FEL2011 - List of Authors (Carlsten, B.E.)

Paper

Title

Page

Harmonic Generation for a Hard X-ray FEL

41

Q.R. Marksteiner, K. Bishofberger, B.E. Carlsten, L.D. Duffy, N.A. Yampolsky
LANL, Los Alamos, New Mexico, USA

Funding: We gratefully acknowledge the support of the US Department of Energy through the LANL LDRD Propgram for this work.
The proposed MaRIE XFEL at Los Alamos National Laboratory will generate ¼ Å, longitudinally coherent x-rays with a 20 GeV electron beam. A masked emittance exchanger can be used to generate coherent electron bunching at nm wavelengths. This masked emittance exchanger must be at 1 GeV in the accelerator, in order to mitigate debunching from incoherent synchrotron radiation (ISR). After this, the harmonic content must be stepped up by a factor of 200 in frequency and the electrons must be accelerated to 20 GeV. The nonlinear debunching effects in the accelerator from emittance must be mitigated by keeping the beam transversely large. There are several schemes to step the coherent bunching up to higher harmonics, all which require modulator and dispersive sections [1]. Echo-Enhanced Harmonic Generation, which requires large dispersion, must be incorporated at low energies, where ISR is reduced. Here we compare the usefulness of different harmonic generation schemes, and examine the possibility of placing successive harmonic generation sections at energies lower than 20 GeV in the accelerator line, with the accelerator sections in between used to introduce dispersion to the beam.
[1] Phys. Rev. E 71, 046501 (2005), etc.

WEOAI1

Controlling the Emittance Partitioning of High-Brightness Electron Beams

B.E. Carlsten, K. Bishofberger, L.D. Duffy, M.A. Holloway, Q.R. Marksteiner, N.A. Yampolsky
LANL, Los Alamos, New Mexico, USA
R.D. Ryne
LBNL, Berkeley, California, USA

High-brightness photoinjectors tend to produce electron beams with equipartitioned emittances, where the transverse emittances are roughly the same as the longitudinal emittance. However, the needs of next generation X-ray free-electron lasers (XFELs) will require transverse emittances up to three orders of magnitude smaller than the longitudinal emittances. Recent work on exotic optic schemes such as flat-beam transforms (FBTs) and emittance exchangers (EEXs) has pointed to significant new opportunities for providing arbitrary control of the beam emittance partitioning. Specifically, we can use initial correlations imposed on the beam as it is formed to control the beam’s eigen-emittances, which can then be recovered later at high energy as the actual beam emittances, in a linear sense. Here we discuss FBTs, EEXs, and other, more general, schemes to arbitrarily control the eigen-emittances, including the use of nonsymplectic beamline elements after the beam has been accelerated.

Slides WEOAI1 [1.916 MB]

Paper	Title	Page
MOPB17	Harmonic Generation for a Hard X-ray FEL	41
	Q.R. Marksteiner, K. Bishofberger, B.E. Carlsten, L.D. Duffy, N.A. Yampolsky LANL, Los Alamos, New Mexico, USA
	Funding: We gratefully acknowledge the support of the US Department of Energy through the LANL LDRD Propgram for this work. The proposed MaRIE XFEL at Los Alamos National Laboratory will generate ¼ Å, longitudinally coherent x-rays with a 20 GeV electron beam. A masked emittance exchanger can be used to generate coherent electron bunching at nm wavelengths. This masked emittance exchanger must be at 1 GeV in the accelerator, in order to mitigate debunching from incoherent synchrotron radiation (ISR). After this, the harmonic content must be stepped up by a factor of 200 in frequency and the electrons must be accelerated to 20 GeV. The nonlinear debunching effects in the accelerator from emittance must be mitigated by keeping the beam transversely large. There are several schemes to step the coherent bunching up to higher harmonics, all which require modulator and dispersive sections [1]. Echo-Enhanced Harmonic Generation, which requires large dispersion, must be incorporated at low energies, where ISR is reduced. Here we compare the usefulness of different harmonic generation schemes, and examine the possibility of placing successive harmonic generation sections at energies lower than 20 GeV in the accelerator line, with the accelerator sections in between used to introduce dispersion to the beam. [1] Phys. Rev. E 71, 046501 (2005), etc.

WEOAI1	Controlling the Emittance Partitioning of High-Brightness Electron Beams
	B.E. Carlsten, K. Bishofberger, L.D. Duffy, M.A. Holloway, Q.R. Marksteiner, N.A. Yampolsky LANL, Los Alamos, New Mexico, USA R.D. Ryne LBNL, Berkeley, California, USA
	High-brightness photoinjectors tend to produce electron beams with equipartitioned emittances, where the transverse emittances are roughly the same as the longitudinal emittance. However, the needs of next generation X-ray free-electron lasers (XFELs) will require transverse emittances up to three orders of magnitude smaller than the longitudinal emittances. Recent work on exotic optic schemes such as flat-beam transforms (FBTs) and emittance exchangers (EEXs) has pointed to significant new opportunities for providing arbitrary control of the beam emittance partitioning. Specifically, we can use initial correlations imposed on the beam as it is formed to control the beam’s eigen-emittances, which can then be recovered later at high energy as the actual beam emittances, in a linear sense. Here we discuss FBTs, EEXs, and other, more general, schemes to arbitrarily control the eigen-emittances, including the use of nonsymplectic beamline elements after the beam has been accelerated.
	Slides WEOAI1 [1.916 MB]