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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