Laser Textured Surfaces for Electron Yield Reduction
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Solution Overview
Problem
Photoelectron emission and secondary electron emission pose significant challenges in various apparatus, leading to issues like electron cloud build-up, pressure increases, beam losses, and reduced sensitivity, particularly in particle accelerators and other sensitive equipment.
Innovation Solution
A method involving the application of pulsed laser radiation to create periodic surface structures with specific power densities and pulse durations, altering the surface properties to reduce photoelectron yield (PEY) and secondary electron yield (SEY) below 1.5, thereby minimizing electron emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional surfaces are used, then apparatus structure is simple, but photoelectron yield and secondary electron yield are high causing electron cloud build-up and beam losses
Solution Approach 1:
The patent applies parameter changes by modifying the surface physical structure through laser texturing, creating periodic microstructures with specific geometric parameters (peak-to-trough distance, depth, width) that alter the surface's electronic properties. This changes the surface's interaction with photons and electrons, reducing photoelectron and secondary electron yields without adding complex external systems
Solution Approach 2:
The patent segments the surface into periodic microstructures (peaks and troughs) through laser texturing. This segmentation creates multiple small-scale features that collectively reduce electron emission by modifying the surface's electronic band structure and electron transport properties, transforming a flat surface into a structured array of micro-features
2Reliability
If laser texturing is applied to reduce electron yield, then electron cloud build-up is reduced, but manufacturing process complexity increases
Solution Approach 1:
The patent uses periodic action by applying pulsed laser radiation in a systematic scanning pattern to create periodic surface structures. The laser pulses are applied at controlled intervals and positions, creating repeating microstructural motifs that provide consistent electron suppression across the surface while maintaining manufacturing controllability
Solution Approach 2:
The patent replaces mechanical surface treatment methods with laser-based processing. Instead of mechanical machining or chemical etching, the laser field directly modifies the surface material through photothermal and photomechanical effects, eliminating the need for mechanical tooling, fixtures, and chemical baths while achieving precise microstructural control
3Shape
If high power density laser pulses are used, then surface structures are effectively formed, but melting and material removal occur
Solution Approach 1:
The patent applies dynamics by using ultrashort laser pulses (femtosecond to picosecond duration) that deliver energy faster than the material's thermal response time. This dynamic approach allows the laser to ablate material through direct bond breaking and Coulomb explosion before heat can diffuse, creating precise microstructures without the melting and resolidification that occurs with slower heating rates
Solution Approach 2:
The patent exploits phase transitions by inducing direct solid-to-plasma transitions through ultrashort laser pulses. The extreme peak power densities cause instantaneous ionization and ablation of surface material without passing through a liquid phase, avoiding melting and resolidification. This phase transition mechanism enables precise material removal and structuring with minimal heat-affected zones
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 method effectively reduces SEY to desired levels, improving apparatus performance by reducing electron cloud formation and increasing sensitivity, while maintaining surface integrity without substantial melting or material removal.
Implementation Method 1
The laser pulses may have a duration such that material of the surface is at least one of evaporated or vaporised or removed without substantial melting and/or flowing of the surface
Implementation Method 2
The laser pulses may have a duration such that material of the surface is at least one of evaporated or vaporised or removed
Data Source
Figure 1
Figure 2a~2c
Figure 3a~3b
AI summary
A method of reducing photoelectron yield (PEY) and/or secondary electron yield (SEY) of a surface of a target (10), comprises applying laser radiation to the surface of the target (10) to produce a periodic arrangement of structures on the surface, wherein the laser radiation comprises pulsed laser radiation comprising a series of laser pulses and the power density of the pulses is in a range 0.01 TW/cm2 to 3 TW/cm2, optionally 0.1 TW/cm2 to 3 TW/cm2.