I suppose it would depend on how you wanted to simulate it. In my case I was targeting taking the signal from an unmodified test instrument that thought it was talking to a CRT and using that to figure out what display it wanted. That would be equivalent to taking the X/Y/Intensity lines from the mainboard of a Vectrex and just doing what the vector scope would have done. I drilled down enough to find the non-linear, temperature dependent, curve of phosphor decay times on the CRT used in some HP gear. It was pretty wild. If you buy third party kits they don't even bother simulating phosphor. Instead they just take the signals, figure out the information content of the display, and put that on an LCD. (Monochrome generally)