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A FIXED EXIT BEAM X-RAY MONOCHROMATOR FOR THE XACT FACILITY Carlo Pelliciari ¹

A FIXED EXIT BEAM X-RAY MONOCHROMATOR FOR THE XACT FACILITY Carlo Pelliciari ¹. (1) Osservatorio Astronomico G.S Vaiana, Palermo. An example of monochromator XACT facility present configuration: vacuum system, X ray source, monochromator. The Bragg law

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A FIXED EXIT BEAM X-RAY MONOCHROMATOR FOR THE XACT FACILITY Carlo Pelliciari ¹

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  1. A FIXED EXIT BEAM X-RAY MONOCHROMATORFOR THE XACT FACILITYCarlo Pelliciari¹ (1) Osservatorio Astronomico G.S Vaiana, Palermo

  2. An example of monochromator • XACT facility present configuration: vacuum system, X ray source, monochromator. • The Bragg law • Perfect, mosaic and doped crystals, multilayers • Monochromators double “reflection” • The Project: configuration and technical characteristic • Monochromator elements: crystals (perfect, mosaic, organic), multilayers, gratings • Expected performances • Conclusions What I am going to show

  3. A monochromator is… …un attrezzo usa e getta (mono-uso) per cromare un’autovettura, una bici o quello che ti pare…ma una sola volta* *…A tool (use it once and throw it out) that permits one to plate a car or a bike with a chromium (it doesn’t matter) but only once…

  4. Filters calibration Test for X ray optics A monochromator system What is it? It is a light-dispersing instrument which is used to obtain electromagnetic radiation of substantially one wavelength or at least of a very narrow band of the spectrum. Detector characterization

  5. 100 63 55 40 50 35 25 30 25 30 20 20 50 100 100 100 100 100 100 200 200 200 200 200 100 18 m XACT Facility, vacuum beamline • 18 meter distance between x-ray source and test chamber. • The beam travels in vacuum (10-6 mbar) • The vacuum system consists of several tubes with diameter varying from 150 mm up to 630 mm in order to minimize the air volume and thus the pumping time. • Each section has a side port that permits to use it as a chamber test. • Main test chamber: 1 meter long x 1 meter diameter. It can be isolated from the pipe by sliding gate valve. • A clean room class 1000 is located at the end of the vacuum system. Test chamber X ray source

  6. XACT Facility, the X ray source The X ray source is a multi anode system mounting up to 6 anodes and 4 filters that can be selected without breaking the vacuum. It is low power consuming, so it does not require anode cooling system. Flux = 105 photons/s/cm2 @ 16 meters. The source produces 2 orthogonal beams. The second one is used to monitor the flux. The X ray source has a radius smaller then 0.1 mm. The laboratory has several anodes in order to cover the energy range 0.1- 20 keV: Cu(0.93; 8.04), Fe(6.4), Cr(5.41), Ti(4.51), Al(1.49), C (0.28) …

  7. XACT Facility, themonochromator Monochromatic X-ray beam (after interaction with the grating) Original X ray white beam (before interaction with the grating)

  8. Mirror testing apparatus Background 40 mm 1-st order 40 mm MCP (detector) x = 150 mm * tan (2) 5 5 150 mm Direct Beam 2 Reflected Beam Rotational stage Mirror sample  150 mm Slit 1 Linear stage 1 (direct beam) 75 mm Slit2 Linear stage 2 (reflected beam) Source direction

  9. The new monochromator system forthe XACT facility • Key features: • The system will provide a monochromatic beam for the full energy range: 0.1 up to 20 keV; • Energy resolution: E / E = 10% ; • Fixed position of the monochromatic beam for all energies ; • Compatible vacuum 10-7 mbar; • Beam section: 60 x 60 cm2 @ 20 meters.

  10. Bragg’s law (crystals, multilayers) • nl = 2d sinq • d = distance between atomic layers in crystal or bi-layer thickness in a multilayer • l = wavelength of the incident X-ray beam • n = diffraction order (integer); • q = grazing incidence angle; Bragg’s law defines the angle for constructive interference in the wave scattered by the crystal lattice. A multilayer consists of many alternating layers of high and low Z materials (ex. W/Si). The multilayer diffraction pattern is also described by Bragg’s law.

  11. Perfect, mosaic and doped crystals (1) Perfect crystals: high efficiency, high resolution, low integrated reflectivity Doped crystals: Low resolution, high integrated reflectivity. Mosaic crystals: Focusing properties, low transmission, low resolution, high integrated reflectivity.

