Electron Bunch Length Diagnostic Device

72316S03-I This project will develop a diagnostic device for the measurement of electron bunch length in a beam transport line at a linear accelerator facility. The device will be based on the detection and spectral analysis of wake field (Cerenkov) radiation generated when an electron bunch, or train of bunches, passes along the axis of a dielectric-lined beam pipe. This diagnostic method will be non-intercepting and nearly non-perturbative, and, therefore, it would have advantages over other means of bunch length measurement because it would not significantly alter bunch properties. In Phase I, an analysis of wake field radiation spectra, arising from the passage of a charge bunch or bunches along a dielectric-lined cylinder, will be performed. Mesh filters and/or a millimeter-wave spectrometer will be used to make preliminary observations of the wake field radiation. Comparisons of measurements and theory will guide the design of an improved diagnostic module for more detailed bunch length measurements to be carried out in Phase II. Commercial Applications and Other Benefits as described by awardee: Modern linear accelerators for electrons can generate electron bunches with durations in the picosecond and sub-picosecond range. Knowledge of the bunch length is critical for research uses of the bunches, and for practical applications of potential importance in medicine and industry.