MALDI Laser Beam Shaping for Uniform Ionization
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Solution Overview
Problem
Conventional MALDI mass spectrometers face challenges with low ionization efficiency, high energy consumption, and short laser system lifetime due to the use of nitrogen lasers, which are replaced by Nd:YAG lasers with a Gaussian beam profile, leading to decreased ionization and increased sample consumption.
Innovation Solution
A mass spectrometer with a pulsed solid-state laser system, conversion crystals, and a pattern generator that converts the circular Gaussian laser beam into a rectangular beam with homogeneous energy density, allowing for a spatially distributed spot pattern with uniform energy peaks, increasing ionization efficiency and extending laser system lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitrogen lasers are used for MALDI ionization, then ionization efficiency is high, but laser system lifetime is short and energy consumption is high
Solution Approach 1:
The patent changes the fundamental parameters of the laser system by replacing nitrogen lasers with Nd:YAG solid-state lasers operating at different wavelengths (1064 nm, 532 nm, or 355 nm). This parameter change enables long operational lifetime while maintaining ionization efficiency through optimized pulse durations (3-8 ns) and energy densities (10-100 mJ/cm²).
Solution Approach 2:
The patent substitutes the gas-based nitrogen laser system with a solid-state Nd:YAG laser system. This replacement eliminates the limitations of nitrogen lasers (short lifetime, high energy consumption) while achieving comparable or superior ionization performance through controlled laser pulse parameters and beam profile optimization.
2Duration of action of stationary object
If Nd:YAG lasers with Gaussian beam profile are used, then laser system lifetime is extended, but ionization efficiency decreases and sample consumption increases
Solution Approach 1:
The patent applies local quality modification by using beam-shaping optics to transform the Gaussian beam profile into a top-hat or flat-top profile. This creates a uniform energy distribution across the laser spot, ensuring consistent ionization efficiency across the entire illuminated area and reducing sample consumption by eliminating hot spots that cause excessive local heating and fragmentation.
Solution Approach 2:
The patent introduces dynamic control of laser parameters including pulse duration (3-8 ns), energy density (10-100 mJ/cm²), and beam profile shape. These dynamic adjustments optimize the interaction between laser energy and the MALDI matrix, maintaining high ionization efficiency while extending laser system lifetime and reducing sample consumption.
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
The solution achieves a significant increase in analyte ionization efficiency, reduces energy consumption, and extends the laser system's operational life, enabling higher pulse rates with lower energy expenditure and reduced sample consumption.
Implementation Method 1
A beam-shaping element is located between the solid-state laser system and the conversion crystals. The beam-shaping element converts the circular laser beam with Gaussian profile into a beam with approximately rectangular cross-section and an approximately homogeneous energy density across the whole rectangular cross-section.
Implementation Method 2
conversion crystals to increase the frequency, and a pattern generator in the laser beam. A beam-shaping element is located between the solid-state laser system and the conversion crystals.
Data Source
AI summary
The invention relates to a mass spectrometer comprising a laser system for mass-spectrometric analysis with ionization of analyte molecules in a sample by matrix-assisted laser desorption. A mass spectrometer with a pulsed UV laser system produces a spatially distributed spot pattern with peaks of uniform energy density on the sample, increasing thereby the degree of ionization for analyte ions as compared to conventional spot patterns. The spot pattern with peaks of uniform energy density can be produced by homogeneous illumination of a pattern generator, for example a lens array. The homogeneous illumination can be generated by a low-cost beam-shaping element, which does not act on the UV beam but on the original infrared beam, in conjunction with changes to the beam cross-section and beam profile brought about by the nonlinear conversion crystals. This beam shaping not only produces a beam profile which illuminates the pattern generator homogeneously with low losses, but at the same time increases the efficiency of the frequency multiplication and the lifetime of the conversion crystals so that cost savings are achieved because less laser energy is required and the lifetime is increased.