Chad and I leak checked the heat shield circuit after sic 27 target  installed. It took 20minutes  to pump down the circuit to the leak detector bottom scales. The leak detector is calibrated today,and all the vacuum lines and connections are leak checked by spraying helium. Chad sprayed helium to each vc fittings for 2 seconds. There is no any response on leak detector . The test repeated one time and the result is same. Chad flushed  helium around the target for 10 second .This time leak detector also have no respone.  The heat shield circuit is leak  tight at this stage . We will move TM4 to conditioning station and pressure helium test the circuit.