Abstract

The ROSAT wide field camera (WFC) is an XUV telescope operating in the 12–250-eV energy band. The mirror system utilizes Wolter-Schwarzschild type I (WS I) grazing incidence optics with a focal length of 525 mm, comprised of three nested aluminum shells with an outermost diameter of 576 mm providing a geometric aperture area of 456 cm2. The reflecting surfaces are electroless nickel plated and coated with gold to enhance their reflectivity in the XUV. The mirrors have undergone full aperture optical testing, narrow beam XUV testing, and full aperture XUV testing. Measurements of the reflectivity are compared to theoretical values derived from the optical constants of gold in the XUV range. Analysis of the focused distribution is used to estimate the surface roughness and figuring errors of the polished surfaces. The results are compared to the mechanical metrology data collected during manufacture of the shells and the power spectral density of the reflecting surfaces is found to have a power-law form.

© 1988 Optical Society of America

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References

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  1. R. C. Chase, L. P. VanSpeybroeck, “Wolter-Schwarzchild Telescopes for X-Ray Astronomy,” Appl. Opt. 12, 1042 (1973).
    [CrossRef] [PubMed]
  2. M. A. Barstow, R. Willingale, B. J. Kent, A. Wells, “Early Performance Data from the ROSAT XUV Wide Field Camera,” Opt. Acta 32, 197 (1985).
    [CrossRef]
  3. M. A. Barstow, G. W. Fraser, S. R. Milward, “Imaging Microchannel Plate Detectors for XUV Sky Survey Experiments,” paper presented at meeting on X-Ray Instrumentation in Astronomy, Cannes (2–4 Dec. 1985).
  4. R. Willingale, S. R. Milward, M. R. Sims, “XUV Reflectivity Measurements on the ROSAT WFC Mirrors,” paper presented at BESSY/SPIE meeting on Soft X-Ray Optics and Technology, Berlin (Dec. 1986).
  5. B. Aschenbach, H. Brauninger, K. H. Stephan, J. Trumper, “X-Ray Test Facilities at MPE Garching,” Proc. Soc. Photo-Opt. Instrum. Eng. 184, 234 (1979).
  6. B. L. Henke, P. Lee, J. Tanaka, R. L. Shimbukuro, B. K. Fujikawa, “Low-Energy X-Ray Interaction Coefficients: Photoabsorption, Scattering and Reflection. E = 100-2000 eV Z = 1–94,” At. Data Nucl. Data Tables 27, No 1 (1982).
    [CrossRef]
  7. H.-J. Hagemann, W. Gudat, C. Kunz, “Optical Constants from the Far Infrared to the X-Ray Region,” DESY Report SR-74/7 (May1974).
  8. R. O. Rice, “Reflection of Electromagnetic Waves from Slightly Rough Surfaces,” Commun. Pure Appl. Math. 351, 4 (1951).
  9. P. Beckmann, A. Spizzichino, The Scattering of Electromagnetic Waves from Rough Surfaces (Pergamon, New York, 1963).
  10. H. Kunieda et al., “Roughness Measurement of X-Ray Mirror Surfaces,” Jpn. J. Appl. Phys. 25, 1292 (1986).
    [CrossRef]

1986 (1)

H. Kunieda et al., “Roughness Measurement of X-Ray Mirror Surfaces,” Jpn. J. Appl. Phys. 25, 1292 (1986).
[CrossRef]

1985 (1)

M. A. Barstow, R. Willingale, B. J. Kent, A. Wells, “Early Performance Data from the ROSAT XUV Wide Field Camera,” Opt. Acta 32, 197 (1985).
[CrossRef]

1982 (1)

B. L. Henke, P. Lee, J. Tanaka, R. L. Shimbukuro, B. K. Fujikawa, “Low-Energy X-Ray Interaction Coefficients: Photoabsorption, Scattering and Reflection. E = 100-2000 eV Z = 1–94,” At. Data Nucl. Data Tables 27, No 1 (1982).
[CrossRef]

1979 (1)

B. Aschenbach, H. Brauninger, K. H. Stephan, J. Trumper, “X-Ray Test Facilities at MPE Garching,” Proc. Soc. Photo-Opt. Instrum. Eng. 184, 234 (1979).

1973 (1)

1951 (1)

R. O. Rice, “Reflection of Electromagnetic Waves from Slightly Rough Surfaces,” Commun. Pure Appl. Math. 351, 4 (1951).

Aschenbach, B.

B. Aschenbach, H. Brauninger, K. H. Stephan, J. Trumper, “X-Ray Test Facilities at MPE Garching,” Proc. Soc. Photo-Opt. Instrum. Eng. 184, 234 (1979).

Barstow, M. A.

M. A. Barstow, R. Willingale, B. J. Kent, A. Wells, “Early Performance Data from the ROSAT XUV Wide Field Camera,” Opt. Acta 32, 197 (1985).
[CrossRef]

M. A. Barstow, G. W. Fraser, S. R. Milward, “Imaging Microchannel Plate Detectors for XUV Sky Survey Experiments,” paper presented at meeting on X-Ray Instrumentation in Astronomy, Cannes (2–4 Dec. 1985).

