Laser-Plasma Pulse Trains for Higher-Charge Electron Beams
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Solution Overview
Problem
Current laser-plasma accelerators face challenges in efficiently producing high-charged energetic electron beams, as existing methods are complex, expensive, and sensitive to space charge effects, requiring high-power lasers and fragile phase plates.
Innovation Solution
A method involving a laser-plasma accelerator that generates a pulse train with a delay between pulses, ranging from three to thirty times the plasma period, to create a series of plasma waves for electron acceleration, using a lower-power laser and a gas cloud in a vacuum chamber, reducing the impact of space charge and increasing electron trapping efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single high-power laser pulse is used to accelerate electrons, then high electron energy can be achieved, but the electron charge is limited and space charge effects reduce efficiency
Solution Approach 1:
The invention divides a single high-power laser pulse into multiple lower-power sub-pulses separated by a time delay of 3-30 plasma periods. Each sub-pulse generates an independent plasma wave that accelerates electrons, creating multiple electron bunches instead of one large bunch. This segmentation reduces space charge effects within each bunch while increasing total electron charge, directly resolving the contradiction between electron charge quantity and space charge harmful effects.
2Quantity of substance
If multiple parallel laser pulses are used to increase electron charge, then large quantities of energetic electrons can be produced, but the system becomes complex and expensive requiring fragile phase plates
Solution Approach 1:
The invention uses a single laser pulse that is temporally modulated to create periodic sub-pulses separated by plasma periods. This periodic structure in the time domain achieves the electron charge multiplication effect without requiring multiple spatially separated laser beams, phase plates, or complex beam alignment systems. The periodic action principle transforms a spatially complex multi-beam system into a temporally structured single-beam system, dramatically reducing device complexity while maintaining high electron charge output.
3Reliability
If laser pulses are separated by large distances to prevent merging, then beam quality is maintained, but the overall electron source size becomes large
Solution Approach 1:
The invention transitions from spatial separation of laser beams to temporal separation of laser sub-pulses. Instead of separating beams in space (which increases source size), the invention separates pulse energy delivery in time by introducing delays of 3-30 plasma periods between sub-pulses. This dimensionality change from spatial to temporal domain maintains beam quality through proper timing while keeping all sub-pulses focused to the same spatial location, thereby minimizing electron source size.
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 enhances the electron charge by a factor of two, reduces the cost of the laser-plasma accelerator, and allows for compact, efficient production of electron beams and X-rays from 1 to 200 MeV, with improved performance and reduced divergence due to lower laser power and simpler implementation.
Implementation Method 1
focusing an intense laser pulse into a gas cloud... create a plasma
Implementation Method 2
The laser-plasma accelerator uses a laser to create a wake wave in a plasma
Implementation Method 3
the wave generates an accelerator field in which other electrons are accelerated over very short distances up to very high energies
Data Source
AI summary
A method for producing energetic electron beams using a laser-plasma accelerator including a laser and a device for producing a gas cloud in a vacuum chamber, the method including a step of generating a laser pulse which is focused into the gas cloud to create a plasma. The step of generating a laser pulse includes at least the generation of a laser pulse-train with a delay between two successive laser pulses of between three times and thirty times the plasma period TP, such that: TP=λp/c, λp being the plasma wavelength defined by: λp=(2π/C)*(n e2/(m ε0))−½, where c is the speed of light, n is the electron density of the plasma in cm3, e=1.6e−19 C is the charge of an electron, m=9.1e−31 kg is the mass of an electron, and ε0=8.85×10−12 m−3 kg−1 s4 A2 is the permittivity of vacuum.