200ns not 20ns
no way will you will beable to collect full data at full speed of the sensor
your max conversion is 13?s (from the data sheet of the Mega)
& likely longer (set up & etc)
you could decimate & get only 31 samples at full sensor speed (must use the built in sample & hold)
better to slow the sensor to the same speed as the sampling ....
the DUE has a max conversion speed of 1us / sample & i expect to run at about 1/2 that
(full sensor read taking 2048*2us+overhead ~= 200sensor readings a second )