Beckmann, P.

P. Beckmann, A. Spizzichino, The Scattering of Electromagnetic Waves from Rough Surfaces (Pergamon, New York, 1963).

Brauninger, H.

B. Aschenbach, H. Brauninger, K. H. Stephan, J. Trumper, “X-Ray Test Facilities at MPE Garching,” Proc. Soc. Photo-Opt. Instrum. Eng. 184, 234 (1979).

Chase, R. C.

Fraser, G. W.

M. A. Barstow, G. W. Fraser, S. R. Milward, “Imaging Microchannel Plate Detectors for XUV Sky Survey Experiments,” paper presented at meeting on X-Ray Instrumentation in Astronomy, Cannes (2–4 Dec. 1985).

Fujikawa, B. K.

B. L. Henke, P. Lee, J. Tanaka, R. L. Shimbukuro, B. K. Fujikawa, “Low-Energy X-Ray Interaction Coefficients: Photoabsorption, Scattering and Reflection. E = 100-2000 eV Z = 1–94,” At. Data Nucl. Data Tables 27, No 1 (1982).
[CrossRef]

Gudat, W.

H.-J. Hagemann, W. Gudat, C. Kunz, “Optical Constants from the Far Infrared to the X-Ray Region,” DESY Report SR-74/7 (May1974).

Hagemann, H.-J.

H.-J. Hagemann, W. Gudat, C. Kunz, “Optical Constants from the Far Infrared to the X-Ray Region,” DESY Report SR-74/7 (May1974).

Henke, B. L.

B. L. Henke, P. Lee, J. Tanaka, R. L. Shimbukuro, B. K. Fujikawa, “Low-Energy X-Ray Interaction Coefficients: Photoabsorption, Scattering and Reflection. E = 100-2000 eV Z = 1–94,” At. Data Nucl. Data Tables 27, No 1 (1982).
[CrossRef]

Kent, B. J.

M. A. Barstow, R. Willingale, B. J. Kent, A. Wells, “Early Performance Data from the ROSAT XUV Wide Field Camera,” Opt. Acta 32, 197 (1985).
[CrossRef]

Kunieda, H.

H. Kunieda et al., “Roughness Measurement of X-Ray Mirror Surfaces,” Jpn. J. Appl. Phys. 25, 1292 (1986).
[CrossRef]

Kunz, C.

H.-J. Hagemann, W. Gudat, C. Kunz, “Optical Constants from the Far Infrared to the X-Ray Region,” DESY Report SR-74/7 (May1974).

Lee, P.

B. L. Henke, P. Lee, J. Tanaka, R. L. Shimbukuro, B. K. Fujikawa, “Low-Energy X-Ray Interaction Coefficients: Photoabsorption, Scattering and Reflection. E = 100-2000 eV Z = 1–94,” At. Data Nucl. Data Tables 27, No 1 (1982).
[CrossRef]

Milward, S. R.

M. A. Barstow, G. W. Fraser, S. R. Milward, “Imaging Microchannel Plate Detectors for XUV Sky Survey Experiments,” paper presented at meeting on X-Ray Instrumentation in Astronomy, Cannes (2–4 Dec. 1985).

R. Willingale, S. R. Milward, M. R. Sims, “XUV Reflectivity Measurements on the ROSAT WFC Mirrors,” paper presented at BESSY/SPIE meeting on Soft X-Ray Optics and Technology, Berlin (Dec. 1986).

Rice, R. O.

R. O. Rice, “Reflection of Electromagnetic Waves from Slightly Rough Surfaces,” Commun. Pure Appl. Math. 351, 4 (1951).

Shimbukuro, R. L.

B. L. Henke, P. Lee, J. Tanaka, R. L. Shimbukuro, B. K. Fujikawa, “Low-Energy X-Ray Interaction Coefficients: Photoabsorption, Scattering and Reflection. E = 100-2000 eV Z = 1–94,” At. Data Nucl. Data Tables 27, No 1 (1982).
[CrossRef]

Sims, M. R.

R. Willingale, S. R. Milward, M. R. Sims, “XUV Reflectivity Measurements on the ROSAT WFC Mirrors,” paper presented at BESSY/SPIE meeting on Soft X-Ray Optics and Technology, Berlin (Dec. 1986).

Spizzichino, A.

P. Beckmann, A. Spizzichino, The Scattering of Electromagnetic Waves from Rough Surfaces (Pergamon, New York, 1963).

Stephan, K. H.

B. Aschenbach, H. Brauninger, K. H. Stephan, J. Trumper, “X-Ray Test Facilities at MPE Garching,” Proc. Soc. Photo-Opt. Instrum. Eng. 184, 234 (1979).

Tanaka, J.

B. L. Henke, P. Lee, J. Tanaka, R. L. Shimbukuro, B. K. Fujikawa, “Low-Energy X-Ray Interaction Coefficients: Photoabsorption, Scattering and Reflection. E = 100-2000 eV Z = 1–94,” At. Data Nucl. Data Tables 27, No 1 (1982).
[CrossRef]

Trumper, J.

