McDonald Observatory nRG Detector Electronics

The McDonald Observatory detector group recently added IR capability to their Version 2 (V2) CCD controller. With minimal hardware and software modifications, we are operating HAWAII-nRG devices. Principally modified to support a HA WAH-1RG detector for LRS-J, a J-band extension to the HET's low-resolution spectrograph, our existing system can be used to operate 2RG devices in 4-amplifier mode as well. LRS-J based on a cryogenic prime focus camera optical design, uses an unusual approach to mounting a 1RG device, and it requires custom cryostat circuitry to minimize heat load, obscuration, and changes to the CCD-based electronics. It takes advantage of the nRGs programmability and makes dual use of the serial interface programming lines. AC coupling the preamplifier to the detector requires line-by-line DC restoration, but yields stable reference pixel values between frames. The performance of the reference amplifier and reference pixels are under investigation for use in long integration time, low background spectrometry.