Boost Up Converter; need higher voltage.

[DavidWarden38]

[Faraday88]

Hi, this is my first post and I am a student/electrical hobbyist so I apology if something is incorrect and would like to learn. I learned about boost converters and understand their basic function. I have built a boost converter my self with some parts I had lying around. Right now, my circuit looks like the schematic above. I am using a 555 timer in astable mode to switch the power with the n-type MOSFET at 15.6kHz. The variable resistor(R5) is used to adjust the voltage and the circuit is intended to charge to roughly 100V. I got this design online where it was intended to power NIXIE tubes using 180 volts(with a different diode, MOSFET and NPN transistor). Unfortunately, my circuit only outputs a max 75 volts. I've build multiple designs with different frequencys and still have only gotten to 75 volts. I want it to charge my cap at least to 100 volts. I would also like to know if my problem is the speed of my diode or transistor. I have heard of "reverse recovery time". Could my transistor or diode have too high of a recovery time or does my circuit have something else holding it back? I know my MOSFET is rated for only 60 volts so I am going to get a higher rated one but, should I look for a specific type?

Hi,
Schematic missing!!
Rgds,
Faraday88.