were made and the resulting printed photographs were then examined.) A wire chamber is a chamber with many parallel wires, arranged as a grid and put on high voltage, with the metal casing being on ground potential. As in the Geiger counter, a particle leaves a trace of ions and electrons, which drift toward the case or the nearest wire, respectively. By marking off the wires which had a pulse of current, one can see the particle's path. The chamber has a very good relative time resolution, good positional accuracy, and self-triggered operation (Ferbel 1977). The development of the chamber enabled scientists to study the trajectories of particles with much-improved precision, and also for the first time to observe and study the rarer interactions that occur through particle interaction. Drift chambers If one also precisely measures the timing of the current pulses of the wires and takes into account that the ions need some time to drift to the nearest wire, one can infer the distance at which the particle passed the wire. This greatly increases the accuracy of the path reconstruction and is known as a drift chamber. A drift chamber functions by balancing the loss of energy from particles caused by impacts with particles of gas with the accretion of energy created with high-energy electrical fields in use to cause the particle acceleration. Design is similar to the multi-wire proportional chamber but with a greater distance between central-layer wires. The detection of charged particles within the chamber is possible by the ionizing of gas particles due to the motion of the charged particle. The Fermilab detector CDF II contains a drift chamber called the Central Outer Tracker. The chamber contains argon and ethane gas, and wires separated by 3.56-millimetre gaps. If two drift chambers are used with the wires of one orthogonal to the wires of the other, both orthogonal to the beam direction, a more precise detection of the position is obtained. If an additional simple detector (like the one used in a veto counter) is used to detect, with poor or null positional resolution, the particle at a fixed distance before or after the wires, a tri-dimensional reconstruction can be made and the speed of the particle deduced from the difference in time of the passage of the particle in the different parts of the detector. This setup gives us a detector called a time projection