Novel design of large X-ray optical system for astrophysical application L. Pina 1, R. Hudec 1, V. Tichy 1, A. Inneman 2, D. Cerna 2, J. Marsik 2, V. Marsikova 2, W. Cash 3, A. F. Shipley 3 and B. R. Zeiger 3, T. D. Rogers 3, R. Melich 4 1 Czech Technical Univ. in Prague, Czech Republic 2 Rigaku Innovative Technologies Europe, Czech Republic 3 Univ. of Colorado at Boulder, United States 4 CAS IPP, TOPTEC, Turnov, Czech Republic AXRO December Motivation Study of new technologies for large X-ray telescopes Extraordinary requirements on accuracy resolution of optical system around few arcsec This type of optical system has to be assembled from many small segments and thousands of mirrors (unlike only a few nested mirrors in other projects) Manufacturing of Wolter I system needs very expensive mandrels (3D aspheric) Manufacturing of KB system can be easier and cheaper (2D aspheric) Substrates can be glass and/or silicon with excellent flatness and micro-roughness which is necessary for long-focal optics AXRO December Wolter system Double reflection X-ray optics Rotationally symmetric mirrors of parabolic and hyperbolic shape Set of nested mirrors is arranged concentrically to the optical axis Each ray is reflected at the parabolic surface first, then at the hyperbolic surface Quality of the focal spot depends on quality of substrates (shape, microroughness) Optical error is rectified (astigmatic and coma error) Replicated technology requires expensive mandrels XMMAXRO December horizontal focusing mirror vertical focusing mirror Kirkpatrick-Baez system Double reflection X-ray Optics Two mirror sets vertical and horizontal Mirrors in both sets have to be curved parabolically Single focal point is formed in the intersection of the horizontal and vertical focal planes Quality of the focal spot depends on quality of substrates (shape, microroughness) Technology is not necessarily based on precise and expensive mandrel Classical manufacturing technology of laboratory KB optics is expensive AXRO December Apertures for ray-tracing simulation AXRO December Wolter IKirkpatrick-Baez Comparison of aperture sizes of W and KB systems Diameter of Wolter 2 m, KB aperture 2 2 m Similar reflection angle considered Reflectivity of edge mirror 70% (for energy 1 keV) AXRO December KBW Type of opticsParabolic-parabolic planar Parabolic-hyperbolic rotational Number of reflections 22 Focal length - Aperture 20 m 913 x 913 mm 40 m 1826 x 1826 mm 10 m radius 913 mm 20 m radius 1826 mm First mirror 134 mm from axis 268 mm from axis 134 mm from axis 268 mm from axis Number of mirrors Length of substrate300 mm Material substratesiliconglass Surfacegold Ray-tracing simulations Large X-ray telescope composed of modules Sunflower configuration uses Fibonacci numbers (the lines from the centre to the corner of each module indicate the direction in which 2-reflection rays are deflected) Radial packing of modules used for the Wolter I design The simple cartesian packing used as an alternative to the sunflower tessellation for the KB design Radial design Cartesian designSunflower design The design, manufacture and predicted performance of Kirkpatrick-Baez Silicon stacks for the International X-ray Observatory or similar applications, Optics for EUV, X-ray and Gamma-ray Astronomy IV (Proc. of SPIE Vol.7437) Willingal and Spaan, AXRO December Studied KB X-ray modules Modules are assembled from o thin reflection foils (Schmidt arrangement) or o rectangular channels (Angel arrangement) with precise shape and with low microroughness AXRO December Novel design of X-ray optical KB Flower system (KBF) X-ray KBF optical system is assembled from minimally 5 segments (petals) Each segment (petal) is assembled from modules (one or more) Each module is assembled from thin reflection foils or rectangular channels Energy range 50 eV 10 keV (EUV, SXR, XR) AXRO December X-ray segment of KBF system Segment is a sector of a