Although fraudulent behavior is the subject, a qui tam suit is a civil action, not a criminal action. For that reason, imprisonment is not a potential sanction in a qui tam case.
However, filing a qui tam action may trigger a criminal investigation and prosecution by the government which could lead to criminal fines or jail time for the wrongdoer(s). Any criminal action does not necessarily result from the qui tam action and would be separate from it. You would have no control over the government's criminal action, but you may be asked for assistance.