Record high extreme-ultraviolet efficiency at near-normal incidence from a multilayer-coated polymer-overcoated blazed ion-etched holographic grating.

We have measured the extreme-ultraviolet (EUV) efficiency of a polymer-overcoated blazed ion-etched holographic test grating. The grating had a magnetron-sputtered Mo2C/Si multilayer coating matched to the grating blaze angle of 2.78 degrees. At an angle of incidence of 5.6 degrees and a wavelength of 15.79 nm, the measured efficiency peaks in the second outside order at 29.9%. The derived groove efficiency is 53.0%. To the best of our knowledge these are the highest values obtained yet at EUV wavelengths from a holographic ion-etched blazed grating.

Investigation of the properties of an ion-etched plane laminar holographic grating.

We have measured the efficiency over the range 125-225 A of a bare ion-etched plane laminar holographic grating made of fused silica and with 1000 grooves/mm. The measured efficiency of each order oscillates with wavelength because of constructive and destructive interference between radiation diffracted from the lands and the grooves. We measured the grating groove profile with an atomic force microscope, and the resulting groove depth of 434 ? 6 A agrees well with the values determined independently from the oscillatory behavior of the efficiency measurements. Grating efficiency in the +1 order peaked at values of 0.027%, 0.011%, and 0.005% at wavelengths of 191, 157, and 132 A, respectively; and the derived groove efficiencies are 27%, 25%, and 27%. The irregular shape at the land-groove edges dominates the large grating roughness of 23-45-A rms, but even regions far from the edges have a roughness of 10-18-A rms. The average groove profile was used to model the grating efficiency, and the resulting wavelengths predicted for different order maxima and minima agree well with measured wavelengths, although the calculated efficiencies are greater than the measured results by 10-20%.

Escherichia coli thymidylate synthase expression protects human cells from the cytotoxic effects of 5-fluorodeoxyuridine more effectively than human thymidylate synthase overexpression.

In this study, we compared the relative abilities of human thymidylate synthase (hTS) and Escherichia coli thymidylate synthase (eTS) expression to confer resistance to the cytotoxic effects of treatment with the TS inhibitor 5-fluorodeoxyuridine (FdUrd). G418-selected clones expressing either form of the protein were significantly more resistant than the lacZ-expressing clone, VALZ2, to FdUrd-induced cytotoxicity. Although eTS-expressing clones expressed 2- to 3-fold more TS protein than hTS-overexpressing clones, the representative eTS-expressing clone, VAEG8, and hTS-overexpressing clone, VAHGC, were equally sensitive to an FdUrd-induced loss of clonogenicity; in addition, a large fraction of either form of exogenously expressed TS appeared to be inactive in the intact cell. The clones differed, however, in their responses to leucovorin (LV). Although LV significantly enhanced FdUrd-induced TS inhibition, growth inhibition, and cytotoxicity in VAHGC cells, it had no effect on these parameters in VAEG8 cells. These results suggest that eTS may more efficiently confer resistance to FdUrd plus LV when expressed for the purposes of a "host protection" strategy in vivo.

Efficiency calibration of the first multilayer-coated holographic ion-etched flight grating for a sounding rocket high-resolution spectrometer.

We have fabricated the four flight gratings for a sounding rocket high-resolution spectrometer using a holographic ion-etching technique. The gratings are spherical (4000-mm radius of curvature), large (160 mm x 90 mm), and have a laminar groove profile of high density (3600 grooves/mm). They have been coated with a high-reflectance multilayer of Mo/Si. Using an atomic force microscope, we examined the surface characteristics of the first grating before and after multilayer coating. The average roughness is approximately 3 A rms after coating. Using synchrotron radiation, we completed an efficiency calibration map over the wavelength range 225-245 A. At an angle of incidence of 5 degrees and a wavelength of 234 A, the average efficiency in the first inside order is 10.4 +/- 0.5%, and the derived groove efficiency is 34.8 +/- 1.6%. These values exceed all previously published results for a high-density grating.

