Charged Particle Spectrometer Calibration Using Evanescent Laser Coupling
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Solution Overview
Problem
Existing methods for calibrating spectrometers for loaded particles, such as electrons, suffer from significant uncertainties due to linear and non-linear errors, as well as uncertainties related to electron trajectory deviations in optical elements and aberrations.
Innovation Solution
A method involving the coupling of a laser beam and a bundle of loaded particles via an evanescent electromagnetic field to generate a spectrum with distinct energy peaks, allowing for the determination of the scale factor and shift specific to the spectrometer's measurement, thereby improving calibration precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard materials with known spectral characteristics are used for calibration, then the calibration process can be performed, but uncertainties in transition energy lead to limited precision (approximately 1%) in determining scale factor and shift
Solution Approach 1:
The patent introduces an optical field (laser) as an intermediary to transfer precise energy information to the charged particle beam. The laser's known energy serves as a reference that mediates the calibration process, allowing the spectrometer to be calibrated against this stable reference rather than relying on material standards with uncertain transition energies.
Solution Approach 2:
The patent replaces the mechanical/material-based calibration approach (using physical standards with known spectral characteristics) with an optical field-based approach. The laser optical field provides a more stable and precise energy reference, substituting the uncertain material transition energies with the well-defined laser photon energy.
2Measurement precision
If electron beam energy is modified by magnetic fields or electric potentials for calibration, then scale factor and shift can be determined, but uncertainties due to electron trajectory deviations and aberrations limit the precision
Solution Approach 1:
The optical field acts as an intermediary that transfers energy information to electrons without requiring direct manipulation of electron trajectories. The laser field provides the energy reference, and electrons interact with this field to gain or lose energy in quantized amounts, avoiding the need to precisely control electron paths through magnetic or electric fields.
Solution Approach 2:
The patent changes the calibration approach from modifying electron beam parameters (energy, trajectory) to using optical field parameters (laser energy, wavelength). By changing to optical parameters that are more stable and easier to control with high precision, the method achieves better calibration accuracy without suffering from electron trajectory deviations.
3Ease of operation
If linear calibration methods are used, then the process is simple, but the precision is limited to approximately 1% due to various systematic errors
Solution Approach 1:
The patent uses the periodic nature of the laser field (with well-defined frequency and energy) to create a calibration reference. The laser's oscillating electromagnetic field provides a stable, repeating reference that can be used to precisely determine energy scales, improving upon simple linear calibration methods.
Solution Approach 2:
The patent transitions from simple linear calibration parameters to using optical field parameters (laser energy, wavelength, frequency) that offer higher precision. This parameter change enables more accurate determination of scale factor and shift while maintaining operational simplicity through automated laser energy measurement.
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 method enables the determination of the scale factor and shift with limited precision by the laser beam's energy, achieving several orders of magnitude improvement over existing methods, with potential precision of 0.01% or less for the scale factor and shift.
Implementation Method 1
illuminate a sample surface with the incident laser beam to generate an evanescent electromagnetic field in a region near said surface
Implementation Method 2
spatially and temporally superimpose the incident laser beam and the charged particle beam incident in said region to couple them via said evanescent electromagnetic field
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2A~2F
AI summary
A method for calibrating a charged particle spectrometer (SM) comprising the following steps: A. generate a monochromatic incident charged particle beam (FP) having a first energy E1; B. generate an incident laser beam (FL) having a second energy E2; C. illuminate a surface (SE) of a sample (Ech) with the incident laser beam (FL) in order to generate an evanescent electromagnetic field (EV) in a region (R) near said surface; D. spatially and temporally superimpose the incident laser beam and the incident charged particle beam in said region in order to couple them via said evanescent electromagnetic field by generating a charged particle beam called the output beam (FS) having a spectrum comprising a plurality of distinct energy peaks spectrally separated by a value equal to the second energy E2; E.measure, by the spectrometer, all or part of the spectrum of the output beam, then determine an energy variation ΔE of at least two of the distinct energy peaks with respect to the first energy E1; F. determine a value of the scale factor S and a value of the shift O specific to said measurement of the spectrum of the output beam by the spectrometer from the energy variations ΔE.