Abstract

In Wolter type I grazing incidence telescopes, ghost images result whenever unreflected x rays or singly reflected x rays pass through the telescope and impinge on the focal plane. These ghost images degrade image quality and can be eliminated by appropriately positioned stops and baffles. However, conflicting demands can be placed on an aperture design by requirements for field of view, vignetting, and ghost image control. These problems are particularly severe for high energy x-ray telescopes which require very small grazing angles of incidence. We have developed and used analytical and numerical tools to perform parametric analyses of ghost image behavior and to obtain an aperture plate design capability that can be utilized to satisfy specific ghost image requirements.

© 1988 Optical Society of America

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References

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  1. H. Wolter, “Spiegelsysteme streifenden Einfalls als abbildende Optiken fur Rontgenstrahlen,” Ann. Phys. 10, 94 (1952).
    [CrossRef]
  2. L. P. Van Speybroeck, R. C. Chase, “Design Parameters of Paraboloid-Hyperboloid Telescopes for X-Ray Astronomy,” Appl. Opt. 11, 440 (1972).
    [CrossRef]
  3. M. V. Zombeck, G. K. Austin, D. T. Torgerson, “High Resolution Mirror Assembly (HRMA) Optical Systems Study,” Smithsonian Astrophysical Observatory Technical Report SAO-AXAF-80-003, 3–27 (1980).
  4. L. P. Van Speybroeck, R. C. Chase, T. F. Zehnpfennig, “Orthogonal Mirror Telescopes for X-Ray Astronomy,” Appl. Opt. 10, 945 (1971).
    [CrossRef]
  5. A. Bunner, “CXGT X-Ray Telescope Design Study,” Perkin-Elmer Engineering Report ER-526, 107 (1982).
  6. P. Young, K. Chisholm, Perkin-Elmer Corp., private communication (1987).

1972 (1)

1971 (1)

1952 (1)

H. Wolter, “Spiegelsysteme streifenden Einfalls als abbildende Optiken fur Rontgenstrahlen,” Ann. Phys. 10, 94 (1952).
[CrossRef]

Austin, G. K.

M. V. Zombeck, G. K. Austin, D. T. Torgerson, “High Resolution Mirror Assembly (HRMA) Optical Systems Study,” Smithsonian Astrophysical Observatory Technical Report SAO-AXAF-80-003, 3–27 (1980).

Bunner, A.

A. Bunner, “CXGT X-Ray Telescope Design Study,” Perkin-Elmer Engineering Report ER-526, 107 (1982).

Chase, R. C.

Chisholm, K.

P. Young, K. Chisholm, Perkin-Elmer Corp., private communication (1987).

Torgerson, D. T.

M. V. Zombeck, G. K. Austin, D. T. Torgerson, “High Resolution Mirror Assembly (HRMA) Optical Systems Study,” Smithsonian Astrophysical Observatory Technical Report SAO-AXAF-80-003, 3–27 (1980).

Van Speybroeck, L. P.

Wolter, H.

H. Wolter, “Spiegelsysteme streifenden Einfalls als abbildende Optiken fur Rontgenstrahlen,” Ann. Phys. 10, 94 (1952).
[CrossRef]

Young, P.

P. Young, K. Chisholm, Perkin-Elmer Corp., private communication (1987).

Zehnpfennig, T. F.

Zombeck, M. V.

M. V. Zombeck, G. K. Austin, D. T. Torgerson, “High Resolution Mirror Assembly (HRMA) Optical Systems Study,” Smithsonian Astrophysical Observatory Technical Report SAO-AXAF-80-003, 3–27 (1980).

Ann. Phys. (1)

H. Wolter, “Spiegelsysteme streifenden Einfalls als abbildende Optiken fur Rontgenstrahlen,” Ann. Phys. 10, 94 (1952).
[CrossRef]

Appl. Opt. (2)

Other (3)

M. V. Zombeck, G. K. Austin, D. T. Torgerson, “High Resolution Mirror Assembly (HRMA) Optical Systems Study,” Smithsonian Astrophysical Observatory Technical Report SAO-AXAF-80-003, 3–27 (1980).

A. Bunner, “CXGT X-Ray Telescope Design Study,” Perkin-Elmer Engineering Report ER-526, 107 (1982).

P. Young, K. Chisholm, Perkin-Elmer Corp., private communication (1987).

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Figures (11)

Fig. 1
Fig. 1

Ghost images in Wolter I telescopes originate from rays which reach the focal plane unreflected or singly reflected and can seriously degrade image quality.

Fig. 2
Fig. 2

There are five functionally independent positions for the placement of aperture plates to control ghost images.

Fig. 3
Fig. 3

Coordinate system for the Wolter I telescope used in this paper.

Fig. 4
Fig. 4

Ghost image characteristics as aperture plates are sequentially added to a Wolter I telescope.

Fig. 5
Fig. 5

(a) Placement of the fore aperture plate; (b) ghost images for various positions of the fore aperture plate; (c) closest ghost ray vs axial distance of the fore aperture plate.

Fig. 6
Fig. 6

(a) Placement of the rear aperture plate; (b) ghost image for various positions of the rear aperture plate; (c) furthest ghost ray vs axial position of the rear aperture plate.

Fig. 7
Fig. 7

Location of the central and intermediate aperture plates.

Fig. 8
Fig. 8

(a) Typical ghost image consisting of singly reflected rays from a point source at a field angle of 40 min of arc; (b) decomposition of the ghost image into rays singly reflected from the paraboloid or hyperboloid only; (c) dramatic improvement of ghost image behavior with inclusion of intermediate aperture plates.

Fig. 9
Fig. 9

Ghost images produced by each of the concentric shells of the nested Wolter I telescope described in Table I for an out-of-field source at 40 min of arc. The ghost image problem is much more severe for the smaller grazing angles.

Fig. 10
Fig. 10

Position of the closest ghost ray vs fore aperture plate distance Lf for each of the five shells (numbered) of our Wolter I telescope design. The plots are for ghost rays singly reflected from the primary or secondary mirror with the central [(a),(b)] or an intermediate [(c),(d)] plate acting as the limiting aperture.

Fig. 11
Fig. 11

Position of the closest ghost ray vs source field angle for the fore aperture distance Lf shown in Fig. 10(b) which just satisfies the ghost image requirement.

Tables (1)

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Table I Wolter I Grazing Incidence Telescope Design

Equations (10)

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r fore 2 = r p 2 + [ ( z fore z p 2 ) * tan ( υ ) ] ,
r fore 1 = r p 1 [ ( z fore z p 1 ) * tan ( υ ) ] ,
r rear 2 = r h 1 [ ( z h 1 z rear ) * tan ( 4 α υ ) ] ,
r rear 1 = r h 2 [ ( z h 2 z rear ) * tan ( 4 α + υ ) ] ,
r cent 1 = ( m c * z cent ) + b c ,
m c = ( r p 2 r h 1 ) / ( z p 2 z h 1 ) , b c = r p 2 ( m c * z p 2 )
z f int = ( b f b c ) / ( m c m f ) ,
r f int = ( m c * z f int ) + b c ,
z r int = ( b r b c ) / ( m c m r ) ,
r r int = ( m c * z r int ) + b c .

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