Quantitative research on higher order harmonics in metrology beamline

Abstract

The synchrotron radiation spectra of the spherical grating monochromator (SGM) working in the soft X-ray and VUV region are often contaminated by significant amounts of higher order harmonics. They cannot be suppressed completely by suitable filters. Higher order contributions in the spectral radiation standard and metrology beamline were researched using transmission grating (made in-house) and IRD AXUV100G (USA) photodiode detector. The exit beam was dispersed with the transmission grating behind the exit slit of the monochromator, and the contributions of the different orders were analyzed. The higher order distributions were quantitatively determined for three gratings with line densities of 1800, 600 and 200 l/mm. Experiment results show that in wavelengths between 5 nm and 15 nm the contributions of the higher orders to the detector signal are restricted to less than 7% even without the use of filters. In wavelength regions between 5 nm and 34 nm, the contributions of the higher orders to the detector signal are less than 14% with proper Al, Si₃N₄ and Zr filters, and after being modified by quantum efficiency of the detector, the higher order contributions are restricted to less than 6.5%. The study also shows that higher orders are almost totally suppressed by MgF₂ filter when the wavelength ranges between 115–140 nm.

References

1. Hunter W R Long J P Thin-film interference mirrorto suppress grating harmonics in vacuum-ultraviolet radiationApplied Optics 1994 33(7)12641269
2. Kühne M Müller P Higher order contributionsin the synchrotron radiation spectrum of a toroidal grating monochromatordetermined by the use of a transmission gratingReview of Scientific Instruments 1989 60(7)21022104
3. Erko A Langhoff N Bjeoumikhov A A et al.High-order harmonic suppression by a glass capillaryarrayNuclear Instruments and Methods inPhysics Research A 2001 467–468832835
4. Matsushita T Hashizume H X-ray monochromators. Handbookon Synchrotron RadiationAmsterdamNorth-Holland 1983
5. Suits A G Heimann P Yang X M et al.A differential pumped harmonic filter on the chemicaldynamics beamline at the advanced light sourceReview of Scientific Instruments 1995 66(10)48414844
6. Gullikson E M Mrowka S Kaufmann B B Recent developments in EUV reflectometry at the advancedlight sourceSPIE 2001 4343363373
7. Kjornrattanawanich B Korde R Boyer C N et al.Temperature dependence of the EUV responsivity ofsilicon photodiode detectorsIEEE Transactionson Electron Devices 2006 53218223
8. Korde R Prince C Cunningham D et al.Present status of radiometric quality silicon photodiadesMetrologia 2003 40(1)S145S149
9. Gullikson E M Korde R Canfield L R et al.Stable silicon photodiodes for absolute intensitymeasurements in the VUV and soft x-ray regionsJournal of Electron Spectroscopy and Related Phenomena 1996 80313316
10. Canfield L R Vest R E Korde R et al.Absolute silicon Photodiodes for 169 nm to 254 nmphotonsMetrologia 1998 35(4)329334
11. Xue S Shao J H Lu Q P et al.Reflectivity measuring device in the national synchrotronradiation laboratoryOptics and PrecisionEngineering 2004 12(5)480484 (in Chinese)
12. Cao J H Ni Q L Chen B Calibration of soft X-ray detectorOptics and Precision Engineering 2004 12(1)118121 (in Chinese)
13. Zhou H J Wang Q P Zheng J J et al.Design and measurement of a portable ionizationchamberOptics and Precision Engineering 2006 14(3)351355 (in Chinese)
14. Feigl T Yulin S Benoit N et al.Multilayer optics for the EUV and soft X-raysOptics and Precision Engineering 2005 13(4)421429
15. Wang Z S Wang F L Zhang Z et al.Research of multilayers in EUV, soft X-ray and X-rayOptics and Precision Engineering 2005 13(4)512518