  12. Silicon, 20 keV, perfect; FWHM= 3 eV Graphite, 10 keV, mosaic  = 3°, FWHM= 2 keV Silicon, 20 keV, mosaic,  = 60”, FWHM= 90 eV Graphite, 10 keV, HOPG,  = 0.3°, FWHM= 600 eV Perfect and mosaic crystals (2)

  13. h h Double reflection monochromators rotation center Channel cut: 2 or more elements etched in a monolithic structure. w = 2 h cos ; Configuration Laue-Bragg: 2 orthogonal elements in a monolithic structure. w = 2 h. rotation center

  14. = w l Fixed exit double diffraction monochromator The system consists of 2 monochromators. The incoming beam always hits crystal 2 in the same position. Crystal 2 translates orthogonally to its surface. Crystal 1 moves to intercept the beam. w = l sin(2) l = p / sin P = h / cos w = h sin(2)/(sin cos) = 2 h

  15. Choice of the configuration

  16. Monochromator Project (1) • Mechanical system: • # 1 rotating stage for the rotation of the entire system. Res: 0.001° • # 2 translationstages for the crystals position. Resolution 1m m. • # 4 rotating stages for crystals alignment. • # 1 translationstage to align and translate crystal 1. • # 2 holders with 6 faces. • # 1 translation stage for the collimator system . Res:1mm.

  17. Monochromator Project (2)

  18. Monochromator Project (3) The monochromator will be mounted in a vacuum chamber 1 meter from the X-ray source.

  19. Monochromator elements Energy range: from 10 up to 20 keV few fluorescence lines continuum Energy range: from 0.1 up to 10 keV fluorescence lines; We investigated several materials as candidate for monochromators with different geometry (flat, concave and convex with different curvature radius).

  20. Figure 6 Figure 4 Figure 5 Figure 3 Figure 7 Figure 8 Figure 2 Multilayers (100 – 600 eV) • [AlO3(2.5 nm)/V(1.9 nm)]x 100 on V [480-520 eV] • [AlO3(2.5 nm)/V(2.0 nm)]x 100 on V [480-520 eV] • [Cr(0.76 nm)/Sc(0.86 nm)]x 200 on Cr [350-450 eV] • [ Mo(3.5 nm)/Si(4.5 nm)]x 100 on Mo [80-160 eV] • [ Mo(5.5 nm)/Si(4.5 nm)]x 100 on Mo [80-160 eV] • [ Ni(2.5nm)/C(2.5nm)]x 200 on Ni [200-400 eV] • [ Ni(1.2 nm)/C(2.8 nm)]x 200 on Ni [150-600 eV] • [ W(3.0 nm)/Si(4.5 nm)]x 100 on W [100-120 eV] Figure 1

  21. KAP, TlAP and RbAP crystals are based on the chemical structure of o-phtalic acid (Acid Phthalates [C6H4(COOH)2]). Crystallographic structure: orthorhombic (a¹b¹c; a=b =g= 90°). • TlAP (001) : Thallium Acid Phthalates (CO2HC6H4CO2Tl); cell parameters (Å): a=6.63 , b=10.54 , c=12.95; 25.9 Å; • RbAP (001) : Rubidium Acid Phthalates (CO2HC6H4CO2Rb ); cell parameters (Å): a=6.55 , b=10.02 , c=13.069.61; 2d = 26.12 Å; • KAP (001) : Potassium Acid Phthalates (CO2HC6H4CO2K); cell parameters (Å): a=6.46 , b=9.61 , c=13.32; 2d = 26.64 Å; Organic crystals

  22. diamond hexagonal Graphite, has an hexagonal structure (a1=a2=2.4613 Å, c = 6.708 Å) . It grows with a very high mosaic degree (4°) After manipulation it is possible to have HOGP (high oriented pyrolytic graphite) with 0.4°. Low efficiency and resolution, high intensity. Silicon (a=5.43095 Å) and Germanium (a=5.64613 Å) have diamond crystallographic structure. It is possible to introduce a mosaic structure (2 arcmin mosaic = 0.03°) with several method (lapping, doping). High efficiency and resolution, low intensity. Graphite, Silicon and Germanium

  23.  = standard deviation of mosaic distribution; •  = 2.355 ; • B = Bragg angle; • r concave/convex = curvature radius 1st and 2nd crystal; • xl z dim: z crystal dimension (mm); • xls prj: crystal dimension projection (seen from source) • div (rad): angular spread Simulation results

  24. Beam features: Graphite

  25. Conclusions • Mechanical system: the components are ordered and they will arrive soon. We plan to mount the system next month and to have the first test in January 2005. • The system will be driven remotely. • Monochromator elements: we are able to cover the full energy range; we are still analysing other materials in order to optimise the monochromator system. • Contacts: • Service d'Astrophysique (SAp), CEA, Saclay, France • Laboratorio Astrofisica Alte Energie, Dip. Fisica, Ferrara, Italy(HOPG). • ESRF, Grenoble, France (Silicon). • Oss. Astronomico di Brera, Merate, Lecco, Italy, (multilayers). • IMEM CNR, Fontanini , Parma, Italy (Silicon, Yttrium tungstate…).

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