FIGURE 4 - uploaded by Jeffrey Michael Neilson
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Photo of the cathode emitter from the prototype BWO. The desired emission region is indicated by the rectangular box.
Source publication
Calabazas Creek Research, Inc. is funded by the National Aeronautics and Space Administration to develop submillimeter-wave backward wave oscillators (BWOs) for spectroscopy of planetary atmospheres, nebulas, and comets. Recently, applications related to detection of biological, chemical, and explosive agents have been identified. Submillimeter-wav...
Context in source publication
Context 1
... BWO was disassembled and microscopically examined. There was obvious damage to the cathode such that it was no longer capable of producing an electron beam with the required configuration. A photograph of the emitter is shown in Fig. 4. The emitter should be a rectangular structure approximately 100 × 300 microns. The image shows a circular depression in the emitter surface and ion damage (white areas). Power Supplies Figure 5 shows the entrance to the rectangular beam tunnel. It provides evidence of beam impact both above and below the tunnel entrance. In theory, ...
Citations
... In the research of THz mixers, GaAs Schottky diodes are widely used due to their low noise performance at room temperature and structural stability [3]. The mature semiconductor device processing technology has made planar Schottky diodes widely used in mixers. ...
Here, the tenth harmonic mixing technology based on planar GaAs Schottky diode is first proposed for the 1.1 terahertz (THz) frequency conversion module. The first higher order mode cut‐off frequency of the suspended microstrip line has been investigated to determine the appropriate cross‐sectional dimension of transmission line shield cavity in the radio frequency (RF) circuit portion. The height of shield cavity of transmission line is designed to be discontinuous in order to facilitate the assembly of the diode. A modelling approach combining field and circuit is used to achieve joint simulation of linear passive structure and diode non‐linear characteristics. The simulation results show that the frequency conversion loss of this mixer is <55 dB in the RF frequency range of 1.03–1.154 THz, and the best frequency conversion loss is 50 dB at RF of 1.098 THz.
The paper reports on the design and performance of a high power backward wave oscillator (BWO), working at Ku-band frequencies. The rectangular waveguide grating structure is used as its slow wave structure. The backward wave oscillator is driven by a sheet beam with cross sectional area of 30mm×1mm which is generated by a thin cathode. For a beam voltage 185kV, and beam current 3.2kA, the output power is 2.5MW at 14.3GHz.
Backward-wave oscillator (BWO) is a promising candidate as a millimeter-wave and submillimeter-wave (MMW/SMMW) power source and has a compact configuration, moderate output power, and frequency-tuning abilities. The physical conditions for increasing the threshold current of a typical MMW/SMMW-BWO are theoretically studied in this paper. We demonstrate the greater effect of axial phase velocity variation of deformed slow-wave structures on the threshold current in a 220-GHz folded waveguide (FW) BWO in comparison with other insensitive factors. For further verification, a prototype tube of FW BWO is developed. This tube exhibited increased threshold current during experiments. This finding is consistent with the error analysis proposed by our theory.
3-D electromagnetic simulation software is used to calculate the dispersion and interaction impedance of circular comb Slow-Wave Structure (SWS) which works for Terahertz (THz) Backward-wave Oscillators (BWO). The results show that the inner radius of SWS is 0.175 mm in the band of 430-570 GHz, and the inner radius of SWS is 0.1 mm in the band of 760-940 GHz. The large radius of SWS is a great help for improving beam transmission. The interaction impedance of fundamental backward wave of the SWS is smaller than 1Ω is a good explain to the truth that the electronic efficiency of THz BWO is smaller than 0.01%.
A 600-700 GHz BWO is currently being rebuilt for testing. Previous tests identified problems with the cathode and materials used in the structure. These were addressed and the BWO is now being assembled for testing in July 2006. The modifications to the design are described and test results will be presented.
We investigate the application of sheet beams to slow wave sources as a means to increase output power. Our interest is for compact vacuum electronic devices in the millimeter and submillimeter regimes. We consider previous work done on orotrons, clinitrons & backward wave oscillators, and investigate methods to enhance operation into the submillimeter region of the spectrum. We use MICHELLE to model ~40 micron thin sheet beams for such devices
This paper describes research on the generation of a 10 keV, 50 times 300 micron elliptical electron beam for a 650 GHz TWT amplifier
Computer optimization can explore a wider parameter space than practical with manual design, particularly for 3D geometries. This allows rapid, economical development of higher performance devices. The proliferation of parametric solid modeling programs allows optimization of both geometry and operating parameters. This presentation described computer optimization in the 3D trajectory code beam optics analysis (BOA). This is possible because meshing in BOA is completely automatic, allowing the program to be controlled by the optimization routines.
