EP20 e m Manual - Instruction Manual for EP-20 e/m of the...

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FAX (978)745-3065, www.daedalon.com, e-mail:daedalon@cove.com DAEDALON CORPORATION Instruction Manual for EP-20 e/m of the Electron Apparatus Introduction This self-contained apparatus is designed for the measurement of e/m of the electron by observing the radius of the circular path under the influence of a uniform magnetic field. The magnetic field is provided by a pair of Helmholtz coils surrounding the vacuum tube. The vacuum tube has a downward pointing electron gun in an evacuated bulb that has a little helium added so that the path of the electrons in the tube is visible. The overall appearance of the apparatus is shown in Figure One, e/m OF THE ELECTRON ON OFF HV ADJUST ACCELERATING VOLTAGE COIL CURRENT CURRENT ADJUST DAEDALON CORPORATION Figure One Three internal power supplies provide the filament power, the coil current and the accelerating potential for the electron beam. The filament supply is fixed, while the accelerating voltage and the coil current are set by front panel controls. The accelerating potential and the coil current can be measured by digital meters on the front panel. The meters make it simple to accurately determine the forces affecting the motion of the electrons within the tube. The diameter of the electron path in the magnetic field can be measured using the etched glass internal scale in the tube. The graduations and numerals of the scale are illuminated by the collision of the electrons, making observation and reading even easier.
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EP-20 e/m of the Electron Apparatus 2 The helium gas added to the tube fluoresces when struck by the moving electrons and produces a bright, clear view of the electron beam. An electrode is provided for absorbing electrons after they have traced their circular path. Thus, the circular tracing of the electron path is undisturbed by previously emitted electrons, contributing to more accurate measurement. Principle of Operation The general configuration of the electron gun Is shown in Figure Two. Electrons are emitted by an indirectly heated cathode at the top of the figure. The cathode is connected to the negative of the high voltage supply. It is partially shielded by a surrounding grid which has a small aperture to let some electrons pass through. The anode is mounted below the grid and is connected to the high voltage positive. Electrons escaping through the grid hole are rapidly accelerated toward the anode by the
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This note was uploaded on 11/26/2009 for the course PHY 124 taught by Professor Staff during the Fall '08 term at SUNY Stony Brook.

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EP20 e m Manual - Instruction Manual for EP-20 e/m of the...

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