Reconstruction of Longitudinal Beam Profiies from Nondestructive Electromagnetic Probes

The Fusion Materials Irradiation Test (FMIT) 2-MeV accelerator has nondestructive diagnostic probes that sense changes in the electromagnetic fields of the bunched beam. These probes accurately perform their primary functions, but do not have well-behaved, frequency-domain characteristics from which the longitudinal beam profile can be measured using convolution-integral processing techniques. Therefore, each of the probes transfer function was determined using a tightly bunched electron beam as a source for impulse response tests. Using the Signal Processing Analyzer (SPA) code, output signals from these probes mounted on the FMIT beamline were deconvolved with sampled impulse response data to produce a longitudinal electromagnetic field distribution of a beam bunch. With SPA's signal-processing techniques, any electromagnetic probe shorter than ß λ and having significant signal-to-noise ratios can reconstruct longitudinal profiles, provided the probe's transfer function is known.