Influence of the magnetic field on the gating of a time projection chamber

A large cylindrical time projection chamber (TPC 90), 60 cm in diameter, a driftlength of 130 cm, as well as a smaller test-chamber of 30 7 30 7 15 cm3 have been used to investigate the effects of the magnetic field on the operation of a gated grid. The magnetic field is found to affect strongly the drifting electrons, but not for the positive ions. The results can be well explained by the specific configuration of the combined E and B fields near the gating grid wires and in the region of the proportional wires