Abstract

We present an investigation of the occurrence of stimulated Raman scattering and other nonlinear optical effects during Raman calibrations of Thomson scattering diagnostic systems for magnetic fusion plasmas. When these effects take place, the intensity of the Raman lines is unpredictable, and the calibrations are impossible. In this research Raman scattering from H2 and D2 at filling pressures up to 1 atm has been experimentally investigated using the Thomson scattering system of the ETA-BETA II reversed field pinch device. Stimulated Raman Stokes light has been observed at filling pressures above 230 and 500 mbars for H2 and D2, respectively, for input laser pulses of 8 J and 30 ns (FWHM) duration. Evidence has been found that the stimulated Raman light does not originate from the observed scattering volume but is detected as light diffused into the vacuum chamber. To explain these results, the Raman gain and the intensity of the stimulated Raman light are calculated, taking into account the multimode structure of the laser beam. We find that significant power conversion from the input laser beam to the Stokes wave takes place near the output window of the vacuum chamber. Part of this radiation is diffused back into the machine, and this part is detected as superimposed on the spontaneous Raman signal. Finally we discuss the Raman calibrations in RFX, a larger plasma device in which the Raman medium will be N2 at a temperature up to 350 °C, and show that a filling pressure of 100 mbar gives a sufficient calibration signal, avoiding any nonlinear effect.

© 1993 Optical Society of America

Full Article  |  PDF Article
OSA Recommended Articles
Complete calibration of a Thomson scattering spectrometer system by rotational Raman scattering in H2

Francesco Flora and Leonardo Giudicotti
Appl. Opt. 26(18) 4001-4008 (1987)

Rotational Raman scattering of hydrogen for calibrating a Thomson scattering device

Toshihiko Yamauchi and Ichiro Yanagisawa
Appl. Opt. 24(5) 700-709 (1985)

Experimental investigation of high-power single-pass Raman shifters in the ultraviolet with Nd:YAG and KrF lasers

Laurent de Schoulepnikoff, Valentin Mitev, Valentin Simeonov, Bertrand Calpini, and Hubert van den Bergh
Appl. Opt. 36(21) 5026-5043 (1997)

References

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Figures (10)

You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Equations (14)

You do not have subscription access to this journal. Equations are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Metrics

You do not have subscription access to this journal. Article level metrics are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription