1 Journal of large-scale research facilities, 1, A33 (2015) http://dx.doi.org/10.17815/jlsrf-1-55 Published: 09.11.2015 UE112_PGM-1: An open-port low-energy beamline at the BESSY II undulator UE112 Helmholtz-Zentrum Berlin für Materialien und Energie Instrument Scientists: - G. Schiwietz, Helmholtz-Zentrum Berlin für Materialien und Energie, phone: +49 30 8062-15032, e-mail: schiwietz@helmholtz-berlin.de - M. Beye, Helmholtz-Zentrum Berlin für Materialien und Energie, phone: +49 30 8062- 14677, e-mail: martin.beye@helmholtz-berlin.de - T. Kachel, Helmholtz-Zentrum Berlin für Materialien und Energie, phone: +49 30 8062-12942, e-mail: torsten.kachel@helmholtz-berlin.de Abstract: The X-ray optical and mechanical designs of a low-energy high-flux VUV- to soft-X-ray beamline for photon energies between 17 and 200 eV (with lower flux up to 690 eV) are presented. 1 Introduction The UE112_PGM-1 installation is a low-energy high-flux X-ray beamline with variable (linear and elliptical) polarization. It is a combination of the UE112, a modern APPLE-II-type undulator, coupled to a collimated plane-grating monochromator (Follath et al., 1997, 1998, 2001). It features high resolving power, high throughput and small spot size at the experiment for X-ray energies between 17 eV and 690 eV. The X-ray beam is focused into a small spot with a diameter of about 80 m, without a significant halo. The focal distance from the last beamline valve is about 1 m and the available target area on the floor is large enough to enable the installation of relatively large experimental setups. Thus, the beamline includes no fixed end station and it is optimized for variable modes of operation using very different experimental chambers (typically these are end stations). https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/ Journal of large-scale research facilities, 1, A33 (2015) http://dx.doi.org/10.17815/jlsrf-1-55 2 2 Source The insertion device is an APPLE-II-type elliptical undulator with the following parameters: Location H13 Source undulator UE112 Polarization linear horizontal, linear vertical, elliptical, and circular Period 112.0 mm Number of Periods 32 Minimum Energy 4.93 eV Table 1: Information summary on the insertion device 3 Optical Design The optical layout of the beamline (all values in the subsequent schema are design parameters, dimensions given in mm) (Follath et al., 1997, 1998, 2001) is described in the following. M1 is a toroidal mirror which collimates the light in the horizontal and vertical directions. The plane mirror M2 is used to vary the deviation angle at the plane grating G. Vertically, the diffracted light is focused onto the (horizontal) exit slit S by the cylindrical mirror M3. Al (150 nm thick) and Mg foils (240 nm thick) allow for a suppression of higher order X-rays at E > 73 eV (Al) or E > 50 eV (Mg). The subsequent refocusing is performed by the mirrors M4 and M5 in the vertical and horizontal directions, respectively. Actual measured values of the focus position are given in the instrument- data table further below. Figure 1: The optical layout of beamline UE112_PGM-1. http://dx.doi.org/ https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-1-55 Journal of large-scale research facilities, 1, A33 (2015) 3 4 All-over Performance Data Performance data related to the focal point are given in the following (Follath et al., 1997, 1998, 2001; Savci & Schiwietz, 2013): Location 14.2 Energy range 17 – 690 eV Energy resolution * 30,000 (17-150eV) > 20,000 (150-350eV) Flux * > 1012 ph/s (20-280eV) > 2 x 1013 ph/s (50-150eV) Polarization variable Divergence horizontal 1.4 @ 63.5eV mrad Divergence vertical 0.6 @ 63.5eV mrad Focus size (hor. x vert.) optimum: ca. 0.08 x 0.08 mm Distance: Focus-last valve ca. 1068 mm Height: Focus-floor level ca. 1396.5 mm (1393 mm at the exit of the refocusing chamber) Fixed end station no * parameters given for standard grating1 Table 2: Instrument-data table: technical summary on the undulator/monochromator combination. Figure 2: Normalized photon flux (wrt. the synchrotron-ring current) at the exit of the beamline UE112_PGM-1 for standard conditions and three different undulator harmonics.1 Typically BESSY II runs with a ring current of 300 mA 1 Savci A. & Schiwietz G. (2013). Actual measurements of beamline parameters have been performed in the years 2013 and 2014. http://dx.doi.org/ https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 1, A33 (2015) http://dx.doi.org/10.17815/jlsrf-1-55 4 5 User Chambers Some selected examples for user chambers attached to UE112_PGM-1:  PHOENEXS – a (Spin Resolved) Photoemission and Near Edge X-ray Station, operated by HZB.  ArTOF – various Angle-Resolved Time-of-Flight systems featuring high resolution and large detection solid-angle, operated by groups of Uppsala University and HZB.  COLTRIMS – a system for Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) for electron/ion coincidences in the gas phase, operated by groups of Goethe-Universität Frankfurt.  ET – the electron timing chamber (Schiwietz et al, 2015) equipped with the retarding Bessel Box (RBB) electrostatic electron spectrometer, operated by HZB (Schiwietz et al., 2015).  Liquid or solid FlexRIXS –end stations with soft X-ray emission spectrometers for RIXS (Resonant Inelastic X-ray Scattering) investigations of fluid and solid-state targets respectively, operated by HZB. References Follath, R. (2001). The versatility of collimated plane grating monochromators. Nuclear Instruments and Methods in Physics, 467, 418-425. http://dx.doi.org/10.1016/S0168-9002(01)00338-2 Follath, R., & Senf, F. (1997). New plane-grating monochromators for third generation synchrotron radiation light sources. Nuclear Instruments and Methods in Physics, 390(3), 388-394. http://dx.doi.org/10.1016/S0168-9002(97)00401-4 Follath, R., Senf, F., & Gudat, W. (1998). Plane-grating monochromator at BESSY II using collimated light. Journal of Synchrotron Radiation, 5, 769-771. http://dx.doi.org/10.1107/S090904959800079X Schiwietz, G., Beye, M., Kühn, D., & Xiao, G. (2015). The retarding bessel–box—an electron spectrometer designed for pump/probe experiments. Journal of Electron Spectroscopy and Related Phenomena, 203, 51 - 59. http://dx.doi.org/http://dx.doi.org/10.1016/j.elspec.2015.06.011 http://dx.doi.org/ https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.1016/S0168-9002(01)00338-2 http://dx.doi.org/10.1016/S0168-9002(97)00401-4 http://dx.doi.org/10.1107/S090904959800079X