Simple 'package design' ion chamber monitors for TRIUMF's proton beamlines

In the beam line designed to supply 100 μA of 500 MeV protons to the two ISAC production targets at TRIUMF, 13 profile monitor stations were required. The design allows each station to be fitted with either an air driven wire scanner module for high currents or an ionization chamber for low currents. Ring shaped multilayer G10 circuit boards were designed for the latter to enable a simple modular 'gas package' that is easily serviced and aligned. These gas packages have only five basic parts, two outer window frames with 0.010 in. thick E-beam welded Al windows, two ring shaped circuit boards with 2 mm wire spacing and edge card connectors (X and Y use the same design of board) and one center frame for mounting to the inserting mechanism and holding a .001 in. Al foil. The circuit boards are critical components due to the necessity to hold vacuum along their edges. Signal traces pass from the inner part of the ring that is gas filled to the outside of the ring that is in vacuum. The windows and center foil frame are at -300 V bias. This gas package design led to a similar design used to upgrade the existing (1970's vintage) proton beamline ion chamber monitors