Spectrum Analyzing Equipment
Precision Analytical Instrument for High Spectral/Temporal Resolution Spectroscopy
Tech Area / Field
- INS-MEA/Measuring Instruments/Instrumentation
3 Approved without Funding
Russian Academy of Sciences / Physical Technical Institute, Russia, St Petersburg
- Scientific Research Institute for Optophysical Measurements, Russia, Moscow\nVNIIEF, Russia, N. Novgorod reg., Sarov
- University of Florida / Department of Electrical and Computer Engineering, USA, FL, Gainesville\nTechnical University of Helsinki, Finland, Helsinki\nChubu University, Japan, Aichi
Project summaryThe main purpose of the project is the creation of the precision analytical instruments for time-resolved spectrum analysis with fine spectral resolution and the ability to discriminate low intensity spectra against a background of powerful monochromatic stray light.
Such an arrangement is especially acquired to deal with,
- application of resonant Raman scattering of light for plasma diagnostics,
- application of Thomson scattering to specify and monitor the operations of various plasma devices,
- emissive spectroscopy to be in use for measuring of isotope and impurity traces.
The essence of the Raman scattering of light is that scattered radiation is observed at the wavelengths corresponding to transitions from a virtual into shifted levels. In spite of application shortcomings followed from very small scattering cross section, the Raman scattering of laser radiation has proven to be an effective tool for studying the structure of molecules and their interaction with a medium also as for studying the microscopic environments and dynamic structures of surface and interfaces. Grating polychromator coupled to a streak camera achieved a highest temporal resolution is a technique capable of time resolved capturing a Raman scattering spectra. The corresponding products of Hamamatsu Corporation are available to deal with physics and chemistry of organic liquids and solids. As for example C4780 system can be pointed to use for picosecond fluorescents lifetime measurements. The plasma processing technology has highlighted the fundamental need to expand the range of objects accessible with an emphasis laid on plasma and rare gases. But for the objects investigation the higher spectral resolution are required. This is achievable due to, first and foremost, the possibility of selecting a lasing wavelength near an optical resonance, as a result of which the Raman scattering cross section is many orders of magnitude larger. The decrease in the spectral offset is sensible only under a proper coupling with the spectrometers employed. The newly developed spectrometers of high resolution and gathering power are beneficial to collect the radiation with smaller spectral offset, thus, substantially reducing the energy requirements for plasma and gas probing.
Thomson scattering is suggesting an exclusive ability to local, non-intrusive measurements of electron parameters. The preferential pathway to laser-aided diagnostic technique is a time-of-flight LIDAR principle of Thomson scattering spectrum recording. Photomultipliers based on MCP used now have rather restricted temporal resolution (no better than 300psec). In order to improve a spatial resolution the possibly high temporal resolution is required, which can be provided by a high speed streak camera design. The grating spectrometer capable of substantial discriminating of stray laser light coupled to an array of compact size high speed steak cameras, as an alternative to commonly used photomultipliers of lower temporal resolution, shows a promise as a technique for high resolution LIDAR diagnostics.
Emissive spectroscopy is known to be one of the most sensitive methods used for measuring of impurity traces. The lower detection limit of the method is mainly determined by the widths of spectral lines in plasma to be 0.02-0.04A, which is close to a limiting value resolved by the modern spectral devices. The improvement of the detection limit is in line with the development of high resolution analytical instruments capable of gainful multichannel detecting of spectra with use of image intensifier. Ultra-high sensitivity and simultaneous multiple-wavelength measurement capabilities are realized by the combination of photon counting and streak camera techniques.
Research into the creation of the spectral analyzing facility will be completed by devising a series of multipurpose instruments:
- High resolution Automated Scanning Spectrometer.
- Double grating polychromator with high rejection of the monochromatic background emission.
- Multipurpose streak camera for spatial/temporal analysis of optical events.
- Chronographic spectral instrumentation.
High resolution Automated Scanning Spectrometer is the next step of new generation high throughput spectrometer designs suggested by the authors in 90’s. The design based on the principles reported for the first time in Rev.Sci.Instrum 1999  is suggesting the ultimate precision of measurements with the resolving power λ/δλ~2 105. The spectrometer is build as a double grating scanning monochromator utilizing the grazing incidence of light on gratings. The entire spectrum is scanned within a broad wavelength range in such a way that the angular dispersion remains invariant to a wavelength setting.
Double grating polychromator with high rejection of the monochromatic background emission is devised on the principles reported for the first time in Rev.Sci.Instrum 2004 . The stray light interference may be avoided with the special double polychromator mount utilizing the subtractive non-equal dispersions. This new design significantly reduces the stray light while still maintaining a high transmission.
Multipurpose streak camera for spatial/temporal analysis of optical events.
Quality of the designed streak camera responds to the demands of simplicity and universality. It does not mean a theoretical top quality, but appropriate quality for the multiple functions to be performed operating in both a single frame and a streak mode in nano-, micro-, and millisecond time ranges. The developed streak camera compares favorably the products of the leading companies with respect to more compact size and cheaper costing.
The project products represent the equipment of choice for spectroscopy (whether your samples are plasma, gases or something else) distinguished by high resolution, high rejection and high transmission capability.
This project is a milestone in long term collaboration between the plasma physics laboratory of Ioffe Institute and the electro-optical registration of fast events laboratory of VNIIOFI in devising the spectrometers and streak cameras equipment for plasma diagnostics.
The project promotes the integration of weapon scientists and engineers into the project activities. The provision is made for commercializing the project products within the framework specified in ISTC agreement. The total number of weapon-scientists and engineers involved in the project is 20.
Total duration of the project - 3 years.
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