For years, Princeton Instruments has led the way in developing new imaging and spectroscopy solutions for combustion science research, a field of investigation that is vitally important to many daily activities, including transportation, energy production, heating, fire safety, manufacturing, and cooking. Between fuel consumption and pollutant emissions, combustion affects people and the environment.
Many researchers rely on laser-based diagnostic techniques as essential tools in understanding and improving the combustion process. Quantitative data obtained via planar laser-induced fluorescence (PLIF) techniques, for example, often facilitate the study of processes such as internal combustion engines and hypervelocity combustion. Advanced spectroscopy techniques like time-resolved spontaneous Raman scattering (SRS) spectroscopy are also employed, particularly within aeronautics, where future high-speed (supersonic) aircraft are poised to have a massive impact on environmental and human health, as well as quality of life.
Recently, by combining our high-speed, high-sensitivity emICCD technology with a noise-canceling architecture patented by NASA’s Glenn Research Center (U.S. Patent No. 8,310,671), an innovative diagnostic system was created that measures chemical components and temperature in combustors, primarily for aeronautics research. This cutting-edge Raman spectroscopy tool, known as the HSS-RSI, uses a PI-MAX4:512EMB emICCD camera in concert with polarization-sensitive collection optics and a custom spectrograph.
The groundbreaking union of opto-electronics technologies implemented in the HSS-RSI achieves a tenfold increase in signal-to-noise ratio and provides diagnostic capabilities far beyond those of other Raman spectroscopy techniques. It dramatically advances the field of quantitative chemical analysis, and will lead to the development of more efficient, more environmentally friendly, and safer aircraft and automobiles. The system also has benefits for medicine, biological/chemical science, and engineering.
or combustion science research involving advanced spectroscopy techniques such as time-resolved SRS spectroscopy, we recommend using the PI-MAX4:512EMB camera, which leverages the key advantages of electron-multiplying CCDs (EMCCDs) as well as intensified CCDs (ICCDs) by fiberoptically coupling an EMCCD to an image intensifier. This innovative emICCD technology lets the camera deliver an unrivaled combination of precision, sensitivity, intelligence, and speed.
In addition, the camera’s back-illuminated EMCCD boasts 95% QE at 532 nm, the wavelength typically used for SRS spectroscopy in combustion. Coupling the EMCCD to an image intensifier via fiberoptics delivers 6x higher light throughput between the image intensifier and the detector than lens-coupled configurations. Fiberoptic bonding also provides a much better signal-to-noise ratio than lens-coupled devices. The exceptional linearity and dynamic range of this emICCD camera, achieved by intelligently programming gains between the image intensifier and the EMCCD, are critical for quantitative combustion applications.
Our PI-MAX4:1024i, meanwhile, is recommended for use with techniques like PLIF. The camera’s DIF capability utilizes an interline CCD to capture two full-resolution images in rapid succession. It quickly transfers a full-resolution image under the CCD pixel’s adjacent mask area, enabling a second frame to be acquired in as little as 450 nsec (limit imposed by P46 phosphor decay time). The ability to apply the intensifier gate within two frames means lower background even when used with CW laser sources.
The PI-MAX4 family offers readout ranging from video rates to thousands of frames per second for capturing dynamics, while a sustained gating repetition rate of 1 MHz (2x better than most research-grade ICCD cameras available today) lets them keep up with the ever-increasing repetition rates of lasers. Their exclusive picosecond gating technology can achieve <500 psec gating, thus delivering exceptionally high temporal resolution for effective background discrimination. Best of all, this is achieved without sacrificing standard intensifiers’ QE. Furthermore, exclusive SuperSynchro and SuperHV technologies provide ultimate gating control in an easy-to-use configuration, and a GigE data interface allows remote operation of the cameras (more than 50 m from host computers). Complete control of combustion experiments is easy with the latest version of innovative LightField software.
Performing time-resolved SRS spectroscopy with the High-Speed High-SNR Raman Spectral Imager (HSS-RSI), a tool developed collaboratively by NASA’s Glenn Research Center, the Ohio Aerospace Institute (OAI), and Princeton Instruments.Top image: Close-up of a flame. Bottom image: Time-series Stokes Raman scattering spectra recorded at a sampling rate of 1 kHz over 1 sec in an oscillating, fuel-lean, hydrogen-air flame. Courtesy of Dr. Jun Kojima and David G. Fischer (OAI/NASA). Refer to “Ultra-High-Speed, Time-Resolved Spontaneous Raman Scattering Spectroscopy in Combustion” for additional details.
Three instantaneous sequential side-view OH-PLIF images at Mach 13 conditions. Conditions: pure oxygen; burner entry Mach number = 4.7; temperature = 1300 K; pressure = 0.05 atm; velocity = 3300 m/sec (Mach 13). Courtesy of Drs. Adela Ben-Yakar and Ronald K. Hanson (Stanford High Temperature Gasdynamics Laboratory). Refer to “Planar Laser-Induced Fluorescence Imaging of OH Radicals (OH-PLIF) in Hypervelocity Combustion with an Intensified CCD System” for additional details.
|Example of an experimental setup for combustion science using an ultrafast spectral imaging system:|
The High-Speed High-SNR Raman Spectral Imager (HSS-RSI), developed collaboratively by NASA’s Glenn Research Center, the Ohio Aerospace Institute (OAI), and Princeton Instruments, is shown within an experimental apparatus. The HSS-RSI includes a PI-MAX4:512EMB emICCD camera, a custom Raman spectrograph, and fiber-coupled polarization-sensitive collection lens optics. Courtesy of Dr. Jun Kojima and David G. Fischer (OAI/NASA). Refer to “Ultra-High-Speed, Time-Resolved Spontaneous Raman Scattering Spectroscopy in Combustion” for additional details.
Ultra-High-Speed, Time-Resolved Spontaneous Raman Scattering Spectroscopy in Combustion
The recent use of a new diagnostic apparatus to measure the dynamics of each individual molecular species, as opposed to simply acquire bulk information (e.g., pressure), points to the possibility of performing temperature and frequency analyses of species in combustion.
emICCD: The Ultimate in Scientific ICCD Technology
With the rapid expansion of research in areas such as nanotechnology, quantum computing, and combustion, the development of higher-performance time-gated cameras is becoming a necessity. This technical note describes the latest breakthrough in scientific intensified CCD (ICCD) technology: the world’s first emICCD.
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