Filament and Electrometer Testing
Electronics are emitted via thermionic emission from an ES-020 tungsten filament. This is powered from an adjustable DC supply with constant current control. Filament current is kept around 2.25A. A separate DC supply biases the filament to -300VDC, adding energy to the emitted electrons. Ultimately, electrons from the filament ionize hydrogen atoms in the chamber, creating free protons ready for acceleration. In these tests, electron emissions from the filament were measured to test the filament and beam measurement ability.
Particle beam measurement is centered around a Keithley 617 electrometer. This meter can measure currents as low as 0.1 femtoamps. A pseudo-Faraday cup created from a 6 AWG crimp lug picks up particles in the beam, creating a current measured by the electrometer. Although the 617 has a built-in voltage source, using it here added some noise to the measured current. A string of 20 9V batteries was used as the bias voltage source.
Coax cable is used to shield the electrometer input, and shield cabled is also used for the filament power. Achieved current resolution is 0.1 picoamps (1E-10 amps).
Particle beam measurement is centered around a Keithley 617 electrometer. This meter can measure currents as low as 0.1 femtoamps. A pseudo-Faraday cup created from a 6 AWG crimp lug picks up particles in the beam, creating a current measured by the electrometer. Although the 617 has a built-in voltage source, using it here added some noise to the measured current. A string of 20 9V batteries was used as the bias voltage source.
Coax cable is used to shield the electrometer input, and shield cabled is also used for the filament power. Achieved current resolution is 0.1 picoamps (1E-10 amps).