Prototype Active-Target Time-Projection-Chamber

The Prototype Active-Target Time-Projection Chamber (PAT-TPC) is an active-target detector that is uses a gas volume as both the target and tracking medium. Charged-particle tracks are imaged in the device and using these images, reaction cross sections, and charged-particle decays can be measured with high efficiency, large angular coverage, and precise angle and energy measurements. The gas volume also provides large areal densities, which is advantageous for experiments that have low beam rates.

The gas volume is cylindrical with dimensions 50 cm long and having a diameter of 25 cm. Up to 1 atm of gas can be used and we have run as low as 14 Torr. He, isobutane and P10 gas targets were used to study reactions with protons, He, and Ar. More gas mixtures are planned for the future. Ionization tracks are amplified with proportional counting device called the Micromegas. The Micromegas can provide gains typically from 10 to greater than 1,000 depending on the application. The segmentation of the Micromegas anode pad plane also allow for setting different gains for individual pads, which allow for measurements of particles that have very large differences in ionization track densities.

A number of reactions and decays after implantation can be studied using in-flight radioactive beams produced with TwinSol. Recently we have performed experiments with radioactive beams of 6He, 10Be, 12B, 12N, and 10C using the PAT-TPC. Experiments were aimed at studying cluster structure through resonant alpha scattering, study of fusion cross sections with neutron-rich radioactive beams, and decay modes of the Hoyle state.