We have demonstrated a diode-end-pumped Nd:YAG laser that produces an output power of 60 W in a near-diffraction-limited beam (i.e., M(2) < 1.3). In multimode operation, the laser produces an output power of 92 W. The optical-to-optical efficiency (i.e., the ratio of laser power to diode power) is 26% for TEM(00) operation and 44% for multimode operation.
The design and performance of a 15-W output-power, diode-pumped cw Nd:YAG laser is described. With the use of geometrically multiplexed end pumping, the combined power of four 10-W diode-laser bars is deposited in the active-medium mode volume with an efficiency of 80%. While operating on several transverse modes the laser has a threshold of 3 W, an optical slope efficiency of 60%, and an overall electrical efficiency of 10.5%. Thermally induced higher-order spherical aberration of 1.2 waves limits the output power in the TEM(00) mode to approximately 6 W.
The design and characterization of a Faraday cup utilizing modular components are presented. Design specifications were primarily tailored to satisfy the specific electron beam (e-beam) energy (∼375 keV), rise time (∼60 ns), and magnitude (30 A/cm2, peak) used in this work and permit convenient sampling of large e-beam areas up to 7 cm×7 cm. Characterization during evacuated conditions included Z-dependence measurements using beryllium, carbon, aluminum, and lead collector plates. Electron beam transmission measurements were made utilizing combinations of various metal screens and Kapton foils in both gas and evacuated conditions. Gas environments tested were air, krypton, and a Kr/Ar mixture. An attacher gas, SF6, was also added inside the Faraday cup. Results reveal decreasing current densities with increasing gas stopping power and increasing electron propagation distance in a gas. Employing a carbon collector plate and a 25-μm Kapton foil insulator, current densities measured through a 3.6-cm thick 760 Torr air slab are reduced ≤6% from the evacuated Kapton-free condition. Applying profile and full-aperture Faraday cup measurements, a consistent description of the e-beam is also presented.
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