IPAC2013 - List of Authors (Wu, J.)

Paper

Title

Page

Femtosecond Electron Beam and X-ray Beams at the Linac Coherent Light Source

1316

Y.T. Ding, A. Brachmann, F.-J. Decker, R.C. Field, J.C. Frisch, Z. Huang, R.H. Iverson, H. Loos, H.-D. Nuhn, D.F. Ratner, J.L. Turner, J.J. Welch, J. Wu, F. Zhou
SLAC, Menlo Park, California, USA
P. Emma
LBNL, Berkeley, California, USA

Generation of ultrashort x-ray pulses (femtoseconds to attoseconds) is attracting much attention within the x-ray FEL user community. At the Linac Coherent Light Source (LCLS), we have successfully delivered femtosecond x-ray pulses to the users with two operating modes – low-charge (20-40pC) scheme and emittance spoiling foil method. Diagnostics on the femtosecond beams is also a challenging topic and good progresses have been made at LCLS. In this paper we report the experimental studies on the two femtosecond operation schemes, the x-ray performance and also the diagnostic progress.

TUPWO064

Online Optimization Algorithms for Accelerators and Experimental Results

2012

X. Huang, W.J. Corbett, J.A. Safranek, J. Wu
SLAC, Menlo Park, California, USA

Online optimization of accelerators is becoming increasingly more important as accelerator systems become more and more complex. Online accelerator optimization is generally a multi-variant nonlinear problem with considerable noise. Efficiency and robustness are critical for online applications. Therefore optimization algorithms require special considerations. In this study we evaluate the viability of several online optimization algorithms for both ring and linac machines. Numerical simulations and experimental tests are presented to investigate performance of the algorithms.

WEODB101

X-ray Spectra and Peak Power Control with iSASE

2068

J. Wu, F.-J. Decker, Y. Feng, J. Krzywinski, H. Loos, A.A. Lutman, A. Marinelli, H.-D. Nuhn, C. Pellegrini, D.F. Ratner, D.H. Zhang, D. Zhu
SLAC, Menlo Park, California, USA

Funding: Work is supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515.
We report the first measurement of spectral line-width reduction in a self-amplified spontaneous emission (SASE) X-ray free-electron laser (FEL) obtained by introducing repeated delays of the electron bunch with respect to the radiation field pulse. The improved longitudinal coherence obtained by this method reduces the intensity spiking effect characteristic of a SASE FEL. The electron-photon delays introduced along the FEL undulator mix the spikes phase and amplitude, increasing the cooperation length and generating a smaller bandwidth than in the conventional SASE mode of operation of an FEL. We call this mode of operation, based on repeated electron-photon delays, ‘‘improved SASE'' (iSASE). We also show with theoretical and simulation analysis that in the iSASE mode it is possible to choose the separation and magnitude of the delays to obtain a nearly transform limited X-ray pulse. This analysis is carried out using a time dependent, one-dimensional model and with GENESIS numerical simulation, including three-dimensional effects.

Slides WEODB101 [7.647 MB]

THPEA059

Database for Accelerator Modeling

3273

C.P. Chu, J. Wu
SLAC, Menlo Park, California, USA
D. Dohan, G. Shen
BNL, Upton, Long Island, New York, USA
H.H. Lv
IHEP, Beijing, People's Republic of China
Y. Zhang
FRIB, East Lansing, Michigan, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661.
A database for model data is design for the Facility for Rare Isotope Beams (FRIB) Project. The database schema design takes most general approach and is not limited to FRIB models. Programmatically access to the database can be done through a set of Application Programming Interfaces (APIs). Initial data population demonstrates that the database is suitable for XAL application framework. The model database is also part of a collaboration for complete database needs among various domains across an accelerator.

Paper	Title	Page
TUPEA086	Femtosecond Electron Beam and X-ray Beams at the Linac Coherent Light Source	1316
	Y.T. Ding, A. Brachmann, F.-J. Decker, R.C. Field, J.C. Frisch, Z. Huang, R.H. Iverson, H. Loos, H.-D. Nuhn, D.F. Ratner, J.L. Turner, J.J. Welch, J. Wu, F. Zhou SLAC, Menlo Park, California, USA P. Emma LBNL, Berkeley, California, USA
	Generation of ultrashort x-ray pulses (femtoseconds to attoseconds) is attracting much attention within the x-ray FEL user community. At the Linac Coherent Light Source (LCLS), we have successfully delivered femtosecond x-ray pulses to the users with two operating modes – low-charge (20-40pC) scheme and emittance spoiling foil method. Diagnostics on the femtosecond beams is also a challenging topic and good progresses have been made at LCLS. In this paper we report the experimental studies on the two femtosecond operation schemes, the x-ray performance and also the diagnostic progress.

TUPWO064	Online Optimization Algorithms for Accelerators and Experimental Results	2012
	X. Huang, W.J. Corbett, J.A. Safranek, J. Wu SLAC, Menlo Park, California, USA
	Online optimization of accelerators is becoming increasingly more important as accelerator systems become more and more complex. Online accelerator optimization is generally a multi-variant nonlinear problem with considerable noise. Efficiency and robustness are critical for online applications. Therefore optimization algorithms require special considerations. In this study we evaluate the viability of several online optimization algorithms for both ring and linac machines. Numerical simulations and experimental tests are presented to investigate performance of the algorithms.

WEODB101	X-ray Spectra and Peak Power Control with iSASE	2068
	J. Wu, F.-J. Decker, Y. Feng, J. Krzywinski, H. Loos, A.A. Lutman, A. Marinelli, H.-D. Nuhn, C. Pellegrini, D.F. Ratner, D.H. Zhang, D. Zhu SLAC, Menlo Park, California, USA
	Funding: Work is supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515. We report the first measurement of spectral line-width reduction in a self-amplified spontaneous emission (SASE) X-ray free-electron laser (FEL) obtained by introducing repeated delays of the electron bunch with respect to the radiation field pulse. The improved longitudinal coherence obtained by this method reduces the intensity spiking effect characteristic of a SASE FEL. The electron-photon delays introduced along the FEL undulator mix the spikes phase and amplitude, increasing the cooperation length and generating a smaller bandwidth than in the conventional SASE mode of operation of an FEL. We call this mode of operation, based on repeated electron-photon delays, ‘‘improved SASE'' (iSASE). We also show with theoretical and simulation analysis that in the iSASE mode it is possible to choose the separation and magnitude of the delays to obtain a nearly transform limited X-ray pulse. This analysis is carried out using a time dependent, one-dimensional model and with GENESIS numerical simulation, including three-dimensional effects.
	Slides WEODB101 [7.647 MB]

THPEA059	Database for Accelerator Modeling	3273
	C.P. Chu, J. Wu SLAC, Menlo Park, California, USA D. Dohan, G. Shen BNL, Upton, Long Island, New York, USA H.H. Lv IHEP, Beijing, People's Republic of China Y. Zhang FRIB, East Lansing, Michigan, USA
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. A database for model data is design for the Facility for Rare Isotope Beams (FRIB) Project. The database schema design takes most general approach and is not limited to FRIB models. Programmatically access to the database can be done through a set of Application Programming Interfaces (APIs). Initial data population demonstrates that the database is suitable for XAL application framework. The model database is also part of a collaboration for complete database needs among various domains across an accelerator.