Bench testing of a heterodyne CO2 laser dispersion interferometer for high temporal resolution plasma density measurements

Akiyama, T.; Van Zeeland, M. A.; Boivin, R. L.; Carlstrom, T. N.; Chavez, J. A.; Muscatello, C. M.; O'Neill, R. C.; Vasquez, J.; Watkins, M.; Martin, W.; Colio, A.; Finkenthal, D. K.; Brower, D. L.; Chen, J.; Ding, W. X.; Perry, M.
December 2016
Review of Scientific Instruments;Dec2016, Vol. 87 Issue 12, p1
Academic Journal
A heterodyne detection scheme is combined with a 10.59 μm CO2 laser dispersion interferometer for the first time to allow large bandwidth measurements in the 10-100 MHz range. The approach employed utilizes a 40 MHz acousto-optic cell operating on the frequency doubled CO2 beam which is obtained using a high 2nd harmonic conversion efficiency orientation patterned gallium arsenide crystal. The measured standard deviation of the line integrated electron density equivalent phase resolution obtained with digital phase demodulation technique, is 4 × 1017 m-2. Air flow was found to significantly affect the baseline of the phase signal, which an optical table cover was able to reduce considerably. The heterodyne dispersion interferometer (DI) approach is found to be robustly insensitive to motion, with measured phase shifts below baseline drifts even in the presence of several centimeters of retroreflector induced path length variations. Plasma induced dispersion was simulated with a wedged ZnSe plate and the measured DI phase shifts are consistent with expectations.


Related Articles

  • Simplified homodyne small-angle scattering technique which uses a diffraction pattern as local oscillator. Philipona, R. // Review of Scientific Instruments;Sep87, Vol. 58 Issue 9, p1572 

    A CO2 laser small-angle scattering experiment has been set up and used for the investigation of plasma density fluctuations in a magnetized plasma. The local oscillator reference beam for homodyne mixing is produced by diffraction from a thin tungsten wire which lies in the main probe beam near...

  • Data recording system of a dispersion interferometer based on a CO2 laser. Khil'chenko, A. D.; Kvashnin, A. N.; Ivanenko, S. V. I.; Zubarev, P. V.; Moiseev, D. V.; Kovalenko, Yu. V. // Instruments & Experimental Techniques;May2009, Vol. 52 Issue 3, p382 

    The data recording system of a multichannel double-pass dispersion interferometer based on a CO2 laser is described. This system has been designed to record the linear density of plasmas in a real-time mode with a time discreteness of 4 μs and resolution 〈 N e L〉 ∼ 0.34...

  • Dual CO[sub 2] laser interferometer with a wavelength combination of 10.6 and 9.27 mum for... Kawano, Yasunori; Nagashim, Akira; Hatae, Takaki; Gunji, Soichi // Review of Scientific Instruments;Apr96, Vol. 67 Issue 4, p1520 

    Describes a dual carbon dioxide laser interferometer for measuring the electron density of tokamak plasmas. Description of the different wavelength oscillators; Advantages provided the system; density behavior during a fast disruption.

  • Two-color CO2 interferometer with single Bragg cell and improved vibration compensation at 3.39 μm. Innocente, P.; Martini, S. // Review of Scientific Instruments;Aug1988, Vol. 59 Issue 8, p1571 

    A single-chord CO[sub 2] (10.6-µm) He-Ne (3.39-µm) two-color laser interferometer which has been developed for the ETA-BETA II RFP machine is presented. Compared to the usual 0.633-µm vibration compensation systems, the 3.39-µm interferometer allows faster optical path-length...

  • CO2 laser scintillation interferometer for the measurement of density fluctuations in plasma confinement devices. Nazikian, R.; Sharp, L. E. // Review of Scientific Instruments;Nov87, Vol. 58 Issue 11, p2086 

    Density fluctuations in magnetically confined plasmas have been measured from the phase scintillations impressed onto a 10.6-μm wavelength laser beam probe, using a Mach–Zender interferometer operating in the optical near field. By careful design, the effects of vibration and air-borne...

  • Two-dimensional phase contrast interferometer for fluctuations study on LHD. Sanin, A. L.; Tanaka, K.; Vyacheslavov, L. N.; Kawahata, K.; Akiyama, T. // Review of Scientific Instruments;Oct2004 Part I & II, Vol. 75 Issue 10, p3439 

    CO2 laser based phase contrast interferometer was used previously on LHD to study plasma density microfluctuations. New two-dimensional 6×8 elements array of CdHgTe photoconductors was employed for detection. In addition to commonly measured intensity, frequency spectrum, and two-point...

  • Production of Multi-Terawatt Time-Structured CO2 Laser Pulses for Ion Acceleration. Haberberger, Dan; Tochitsky, Sergei; Gong, Chao; Joshi, Chan // AIP Conference Proceedings;11/5/2010, Vol. 1299 Issue 1, p737 

    The UCLA Neptune Laboratory CO2 laser system has been recently upgraded to produce 3ps multi-terawatt 10μm laser pulses. The laser energy is distributed over several 3 ps pulses separated by 18 ps. These temporally structured pulses are applied for laser driven ion acceleration in an H2 gas...

  • Novel scanning interferometer for two-dimensional plasma density measurements. Howard, John // Review of Scientific Instruments;Mar90, Vol. 61 Issue 3, p1086 

    A novel multichannel scanning interferometer designed for tomographically inferring contours of electron density in magnetically confined plasmas is described. The scanning element is a multisectored blazed rotating grating. The diffracted beam emerges at a different angle from each sector,...

  • Development of a FIR interferometer for ATF: Part I—High-power FIR laser development. Casson, W. H.; Hutchinson, D. P. // Review of Scientific Instruments;Aug1986, Vol. 57 Issue 8, p1998 

    A FIR interferometer system for the Advanced Toroidal Facility (ATF) at Oak Ridge National Laboratory has been developed with some major modifications to previous designs used at ORNL.Due to the highly elliptical cross section of the plasma and the projected plasma densities, 1 15-channel...


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics