GHz Electron Beam Pulsing via Transverse Deflecting Cavity
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Solution Overview
Problem
Current methods for generating low and medium energy electron beams are limited by low repetition rates and significant transverse and longitudinal dispersion, especially at high duty cycles and short pulse lengths, making them unsuitable for advanced industrial, medical, and research applications.
Innovation Solution
A combined ElectroMagnetic-Mechanical Pulser (EMMP) system using a Transverse Deflecting Cavity, Chopping Collimating Aperture, and dispersion suppressing sections with pillbox cavity resonators and magnetic quadrupoles to produce high-repetition-rate electron pulses with minimal dispersion, capable of switching between continuous and pulsed modes without deteriorating beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If laser-excited photocathode electron emitters are used to generate electron pulses, then pulse lengths as short as 100 fs or less can be obtained, but high repetition rates of at least 1 GHz are not available because modern lasers are only capable of repetition rates on the order of 100 MHz or less
Solution Approach 1:
The patent replaces the laser-based excitation mechanism with a purely electromagnetic field-based mechanism. An RF-driven transverse deflecting cavity (TDC) modulates a continuous electron beam, and electromagnetic fields in pillbox cavity resonators chop the modulated beam into pulses. This substitution of optical excitation with electromagnetic field modulation enables repetition rates exceeding 1 GHz while maintaining short pulse lengths of 100 fs or less.
2Productivity
If deflecting cavity technology is used to chop electron beams at GHz frequencies, then high repetition rates can be achieved, but extensive electron beam quality deterioration occurs in both transverse direction (beam diameter and divergence) and longitudinal direction (temporal coherence)
Solution Approach 1:
The patent segments the beam manipulation process into distinct functional sections: a transverse deflecting cavity (TDC) for initial modulation, a chopping collimating aperture (CCA) for pulse formation, and a dispersion suppressing section with multiple pillbox cavity resonators for quality preservation. This segmentation allows each component to perform its specific function optimally while working together to maintain overall beam quality at GHz repetition rates.
Solution Approach 2:
The patent introduces an intermediary continuous electron beam from a thermionic or field emission source that serves as the input to the electromagnetic modulation system. This continuous beam acts as a carrier that can be modulated by the RF-driven TDC without the limitations of photocathode materials, enabling high repetition rates while preserving beam quality through careful electromagnetic field control in the subsequent chopping and dispersion suppressing sections.
3Duration of action of moving object
If a photocathode and fs-laser combination is used for pulsed beam generation, then short pulse lengths can be achieved, but the required continuous beam must be generated using a separate thermionic or field emission source, increasing system complexity
Solution Approach 1:
The patent merges the pulsed beam generation function and continuous beam generation function into a single integrated system. A continuous electron beam from a thermionic or field emission source is fed into an RF-driven transverse deflecting cavity for electromagnetic modulation and pulsing. This consolidation eliminates the need for separate photocathode and laser systems, reducing overall system complexity while achieving sub-100 fs pulse lengths and repetition rates exceeding 1 GHz.
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
Enables electron pulses with repetition rates up to 50 GHz and pulse lengths from 100 fs to 10 ps, maintaining original beam quality and phase-space characteristics, suitable for GHz stroboscopic modes in SEMs, TEMs, and HABs/VABs, without requiring specialty photocathodes or lasers.
Implementation Method 1
A metallic single-cell transverse deflecting cavity (TDC), referred to herein as the first or 'modulating' TDC, operated in any of TE11n or TM11n modes, where n can be any integer, n=0, 1, 2, 3 and higher, and configured to modulate the incoming continuous electron beam transversely, i.e. perpendicularly its line of propagation, into a sinusoid according to a magnetic component (for TM modes) or electric component (for TE modes) of an electromagnetic field introduced into the TDC by an external RF generator
Implementation Method 2
A dispersion suppressing section comprising additional TDCs and/or magnetic quadrupoles positioned downstream of the CCA and configured to further demodulate the electron beam and/or reduce its spatial and/or temporal dispersion
Data Source
AI summary
An ElectroMagnetic-Mechanical Pulser can generate electron pulses at rates up to 50 GHz, energies up to 1 MeV, duty cycles up to 10%, and pulse widths between 100 fs and 10 ps. A modulating Transverse Deflecting Cavity (“TDC”) imposes a transverse modulation on a continuous electron beam, which is then chopped into pulses by an adjustable Chopping Collimating Aperture. Pulse dispersion due to the modulating TDC is minimized by a suppressing section comprising a plurality of additional TDC's and/or magnetic quadrupoles. In embodiments the suppression section includes a magnetic quadrupole and a TDC followed by four additional magnetic quadrupoles. The TDC's can be single-cell or triple-cell. A fundamental frequency of at least one TDC can be tuned by literally or virtually adjusting its volume. TDC's can be filled with vacuum, air, or a dielectric or ferroelectric material. Embodiments are easily switchable between passive, continuous mode and active pulsed mode.