Effects of non-parallel magnetic fields on hexagonal cell drift chambers

The effect of magnetic field on drift velocity was measured in a wire chamber with an hexagonal cell geometry and an argon-ethane (50:50 by weight) gas mixture. The CLAS (CEBAF large acceptance spectrometer) prototype drift chamber was tested in a magnetic field using cosmic rays. The drift time to distance correlation was studied as a function of magnetic field strength using cosmic ray tracks. Particular attention was paid to the corrections due to differing track entrance angles and differing angles of the magnetic field direction with respect to the wire axis. Spatial resolutions better than 190 mu m were achieved for field strengths up to 1.5 T and angles between wire and field direction ranging from 0 degrees to 30 degrees . An argon-ethane mixture diluted with 60% helium showed less sensitivity to magnetic field effects, and only slightly worse resolution.<>