FEL2014 - List of Authors (MacArthur, J.P.)

Paper	Title	Page
TUP035	Investigation of Reverse Taper to Optimize the Degree of Polarization for the Delta Undulator at the LCLS	465
	J.P. MacArthur Stanford University, Stanford, California, USA Z. Huang, A. Lutmann, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner SLAC, Menlo Park, California, USA
	Funding: U.S. Department of Energy under contract No. DE-AC02-76SF00515 A 3.2 m adjustable phase Delta undulator* will soon be installed on the last girder of the LCLS undulator line. The Delta undulator will act as an afterburner terminating the 33 undulator line, providing arbitrary polarization control to users. Two important figures of merit for users will be the degree of polarization and the x-ray yield. In anticipation of this installation, machine development time at the LCLS was devoted to maximizing the final undulator x-ray contrast and yield with a standard canted pole undulator acting as a stand in for the Delta undulator. Following the recent suggestion** that a reverse taper (dK/dz > 0) in the main undulator line could suppress linearly polarized light generated before an afterburner while still producing the requisite microbunching, we report on a reverse taper study at the LCLS wherein a yield contrast of 15 was measured along the afterburner. We also present 1D simulations comparing the reverse taper technique to other schemes. * Nuhn, H.-D., Anderson, S., Bowden, G., Ding, Y., Gassner, G., et al., (2013). ** Schneidmiller, E. A. and Yurkov, M. V., Phys. Rev. ST Accel. Beams 16, 110702 (2013).

Paper

Title

Page

Investigation of Reverse Taper to Optimize the Degree of Polarization for the Delta Undulator at the LCLS

465

J.P. MacArthur
Stanford University, Stanford, California, USA
Z. Huang, A. Lutmann, A. Marinelli, T.J. Maxwell, H.-D. Nuhn, D.F. Ratner
SLAC, Menlo Park, California, USA

Funding: U.S. Department of Energy under contract No. DE-AC02-76SF00515
A 3.2 m adjustable phase Delta undulator* will soon be installed on the last girder of the LCLS undulator line. The Delta undulator will act as an afterburner terminating the 33 undulator line, providing arbitrary polarization control to users. Two important figures of merit for users will be the degree of polarization and the x-ray yield. In anticipation of this installation, machine development time at the LCLS was devoted to maximizing the final undulator x-ray contrast and yield with a standard canted pole undulator acting as a stand in for the Delta undulator. Following the recent suggestion** that a reverse taper (dK/dz > 0) in the main undulator line could suppress linearly polarized light generated before an afterburner while still producing the requisite microbunching, we report on a reverse taper study at the LCLS wherein a yield contrast of 15 was measured along the afterburner. We also present 1D simulations comparing the reverse taper technique to other schemes.
* Nuhn, H.-D., Anderson, S., Bowden, G., Ding, Y., Gassner, G., et al., (2013).
** Schneidmiller, E. A. and Yurkov, M. V., Phys. Rev. ST Accel. Beams 16, 110702 (2013).