calculates a two-dimensional polynomial phasefront based on weighted moments of intensity measurements. Since this novel formulation calculates the moments of quasioptical Gaussian-like beams, the moment method has the very important advantage of quantifying and compensating for measurement error. The validity of the moment method is tested and confirmed by examining a simple case of an ideal Gaussian beam. The effectiveness of this approach is further demonstrated by applying intensity measurements from cold-test gyrotron data to produce a phasefront solution calculated via the moment method. The accuracy of these results is shown to be comparable with that obtained from the previously developed iteration method.
Keywords :
electron beams; gyrotrons; method of moments; microwave measurement; phase measurement; cold-test gyrotron data; gyrotron beams; ideal Gaussian beam; intensity measurements; iterative error-reduction algorithm; measurement error; microwave beams; microwave output phase; phase characterization; phase profiles; phase-retrieving moment method; quasioptical Gaussian-like beams; two-dimensional polynomial phasefront; weighted moments; Gaussian processes; Gyrotrons; Iterative algorithms; Iterative methods; Measurement errors; Microwave theory and techniques; Moment methods; Phase measurement; Polynomials; Testing;
Conference_Titel :
Antennas and Propagation Society International Symposium, 2001. IEEE
Conference_Location :
Boston, MA, USA
Print_ISBN :
0-7803-7070-8
DOI :
10.1109/APS.2001.958852
