Measuring flux, current, or integrated charge of low energy particles

A method of measuring an attribute of a beam comprising:

• providing an inner cylinder with a surface, the inner cylinder configured to provide an output;
• providing a coaxial cylinder that surrounds the inner cylinder and is electrically insulated therefrom;
• and
• providing an offset current source in electrical communication with the inner cylinder and configured to generate an offset current that opposes a leakage current in the system.

A method of measuring a flux of a beam using a cup having a coaxial cylinder that surrounds an inner cylinder and is insulated therefrom, the cup including an aperture and in communication with an electrometer, a current integrator, and a counter, the method comprising:

• grounding the coaxial cylinder;
• upon determining that the beam is incident on the cup, removing the beam;
• receiving measurements from the electrometer indicative of the leakage current of the cup;
• adjusting an offset current;
• aligning the beam with the cup;
• measuring a beam current with the electrometer;
• and
• determining the flux from beam current and the area of the aperture.