Performance estimations for the ITER bolometer diagnostic

Highlights: • Signal intensities and noise for current ITER bolometer diagnostic design estimated. • SNR for most lines-of-sight (LOS) is good or acceptable. • Signal intensities for optimised LOS in upper ports increased by factor of 4. • Low SNR for LOS observing plasma edge; reduced absorber thickness could help. -- Abstract: The ITER bolometer diagnostic shall provide the measurement of the total radiation emitted from the plasma, a part of the overall energy balance. Up to 550 lines-of-sight (LOS) will be installed in ITER observing the whole plasma from many different angles to enable reliable measurements and tomographic reconstructions of the spatially resolved radiation profile. The performance of the diagnostic is intimately linked to the constraints imposed by the design requirements, the sensor and data acquisition design, as well as expected noise levels. The results presented contain the estimated signal intensities for the current design and integration of bolometer cameras in ITER, based on the simulated radiation profile for the ITER standard scenario (DT-plasma at 15 MA, 500 MW with low impurity content). The corresponding power deposited onto the absorber ranges between 0.5 μW and 2 mW. The expected noise levels derived mainly from lab measurements and compared to operating bolometer systems yield estimated values for ITER in the order of 1 μW, clearly indicating a need for optimizing the diagnostic. The optimization potential is discussed. Cameras for which the light yield could be increased are identified. Also, the potential for enhancing the sensitivity by using different absorber thicknesses is explored.