circle with central angle 18- 72 (usually 45) Segment is assembled from modules Diagonals of all modules are parallel with symmetry axis of segment Black narrow area is nonfunctional area AXRO December Design of KBF system X-ray optical system is assembled from segments (minimally 5) Symmetry axis of each segment intersects symmetry axis of the optical system Arrangement of segments approaches a circular aperture Patent pending (PV ) AXRO December X-ray optical systems - apertures Kirkpatrick-Baez system Wolter system Flower system AXRO December Size limited by the critical angle the same maximum incident angle for all systems for 1 keV (reflectivity 70% after 1 st reflection, 50% after 2 nd reflection) Wolter I and KB systems have the same aperture size KBF system has more than two times larger aperture than the others X-ray optical systems - comparison System Focal length (m) Active aperture (m 2 ) Number of reflections KB (R = 50%) W (R = 50%) KBF (R = 50%) P (R = 70%) AXRO December W Wolter system, KB Kirkpatrick-Baez system, KBF KB Flower system, P Parabolic system (Wolter without hyperbolic part) Focal length of KB, KBF and Parabolic system is two times larger than that of Wolter system X-ray optical systems - comparison KB Kirkpatrick-Baez system W Wolter system KBF - KB Flower system P Parabolic system KBFPWKB 1 keV : KBF (F=20m) > P (F=20m) > W (F=10m) > KB (F=20m) PWKBFKB 10 keV : P (F=20m) > W (F=10m) KBF (F=20m) > KB (F=20m) COMBINATION AXRO December X-ray optical systems - comparison => COMBINATION KBFP KBF and P (in SXR - XR region) logarithmic scale AXRO December linear scale Novel X-ray optical system KBF+P combination Non-functional (blind) central area of KBF system can be filled with thin rotationally symmetric foils (classical nested mirrors with parabolic shape P) => improvement of KBF optical system aperture effective area for higher energies Patent pending (PV ) AXRO December Advantages of KBF+P combination: KBF design has the largest effective aperture in SXR region KBF design allows higher efficiency in XR region using combination with parabolic mirrors filling the KBF non-functional area more homogeneous beam can be achieved by rotation of the whole optical system precise expensive mandrels are not needed for KBF part silicon or glass thin planar mirrors can be used in KBF part AXRO December X-ray optical system KBF+P combination Applications of KBF+P system Astrophysical application (X-ray telescopes) Laboratory application (EUV, XUV, SXR and XR optics) EUV /XUV microscopy and tomography EUV/XUV lithography X-ray Compton imaging Focusing of electrons and/or neutrons XRF analysis AXRO December Experiments X-ray tests of KBF elements X-ray testing of astronomical long-focal optics requires parallel beam and long vacuum chambers, which makes testing rather difficult New testing method was proposed Testing is divided into two parts: 1.Testing of optics assembling technology and focusing properties in elliptic geometry (point-to-point imaging) 2.Application of verified optical technologies to final optics design with parabolic geometry KB modules were tested in vacuum chamber in Center for Astrophysics and Space Astronomy (CASA, University of Colorado at Boulder, USA) AXRO December Testing vacuum chamber at CASA UC X-Ray source with Ti anode (L, 453 eV, 2.73 nm) X-Ray beam diameter (diameter of vacuum tube) 8 cm Total vacuum chamber length 20 m MCP detector, diameter 1 AXRO December Comparison of glass and Si mirrors 2 modules were assembled from glass mirrors and Si standard wafers Housing - Al profile Mirror size: 100 100 mm (glass), 100 75 mm (Si) Mirror thickness: 0.4 mm (glass), 0.7 mm (Si) Au surface coating AXRO December AXRO December Comparison of glass and Si mirrors Simulation and test results Ray-tracing simulation (ideally flat mirrors considered) X-ray tests at CASA CU Symmetric geometry, flat mirrors, focal length 9 m Glass module