Apparatus and methods for optical emission spectroscopy
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Solution Overview
Problem
Conventional spark generators for optical emission spectroscopy lack control over the current waveform, leading to poor reproducibility and accuracy in elemental analysis, particularly for trace elements and alloying elements in metal samples, and CCD detector deterioration due to intense UV light from single peak spark sources.
Innovation Solution
A programmable spark generator producing a modulated current waveform with multiple high current peaks and a low current plateau, allowing separate control of energy delivery for vaporization and excitation, reducing detector deterioration by spreading energy across multiple peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single high current peak is used for vaporization, then vaporization efficiency is improved, but measurement precision deteriorates due to insufficient excitation control
Solution Approach 1:
The single high current peak is segmented into multiple high current peaks (first, second, and third peaks) with different amplitudes and durations. This segmentation allows independent optimization of each peak's parameters - earlier peaks provide vigorous vaporization while later peaks provide controlled excitation, resolving the contradiction between vaporization efficiency and measurement precision.
Solution Approach 2:
The spark current is structured as a periodic sequence of multiple peaks rather than a single continuous pulse. Each peak serves a specific function in the analytical sequence (vaporization, excitation, stabilization), creating a rhythmic pattern that balances the competing requirements of efficient sample introduction and precise spectral measurement.
2Power
If high current intensity is concentrated in a single peak, then energy delivery efficiency is improved, but spark reproducibility deteriorates
Solution Approach 1:
The concentrated energy delivery is segmented across multiple peaks with progressively decreasing amplitudes. This distribution prevents the instability associated with single-peak high current while maintaining total energy efficiency. Each peak contributes to the overall energy delivery in a controlled, reproducible manner.
Solution Approach 2:
The current waveform parameters (amplitude, duration, inter-peak intervals) are systematically changed across the sequence of peaks. This parameter modulation allows the system to achieve reproducible results by maintaining consistent temporal and amplitude relationships between peaks, while the cumulative energy delivery remains efficient.
3Power
If intense UV light is delivered in a single peak, then excitation efficiency is improved, but CCD detector deterioration accelerates
Solution Approach 1:
The intense UV light delivery is periodic rather than continuous, distributed across multiple peaks separated by time intervals. This periodic structure maintains excitation efficiency through cumulative light delivery while allowing detector recovery between peaks, thereby reducing cumulative deterioration from intense UV exposure.
Solution Approach 2:
The intense excitation energy is segmented into multiple lower-intensity pulses rather than one concentrated peak. This segmentation reduces the peak UV intensity that causes detector damage while maintaining total excitation efficiency through the cumulative effect of multiple peaks, each contributing to element excitation.
4Device complexity
If unmodulated spark current is used, then device complexity is reduced, but measurement precision deteriorates due to poor control over current waveform
Solution Approach 1:
The spark generator produces a periodic modulated current waveform with multiple peaks at controlled intervals. This periodic modulation provides precise control over the temporal distribution of energy, enabling separate optimization of vaporization and excitation phases while maintaining manageable device complexity through systematic waveform design.
Solution Approach 2:
The current waveform parameters (amplitude, duration, rise time, inter-peak intervals) are systematically changed across the sequence of peaks. This parameter modulation provides precise control over the spark characteristics without requiring complex additional hardware, achieving high measurement precision through intelligent waveform design rather than hardware complexity.
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
Improves precision in determining both trace and alloying elements, reduces acquisition time, and slows CCD detector deterioration by providing controlled energy delivery and minimizing spectral background interference.
Implementation Method 1
a spark generator for generating a modulated current waveform which includes a first modulated portion of relatively high current and a second modulated portion of relatively low current
Implementation Method 2
Light is emitted by the excited elements of the sample as transitions occur from an excited state to a lower energy state. Each element emits light of discrete wavelengths characteristic of its electronic structure
Implementation Method 3
an optical system for dispersing the emitted light into discrete wavelengths
Implementation Method 4
a detection system for detecting the light intensity of the dispersed light
Data Source
Figure 1~2A
Figure 2B~2C
Figure 2D~2E
AI summary
The invention provides a spark generator for generating a spark for optical emission spectroscopy (OES), wherein the spark has a current waveform comprising a first modulated portion which comprises a plurality of relatively high current and high gradient peaks of variable amplitude and/or inter-peak duration and a second modulated portion of relatively low current and low gradient which is substantially without modulated peaks. The spark is preferably generated from two or more programmable current sources. The invention also provides an optical emission spectrometer comprising the spark generator and a method of optical emission spectroscopy using the spark generator.