Voltage Multiplier Circuit Design

[ayaz15m]

I have made a 3 stage voltage multiplier. My input is from the outlet so 120 V ac. I measure my output from the first and last capacitors of the bottom row as shown in the image. The output I am getting is 120 V dc. From the equation Vout(dc) = Vin(ac)*sqrt(2)*number of stages. With this equation I should be getting around 500 V dc theoretically. I am not sure what is going on, anybody have any insight. Thank in advance.

[pebe]

What value are the caps, and what voltage rating?
What ID number (type) are the recifiers.
Does the '+' sign near the AC source indicate the polarity of the adjacent cap? If so it is wrongly connected.

[ayaz15m]

The caps are 2.2nF @ 20kV. I am not sure about the id number for the diodes but they are hv diodes rated at 20kV also. The caps are not polarized. The positive sign it the positive or hot lead from the ac source going into the capacitor on the top row.