scholarly journals Extending the Photon Energy Coverage of a Seeded Free-Electron Laser via Reverse Taper Enhanced Harmonic Cascade

Photonics ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 44
Author(s):  
Kaiqing Zhang ◽  
Tao Liu ◽  
Zheng Qi ◽  
Xiaoxi Fu ◽  
Chao Feng ◽  
...  
Keyword(s):  
Electron Beam ◽  
Photon Energy ◽  
Free Electron ◽  
Three Dimensional ◽  
High Harmonics ◽  
Reverse Taper ◽  
Novel Method ◽  
Conversion Efficiencies ◽  
Seeded Fel ◽  
Conventional Laser

External seeded free-electron lasers (FELs) hold promising prospects for producing intense coherent radiation at high harmonics of a conventional laser. The practical harmonic up-conversion efficiencies of current seeding techniques are limited by various three-dimensional effects on the electron beam. In this paper, a novel method is proposed to extend the wavelength coverage of a seeded FEL by combining the reverse taper undulator with the echo-enabled harmonic generation. The proposed technique can significantly enhance the bunching at ultra-high harmonics and preserve the electron beam qualities from degradation by deleterious effects. Theoretical analysis and numerical simulation are performed, and the results demonstrate that stable, intense, nearly fully coherent FEL pulses with photon energy up to 1 keV can be generated. The proposed technique may open up new opportunities to obtain laser-like pulses at sub-nanometer wavelength.

scholarly journals Perspectives towards Sub-Ångström Working Regime of the European X-ray Free-Electron Laser with Low-Emittance Electron Beams

2021 ◽  
Vol 11 (22) ◽  
pp. 10768
Author(s):  
Ye Chen ◽  
Frank Brinker ◽  
Winfried Decking ◽  
Matthias Scholz ◽  
Lutz Winkelmann
Keyword(s):  
Electron Beam ◽  
Photon Energy ◽  
Free Electron ◽  
Free Electron Laser ◽  
Electron Beams ◽  
Energy Levels ◽  
Energetic Electron ◽  
X Rays ◽  
X Ray ◽  
Low Emittance

Sub-ångström working regime refers to a working state of free-electron lasers which allows the generation of hard X-rays at a photon wavelength of 1 ångström and below, that is, a photon energy of 12.5 keV and above. It is demonstrated that the accelerators of the European X-ray Free-Electron Laser can provide highly energetic electron beams of up to 17.5 GeV. Along with long variable-gap undulators, the facility offers superior conditions for exploring self-amplified spontaneous emission (SASE) in the sub-ångström regime. However, the overall FEL performance relies quantitatively on achievable electron beam qualities through a kilometers-long accelerator beamline. Low-emittance electron beam production and the associated start-to-end beam physics thus becomes a prerequisite to dig in the potentials of SASE performance towards higher photon energies. In this article, we present the obtained results on electron beam qualities produced with different accelerating gradients of 40 MV/m–56 MV/m at the cathode, as well as the final beam qualities in front of the undulators via start-to-end simulations considering realistic conditions. SASE studies in the sub-ångström regime, using optimized electron beams, are carried out at varied energy levels according to the present state of the facility, that is, a pulsed mode operating with a 10 Hz-repetition 0.65 ms-long bunch train energized to 14 GeV and 17.5 GeV. Millijoule-level SASE intensity is obtained at a photon energy of 25 keV at 14 GeV electron beam energy using a gain length of about 7 m. At 17.5 GeV, half-millijoule lasing is achieved at 40 keV. Lasing at up to 50 keV is demonstrated with pulse energies in the range of a few hundreds and tens of microjoules with existing undulators and currently achievable electron beam qualities.

scholarly journals Compensation of thermal loss in free-electron laser with optimal tapering and pre-bunching

2020 ◽  
Vol 38 (2) ◽  
pp. 141-147
Author(s):  
F. Bazouband
Keyword(s):  
Electron Beam ◽  
Free Electron ◽  
Free Electron Laser ◽  
Nonlinear Differential Equations ◽  
Three Dimensional ◽  
Energy Spread ◽  
Thermal Electron ◽  
Simulation Code ◽  
Runge Kutta Method ◽  
Saturation Power

