$\mathrm{B}=\frac{\mathrm{ma}}{\mathrm{qv}}=\frac{\mathrm{ma} \sqrt{\mathrm{m}}}{\sqrt{2 \mathrm{k}}}$
$=\frac{\mathrm{m}^{3 / 2} \mathrm{a}}{\mathrm{e} \sqrt{2 \mathrm{k}}}=\frac{\left(1.6 \times 10^{-27}\right)^{3 / 2} \times 10^{12}}{1.6 \times 10^{-19} \sqrt{2 \times 1 \times 10^{6} \times 1.6 \times 10^{-19}}}$
$=0.71 \mathrm{mT}$



