Patent Number: 
Section: description

As seen in FIG. 3, one preferred embodiment of the present invention comprises a capillary polarimeter system generally indicated by reference number 300. Polarimeter 300 comprises filter 306, reflective surface 308, capillary array 310, and detector 312. A radiation source 302 produces radiation 304 that is directed toward filter 306. Filter 306 absorbs or blocks unwanted radiation, such as infrared, visible, and ultraviolet radiation. Filter 306 may be a plastic or metal film that is capable of absorbing the undesired radiation. After passing through filter 306, radiation 304 falls on reflective surface 308. Reflective surface 308 is preferably a multi-layer mirror for spectral region 50.0 nm greater than xcex greater than 2.5 nm or crystal for spectral region xcex less than 2.5 nm of a type that is well known in the art and is capable of reflecting radiation 304 in the EUV, SXR, and XR wavelengths. In the embodiment shown in FIG. 3, reflective surface 308 is concave having a parabolic, toroidal, or hemispherical cross-section. This shape allows reflective surface 308 to focus and concentrate radiation on a receiving end 316 of capillary array 310. The angle between the axis of the incident radiation and the axis of the reflected radiation is preferably less than 10xc2x0. Reflective surface 308 produces a negligible influence on the polarization of radiation 304 when the angle of reflection is close to normal. As seen in FIG. 3A, capillary array 310 comprises a plurality of hollow glass or quartz capillaries combined to form an array or bundle. It is well known in the art that hollow glass or quartz capillaries with open ends may be used to guide or direct short wavelength radiation. For example, the device disclosed in U.S. Pat. No. 5,192,869 utilizes capillaries to direct and focus beams of radiation. The individual capillaries in capillary array 310 may range from 4 micrometers to 1.5 millimeters. Capillary array 310 also comprises a proximal end or receiving end 316 and a distal end or emitting end 318. Proximal end 316 is positioned to receive radiation 304 reflected from reflective surface 308 and distal end 318 is positioned to emit radiation 304 on to detector 312. Capillary array 310 may be formed in a number shapes to guide or direct radiation in different paths to achieve different results. The embodiment illustrated in FIGS. 3 and 3A utilizes a curved shape that redirects the radiation by ninety degrees. The multiple reflections that occur during the transmission of radiation through these bent capillaries results in an amplification of the differences in the coefficients of transmission of p-type and s-type radiation. However, it is recognized that other embodiments may utilize linear capillary arrays. The individual capillaries in capillary array 310 may have a variety of cross-sections, such as square, circular, and triangular, and they may be coated with a variety of reflective substances. The accuracy of measurements of the degree of polarization depends on the ratio of intensities of meridional and sagittal rays exiting capillary array 310. The meridional rays are propagated in the same way inside capillaries of any cross sectional shape (circular, square, or triangular), if reflections take place along the longitudinal inner surface of capillary. For square or triangular cross sectional shaped capillaries, the attenuation of sagittal rays is much larger than it is for meridional rays. The situation is more complicated for circular capillaries as the sagittal rays always have a larger number of reflections and smaller reflection angles than do meridional rays. However, because of a dependence of the coefficient of reflection of radiation in the EUV spectral region upon the incidence angle, the difference in this coefficient is negligible for incidence angles between 85xc2x0-89xc2x0. The number of reflections of the rays inside the capillary is the primary factor if the capillary is long enough. For example, using the results reported in references, in a circular quartz capillary (inner diameter xcfx86=0.5 mm, radius of curvature r=100 mm, angle of curvature of the capillary from 45xc2x0 to 90xc2x0, xcex≈30.0-60.0 nm) the intensity of meridional rays are several times larger than the intensity of sagittal rays. Therefore, a capillary array with a circular cross section shape can also be used for polarization measurements in the EUV spectral region, but only if r/xcfx86 greater than 500-1000 (for xcfx86 greater than 50 xcexcm). Capillary array 310 may also comprise a tapered cross-section to focus and intensify the transmitted radiation. In this embodiment, the inner diameter of each capillary gradually narrows from proximal end 316 to distal end 318. As radiation is transmitted through a capillary, it is reflected many times and concentrated into a smaller area at distal end 318, thereby increasing the flux density of the radiation. Detector 312 is a detector that is well known in the art that is capable of detecting EUV, SXR, and XR radiation. It may be linked to a computer system (not shown) for recording measurements. In the embodiment shown in FIG. 3, detector 312 is mechanically linked to capillary array 310 so that the capillary array and detector may be rotated around axis 314. When system 300 is operating, capillary array 310 and detector 312 are rotated up to 90 degree around axis 314 to measure radiation 304 in different planes or vibration. The polarization of radiation 304 may then be determined by comparing the intensities of the radiation in different angular orientations. Axis 314 is substantially parallel to the incoming path of radiation 404. Most of the components of system 300 are housed in a vacuum chamber 320. Because of the large coefficients of attenuation of radiation with wavelength greater than 0.3 nm in air, all measurements in this spectral region must be conducted in a vacuum. Vacuum chamber 320 provides this vacuum. FIG. 4 discloses an alternative preferred embodiment of a capillary polarimeter system generally indicated by reference number 400. Polarimeter 400 comprises filter 406, reflective surface 408, capillary array 410, and detector 312. As in the previous embodiment, a radiation source 402 produces radiation 404 that is directed toward filter 406. Filter 406 absorbs or blocks unwanted radiation, such as infrared, visible, and ultraviolet radiation and it may be manufactured from plastic or metal film that is capable of absorbing the undesired radiation. After passing through filter 406, radiation 404 falls on reflective surface 408. In the embodiment shown in FIG. 4, reflective surface 408 is flat having a substantially planar surface that is mounted so that the angle of incidence of radiation 404 is approximately 45 degrees to the planar surface. Reflective surface 408 is adapted to rotate around an axis that is substantially parallel to the axis of radiation 404. As in the previous embodiment, reflective surface 408 may be either a multi-layer mirror or a crystal. Capillary array 410 is mounted such that radiation 404 reflected from reflective surface 408 falls on proximal or receiving end 416 and distal or emitting end 418 emits radiation on to detector 412. In this embodiment, capillary array 410 is not curved like capillary array 310 illustrated in FIG. 3. As seen in FIG. 4A, capillary array 410 has a generally conical shape. The inner diameter of the individual capillaries gradually decreases from proximal end 416 to the distal end 418 of capillary array 410. As in the previous embodiment, the decreasing inner diameter increases the flux density of the transmitted radiation. Most of the components of polarimeter 400 are housed in a vacuum chamber to provide a vacuum for decreasing attenuation due to atmospheric gases. In normal operation, reflective surface 408, capillary array 410, and detector 412 are rotated in unison from zero to 90 degrees when radiation 404 is being produced by source 402. This reflected beam of radiation is monochromized and it is directed to proximal end 416 of capillary array 410. Capillary array 410 intensifies radiation 404 and transmits it to detector 412. The measurement of the polarization of radiation 404 is made by comparing the intensity of the beam on the detector before and after the rotation of the reflective surface 408. The ratio of intensities of p and s polarizations being dependent upon the angular position of reflective surface 408. This device is applicable for measurements in the short wavelength spectral region xcex less than 2.5 nm (if a crystal is used for reflective surface 408) or in the spectral region 50.0 nm greater than xcex greater than 2.5 nm (if a multi-layer mirror is used for reflective surface 408). Although the description above contains many specifications, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of presently preferred embodiments of this invention. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents rather than by the examples given.