Transmitted laser beam diagnostic at the Omega laser facility

We have developed and commissioned a transmitted beam diagnostic (TBD) for the 2omega high intensity interaction beam at the Omega laser facility. The TBD consists of a bare-surface reflector mounted near the target, which collects and reflects 4% of the transmitted light to a detector assembly outside the vacuum chamber. The detector includes a time integrating near-field camera that measures beam spray, deflection, and the absolute transmitted power. We present a detailed description of the instrument and the calibration method and include first measurements on laser heated gas bag targets to demonstrate the performance of the diagnostic. (C) 2004 American Institute of Physics.