Chamber (LArTPC) In 1974, William J. Willis and Veljko Radeka demonstrated that total absorption calorimetry was possible in liquid argon detectors without the amplification that normally occurs in a gaseous ionization detector. This critical technology enabled the possibility of a time projection chamber based on Nygren's original design, but using liquid argon as the sensitive medium instead of gas. In 1976, Herbert H. Chen, with collaborators at University of California, Irvine and the California Institute of Technology, proposed one of the earliest uses of liquid argon in a time projection chamber (LArTPC). Chen's initial goals with such a detector were to study neutrino-elecron scattering, but the goals evolved to measure solar or cosmic neutrinos or proton decay. In 1977, Carlo Rubbia independently, and nearly simultaneously, proposed to construct an LArTPC at CERN for rare event particle physics experiments. Detector design and properties Liquid argon is advantageous as a sensitive medium for several reasons. The fact that argon is a noble element and therefore has a vanishing electronegativity means that electrons produced by ionizing radiation will not be absorbed as they drift toward the detector readout. Argon also scintillates when an energetic charged particle passes by, releasing a number of scintillation photons that is proportional to the energy deposited in the argon by the passing particle. Liquid argon is also relatively inexpensive, making large-scale projects economically feasible. However, one of the primary motivations for using liquid argon as a sensitive medium is its density. Liquid argon is around one thousand times denser than the gas used in Nygren's TPC design, which increases the likelihood of a particle interacting in a detector by a factor of around one thousand. This feature is particularly useful in neutrino physics, where neutrino–nucleon interaction cross sections are small. The body of a typical LArTPC is formed of three parts. On one side of the detector is a high-voltage cathode plane, used to establish a drift electric field across the TPC. Although the exact electric potential at which this is set is dependent on the detector geometry, this high-voltage cathode typically produces a drift field of 500 V/cm across the detector. On the side opposite of the cathode plane is a set of anode wire planes set at potentials much higher (less negative) than that of the cathode. Each plane is separated from its neighbors by a small gap, usually on the order of 1 cm. A