TY - CPAPER
AU - Nuhn, H.-D.
AU - Anderson, S.D.
AU - Buck, J.
AU - Coffee, R.N.
AU - Ding, Y.
AU - Hartmann, G.
AU - Huang, Z.
AU - Ilchen, M.
AU - Levashov, Yu.I.
AU - Lindahl, A.O.
AU - Lutman, A.A.
AU - MacArthur, J.P.
AU - Marinelli, A.
AU - Moeller, S.P.
AU - Peters, F.
AU - Temnykh, A.B.
AU - Viefhaus, J.
AU - Wolf, Z.R.
TI - Commissioning of the Delta Polarizing Undulator at LCLS
J2 - Proc. of FEL2015
AB - The LCLS generates linearly polarized, intense, high brightness x-ray pulses from planar fixed-gap undulators, which provides only limited taper capability and lacks polarization control. The latter is of great importance for soft x-ray experiments. A new 3.2-m-long compact undulator (based on the Cornell University fixed-gap Delta design) has been developed and installed as the last LCLS undulator segment (U33) in October 2014. The Delta undulator provides full control of the polarization degree and K parameter through array position adjustments. Used on its own, it produces fully polarized spontaneous radiation in the selected state (linear, circular or elliptical). To increase the output power by orders of magnitude, the electron beam is micro-bunched by several (5-15) upstream LCLS undulator segments operated in the linear FEL regime. This micro-bunching process produces horizontally linear polarized (background) radiation. This unwanted radiation component has been greatly reduced by a reversed taper configuration, as suggested by Schneidmiller. Full elimination of the linear polarized component was achieved through spatial separation combined with transverse collimation. The paper will describe the methods tested during commissioning and will also present results of polarization measurements showing high degrees of circular polarization in the soft x-ray wavelength range.
PB - JACoW
CY - Geneva, Switzerland
SP - 757
EP - 763
KW - undulator
KW - polarization
KW - radiation
KW - bunching
KW - electron
DA - 2015/12
PY - 2015
SN - 978-3-95450-134-2
DO - 10.18429/JACoW-FEL2015-WED01
UR - http://accelconf.web.cern.ch/AccelConf/FEL2015/papers/wed01.pdf
ER -