Development and Performance of a High Pressure Hydrogen Time Projection Chamber

We describe a high pressure hydrogen gas time projection chamber (TPC) which is presently operating at Fermilab both as target and as recoil detector in an experiment investigating the diffraction dissociation of photons on hydrogen, ¿p ¿ Xp. The TPC, which consists of two cylindrical drift regions each 45 cm in diameter and 75 cm long, measures the polar angle and the energy loss dE/dx of the recoil protons. Typically, at 15 atm of H2 with 2 kV/cm drift field and 7 kV on the 35¿ sense wires, the drift velocity is about 0.5 cm/¿sec and the spatial resolution ± 200¿.