AbstractIncreasing the output power of a long-wavelength free-electron laser (FEL), despite the destroying effects of beam energy spread, is studied using the optimal pre-bunching of the thermal electron beam along with the optimal tapering of the planar wiggler magnetic field. A set of self-consistent coupled nonlinear differential equations in three dimensional that describe the evolution of radiation and electron beam in the interaction zone are solved numerically by the Runge–Kutta method. The axial energy spread is considered and it degrades the FEL performance by reducing the saturation power and increasing the saturation length. To compensate these destroying effects, the optimum function or degree of electron beam pre-bunching and optimum parameters of wiggler tapering are found by the successive runs of the simulation code.

scholarly journals EMITTANCE LIMITATION OF A CONDITIONED BEAM IN A STRONG FOCUSING FEL UNDULATOR

2007 ◽  
Vol 22 (22) ◽  
pp. 3826-3837 ◽  
Author(s):  
Z. HUANG ◽  
G. STUPAKOV ◽  
S. REICHE
Keyword(s):  
Electron Beam ◽  
Free Electron ◽  
Free Electron Laser ◽  
Three Dimensional ◽  
Complete Elimination ◽  
Dimensional Model ◽  
Simulation Code ◽  
One Dimensional ◽  
Strong Focusing ◽  
Dimensional Simulation

Various methods have been proposed to condition an electron beam in order to reduce its emittance effect and to improve the short-wavelength free electron laser (FEL) performance. In this paper, we show that beam conditioning does not result in a complete elimination of the emittance effect in an alternating-gradient focusing FEL undulator. Using a one-dimensional model and a three-dimensional simulation code, we derive a criteria for the emittance limitation of a perfectly conditioned beam that depends on the focusing structure.

scholarly journals Two-color operation of a free-electron laser with a tilted beam

2016 ◽  
Vol 23 (4) ◽  
pp. 869-873 ◽  
Author(s):  
Sven Reiche ◽  
Eduard Prat
Keyword(s):  
Electron Beam ◽  
Photon Energy ◽  
Free Electron ◽  
Free Electron Laser ◽  
Tuning Range ◽  
Free Electron Lasers ◽  
Successful Operation ◽  
X Ray ◽  
Two Photon ◽  
Gap Control

With the successful operation of free-electron lasers (FELs) as user facilities there has been a growing demand for experiments with two photon pulses with variable photon energy and time separation. A configuration of an undulator with variable-gap control and a delaying chicane in the middle of the beamline is proposed. An injected electron beam with a transverse tilt will only yield FEL radiation for the parts which are close to the undulator axis. This allows, after re-aligning and delaying the electron beam, a different part of the bunch to be used to produce a second FEL pulse. This method offers independent control in photon energy and delay. For the parameters of the soft X-ray beamline Athos at the SwissFEL facility the photon energy tuning range is a factor of five with an adjustable delay between the two pulses from −50 to 950 fs.

Three-dimensional Raman free electron laser in a waveguide with annular electron beam

2003 ◽  
Vol 10 (6) ◽  
pp. 2566-2573 ◽  
Author(s):  
B. Farokhi ◽  
Z. Family ◽  
B. Maraghechi
Keyword(s):  
Electron Beam ◽  
Free Electron ◽  
Free Electron Laser ◽  
Three Dimensional ◽  
Annular Electron Beam

Comparative study of electron motion and stability for different focusing regimes in a free-electron laser with three-dimensional helical wiggler

2015 ◽  
Vol 81 (5) ◽  
Author(s):  
Jing-Yue Xu ◽  
S.-J. Wang ◽  
Y.-G. Xu ◽  
Y.-P. Ji ◽  
X.-X. Liu ◽  
...  
Keyword(s):  
Electron Beam ◽  
Ion Channel ◽  
Free Electron ◽  
Free Electron Laser ◽  
Three Dimensional ◽  
Larmor Radius ◽  
Electron Motion ◽  
Magnetic Focusing ◽  
Laser Wave ◽  
The Stability

Since the electromagnetic energy gained by the laser wave in a free-electron laser (FEL) is transferred from the kinetic energy loss of a relativistic electron beam, the stability of electron motion is one of the key factors that affect FEL performance. In this paper the stability of electron motion is compared for different focusing regimes. It is demonstrated that the natural focusing regime of a three-dimensional wiggler is easily broken by the self-field of the electron beam. The magnetic focusing regime of an axial guide magnetic field is based on the superposition of a strong Larmor rotation on the transverse quiver motion of the electrons, while the electric focusing regime of an ion-channel guiding field generates an electric force to counteract the divergent effect of the beam self-field. In comparison with the magnetic focusing regime of an external magnetic system, the electric focusing regime of an ion-channel guiding field may yield smaller instantaneous Larmor radius and slighter Larmor-centre deviation from the axis and provide better motion stability.

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