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Multilayer Overview

Multilayer Overview. Current application Optimization of Multilayers Model Designs for GRI. Grazing Incidence Optics: Past/Present/Future. Chandra and XMM Monolitic and replicated Wolter-1 optics Single layer coated; Ir, Au. Hero, High-energy replicated optics

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Multilayer Overview

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  1. Multilayer Overview • Current application • Optimization of Multilayers • Model Designs for GRI

  2. Grazing Incidence Optics: Past/Present/Future Chandra and XMM Monolitic and replicated Wolter-1 optics Single layer coated; Ir, Au Hero, High-energy replicated optics InFocus, International Focusing Optics Collaboration, Pt/C HEFT, High Energy Focusing Optics, W/Si NuSTAR, XEUS, Constallation-X

  3. High Energy Focusing Telescope (HEFT) 6 m focal length Depth-graded W/Si Multilayers Energy range 20 – 70 keV Effective Area: ~70 cm2 @ 40 keV Over-constrained optics: 1.2’ HPD Field of view: 17’ @ 20 keV Collaboration: California institute of technology, Lawrence Livermore National Lab., Columbia University, Danish National Space Center

  4. The HEFT Optics Parameters: Number: 3 Type : Conical Approximation optic Size : 24 cm x 40 cm Material : W/Si, multilayers Energy range : 5 – 69 keV

  5. Thermally slumped AF 45 borosilicate glass Mirror thickness, 0.3 mm Mirror length = 10 cm Mirror radii: 4 cm < R < 12 cm Multilayers: HEFT Production

  6. Power law: Multilayers: Design

  7. Multilayers: Optimization, The Figure Of Merit • A(E) effective area • A(E) = 2praL * [R(E,a)]2 • [R(E,a)]2 reflectivity matrix, calculated with Nevot-Croce formalism • Winc(a,) angular weigthing function – Very CPU intensive • WE energy weigthing function = E(keV)/100 + 0.7 P. H. Mao et al, Applied Optics 38,p.4766-4775, 1999a

  8. Power law: Multilayers: Optimization • Constants a and b are uniquely determined by Dmin and Dmax • For a given max and min graze angle for a group Dmin and Dmax are determined by the Bragg equation • Multilayer recipes are optimized over: number of bilayers N high Z fraction G power law index c

  9. Model Designs for GRI • Double reflection Radius = 0.1 – 1.0 m • Optimized E range = 20 – 500 keV • Modified Radius = 0.17 – 0.56 m • Double reflection Optimized E range = 40 – 500 keV • Single reflection Radius = 0.09 – 0.44 m • Optimized E range = 80 – 200 keV • Common Parameters: • Substrate thickness = 0.2 mm Mirror length = 0.6 m • Focal length = 150 m Material Combination = W/Si • Substrate = Si Radial Obs. Factor = 20%

  10. Design 1a: Double reflection R = 0.1 – 1.0 m a = 0.57’ – 5.73’

  11. Design 1a Total mass = 2057 kg Number of shells = 1144

  12. Design 1b: modified double reflection R = 0.17 – 0.56 m a = 1.02’ – 3.22’ Design 1a Design 1b Total mass = 824 kg Number of shells = 582

  13. Design 2: Single Reflection R = 0.09 – 0.45 m a = 1.03’ – 5.125’

  14. Design 2 Optionally: Same design can be used at F = 75 m, as a real focusing System, but with a slight loss in effective area. Total mass = 190 kg Number of shells = 433

  15. Conclusions • Mass versus Effective area • Real focusing system or single reflection • Material combinations • W/Si chosen as a baseline • Pt/C, Pt/SiC, WC/SiC, ( Cu/SiC) • Substrate technology • For arcsec performance new developments in substrates are needed • Inherited technology from XEUS, Constallation-X

  16. Grp 1 2 S Emin Emax dmin dmax N c Gamma Thick FOM 1 Si W Si 50 200 53.9 495.9 50 0.160 0.287 0.360 9.96 2 Si W Si 50 200 46.9 431.7 63 0.179 0.314 0.393 13.47 3 Si W Si 50 200 40.9 375.8 97 0.190 0.333 0.517 17.90 4 Si W Si 50 200 35.6 327.1 151 0.195 0.344 0.691 22.22 5 Si W Si 50 200 30.9 284.8 187 0.213 0.371 0.755 26.72 6 Si W Si 50 200 26.9 247.9 332 0.207 0.376 1.145 30.22 7 Si W Si 50 200 23.4 215.8 647 0.205 0.370 1.925 33.03 8 Si W Si 50 200 20.4 187.9 1010 0.202 0.372 2.601 32.74

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