Microfabrication techniques are commonly used to build circuits for millimeter-wave and THz vacuum electron devices. A cost effective solution is becoming available, at least for building prototype circuits intended for cold-testing. Rapid prototyping machines such as 3D printers have advanced to the point that their resolution is below the wavelength of many microwave circuits. This paper reviews the application of this quickly-advancing technology towards waveguide components of vacuum electron devices. The authors use a rapid prototype technique called Direct Metal Laser Sintering (DMLS) to “print” sample 35 GHz circuits in metal. Circuits in two different materials (aluminum and chromium cobalt) are printed and cold-tested. The test data shows good agreement with simulation.

A systematic study of the consequences of Fubini-Dashen-Gell-Mann sum rules for allt-channel helicity amplitudes is given. The necessity of Kronecker deltas in all sense-sense amplitudes atJ=1 is pointed out. The coefficients of these Kronecker deltas are, apart from kinematical factors, the form factors of the target particles.