Volume 77, Issue 1, January 2006
Index of content:
- ELECTRONICS; ELECTROMAGNETIC TECHNOLOGY; MICROWAVES
77(2006); http://dx.doi.org/10.1063/1.2162749View Description Hide Description
A multipactor discharge is a resonant condition for electrons in an alternating electric field. This discharge can be disruptive to rf circuits, cavities, and resonators. The coaxial multipactor experiment (CMX) investigates these discharges in parallel plate and coaxial transmission line geometries at frequencies from with goals of measuring the electron energy distributions. CMX has a unique experimental setup that allows the transmission line to pass continuously through a short vacuum region. Retarding potential analyzers with secondary electron suppression measure the electron current as a function of bias voltage. Both parallel plate and coaxial multipactor experiments provide detailed measurements of the electron energy distributions under a variety of rf frequencies and electrode materials.
Expandable fully reflective focal-plane optics for millimeter- and submillimeter-wave array receivers77(2006); http://dx.doi.org/10.1063/1.2165547View Description Hide Description
We describe a focal-plane optics for millimeter- and submillimeter-wave array receivers which are both fully reflective—thus avoiding the absorption and reflection losses of dielectric lenses—and expandable to an arbitrary number of pixels. The optics unit cell consists of two mirrors and a feedhorn optimized for near-field operation. Employing an integrated optics approach the mirror setup consists of only three mechanical parts, independent of the number of pixels, and requires no internal optical alignment. With a -beam prototype a Gaussicity of and a focal-plane beam separation of 3.6 waist radii was obtained. In this article we present the optics design as well as numerical simulations and measured beam patterns.
Initiation techniques and the vacuum-ultraviolet-radiation efficiency of a stabilized multichannel surface discharge77(2006); http://dx.doi.org/10.1063/1.2163976View Description Hide Description
Multichannel surfacedischarges possess a number of advantageous characteristics for the optical pumping of photochemically driven lasers. This work reports on a type of large-area low-inductance sources of intense UV-VUV (vacuum-ultraviolet) radiation based on spatially stabilized multichannel discharges in gases. The discharges consist of several dozens of closely located parallel plasma channels initiated synchronously along a dielectricsurface on the area of several hundred square centimeters. In comparison with a large-area diffuse surfacedischarge, the plasma confinement within relatively thin channels greatly improves the efficiency of the discharge emission in the VUV spectral range. Several techniques are introduced, which allow a synchronous formation and homogeneous development of multiple spatially stabilized discharge channels. Technical efficiency of the dischargeradiation within the spectral range of reaches 5% and an effective brightness temperature of the radiating plasma exceeds . Synchronous operation of a number of multichannel discharge modules producing high-intensity submicrosecond optical pulses is demonstrated, which is of importance for the pump source scaling and geometrical adaptation.