Thermal Modeling of the Wide-Field Infrared Camera for the CFHT

摘要

In the past decade, new tools have emerged in the arena of thermal modeling. These modeling tools are rarely used for cooled instruments in ground based astronomy. In addition to an overwhelming increase computer capabilities, these tools are now mature enough to drive the design of complex astronomical instruments, in particular if these instruments must be cooled. This is the case of WIRCam, the new wide - field infrared camera recently installed on the CFHT on the Mauna Kea summit. This camera uses four 2K×2K Rockwell Hawaii-2RG infrared detectors and includes 2 optical barrels and 2 filter wheels. This camera is mounted at the prime focus of the 3.6 m CFHT telescope. The mass to be cooled weighs close to 100 kg. The camera uses a Gifford Mac-Mahon closed-cycle cryo-cooler to avoid strenuous daily re-fillings on the telescope due to the camera location. This paper presents the thermal model of the camera using finite-element analysis under the I-deas software. The capabilities of the I-deas thermal module (TMG) are demonstrated for our particular application. Predicted performances (cool down time, warm-up time, and mechanical deformations) are presented and compared to measurements.