Journal of large-scale research facilities, 2, A53 (2016) http://dx.doi.org/10.17815/jlsrf-2-76 Published: 01.03.2016 The U125-2 NIM beamline at BESSY II Helmholtz-Zentrum Berlin für Materialien und Energie * Instrument Scientists: - Dr. Peter Baumgärtel, Helmholtz-Zentrum Berlin für Materialien und Energie, phone: +49 30 8062-15154, email: peter.baumgaertel@helmholtz-berlin.de - Ingo Packe, Helmholtz-Zentrum Berlin für Materialien und Energie, phone: +49 30 8062-12943, email: ingo.packe@helmholtz-berlin.de Abstract: Optical design and technical data of the high-resolution normal incidence monochromator (NIM) beamline U125-2 NIM are presented. 1 Introduction Normal incidence monochromators (NIM) are typically used in synchrotron beamlines which are dedi- cated to experiments operating in an energy range of about 4 to 35 eV only. The decisive advantages of this type of monochromator design are that only small aberration errors occur and highest resolution can be easily achieved. The 10m-NIM beamline (Reichardt et al., 2001) was designed for the quasi-periodic undulator U125-2 (Bahrdt et al., 2001). In this special kind of undulator source the period of the magnets is structured in a way that higher orders are suppressed. The design of the beamline’s monochromator is based on the so called o�-Rowland circle mounting design (Samson, 1967). This implies that the grating has to be rotated and slightly translated in order to get the highest resolution and a small spot size in the experiment. *Cite article as: Helmholtz-Zentrum Berlin für Materialien und Energie. (2016). The U125-2 NIM beamline at BESSY II. Journal of large-scale research facilities, 2, A53. http://dx.doi.org/10.17815/jlsrf-2-76 1 http://jlsrf.org/ http://dx.doi.org/10.17815/jlsrf-2-76 http://dx.doi.org/10.17815/jlsrf-2-76 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 2, A53 (2016) http://dx.doi.org/10.17815/jlsrf-2-76 Figure 1: Views of beamline U125-2 NIM. 2 Instrument application At this beamline the users care for their own experimental setup which �ts to their application. Typical user’s applications and experimental methods are: • absorption spectroscopy • �uorescence spectroscopy • photoelectron spectroscopy • photoionization of molecules and clusters • spectroscopic ellipsometry 3 Source The insertion device is the undulator U125-2 with the following parameters: Type planar hybrid, quasi-periodic Location H03 Periode length 125 mm Periods/Pols 32 n Minimal Energy at 1.7 GeV 2.53 eV Minimal Gap 15.7 mm Polarisation linear horizontal Table 1: Parameters of the undulator U125-2. 2 http://dx.doi.org/10.17815/jlsrf-2-76 https://creativecommons.org/licenses/by/4.0/ http://dx.doi.org/10.17815/jlsrf-2-76 Journal of large-scale research facilities, 2, A53 (2016) 4 Optical Design Figure 2: Optical design of beamline U125-2 NIM. All distances are given in mm. The optical elements are described in Table 2. premonochromator optics M1: toroidal mirror, horizontal de�ection, 2Θ=172°, platinum coated, water cooled, horizontal and vertica demagni�cation 17:6 IF: Intermediate focus M2: plane-elliptical mirror, vertical focussing on entrance slit (15:2), vertical de�ection 2Θ=178° entrance slit (EnS) slit setting: 0-2000 µm, water cooled, rotatable by ±2°, prepared for online laser di�raction slitwidth monitor Monochromator o�-Rowland circle mounting G1-3: spherical gratings, vertical de�ection, 2Θ= 2°, water cooled E [eV] pro�le d[l/mm] R [mm] coating G1 3 - 40 blaze angle: 300 10041 Au 0.8°(max: 12 eV) G2 5 - 40 laminar 1200 10044 Pt G3 5 - 40 laminar 4800 9991 W Exit slit (ExS) slit setting: 0-2000 µm, rotatable by ±2°, prepared for online laser di�raction slit width monitor postmonochromator optics M3: toroidal mirror, horizontal de�ection, 2Θ= 155°, Ruthenium coated, vertical demagni�cation (1:1) of exit slit, horizontal demagni�cation 5:3 M4: toroidal mirror, horizontal de�ection, 2Θ= 155°, Ruthenium coated, vertical demagni�cation (1:1) of intermediate focus, horizontal demagni�cation 5:3 Table 2: Description of the optical elements. 3 http://dx.doi.org/10.17815/jlsrf-2-76 https://creativecommons.org/licenses/by/4.0/ Journal of large-scale research facilities, 2, A53 (2016) http://dx.doi.org/10.17815/jlsrf-2-76 5 Technical Data Location 5.1 Source U125-2 Monochromator 10m-NIM Energy range 6(4) - 40 eV Energy resolution E/dE = 85000 @ d = 1200l/mm, 2nd order, 10 µ m slits Flux 1012 @ 21.75 eV [photons/s/0.1A/0.1%BW] Polarization horizontal Divergence horizontal 5.5 mrad Divergence vertical 12 mrad Focus size (hor. x vert.) 200 x 350 µm2 Distance Focus/last valve 1190 mm Height Focus/�oor level 1760 mm with concrete experiment platform without feet: 1450 mm (30, 50 and 100 mm feet are available) Free photon beam available yes Fixed end station no Table 3: Technical data for U125-2 NIM beamline. References Bahrdt, J., Frentrup, W., Gaupp, A., Scheer, M., Gudat, W., Ingold, G., & Sasaki, S. (2001). A quasi- periodic hybrid undulator at BESSY II. Nuclear Instruments and Methods in Physics Research Section A, 467–468, Part 1, 130 - 133. http://dx.doi.org/10.1016/S0168-9002(01)00236-4 Reichardt, G., Bahrdt, J., Schmidt, J.-S., Gudat, W., Ehresmann, A., Müller-Albrecht, R., . . . Sasaki, S. (2001). A 10 m-normal incidence monochromator at the quasi-periodic undulator U125-2 at BESSY II. Nuclear Instruments and Methods in Physics Research Section A, 467–468, Part 1, 462 - 465. http://dx.doi.org/10.1016/S0168-9002(01)00359-X Samson, J. (1967). Techniques of vacuum ultraviolet spectroscopy. New York: Wiley. 4 http://dx.doi.org/10.17815/jlsrf-2-76 http://dx.doi.org/10.1016/S0168-9002(01)00236-4 http://dx.doi.org/10.1016/S0168-9002(01)00359-X https://creativecommons.org/licenses/by/4.0/ Introduction Instrument application Source Optical Design Technical Data