Research and development program on dense TPC's at LBL

We have initiated a research and development program at LBL to develop high density TPC's. We are motivated by their potential use as tracking calorimeters to study nucleon decay. They may also be useful in the study of cosmic neutrino fluxes, double β decay and other low rate processes. Of these applications, the use of dense TPC's to study nucleon decay is the most challenging one because it requires instrumenting very large masses. Our R and D program is aimed at developing large TPC's which are competitive in cost with other proposed nucleon decay detectors while offering superior capabilities for energy resolution, particle identification and uniformity of response. There are two ways of obtaining high density TPC's: the first is to use a cryogenic liquid such as liquid argon or liquid methane; the second is to pressurize a gas such as argon or methane to several hundred atmospheres where the density of the gas approaches that of the liquid state. While we are interested in studying both approaches, we are concentrating on the high pressure approach since it offers the potential advantage of proportional wire amplification. A wire amplification of about 3 orders of magnitude would eliminate the noise problems which are inherent in ionization mode detectors such as liquid argon chambers. A possible 10 kton detector is described, and its properties are discussed in terms of tracking, energy measurements and particle identification