Laser Pulse Shaping via Flow Chamber Pressure Control for LIBS
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Solution Overview
Problem
Existing systems for temporal shaping of laser pulses are inadequate for achieving precise control over energy deposition in laser-induced breakdown spectroscopy (LIBS), particularly for measuring gases at temperatures below ignitable thresholds and in high-pressure environments.
Innovation Solution
The implementation of a system that induces an initial breakdown along the laser beam path, using a flow chamber to control pressure and gas composition, allowing for precise adjustment of the transition from multiphoton ionization to cascade ionization, thereby minimizing energy deposition and optimizing plasma formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pulsed laser is focused at or in a target medium to generate plasma through dielectric breakdown, then plasma formation is achieved for LIBS analysis, but energy deposition cannot be precisely controlled, leading to ignition in combustible mixtures or insufficient plasma formation at high pressures
Solution Approach 1:
The laser pulse is segmented into two distinct phases: an initial breakdown phase that creates a plasma channel along the beam path, and a subsequent phase where the shaped pulse delivers energy to the target. This segmentation allows the initial plasma to pre-condition the medium, reducing the energy required for final plasma formation at the target while providing precise control over total energy deposition.
Solution Approach 2:
An initial breakdown is induced along the laser beam path before the main pulse reaches the target. This preliminary action creates a plasma channel that modifies the optical and electrical properties of the medium, enabling the subsequent laser pulse to deposit energy more efficiently and precisely at the target location while avoiding unwanted side effects like ignition or window damage.
2Reliability
If laser pulse energy is increased to achieve plasma formation at high pressures or near window surfaces, then plasma generation is improved, but unwanted side effects occur such as ignition in combustible mixtures or damage to optical components
Solution Approach 1:
An initial plasma channel acts as an intermediary along the laser beam path, mediating the energy transfer from the laser to the target. This intermediate plasma structure allows the laser energy to be deposited in a controlled manner, achieving reliable plasma formation at the target while the initial plasma absorbs and distributes excess energy, preventing harmful side effects like ignition or optical component damage.
Solution Approach 2:
The temporal profile of the laser pulse is changed by introducing a sharp trailing edge through the flow chamber with controlled gas pressure. This parameter change in pulse shape allows the laser energy to be delivered in a controlled time window, achieving reliable plasma formation while the reduced tail energy prevents ignition and optical damage by limiting total energy deposition to below harmful thresholds.
3Ease of operation
If conventional laser pulses are used for LIBS measurements, then simple operation is maintained, but temporal shaping capability is insufficient for precise energy control in challenging environments
Solution Approach 1:
A flow chamber containing gas at controlled pressure serves as an intermediary device that automatically performs temporal shaping of the laser pulse. The chamber's gas pressure and composition are adjusted to create the desired pulse profile with a sharp trailing edge, providing precise temporal control without requiring complex external modulation systems, thus maintaining ease of operation while achieving high measurement precision.
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 approach enables precise control over energy deposition, allowing for LIBS measurements in combustible mixtures without ignition, near window surfaces, and at high pressures, thereby expanding the applicability of LIBS techniques.
Implementation Method 1
a pulsed laser is focused at or in a target medium generating a plasma through dielectric breakdown
Implementation Method 2
allowing for precise adjustment of the transition from multiphoton ionization to cascade ionization
Implementation Method 3
generating a plasma through dielectric breakdown
Data Source
AI summary
A system for temporal shaping of a laser pulse. The system includes a flow chamber, the flow chamber having an entry aperture and an exit aperture. A compressed gas supply and a vacuum source are in fluid communication with the flow chamber. A laser is positioned in operative alignment to produce a laser beam that enters the entry aperture and exits the exit aperture. A focusing lens is operatively positioned to focus the laser beam through the entry aperture. A collimating lens is operative positioned to collimate the laser beam exiting the exit aperture. A vacuum regulator is in fluid communication with the vacuum source. The combination of the compressed gas supply and vacuum regulator allow for control of fluid pressure in the flow chamber.