Efficiency of a multilayer-coated, ion-etched laminar holographic grating in the 14.5 16.0-nm wavelength region.

The efficiency of an ion-etched laminar holographic grating was measured at near-normal incidence in the 14.5-16.0-nm wavelength range. The grating had an electron-beam-evaporated Mo/Si multilayer coating matched to the grating groove depth. The efficiency peaked at 16.3% in the first inside order at 15.12 nm and 15.0% in the first outside order at 14.94 nm. These are believed to be the highest efficiencies obtained to date from a multilayer-coated laminar grating at near-normal incidence in the EUV (lambda<30.0nm) . Zero and even orders were almost completely suppressed. The grating groove efficiency in the first order approached the theoretical limit of 40.5%.

Grazing-incidence efficiencies in the 28-42-A wavelength region of replicas of the Skylab 3600-line/mm concave grating with multilayer and gold coatings.

The efficiencies of replicas of the Skylab 3600-line/mm concave grating with multilayer and gold coatings were measured by using synchrotron radiation at an angle of incidence of 79 degrees and in the 28-42-A wavelength range. The blaze angle of the grating facets that faced the incident radiation was 3.1 degrees , and the average angle of the opposite facets was 6 degrees . For the gold grating, the -1 outside order had the highest efficiency of any diffracted order (excluding the zero order) over the entire wavelength range. Calculations of the grating efficiency indicated that the high efficiency in the -1 order resulted from the rather small angle (6 degrees ) of the facets opposite the incident radiation. For the multilayer grating, the efficiency in the on-blaze +2 inside order was enhanced in the 30-34-A wavelength region as a result of the high reflectance of the multilayer coating. The maximum efficiency in the +2 order occurred at the wavelength (32 A) corresponding to the peak of the reflectance of the multilayer coating on the facets facing the incident radiation. These results further demonstrate that a multilayer coating can be used to enhance the efficiency, in a selected wavelength range and in the on-blaze order, of a grating operating at a small grazing angle (11 degrees ).

Multilayer-coated laminar grating with 16% normal-incidence efficiency in the 150-A wavelength region.

We characterized a laminar grating with a Mo/Si multilayer coating by using synchrotron radiation and atomic force microscopy. The grating substrate had 2400 grooves/mm, 40-A groove depth, and 2080-A groove width. The microroughness of the grating substrate was 5 A rms. The multilayer coating was optimized to have peak normal-incidence reflectance at a wavelength near 150 A. For an angle of incidence of 10 degrees the peak grating efficiency was 16.3% in the +1 order and 15.0% in the -1 order. The efficiency in the zero order was lower by a factor of 40 owing to the excellent matching of the groove depth and groove width to the wavelength of the incident radiation. By dividing the grating efficiencies by the measured reflectance of the multilayer coating, we obtained inferred groove efficiencies of 34% and 32% in the +1 and -1 orders, respectively.

Comparison of the calculated and the measured efficiencies of a normal-incidence grating in the 125-225- A wavelength range.

The efficiency of a diffraction grating was measured near normal incidence in the 125-225-A wavelength range with synchrotron radiation. The grating pattern had 2400 grooves/mm and was recorded on a concave fused-silica blank by a holographic technique. The grooves were shaped by ion-beam etching to provide a facet with a blaze angle of 2.5 degrees as determined by atomic force microscopy. Because of the characteristics of the etching process the groove profile was approximately triangular, with the other facet inclined at an angle of 5.5 degrees to the surface. The measured efficiency was compared with the efficiency calculated by a computer program, small enough to run on a personal computer, that solved the periodic boundary-value problem corresponding to electromagnetic radiation incident on a diffraction grating with finite conductivity. The calculation was based on the nominal groove profile that was determined by atomic force microscopy. The measured and the calculated efficiencies were in good agreement. This investigation indicates that the diffraction efficiency of a normal-incidence grating can be calculated in the soft-x-ray region with a personal computer.

