Quick Question on Van de Graaff Particle Accelerators

[Abu]

Hi everyone. Just a small, quick question I have: Can negative ions be accelerated by a Van de Graaff particle accelerator? My initial reaction is no, because the terminal (the sphere with the charges allocated on the outside) is positive, which means negative ions would be attracted and not accelerate away from the ion source. Am I correct about this? I am using the following image as reference, and I am assuming that the voltage starts from a high number and is zero at the end of the beam:

If I am correct, is there any way a negative ion could be accelerated from accelerators like this one, or even a cockcroft-walton particle accelerator, by any chance?

 

[mfb]

You can operate it in reverse.

Or accelerate the ion beam towards the high voltage terminal.