Penetration of RF Fields into Holes in Cavity Walls

Measurements of magnetic fields in cavity wall penetrations were made to provide engineering data for practical cavity design. The data were normalized to cavity wall fields and, as expected, when all coordinates were scaled by the transverse dimension of the penetration, the measured field distributions were similar and differed by only small systematic amounts. These data are thus generally applicable to any standard rf cavity, independent of frequency, provided only that the penetration, when regarded as a waveguide, is well below cutoff frequency. Until the results of three dimensional rf cavity codes are commonly available, these numbers should assist design engineers in detailing the properties of tuning plungers, drive loops, pumping ports and view ports.