Reflectance of a wideband multilayer x-ray mirror at normal and grazing incidences.

The reflectance of a W-B(4)C multilayer mirror, with a period thickness that increased with depth into the multilayer, was measured at near-normal incidence with synchrotron radiation and at grazing incidence with Cu Kα radiation. The period thickness increased linearly from 17.9 Å at the top of the multilayer structure to 21.9 Å at the substrate while the same ratio of nodal layer to period thickness was maintained. For a grazing angle of 80° (10° from normal incidence), the peak reflectance was 1.1% at a wavelength of 36 Å, and the reflectance profile was 1 Å wide. For Cu Kα radiation the reflectance peaked at a grazing angle of 2.4° and was 0.4° wide. Compared with a W-B(4)C multilayer mirror with a constant period thickness, the depth-graded multilayer mirror has wider reflectance profiles at near-normal and grazing incidences, resulting in larger integrated reflectances and wider fields of view.

Normal-incidence efficiencies in the 115-340-Å wavelength region of replicas of the Skylab 3600-line/mm grating with multilayer and gold coatings.

Multilayer and gold coatings were applied to replicas of the 3600-line/mm ruled grating that was developed for the Naval Research Laboratory S082A spectroheliograph that was flown on the Skylab spacecraft. The Mo-Si multilayer coating had a peak normal-incidence reflectance of 50% at a wavelength of 136 Å. The normal-incidence efficiency of the multilayer-coated grating was measured by the use of synchrotron radiation and was compared with the efficiency of the gold-coated replica grating in the 115-340-Å wavelength region. The peak efficiency of the multilayer grating was 1.3% in the 133-137-Å region and was a factor of 65 higher than the efficiency of the gold grating. The multilayer and gold coated gratings, as well as an uncoated replica grating substrate, were characterized by the use of a scanning probe microscope. The rms microroughness of the uncoated and multilayer-coated gratings was 10 Å, and the microroughness of the gold grating was 16 Å.

Efficiency and long-term stability of a multilayer-coated, ion-etched blazed holographic grating in the 125-133-Å wavelength region.

The efficiency of an ion-etched blazed holographic grating was measured by the use of synchrotron radiation in the 125-133-Å wavelength range and at near-normal incidence. The grating had a Mo-Si multilayer interference coating that resulted in a peak normal-incidence efficiency of 13% in the second grating order and at a wavelength of 128 Å. This is the highest efficiency obtained to date from a multilayer-coated grating in this wavelength region and at normal incidence. These measurements are compared with similar measurements performed on the same grating 4.5 years later. Over this time the peak grating efficiency decreased from 13% to 8%, and this result is attributed to the decrease in the reflectance of the multilayer coating from 55% to 42%. Oxidation and contamination of the multilayer with carbon appear to be the causes of these losses. The groove efficiency of the grating substrate in the second order is 23%.

Polarization and efficiency of a concave multilayer grating in the 135-250-Å region and in normal-incidence and SeyaNamioka mounts.

A molybdenum/silicon multilayer coating was applied to a holographic ion-etched blazed grating substrate that had 2400 grooves/mm and a radius of curvature of 2.2 m. Scanning probe microscopy yielded the same surface microroughness (5 Å rms) before and after deposition of the multilayer. The efficiency and polarization performance of the grating was measured by synchrotron radiation in the 135-250-Å wavelength region. In the second grating order and the second Bragg order of the multilayer coating, the peak normal-incidence efficiency was 7.5% at a wavelength of 147 Å, representing a groove efficiency of 27%. At an angle of incidence of 35°, the polarization performance of the grating was 95%-100% in the 210-250-Å wavelength region. In a Seya-Namioka spectrometer mount at an angle of incidence of 30°-40°, the grating is a nearly perfect polarizing optical element in the wavelength bands between 125 and 300 Å, which are covered by the multilayer coating.

