Detection and damping of thermal-acoustic oscillations in low-temperature measurements

Abstract

The spon taneous t herm a l-acoustic oscillations in nonisotherm al columns of helium , hydrogen, nitrogen, argo n, a nd oxygen gas have bee n investigated. Th e pressu re flu ctua-t ions were meas ured with a ba rium t itanate t ransducer a nd t he particl e disp laccme n ts obser ved by asmoke tcchniq ue. T he observed press ure osci ll ations wcre oftc n nonsymmct-rical a nd of s uffi cient a mplitude to indi cate t he neccssity for a nonlinear a pproach in a theoretical treat ment of t he oscillations. An a djustabk " H elmholtz resonato r" attac hed at t he warm end of the oscillating column was fo und to d am p co mp letely t he oscill ations and eliminate t he e nergy transfer which t hey caused.