If the maximum value of accelerating potential provided by a ratio frequency oscillator is 12 kV. The number of revolution made by a proton in a cyclotron to achieve one sixth of the speed of light is ............ $\left[\mathrm{m}_{\mathrm{p}}=1.67 \times 10^{-27} \mathrm{~kg}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}\right.$, Speed of light $\left.=3 \times 10^8 \mathrm{~m} / \mathrm{s}\right]$