Transmittance of a thin Saran film in the 45-584-Å wavelength region.

The transmittance of a free-standing Saran film, 4260 Å thick, has been measured by means of synchrotron radiation in the 45-584-Å wavelength region. The transmittance was calculated by means of the elemental composition of the film material as determined by x-ray photoelectron spectroscopy and the optical constants as derived from atomic-scattering factors. The calculated transmittance agreed with the measured transmittance in the 45-150-Å wavelength region. The calculated transmittance was significantly lower than that measured for the wavelength range 150-340 Å. This difference implies that molecular effects that are not accounted for by atomic-scattering factors become increasingly important at the longer wavelengths.

Dual-waveband operation of a multilayer-coated diffraction grating in the soft x-ray range at near-normal incidence.

A concave diffraction grating (2400 grooves/mm) coated with a Si/Mo multilayer has an efficiency of 2.5% at 290 A and a resolving power of 14,000 in third order of 156 A.

Normal-incidence reflectance of W/B(4) C multilayer mirrors in the 34-50-A wavelength region.

The measured normal-incidence reflectances of W/B(4)C multilayers mirrors are 2% in the 34-50-A wavelength region and are consistent with interfacial roughness in the range of 3-4 A.

Long-term stability of a Mo/Si multilayer structure.

The normal-incidence reflectance of a Mo/Si multilayer mirror, with peak reflectance near 130 A, was measured over a period of 20 months by using synchrotron radiation. The measured reflectances were unchanged over this period of time, and this indicates that the material layers and interfaces were stable.

On-blaze operation of a Mo/Si multilayer-coated, concave diffraction grating in the 136-142-A wavelength region and near normal incidence.

The efficiency and resolving power of a concave, 2400-groove/mm, blazed diffraction grating that had a Mo/Si multilayer coating were determined. The multilayer coating had a peak reflectance of 55% at 140-A near normal incidence. The efficiency of the multilayer grating for wavelengths in the 136-139-A range was 2% near normal incidence. This efficiency was a factor of 150 greater than the efficiency of a sister replica Au-coated grating in the same wavelength region. The resolving power of the multilayercoated grating in the third order of a V viii transition with a first-order wavelength of 140.451 A was 9100. Comparisons with the Au-coated grating indicated that the application of the multilayer coating did not affect the resolving power or the blaze angle.

Optical constants of thin silicon films near the silicon L(2,3) absorption edge.

Using synchrotron radiation, we determined the optical constants of thin silicon films in the wavelength region near the silicon L(2,3) absorption edge. The extinction coefficient was determined from the transmittance of a thin, unbacked silicon film. The refractive index was determined from the reflectance of a sample consisting of an evaporated silicon film on gold. The thickness of the evaporated silicon film was chosen so that an interference feature appeared in the wavelength region above the edge where the silicon is transmissive. The shape of the interference feature is sensitive to the optical constants of silicon near the edge.

Efficiency measurements of reflection gratings in the 100-300-A band.

We have measured zero- and first-order efficiencies of plane diffraction grazings over the 100-300-A band using the NRL beamline facility at the National Synchrotron Light Source. Measurements were taken at grating angles of 5 degrees , 10 degrees , and 15 degrees and the incident radiation was polarized primarily in the transverse magnetic mode. Four (three laminar, one blazed) of the gratings were ion etched in high quality quartz blanks, overcoated with 200 A of gold. A fifth (blazed) grating was ruled in gold. The line densities are 1000, 2000, and 3600 grooves/mm for those with laminar profiles. Both blazed gratings have a blaze angle of 8 degrees and line densities of 3600 grooves/mm. Measured first-order efficiencies up to 15% were obtained for the laminar gratings and up to 8% was obtained for the ion-etched blazed grating. Much lower efficiencies (