The Accuracy of VISAR Instrumentation
Abstract
The accuracy of velocity measurement by VISAR instrumentation was treated in the original VISAR paper 25 years ago, but the subject has received little attention in published papers since then. Error sources can be divided into VPF errors and Fringe Count errors. The accuracy of determining the VISAR's VPF constant is discussed first. It depends on the laser wavelength λ _0, the delay time τ, the index of refraction dispersion parameter δ, and (if a window is used on the specimen surface) on the window index of refraction effect, characterized by Δ ν / ν _0. The calculated VPF uncertainty is only about +/- 0.1% if no window is used; otherwise it is in the 1/2% to 1% range. The main contributor to inaccuracy is often the uncertainty of the fringe count at any particular time, usually about +/- .02 fringe. The percent error in the fringe count, F(t), is therefore (.02/F(t))x100%, and the corresponding error in the velocity is the same percent, of course. Due to the VISAR's high accuracy, experimental verifications of its accuracy are difficult and expensive. Two such verifications are summarized.
- Publication:
-
APS Shock Compression of Condensed Matter Meeting Abstracts
- Pub Date:
- July 1997
- Bibcode:
- 1997APS..SHK..P101B