FOMA-a fast optical multichannel analyzer

A fast optical multichannel analyzer (FOMA) was built for obtaining spectroscopic measurements with fast time resolution on the DIII-D tokamak. The FOMA utilizes a linear photodiode array (RETICON RL 1024 SA) as the detector sensor. An external recharge switch and ultrafast operational amplifiers permit a readout time per pixel of 300 ns. In conjunction with a standard CAMAC digitizer and timing modules, a readout time of 500 μs is achieved for the full 1024-element array. Data acquired in bench tests and in actual spectroscopic measurements on the DIII-D tokamak are presented to illustrate the camera´s capability. The system and the data-acquisition software used are described in detail