Wire Chamber - Drift Chambers

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.

The 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 Mw chamber but instead with central layer wires at a greater distance apart. The detection of charged particles within the chamber is possible by the ionizing of particles of gas 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 millimetres 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 deducted from the difference in time of the passage of the particle in the different part of the detector. This setup gives up the detector called Time Projection Chamber (often written just TPC)

For measuring the velocity of the electrons in a gas (drift velocity) there are special drift chambers, Velocity Drift Chambers which measure the drift time for known location of ionisation.