This new mosaic camera is currently under construction in Gerry Luppino's lab at IfA, University of Hawaii at Manoa. The dewar has been built and leak tested and the cold-surface will begin fabrication in January 1998. The camera will incorporate 12 MIT, Lincoln Labs 2k x 4k 15 micron CCDs arranged in a mosaic of two devices by four to produce overall image dimensions of 8,192 by 12,288 pixels.
The CCDs themselves will be derived from a development effort led by Gerry Luppino and Barry Burke of Lincoln Labs and funded by a consortium comprising CFHT, IfA, ESO, AAO, Keck and Subaru. CFHT has bought IfA's share of the first four wafer runs. The first 11 devices, of which CFHT will receive four, have undergone preliminary testing. Some remarkable CCDs are to be found among these - at least one has shown a read noise of less than one electron, a first for the CCD industry, many have almost perfect charge transfer efficiency, and the first device selected for the CFH12k has only four traps and no hot columns! Some general characteristics of the devices tested so far are:
The simple, single-layer SiO2 anti-reflection coating used on the first devices limits the blue sensitivity (Figure 35). Later devices will have a multi-layer coating tuned for better blue response.
Devices have been made on two types of silicon: standard EPI and high-resistivity. The latter are so-called deep-depletion devices wherein the charge collection fields of the pixels extend deeper into the CCD, and so signal electrons generated by more deeply penetrating red photons are accumulated and the red efficiency is enhanced. However, high resistivity silicon is brittle and hard to handle. Thus only one wafer run was dedicated to this technology and the yield has been less impressive than the EPI runs.