Tapering enhanced stimulated superradiant amplification

Patent metadata

Field	Value
Publication number	US-9819137-B2
Application number	US-201615298032-A
Country	US
Kind code	B2
Filing date	Oct 19, 2016
Priority date	Apr 22, 2014
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

A tapering enhanced stimulated superradiant amplification method and system which utilizes a strongly tapered undulator in reaching significant power outputs and conversion efficiencies. TESSA dramatically increases conversion/amplification efficiencies by violently (sharply) decelerating electrons and taking advantage of produced radiation to further drive interaction toward as it takes advantage of produced radiation to further drive interaction to increase overall radiation output. The system and method configures a strongly tapered undulator to operate in a new mode that is above normal input saturation levels to provide an amplified output with unexpectedly high efficiencies and power.

First claim

What is claimed is:

1. A tapering enhanced stimulated superradiant amplification method, comprising:
(a) generating an intense optical input seed pulse having an intensity exceeding free electron laser (FEL) saturation;
(b) generating a relativistic beam;
(c) directing said intense optical input seed pulse and said relativistic beam into a strong tapered undulator, said undulator having an entrance and an exit, said undulator having a tapering strength that exceeds at least 1% per meter; and
(d) configuring said strongly tapered undulator to interoperate with the intense optical input seed pulse to maintain a resonant condition while making a compromise between deceleration and detrapping to extract efficiency as a result of sharply decelerating electrons and utilizing produced radiation to further drive interaction toward increased overall radiation output, and intensely amplified optical pulse;
(e) wherein said undulator is configured to provide a reduction in resonant energy by more than 5% from the entrance to the exit of the undulator.

2. The method as recited in claim 1 , wherein said strong tapered undulator is configured with both period and magnetic field amplitude being tapered.

3. The method as recited in claim 1 , wherein said strong tapered undulator is configured with either period or magnetic field amplitude being tapered.

4. The method as recited in claim 1 , wherein said tapering enhanced stimulated superradiant amplification configured undulator is characterized by a reduction in resonant energy by more than 10 times an equivalent electron beam energy loss in an optimized non-tapered FEL at saturation.

5. The method as recited in claim 1 , further configuring said relativistic beam as pre-bunched, or configuring said strong tapered undulator with an entrance section configured for pre-bunching the relativistic beam.

6. The method as recited in claim 1 , wherein configuration of said strong tapered undulator comprises processing motion equations for the electrons and Maxwell's field equations to determine laser fields produced in response to interaction of a relativistic beam and electromagnetic radiation in said strong tapered undulator.

7. The method as recited in claim 6 , wherein said configuration of said strong tapered undulator is performed incrementally along the length of said strongly tapered undulator.

8. The method as recited in claim 6 , wherein during said processing motion equation radiation field strength seen by each electron is sampled in order to find a minimum field seen by most electrons in order to assure that they are kept in resonance with the radiation.

9. The method as recited in claim 1 , wherein said strong tapered undulator is configured for reducing the energies of electrons, transferring energy from the electrons to add to optical energy being output.

10. The method as recited in claim 1 , wherein said resonant condition is maintained controlling the resonant energy so that average phase of the electrons in ponderomotive potential is stationary.

11. The method as recited in claim 1 , wherein an intense radiation pulse is obtained from a low repetition rate seed laser, or from the build-up in an oscillator configuration, or from refocusing radiation from an FEL after saturation.

12. The method as recited in claim 1 , wherein a strong intensity input field, beyond that of a non-tapered FEL saturation intensity, can be obtained by using refocusing optics from either an external seed laser, or a saturated FEL amplifier.

13. The method as recited in claim 1 , wherein said method can be operated in a high gain single pass regime, or a low gain oscillator type regime.

14. An undulator apparatus, comprising:
a first array of opposed magnet pairs having a given polarization;
a second array of opposed magnet pairs having a second polarization;
wherein the magnetic field generated by said second array is superimposed to the magnetic field generated by said first array of opposed magnet pairs;
wherein said first and second arrays of opposed magnetic pairs are configured with strong tapering in which tapering strength, described by variation in undulator resonant energy, exceeds at least 1% per meter, which interoperates with a received input pulse energy whose intensity exceeds free electron laser (FEL) saturation; and
wherein said undulator is configured to decelerate input electrons to extract efficiency, while maintaining a resonant condition, with radiation produced further driving interaction toward increased overall radiation output and intensely amplified optical pulse.

15. The apparatus as recited in claim 14 , wherein said undulator with strong tapering is configured for reducing resonant energy by more than 5% from the entrance to the exit of said undulator.

16. The apparatus as recited in claim 14 , wherein said undulator with strong tapering is configured to provide a reduction in undulator resonant energy by more than 10 times an equivalent electron beam energy loss in an optimized non-tapered FEL at saturation.

17. The apparatus as recited in claim 14 , wherein said strong tapering as is achieved in response to (a) reducing undulator field strength at every period, or (b) reducing undulator period length at every period of the undulator, or (c) through a combination of reducing undulator field strength and period length at every period of the undulator.

18. The apparatus as recited in claim 14 , further comprising utilizing a process for configuring the strong tapering of said undulator in response to steps comprising:
solving Maxwell and Lorentz force equations determining evolution of the electron beam distribution and radiation in the undulator over a small section of the undulator;
processing particle and radiation files for each section of said undulator to extract field intensity seen by each particle;
using in reverse IFEL scaling for undulator field strength, or an undulator period length, or a combination of these two, as a function of optical field intensity, to determine taper for a subsequent undulator section to maintain resonance; and

repeating the process until total length of undulator is configured.

19. A tapering enhanced stimulated superradiant amplification method, comprising:
injecting into an undulator an intense radiation seed pulse with intensity larger than the output intensity of non-tapered free electron laser (FEL) at saturation;
tapering the period and the magnetic field amplitude of the undulator to establish a strongly tapered undulator, having tapering strength that exceeds at least 1% per meter, that maintains a resonant condition and sustains a continuous electron beam and laser interaction; and
configuring the tapering to interoperate with said intense radiation seed pulse and to maximize extraction efficiency in relation to deceleration and detrapping;
wherein an output radiation pulse is generated with an intensity greater than the intensity of the seed pulse and the decelerated electrons to radiated light energy conversion efficiency exceeds at least 5%.

20. The method as recited in claim 19 , further comprising obtaining the seed pulse from a low rep-rate seed laser.

21. The method as recited in claim 19 , further comprising obtaining the seed pulse from build-up on an oscillator.

22. The method as recited in claim 19 , further comprising obtaining the seed pulse by refocusing the FEL after saturation.

23. The method as recited in claim 19 , further c

Assignees

• Univ California
• Radiabeam Tech Llc
• The Regents Of The Univerity Of California

Inventors

• Musumeci Pietro
• Duris Joseph
• Murokh Alex

Classifications

• H01S3/0955

  using pumping by high energy particles {(H01S3/0903, H01S3/0906, H01S3/09707 take precedence)} · CPC title

• H01S3/0959

  by an electron beam · CPC title

• H01S3/0903 Primary

  Free-electron laser · CPC title

• H05H2007/041

  for beam bunching, e.g. undulators · CPC title

• H01S3/2308

  Amplifier arrangements, e.g. MOPA · CPC title