capacitor. The other end of the resistor is wired to a bias voltage, and the other end of the capacitor is wired to the front-end electronics. The front-end electronics amplify and digitize the current in the circuit. This amplified and digitized current as a function of time is the "signal" that is passed to the event reconstruction. For a given anode plane wire, the signal produced will have a specific form that depends on whether the wire is located in an induction plane or in a collection plane. As a drift electron moves toward a wire in an induction plane, it induces a current in the wire, producing a "bump" in output current. As the electron moves away from a wire, it induces a current in the opposite direction, producing an output "bump" of the opposite sign as the first. The result is a bipolar signal. In contrast, signals for a collection plane wire are unipolar, since electrons do not pass by the wire but are instead "collected" by it. For both of these geometries, a larger signal amplitude implies that more drift electrons either passed by the wire (for induction planes) or were collected by it (for the collection plane). The signal readout of all of the wires in a given anode plane can be organized into a 2D picture of a particle interaction. Such a picture is a projection of the 3D particle interaction onto a 2D plane whose normal vector is parallel to the wires in the specified anode plane. The 2D projections corresponding to each of the anode planes are combined to fully reconstruct the 3D interaction. Dual-phase TPC The technique itself was first developed for radiation detection using argon in the early 1970s. The ZEPLIN programme pioneered the use of two-phase technology for WIMP searches. The XENON and LUX series of detectors represent the state-of the art implementation of this instrument in physics. Notes References Further reading Particle detectors