A Faraday Cup is device for measuring the current in a beam of charged particles. In its simplest form it consists of a conducting metallic chamber or cup, which intercepts a particle beam. An electrical lead is attached which conducts the current to a measuring instrument. Detection can be as simple as an ammeter in the conducting lead to ground or a voltmeter or oscilloscope displaying the voltage developed across a resistor from the conducting lead to ground. A bias voltage applied either to the cup itself or a repelling grid preceding the cup, or a magnetic field, is usually used to prevent secondary emission from distorting the reading. The design can be significantly more complicated when it is necessary to make measurements of very short pulses or very high energy beams which may not be fully stopped in the thickness of the detector. Some examples can be found at the following sites:
The name of the device is intended to honor Michael Faraday (1791-1867), the discoverer of electro-magnetic induction, electro-magnetic rotations, the magneto-optical effect, diamagnetism, field theory.
The Beam Instrumentation Workshop (BIW) was started to provide a forum for in depth discussions of techniques for measuring charged particle beams produced in high energy accelerators. The large US and European Particle Accelerator Conferences dedicated a few sessions to instrumentation, making it difficult to have significant interaction among those in the field. It became apparent to Dick Witkover at BNL that a conference or workshop dedicated to instrumentation was needed. After meetings with representatives from the other National Labs across the US the first Accelerator Instrumentation Workshop was held at Brookhaven National Laboratory in 1989. The idea for the Award was born during the last day round-table discussion as a means of encouraging young engineers and physicists to become more innovative. Discussions between Bergoz and the Organizing Committee continued through the Beam Instrumentation Workshop (as it was now called) at the Fermi National Laboratory in 1990, with final agreement on how to keep the Award fair and non-commercial reached in 1991. The procedures for selecting the winner were written, primarily by Bob Shafer soon after and have remained virtually unchanged since. The clever name of the Award, referring to both a trophy and a measurement device, is attributed to Bob Webber.
