H L Andrews

We present an analytic theory for the operation of a Smith–Purcell free-electron laser with side walls that includes the effects of transverse diffraction in the optical beam. We allow the width of the electron beam and the width of the grating to vary independently and require the walls to be high compared to the wavelength of the evanescent wave. The results show that the side walls change the empty-grating dispersion relation in important ways. When the separation of the walls is not ...

&NA Brain potential records have been taken on a series of fifty men during maintained addiction to morphine, and on a second series of fifty men whose addiction had been terminated for at least one year. Neither group shows alpha percentage distribution curves in agreement with those found by other workers for normal groups. The addiction state is characterized by an abnormally high alpha output. In some cases the high alpha index is maintained following withdrawal, while in others ...

We describe an analytical theory for the gain of a Cerenkov free-electron laser including diffraction of the optical beam in the direction transverse to the electron beam, parallel to the surface of the dielectric. Since the width of the optical beam depends on the gain, the usual cubic dispersion relation of two-dimensional slow-wave structures is replaced by a 5∕2-power dispersion relation, but three of the five roots are extraneous. The results show that for a narrow electron beam, ...

Cu foils, 200μm in thickness, were heated in two stages by a ∼100-ns-long monoenergetic electron bunch at 19.8 MeV and a current of 1.7 kA (8.5×1014 e−) in a 2-mm-spot to Te∼1 eV. After 45 ns of isochoric heating, the pressure in the foil builds up to >20 GPa (200 kbar), it begins to hydrodynamically disassemble, and a velocity spread is measured. Near the end of the electron pulse, the 1550 nm probe is cut off or absorbed. Photonic Doppler velocimetry measurements were made to quantify ...

The LANL/AES normal-conducting radio-frequency injector has been tested at cw cathode gradients up to 10 MV/m. Field-emission electrons from a roughened copper cathode are accelerated to beam energy as high as 2.5 MeV and impinge on a stainless steel target. The energies of the resulting bremsstrahlung photons are measured at varying levels of injector cavity rf power corresponding to different accelerating gradients. At low cavity power, the bremsstrahlung spectra exhibit well-defined ...