The Instrument

The MAXIMA receiver houses sixteen single-color channels at the focus of the telescope, compared to the single photometer employed in MAX. This array of detectors provides sixteen simultaneous measurements, allowing a much higher level of sensitivity to the extremely small variations in the CMB by effectively increasing the integration time on each point on the sky (in the scan direction) and the number of points measured (in the orthogonal direction along the array). The warm secondary mirror in the current MAX experiment is replaced with cold secondary and tertiary mirrors, which allows a cold baffle to be placed at the optimum spot in the optical path. This baffle rejects millimeter-wave radiation from outside the desired beam pattern. An Adiabatic Demagnetization Refridgerator (ADR) cools the detectors to 100 mK, and a pumped Helium-three stage provides an intermediate temperature of 300 mK.

Figure 1 with Description (32K)
Figure 1. A cross section of the MAXIMA optical system.

MAXIMA Balloon Gondola

The MAXIMA gondola must protect the delicate optics and receiver from the often rough parachute landings. A reaction flywheel system controls the azimuthal pointing of the gondola using information from a CCD camera star tracking system. An important feature of the the MAXIMA gondola is that the large primary mirror is modulated, rather than a secondary mirror. The optical beam on the primary mirror remains stationary therefore, reducing the effects of temperature gradients on the primary mirror which could give false signals.

Figure 2 with Description (12K)
Figure 4. Drawing of MAXIMA gondola with the single-pixel MAX receiver (MAXIMA 0 configuration).

For more details about the MAXIMA instrument, download the 3K Maxima proceedings (postscript format)


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