Gamma detector for the Shintake monitor (IP beam size monitor at ATF2)

A calorimetric detector for inverse-compton photons from the Shintake monitor at the ATF2 test beam facility at KEK is developed. The Shintake monitor is the precision beam size monitor based on laser interferometer, which is planned to be used at a commissioning of the ILC beam delivery system. The detector has original structure to separate the compton signal from Bremsstrahlung background using the difference in shower development. The beam test of the detector was performed at ATF in the 2007’s winter using a laser wire and a wire scanner. It was confirmed to be able to see the difference in the shower development and to separate compton photons from Bremsstrahlung photons. The beamtest plan of Shintake monitor at ATF2 on 2008’s winter is also described.