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By using a power ratio technique, we have lowered our uncertainty for attenuation measurements by a factor of about 4 (typical) when compared to our vector network analyzer uncertainty analysis. The power ratio technique is applicable to insertable 2-port devices with low reflection coefficients such as airlines and attenuators. The method is illustrated with 3 coaxial devices over a frequency range of 2–18 GHz and 2 rectangular waveguide devices over a frequency range of 50–75 GHz. Our results suggest that a significantly lower attenuation uncertainty could be justified by a re-analysis of the vector network analyzer measurements. [ABSTRACT FROM PUBLISHER]

A new design and evaluation technique of a rectangular waveguide microcalorimeter is presented. Its design is based on the NIST new WR-15 microcalorimeter design[1], but an important modification was made so that the principle of the measurement was changed. In this design, not only can take the original evaluation technique, but also take the new method to obtain the final data-reference standard's effective efficiency. By the new evaluation technique, we don't need measure the S-parameter of the trans-line in the microcalorimeter which is the main uncertainty source in obtaining the thermistor mount effective efficiency. [ABSTRACT FROM PUBLISHER]

Summary form only given, as follows. By using a low-impedance Mylar line for pulsed power feed at low voltages (5 kV) and a special power feed to avoid electron ejection by magnetic forces, about 1 kW of microwave power has been produced in the 10-cm band. This orbitron is gas filled to provide electrons by ionization. The second orbitron advance was to use a split cathode coupled to a resonant circuit. This provides a resonant system for the orbiting electrons to couple to, generating more power in a narrow, fixed frequency range. This orbitron uses a tungsten heated cathode for electron injection. The device operates well, producing a narrow line at 145 MHz at a power level of -20 dBm (0.01 mW) as picked up by an external antenna. The coupling has not been optimized [ABSTRACT FROM PUBLISHER]

Summary form only given. Three-dimensional particle-in-cell simulation has confirmed an interaction between a relativistic electron beam and nonaxisymmetric cavity modes, which leads to amplification of the cavity modes. When a relativistic electron beam is injected into a cylindrical cavity, its transverse motion excites nonaxisymmetric electromagnetic modes such as TM110 or TE112. The physical effect exploited and optimized is that of the beam-breakup instability important in high-current accelerator cavity design. Coupling the instability with the transit-time effect of the electron beam in the cavity, rapid exchange of energy between the electron beam and the preselected electromagnetic mode can occur and microwave power can then be extracted. Under optimal conditions, the linear growth time of the cavity mode at 2.44 GHz is expected to be about 3 ns. In addition, the transit-time resonance naturally leads to very narrowband output with typical wavelengths in the range of 1-10 cm depending on the cavity radius. A comparison of the linear growth rate of the TM110 mode with a linear theory prediction for different lengths of the cavity has been made. Simulation results show a slight shift in the cavity length for maximum growth [ABSTRACT FROM PUBLISHER]