Temperature measurements at an implosion focus

Abstract

Sectroscopic temperature measurements were made at the focal point of imploding shock waves in the UTIAS implosion C chamber, which has a 20-cm diameter hemispherical cavity.The chamber was filled with a stoichiometric H2-02 gas mixSture at different initial pressures (14 " 68 atm).The mixture was ignited at the origin by an exploding wire generating an outgoing detonation wave which reflected at the chamber wall as an imploding shock wave (gas-runs).Additional experiments where an explosive shell of PETN was placed at the hemispheriual wall were also conducted The shell was detonated by the impact of the reflected gaseous detonation wave at its surface, thereby generating an intense implosion wave (explosive-run).The temperatures were measured at the implosion focus using a medium quartz Hilger spectrograph with an eight photocell polychromator attachment over the visible wavelength range. The meas'ured radiation intensity distributions were fitted to blackbody curves. The temperatures were 10,000 1-13,000 K for gas runs, and 15,000 v 17,000 K for explosive runs.The cont.nuous spectra from photographic film and the measured emissivities, which were very close to unity, confirmed that the plasma was a blackbody.Numerical studies using the random choice method (RCM) and classical strong-shock theory wore used to analyse the flows in the entire range of the implosion process.Real-gas effects and radiation losses were also considered. The results were compared with the experimental data and good agreement was obtained.

Thermal radiation from a converging shock implosion

“…This is a concrete example that converging shock waves are at least able to create gas conditions that generate similar radiation to that of sonoluminescence. Several authors have made measurements on the light from imploding shocks, concluding that the gas at the focus behaves as a blackbody radiator, [8][9][10][11] based on measurements at discrete wavelengths. The present study confirms the blackbody form of the radiation, but it is difficult to make quantitative comparisons due to different initial pressures and shock wave strengths.…”

Energy concentration by spherical converging shocks generated in a shock tube

“…Saito and Glass 38 continued the experiments and improved upon the measurements. Photographs of the 350-600 nm spectrum were made and they concluded that the plasma emitted as a blackbody.…”

Random-Choice-Method Solutions for Two-Dimensional Planar and Axisymmetric Steady Supersonic Flows.

“…(38) k =0 This is also the binary expansion of the number sequence n = 1, 2, 3, , etc, where i is a binary number that equals only 0 and 1. Then, a set of random numbers On can be obtained by simply writing the digits of these numbers in their reverse order, preceded by a decimal point.…”