BNC HT / MHV
Bayonet coupling miniature high voltage connector, operating in the range DC-2 GHz. 50 ohms / part series R316
Radiall BNC HT connector is fully compatible with MHV. A mated pair of connectors is rated at 10,000 VDC.
Although it looks very similar, BNC HT / MHV is not intermateable with BNC.