Bubble Counting for the Determination of the Velocities of Charged Particles in Bubble Chambers

Abstract

The density of bubbles along tracks in a liquid propane bubble chamber has been measured as a function of particle velocity for positive pions and protons with velocities $\ensuremath{\beta}=\frac{v}{c}>0.4$. For temperatures from 55\ifmmode^\circ\else\textdegree\fi{}C to 59.5\ifmmode^\circ\else\textdegree\fi{}C the bubble density, $b$, is described by $b=(\frac{A}{{\ensuremath{\beta}}^{2}})+B(T)$, where $A=9.2\ifmmode\pm\else\textpm\fi{}0.2$ bubbles/cm and $B$ is a function of temperature only. Velocities can be determined by bubble counting, using fast comparison tracks of known velocity, with a final average error in velocity of 5% for proton tracks 10 cm long. Accurate temperature control is not required to obtain this accuracy by using this method.