Paper  Title  Page 

TUP007  Spectral Limits and Frequency Sumrule of Current and Radiation Noise Measurement  362 


Funding: This research was supported by a grant from the United StatesIsrael Binational Science Foundation(BSF), Jerusalem, ISRAEL The current noise spectrum of an electron beam is generally considered white and expressed by the shotnoise formula (eI0). It is possible to control the spectral energy of a random electron beam current by longitudinal space charge microdynamics and dispersive transport. Both noise suppression (relative to eI0)[1,2] and noise enhancement[3] have been demonstrated, exhibiting sub/superPoissonian particle distribution statistics, respectively. We present a general theory for the current noise of an ebeam and its radiation emission in the entire spectrum. The measurable current noise spectrum is not white. It is cutoff at high frequencies, limited by the measurement length and the beam axial momentum spread (fundamentally limited by quantum uncertainty). We show that under certain conditions the current noise spectrum satisfies a frequency sumrule: exhibiting noise enhancement in one part of the spectrum when suppressed at another part and vice versa. The spontaneous emission (radiation noise) into a single radiation mode or single direction in any scheme (OTR, Undulator etc.) is subradiant when the beam current is subPoissonian and vice versa, but the sumrule does not apply. 