vertical, Si module horizontal Comparison of glass and Si mirrors AXRO December Taylor-Hobson profilometer module RMS (m)RMS (arcsec) glass 1.6 Si 0.4 17.1 simulationmeasurement moduleFWHM (mm)FWHM (arcsec)FWHM (mm)FWHM (arcsec) glass Si Mirrors were measured on Taylor-Hobson profilometer Si mirrors have better flatness High variance of glass mirrors Difference between simulation and experiment (broadening of focus) is caused by poor quality of glass mirrors Comparison of glass and Si mirrors AXRO December Figure error Angular error glassSi Development of improved Si wafers for X-ray optics applications AXRO December Standard wafer Improved surface Standard silicon wafer (150 mm diameter): -thickness in the wafer center: m, minimal measured thickness: m, maximal measured thickness: m, -total thickness variation: 2.10 m, flatness: 1.76 m Highly flat silicon wafer developed for sub-micron technologies in ON Semiconductor Czech Republic (150 mm diameter): -thickness in the wafer center: m, minimal measured thickness: m, maximal measured thickness: m, -total thickness variation: 0.45 m, flatness: 0.29 m improvement by factor of 5! KB modules - specification 144 commercially available 525 m thick Si wafers with Au surface coating 1 st mirror is at a distance of approx. 16 mm from optical axis Mirrors arranged into planar-ellipsoidal shape with axial symmetry Mirror size 100 100 mm 3 sets of 24 (18+6) mirrors in each module Spacing 1.5 2.5 mm AXRO December Experimental arrangement Modules were designed for vacuum chamber at CASA (Univ. of Colorado) Point-to-point imaging - elliptical geometry Source to optics distance: 10 m Optics to detector distance: 8 m Distance between modules: 10 cm Module position adjustment done with visible light (Xe lamp) AXRO December Test results FWHM = 1.63 mm Anglular resolution: 10.2 arcsec (after ellips. correction) AXRO December Ray-tracing simulations Input parameters (mirror material properties, arrangement of mirrors in modules, experiment geometry, ) are the same as in the experiment AXRO December Theoretical focus: FWHM = 0.58 mm 3.7 arcsec Theoretical focus with 0.2 mm source diameter and 2 m manufacturing errors: FWHM = 0.59 mm Optics with piezoelements Piezoelements were studied in order to improve resolution Glued striped piezoelements enable mirrors bending which approximates aspherical shape of KB mirror Two stacked mirrors (optical surfaces) were tested in vacuum chamber Mirror size 100 55 mm Distance of mirrors from optical axis - 40 cm Mirrors bent to radius 250 m AXRO December Focus behavior depending on piezoelement voltages was studied Voltage for optimum focus was found AXRO December Optics with piezoelements Joint focus of two mirrors with piezoelements obtained FWHM = 1.35 mm Anglular resolution: 7 arcsec (after correction) AXRO December Optics with piezoelements Test results Conclusion X-ray optical system based on Kirkpatrick-Baez modules in novel arrangement (KBF) and its combination with nested parabolic mirrors in the KBF center area were studied Proposed system has better light efficiency in comparison with relevant KB and Wolter X-ray optical systems Commercial Si wafers can be effectively used in KBF part, which was experimentally verified within X-ray testing at CASA (University of Colorado) Potential of active optics for resolution improvement was demonstrated Novel KBF system can be used for astrophysical applications as well as for laboratory applications (focusing and imaging in EUV, SXR and XR) Patent pending of KBF design and combination KBF+P (PV ) AXRO December Aknowledgements Ministry of Education, Youth and Sports of the Czech Republic, project ME09028 and ME09004 Team of Prof. Webster Cash, University of Colorado at Boulder ESA PECS Project No MEYS ESF Project CZ.1.07/2.3.00/ Drs. J. Sik and M. Lorenc from ON Semiconductor Czech Republic AXRO December THANK YOU FOR ATTENTION AXRO December Prague AXRO December