B. Aschenbach, H. Brauninger, K. H. Stephan, J. Trumper, “X-Ray Test Facilities at MPE Garching,” Proc. Soc. Photo-Opt. Instrum. Eng. 184, 234 (1979).

VanSpeybroeck, L. P.

Wells, A.

M. A. Barstow, R. Willingale, B. J. Kent, A. Wells, “Early Performance Data from the ROSAT XUV Wide Field Camera,” Opt. Acta 32, 197 (1985).
[CrossRef]

Willingale, R.

M. A. Barstow, R. Willingale, B. J. Kent, A. Wells, “Early Performance Data from the ROSAT XUV Wide Field Camera,” Opt. Acta 32, 197 (1985).
[CrossRef]

R. Willingale, S. R. Milward, M. R. Sims, “XUV Reflectivity Measurements on the ROSAT WFC Mirrors,” paper presented at BESSY/SPIE meeting on Soft X-Ray Optics and Technology, Berlin (Dec. 1986).

Appl. Opt. (1)

At. Data Nucl. Data Tables (1)

B. L. Henke, P. Lee, J. Tanaka, R. L. Shimbukuro, B. K. Fujikawa, “Low-Energy X-Ray Interaction Coefficients: Photoabsorption, Scattering and Reflection. E = 100-2000 eV Z = 1–94,” At. Data Nucl. Data Tables 27, No 1 (1982).
[CrossRef]

Commun. Pure Appl. Math. (1)

R. O. Rice, “Reflection of Electromagnetic Waves from Slightly Rough Surfaces,” Commun. Pure Appl. Math. 351, 4 (1951).

Jpn. J. Appl. Phys. (1)

H. Kunieda et al., “Roughness Measurement of X-Ray Mirror Surfaces,” Jpn. J. Appl. Phys. 25, 1292 (1986).
[CrossRef]

Opt. Acta (1)

M. A. Barstow, R. Willingale, B. J. Kent, A. Wells, “Early Performance Data from the ROSAT XUV Wide Field Camera,” Opt. Acta 32, 197 (1985).
[CrossRef]

Proc. Soc. Photo-Opt. Instrum. Eng. (1)

B. Aschenbach, H. Brauninger, K. H. Stephan, J. Trumper, “X-Ray Test Facilities at MPE Garching,” Proc. Soc. Photo-Opt. Instrum. Eng. 184, 234 (1979).

Other (4)

P. Beckmann, A. Spizzichino, The Scattering of Electromagnetic Waves from Rough Surfaces (Pergamon, New York, 1963).

M. A. Barstow, G. W. Fraser, S. R. Milward, “Imaging Microchannel Plate Detectors for XUV Sky Survey Experiments,” paper presented at meeting on X-Ray Instrumentation in Astronomy, Cannes (2–4 Dec. 1985).

R. Willingale, S. R. Milward, M. R. Sims, “XUV Reflectivity Measurements on the ROSAT WFC Mirrors,” paper presented at BESSY/SPIE meeting on Soft X-Ray Optics and Technology, Berlin (Dec. 1986).

H.-J. Hagemann, W. Gudat, C. Kunz, “Optical Constants from the Far Infrared to the X-Ray Region,” DESY Report SR-74/7 (May1974).

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Figures (10)

Figure 1
Figure 1

Schematic diagram showing the main optical components of the WFC.

Figure 2
Figure 2

Axial profile measurement taken from the inner mirror shell showing the roll-up at the ends of the reflecting surfaces.

Figure 3
Figure 3

Measured efficiency of the WFC mirror nest compared with that predicted by theory as a function of energy.

Figure 4
Figure 4

WFC vignetting function and baffle rejection.

Figure 5
Figure 5

Composite image of eight deep exposures demonstrating the variation of the point response over the field of view.

Figure 6
Figure 6

Half-energy width as a function of off-axis radius measured at 40.8 eV. The lower limit was calculated by ray tracing and the predicted curve is the addition in quadrature of the lower limit and a constant level of 108 sec of arc.

Figure 7
Figure 7

Encircled energy function on-axis at 40.8, 77.5, and 277 eV.

Figure 8
Figure 8

Wings of the on-axis point response seen at 40.8 and 277 eV.

Figure 9
Figure 9

Power spectral density of the WFC mirror surfaces. The data points were derived from the observed XUV scattering wings. The low frequency curves were derived from profile data with (upper) and without (lower) the roll-up at the ends of the surfaces. The mid-frequency curve was calculated from Talystep measurements.

Figure 10
Figure 10

The rms roughness of the WFC mirrors plotted vs (g/λ). The solid curve is derived from the power-law fit to the metrology PSD while the dashed curve is the best fit to the scattering data points alone.

Equations (3)

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D ( a ) d a = 16 · π 2 · λ 3 · g 3 · W ( p ) d a ,
S 2 = C ( α 1 ) 1 · p 0 .
S = [ C / ( α 1 ) ] 0 . 5 a 0 0 . 5 ( 1 α ) ( g / λ ) 0 . 5 ( 1 α ) .

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