Advances in global optimization of high brightness beams

High brightness electron beams play an important role in accelerator-based applications such as driving X-ray free electron laser (FEL) radiation. In this paper, we report on advances in global beam dynamics optimization of an accelerator design using start-to-end simulations and a new parallel multi-objective differential evolution optimization method. The global optimization results in significant improvement of the final electron beam brightness.

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PRODUCTION OF FEMTOSECOND PULSES AND MICRON BEAM SPOTS FOR HIGH BRIGHTNESS ELECTRON BEAM APPLICATIONS

International Journal of Modern Physics A ◽

10.1142/s0217751x0703738x ◽

2007 ◽

Vol 22 (22) ◽

pp. 3726-3735

Author(s):

S. G. ANDERSON ◽

D. J. GIBSON ◽

F. V. HARTEMANN ◽

J. S. JACOB ◽

A. M. TREMAINE ◽

...

Keyword(s):

Electron Beam ◽

Electron Beams ◽

Beam Radiation ◽

High Brightness ◽

X Ray ◽

Inverse Compton Scattering ◽

Inverse Compton ◽

Strong Focusing ◽

Moderate Energy ◽

Low Emittance

Current and future applications of high brightness electron beams, which include advanced accelerators and beam-radiation interactions require both transverse and longitudinal beam sizes on the order of tens of microns. Ultra-high density beams may be produced at moderate energy (50 MeV) by compression and subsequent strong focusing of low emittance, photoinjector sources. We describe the implementation of this method used at the PLEIADES inverse-Compton scattering (ICS) x-ray source at LLNL in which the photoinjector-generated beam has been compressed to 300 fsec rms duration using the velocity bunching technique and focused to 20 μm rms size using an extremely high gradient, permanent magnet quadrupole focusing system.

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

Applied Sciences ◽

10.3390/app112210768 ◽

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.

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Overview of the Semiconductor Photocathode Research in China

Micromachines ◽

10.3390/mi12111376 ◽

2021 ◽

Vol 12 (11) ◽

pp. 1376

Author(s):

Huamu Xie

Keyword(s):

Free Electron Laser ◽

Electron Beams ◽

Spectral Response ◽

Ultrafast Electron Diffraction ◽

High Brightness ◽

X Ray ◽

Rf Gun ◽

Long Lifetime ◽

Diffraction Microscopy ◽

Electron Diffraction Microscopy

With the growing demand from scientific projects such as the X-ray free electron laser (XFEL), ultrafast electron diffraction/microscopy (UED/UEM) and electron ion collider (EIC), the semiconductor photocathode, which is a key technique for a high brightness electron source, has been widely studied in China. Several fabrication systems have been designed and constructed in different institutes and the vacuum of most systems is in the low 10−8 Pa level to grow a high QE and long lifetime photocathode. The QE, dark lifetime/bunch lifetime, spectral response and QE map of photocathodes with different kinds of materials, such as bialkali (K2CsSb, K2NaSb, etc.), Cs2Te and GaAs, have been investigated. These photocathodes will be used to deliver electron beams in a high voltage DC gun, a normal conducting RF gun, and an SRF gun. The emission physics of the semiconductor photocathode and intrinsic emittance reduction are also studied.

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