We observed significant improvement in the performance of the Boeing/LANL free-electron laser (FEL) experiment in the last year. Some of the more graphic demonstrations of this improved performance are presented in the time-resolved optical spectral measurements (streak/spectrometer) and the electron-beam spectral measurements. We have observed an extraction efficiency of about : % for the uniform wiggler and nearly 1% for the tapered-wiggler experiment. We also present experimental evidence consistent with a sideband instability and its suppression by cavity-length detuning.

Gamma scintillation spectra were obtained with several sizes of NaI( Tl) crystal, Pilot B plastic, and liquid detectors which were immersed in solutions of gamma-emitting nuclides contained in a 2,3OO-gal tank. The count rates for gamma photons in the Mev energy range were proportional to detector volumes. Integral count rates with plastic and liquid detectors were, respectively, 39% and 335% of the rate with NaI( Tl) . Factors in the selection of detectors for field use are discussed.

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