According to the pilot, a cart that housed an auxiliary power unit was positioned near the helicopter and used to start it's engine. After engine start, ground personnel did not remove the cart from the helipad. The pilot reported that shortly after lift off to a hover, to perform track and balance checks, the tail rotor struck the forward portion of the cart. The helicopter sustained substantial damage to the tail boom and tail rotor. The pilot reported no preimpact mechanical malfunctions or failures with the helicopter that would have precluded normal operation.