Faraday Cup Offset Current Nullification for Low-Energy Beam Measurement
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Solution Overview
Problem
Existing methods for measuring the flux, current, or integrated charge of low-energy particle beams are prone to errors due to electrical noise and physical barriers, particularly when the beam energy is below 1 MeV, affecting accuracy and reliability in applications such as ion implantation and radiation technology.
Innovation Solution
A system comprising an inner cylinder, a coaxial outer cylinder electrically insulated from the inner cylinder, and an offset current source in communication with the inner cylinder, along with an electrometer and charge integrator, which adjusts the offset current to nullify leakage and noise, enabling precise measurement of beam current and integrated charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional Faraday cups or surface barrier detectors are used to measure low energy particle beams, then measurement can be performed, but measurement precision deteriorates due to electrical noise and leakage currents
Solution Approach 1:
The patent introduces an electrometer as an intermediary device between the Faraday cup and the measurement system. This electrometer is specifically designed with low noise characteristics and high input impedance to measure the tiny currents generated by low energy particle beams without being overwhelmed by electrical noise or leakage currents, thereby resolving the measurement precision problem
Solution Approach 2:
The patent changes the electrical parameters of the measurement system by using an electrometer with extremely high input impedance (10^14 to 10^16 ohms) and very low noise floor. This parameter change allows the system to detect picoampere-level currents from low energy beams while rejecting higher frequency electrical noise and DC leakage currents
2Adaptability or versatility
If beam energy is reduced to below 1 MeV for low energy applications, then application versatility is improved, but measurement reliability deteriorates due to increased susceptibility to noise and leakage
Solution Approach 1:
The electrometer serves as a specialized intermediary that enables reliable measurement of low energy beams by providing electrical isolation and noise filtering. It mediates between the sensitive low energy beam signal and the noisy electronic environment, maintaining measurement reliability across diverse low energy applications
Solution Approach 2:
The system employs feedback mechanisms where the electrometer continuously monitors the current signal and adjusts its measurement parameters to maintain optimal signal-to-noise ratio. This feedback control ensures reliable measurements across varying beam conditions and energy levels
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances sensitivity and accuracy, allowing for reliable measurement of low-current, low-energy beams with energies less than 100 KeV, reducing errors from noise and physical barriers, and providing real-time data on beam charge and flux.
Implementation Method 1
The cup includes a coaxial outer cylinder that provides shielding from external electrical noise
Implementation Method 2
an offset current source in communication with the inner cylinder... adjusting the offset current, without the beam present, until an output of a counter is at a predetermined value
Implementation Method 3
The beam current is measured using an electrometer electrically connected to the cup
Data Source
AI summary
An apparatus and method for measuring flux, current, or integrated charge of a beam are provided. The apparatus and method include a cup on which the beam is incident. The cup includes an inner cylinder, a coaxial cylinder, and an aperture. The coaxial cylinder surrounds the inner cylinder and is electrically insulated therefrom. An offset current source is in electrical communication with the inner cylinder. An electrometer, a charge integrator, or a counter may be electrically connected to the cup and the offset current source. When the beam is incident on the cup and aligned with the aperture, the electrometer can measure the beam current and the charge integrator can measure the integrated charge of the beam.