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Faraday cup with nanosecond response and adjustable impedance for fast electron beam characterization
1Aerospace Plasma Laboratory, Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409, USA. jhgdb@mail.mst.edu
The Review of Scientific Instruments
|August 3, 2011
Summary
This study introduces a new movable Faraday cup for measuring electron beams. Its adjustable impedance and self-biased capabilities enable accurate determination of electron energy distribution functions.
Area of Science:
- Physics
- Electrical Engineering
- Plasma Science
Background:
- Faraday cups are essential for measuring charged particle beams.
- Accurate measurement of electron energy distribution functions is crucial in plasma physics.
- Existing Faraday cup designs may lack flexibility in impedance matching and self-biased operation.
Purpose of the Study:
- To present a novel movable Faraday cup with adjustable impedance.
- To enable self-biased measurements for efficient electron energy distribution function determination.
- To validate the performance of the designed Faraday cup for nanosecond pulse signal measurements.
Main Methods:
- Designed a movable Faraday cup with adjustable shunt resistance and 50 Ω characteristic impedance.
- Utilized a self-biased measurement setup for acquiring electron energy distribution functions.
- Validated performance through response time, amplitude tests, and comparison with a calibrated current transformer using a pseudospark-generated electron beam.
Main Results:
- The Faraday cup demonstrated less than 10% difference in signal fall time and below 6.7% in pulse width for signals >10 ns.
- Output amplitude error was below 10% for pseudospark voltages between 4-14 kV.
- Self-biased measurements successfully yielded a "double-humped" electron energy distribution at 4 kV.
Conclusions:
- The developed movable Faraday cup offers a simple, adjustable, and effective solution for nanosecond pulse measurements.
- The self-biased capability significantly aids in the rapid acquisition of electron energy distribution functions.
- This design is suitable for characterizing electron beams in various plasma applications, including pseudospark discharges.
