• R.J. Dejus, M.S. Jaski
  ANL, Argonne
• S. Sasaki
  HSRC, Higashi-Hiroshima

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

In the selection of a new insertion device optimized for producing intense soft x-rays at the Advanced Photon Source, two different types of circular polarizing quasi-periodic undulators were studied. The magnetic structure of the undulators consists of pure permanent magnets for one of the undulators (an APPLE-II style undulator) and of electromagnets and pole pieces for the other type. The undulator period lengths were chosen so that the first harmonic energy occurs at 200 eV in linear horizontal polarization mode and at 400 eV in both linear vertical and circular polarization modes. Calculations of on-axis brilliance and on-axis flux spectra for both types of undulators and reductions of the spectral harmonics due to quasi-periodicity are presented. The introduction of quasi-periodicity of the magnetic fields shifts the higher spectral harmonics to a lower energy, hence reducing the so-called higher-order contamination dramatically. At the same time however, it reduces the first harmonic intensity by 20 – 40%. The non-sinusoidal shape of the horizontal and vertical magnetic fields of the electromagnetic undulator at high K values enhances the intensity of the first harmonic.

• Y. Ivanyushenkov, K.D. Boerste, T.W. Buffington, C.L. Doose, Q.B. Hasse, M.S. Jaski, M. Kasa, S.H. Kim, R. Kustom, E.R. Moog, D.L. Peters, E. Trakhtenberg, I. Vasserman
  ANL, Argonne
• A.V. Makarov
  Fermilab, Batavia

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

An extensive R&D program is underway at the Advanced Photon Source (APS) with the aim of developing a technology capable of building a 2.4-m-long superconducting planar undulator for APS users. The initial phase of the project concentrates on using a NbTi superconductor and includes magnetic modeling, development of manufacturing techniques for the undulator magnet, and design and test of short prototypes. The current status of the R&D phase of the project is described in this paper.

• M.S. Jaski, E.R. Moog, S. Sasaki
  ANL, Argonne

Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract number DE-AC02-06CH11357.

Investigation into a circular polarizing quasi-periodic undulator is presented here. Electromagnets are used to generate the vertical field. Permanent magnets are used to generate the horizontal field. Calculated maximum effective vertical and horizontal magnetic fields on the undulator axis higher than 8.5 kGauss are achieved at a 10.5-mm gap for a 9-cm-period undulator. Fields of this magnitude are difficult to achieve in purely electromagnetic devices. Switching the sign of the current for the vertical field electromagnets allows for right- or left-handed circular polarization. A laminated core can be introduced to allow for fast helicity switching in order to utilize lock-in detection techniques. Quasi-periodicity can be introduced in the vertical electromagnet field by reducing the current at the quasi-periodic poles and can be turned on, off, or somewhere in between. Quasi-periodicity can be introduced in the horizontal permanent magnet field by inserting weakened magnets at the quasi-periodic poles. Since it is built into the magnet structure, this quasi-periodicity cannot be turned off.

• M. White, J.T. Collins, P.K. Den Hartog, M.S. Jaski, G. Pile, B.M. Rusthoven, S.E. Shoaf, S.J. Stein, E. Trakhtenberg, J.Z. Xu
  ANL, Argonne

Funding: Work at Argonne was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No DE-AC02-06CH11357.

The Linac Coherent Light Source (LCLS), now being commissioned at the Stanford Linear Accelerator Center (SLAC) in California, and coming online for users in the very near future, will be the world’s first x-ray free-electron laser user facility. Design and production of the undulator system was the responsibility of a team from the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). A sophisticated, five-axis, computer-controlled support and motion system positions and stabilizes all beamline components in the undulator system. The system also enables undulators to be retracted from the beam by 80 mm without disturbing the rest of the beamline components. An overview of the support and motion system performance, including achieved results with a production unit that was reserved at Argonne for this purpose, is presented.