In a cyclotron, radius of the circular path,
$r=\frac{m v}{B e}=\frac{2 \times 10^{5}}{5 \times 10^{7} \times 4 \times 10^{-2}}=0.1 \mathrm{m}$


$1^{st}$ Way : By using spring of smaller torsion constant.
$2^{nd}$ Way : By using a smaller coil
$3^{rd}$ Way : By using a stronger magnet
$4^{th}$ Way : By using a coil having fewer number of turns.