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

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 $\beta =\frac{v}{c}>0.4\mathrm{}$. For temperatures from 55°C to 59.5°C the bubble density, $b$, is described by $b=\left(\frac{A}{{\beta }^2}\right)+B\left(T\right)\mathrm{}$, where $A=9.2\mathrm{}\pm 0.2$ 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.