TWTS-EMMP Electron Beam Pulser for 50 GHz Tunability
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Solution Overview
Problem
Existing methods for generating low and medium energy pulsed electron beams are limited by high repetition rates, with laser-excited beams capped at 100 MHz and heat-based methods restricted to 1 GHz or less, and suffer from extensive beam quality deterioration and limited tunability.
Innovation Solution
The introduction of a Travelling Wave Transmission Stripline (TWTS) modulator in an ElectroMagnetic Mechanical Pulser (EMMP) allows for continuous tunability of electron pulse repetition rates between 100 MHz and 50 GHz, maintaining beam coherence and producing pulses as short as 100 fs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If laser excitation is used to generate electron beam pulses, then pulse length can be made very short (100 fs or less), but repetition rate is limited to 100 MHz or less
Solution Approach 1:
The patent replaces the laser-based optical excitation system with an electromagnetic field-based pulser system. Instead of using laser photons to excite the photocathode, the invention uses directly applicable electromagnetic fields (via coaxial cable or waveguide coupling) to generate electron pulses, thereby eliminating the repetition rate limitation imposed by laser technology while maintaining the ability to produce short pulses.
Solution Approach 2:
The pulser system is designed to be universally applicable to various electron beam energies and configurations. The same pulser architecture can be used across different energy ranges (e.g., 30-300 keV) and can be coupled through different transmission media (coaxial cable or waveguide), providing a multi-functional solution that addresses both pulse duration and repetition rate requirements.
2Productivity
If deflecting cavity technology is used to chop electron beams at GHz frequencies, then high repetition rates can be achieved, but beam quality deteriorates extensively in both transverse and longitudinal directions
Solution Approach 1:
The patent introduces an intermediary coupling structure (coaxial cable or waveguide) between the signal source and the electron beam interaction region. This intermediary allows the electromagnetic signal to be transmitted to the beam without requiring complex deflecting cavity structures, thereby maintaining beam quality while achieving GHz repetition rates through a simpler, more direct coupling mechanism.
3Duration of action of moving object
If photocathode and fs-laser combination is used for pulsed beam generation, then short pulse lengths are achieved, but separate thermionic or field emission source is required for continuous beam mode
Solution Approach 1:
The patent designs a universal electron source system that can operate in both continuous and pulsed modes using the same photocathode and electromagnetic field generation infrastructure. By making the electromagnetic field application configurable (continuous or pulsed), the system eliminates the need for separate thermionic or field emission sources, reducing device complexity while maintaining versatility.
4Adaptability or versatility
If heat combined with external electric field is used for electron pulse generation, then control flexibility is achieved, but repetition rate is restricted to 1 GHz or less
Solution Approach 1:
The patent replaces the heat-based thermal field emission mechanism with a directly applicable electromagnetic field mechanism. This substitution removes the thermal time constants that limit repetition rates to 1 GHz or less, while preserving the control flexibility through configurable electromagnetic field application (amplitude, duration, timing) to the photocathode.
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 ultra-wideband, continuous pulse rate variability, enhancing the capability for real-time monitoring and imaging of dynamic processes with improved duty cycles and time-averaged probe currents, suitable for advanced microscopy and analytical techniques.
Implementation Method 1
Radio frequency energy is introduced into the device at a proximal end thereof, and propagates through the device as a traveling wave to a distal end thereof
Implementation Method 2
the modulating TWTS being configured to impose an oscillatory transverse deflection on the electron beam according to a frequency and amplitude of a first RF energy propagated as a traveling wave through the modulating TWTS
Implementation Method 3
a Chopping Collimating Aperture (CCA) downstream of the modulating TWTS and configured to block the electron beam when its deflection exceeds a threshold maximum or minimum, thereby chopping the electron beam into a stream of electron pulses
Implementation Method 4
a demodulating TWTS included in the dispersion suppressing section, the demodulating TWTS being configured to demodulate the oscillatory transverse deflection imposed on the electron beam by the modulating TWTS
Implementation Method 5
the dispersion suppressing section being configured to suppress a residual dispersion of the stream of electron pulses arising from the deflection imposed by the modulating TWTS
Data Source
AI summary
An ElectroMagnetic-Mechanical Pulser (“EMMP”) generates electron pulses at a continuously tunable rate between 100 MHz and 20-50 GHz, with energies up to 0.5 MeV, duty cycles up to 20%, and pulse widths between 100 fs and 10 ps. A dielectric-filled Traveling Wave Transmission Stripline (“TWTS”) that is terminated by an impedance-matching load such as a 50 ohm load imposes a transverse modulation on a continuous electron beam. The dielectric is configured such that the phase velocity of RF propagated through the TWTS matches a desired electron energy, which can be between 100 and 500 keV, thereby transferring electromagnetic energy to the electrons. The beam is then chopped into pulses by an adjustable aperture. Pulse dispersion arising from the modulation is minimized by a suppressing section that includes a mirror demodulating TWTS, so that the spatial and temporal coherence of the pulses is substantially identical to the input beam.