Replace resistor \$R_D\$ by an inductor which gives you a boost converter. That way you start the voltage multiplication already with voltage \$\gg 36V\$.

But make sure that

• the MOSFET can hable the voltage (for BS170 \$V_{DS,max}\$ is 60V) and
• the MOSFET can handle the max. current (mainly depending on switching frequency and incudctance) (for BS170 \$I_{D,max}\$ is 0.5A)

Replace resistor \$R_D\$ by an inductor which gives you a boost converter. That way you start the voltage multiplication already with voltage \$\gg 36V\$.

But make sure that

• the MOSFET can hable the voltage (for BS170 \$V_{DS,max}\$ is 60V) and
• the MOSFET can handle the max. current (mainly depending on operating voltage, switching frequency and inductance); for BS170 \$I_{D,max}\$ is 0.5A.