2011 Particle Accelerator Conference - List of Authors (Loos, H.)

Paper

Title

Page

Improved Energy Changes at the Linac Coherent Light Source

1424

N. Lipkowitz, H. Loos, C.R. Melton, G. Yocky
SLAC, Menlo Park, California, USA

The user requirements and beam time scheduling of the LCLS imposes a demand for fast changes in machine energy across the entire operating range of 3.3-15 GeV (480-10000 eV). Early operational experience during LCLS commissioning revealed this process to be problematic and error-prone, sometimes requiring substantial re-tuning at each change. To streamline the process, a software tool has been developed to gradually ramp the machine energy while the beam remains on, allowing beam-based feedbacks to continue to work during the energy change. The tool has considerably improved the speed and reliability of configuration changes, and also extends the capability of the LCLS, allowing for slow scans of the FEL photon energy over a wide range. This poster presents the basic process, analysis of the performance gains, and possible future improvements.

Slides WEOBS4 [62.503 MB]

THP184

Tuning of the LCLS Linac for User Operation

2462

H. Loos, R. Akre, A. Brachmann, F.-J. Decker, Y.T. Ding, P. Emma, A.S. Fisher, J.C. Frisch, A. Gilevich, P. Hering, Z. Huang, R.H. Iverson, N. Lipkowitz, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, T.J. Smith, J.L. Turner, J.J. Welch, W.E. White, J. Wu, G. Yocky
SLAC, Menlo Park, California, USA

Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515.
With the Linac Coherent Light Source (LCLS) now in its third user run, reliable electron beam delivery at various beam energies and charge levels has become of high operational importance. In order to reduce the beam tuning time required for such changes, several diagnostics and feed-forward procedures have been implemented. We report on improved lattice diagnostics to detect magnet, model, and diagnostics errors as well as on measurements of transverse RF kicks and static field contributions and corresponding correction procedures to facilitate beam energy changes.

THP168

FEL Beam Stability in the LCLS*

2423

J.L. Turner, R. Akre, A. Brachmann, F.-J. Decker, Y.T. Ding, P. Emma, Y. Feng, A.S. Fisher, J.C. Frisch, A. Gilevich, P. Hering, K. Horovitz, Z. Huang, R.H. Iverson, D. Kharakh, A. Krasnykh, J. Krzywinski, H. Loos, M. Messerschmidt, S.P. Moeller, H.-D. Nuhn, D.F. Ratner, T.J. Smith, J.J. Welch, J. Wu
SLAC, Menlo Park, California, USA

Funding: *This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515
During commissioning and operation of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center electron and x-ray beam size, shape, centroid motion have been studied. The studies, sources, and remediation are summarized in this paper.

THP183

Measurement of Femtosecond LCLS Bunches Using the SLAC A-line Spectrometer*

2459

Z. Huang, A. Baker, M. Boyes, J. Craft, F.-J. Decker, Y.T. Ding, P. Emma, J.C. Frisch, R.H. Iverson, J.J. Lipari, H. Loos, D.R. Walz
SLAC, Menlo Park, California, USA
C. Behrens
DESY, Hamburg, Germany

We describe a novel technique and the preliminary experimental results to measure the ultrashort bunch length produced by the LCLS low-charge, highly compressed electron bunch. The technique involves adjusting the LCLS second bunch compressor followed by running the bunch on an rf zero-crossing phase of the final 550-m of linac. As a result, the time coordinate of the bunch is directly mapped onto the energy coordinate at the end of the linac. A high-resolution energy spectrometer located at an existing transport line (A-line) is then commissioned to image the energy profile of the bunch in order to retrieve its temporal information. We present measurements of the single-digit femtosecond LCLS bunch length using the A-line as a spectrometer and compare the results with the transverse cavity measurement as well as numerical simulations.

Paper	Title	Page
WEOBS4	Improved Energy Changes at the Linac Coherent Light Source	1424
	N. Lipkowitz, H. Loos, C.R. Melton, G. Yocky SLAC, Menlo Park, California, USA
	The user requirements and beam time scheduling of the LCLS imposes a demand for fast changes in machine energy across the entire operating range of 3.3-15 GeV (480-10000 eV). Early operational experience during LCLS commissioning revealed this process to be problematic and error-prone, sometimes requiring substantial re-tuning at each change. To streamline the process, a software tool has been developed to gradually ramp the machine energy while the beam remains on, allowing beam-based feedbacks to continue to work during the energy change. The tool has considerably improved the speed and reliability of configuration changes, and also extends the capability of the LCLS, allowing for slow scans of the FEL photon energy over a wide range. This poster presents the basic process, analysis of the performance gains, and possible future improvements.
	Slides WEOBS4 [62.503 MB]

THP184	Tuning of the LCLS Linac for User Operation	2462
	H. Loos, R. Akre, A. Brachmann, F.-J. Decker, Y.T. Ding, P. Emma, A.S. Fisher, J.C. Frisch, A. Gilevich, P. Hering, Z. Huang, R.H. Iverson, N. Lipkowitz, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, T.J. Smith, J.L. Turner, J.J. Welch, W.E. White, J. Wu, G. Yocky SLAC, Menlo Park, California, USA
	Funding: This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515. With the Linac Coherent Light Source (LCLS) now in its third user run, reliable electron beam delivery at various beam energies and charge levels has become of high operational importance. In order to reduce the beam tuning time required for such changes, several diagnostics and feed-forward procedures have been implemented. We report on improved lattice diagnostics to detect magnet, model, and diagnostics errors as well as on measurements of transverse RF kicks and static field contributions and corresponding correction procedures to facilitate beam energy changes.

THP168	FEL Beam Stability in the LCLS*	2423
	J.L. Turner, R. Akre, A. Brachmann, F.-J. Decker, Y.T. Ding, P. Emma, Y. Feng, A.S. Fisher, J.C. Frisch, A. Gilevich, P. Hering, K. Horovitz, Z. Huang, R.H. Iverson, D. Kharakh, A. Krasnykh, J. Krzywinski, H. Loos, M. Messerschmidt, S.P. Moeller, H.-D. Nuhn, D.F. Ratner, T.J. Smith, J.J. Welch, J. Wu SLAC, Menlo Park, California, USA
	Funding: *This work was supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515 During commissioning and operation of the Linac Coherent Light Source (LCLS) x-ray Free Electron Laser (FEL) at the SLAC National Accelerator Center electron and x-ray beam size, shape, centroid motion have been studied. The studies, sources, and remediation are summarized in this paper.

THP183	Measurement of Femtosecond LCLS Bunches Using the SLAC A-line Spectrometer*	2459
	Z. Huang, A. Baker, M. Boyes, J. Craft, F.-J. Decker, Y.T. Ding, P. Emma, J.C. Frisch, R.H. Iverson, J.J. Lipari, H. Loos, D.R. Walz SLAC, Menlo Park, California, USA C. Behrens DESY, Hamburg, Germany
	We describe a novel technique and the preliminary experimental results to measure the ultrashort bunch length produced by the LCLS low-charge, highly compressed electron bunch. The technique involves adjusting the LCLS second bunch compressor followed by running the bunch on an rf zero-crossing phase of the final 550-m of linac. As a result, the time coordinate of the bunch is directly mapped onto the energy coordinate at the end of the linac. A high-resolution energy spectrometer located at an existing transport line (A-line) is then commissioned to image the energy profile of the bunch in order to retrieve its temporal information. We present measurements of the single-digit femtosecond LCLS bunch length using the A-line as a spectrometer and compare the results with the transverse cavity measurement as well as numerical simulations.