A new tungsten wire calorimeter for the negative ion source testbed BATMAN-Upgrade

•IPP Garching has recently upgraded the RF-driven negative ion source testbed BATMAN.•Beam uniformity is going to be investigated using a new tungsten wire calorimeter.•The new TWC is positioned only 19 cm downstream from the extraction system.•The new TWC allows observation of the beamlets for the first time in this testbed.•The new TWC is absolutely calibrated by ohmic heating of a tungsten wire.