6 research outputs found
The Diabolo photometer and the future of ground-based millimetric bolometer devices
The millimetric atmospheric windows at 1 and 2 mm are interesting targets for
cosmological studies. Two broad areas appear leading this field: 1) the search
for high redshift star-forming galaxies and 2) the measurement of
Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies at all redshifts. The
Diabolo photometer is a dual-channel photometer working at 1.2 and 2.1 mm and
dedicated to high angular resolution measurements of the Sunyaev--Zel'dovich
effect towards distant clusters. It uses 2 by 3 bolometers cooled down to 0.1 K
with a compact open dilution cryostat. The high resolution is provided by the
IRAM 30 m telescope. The result of several Winter campaigns are reported here,
including the first millimetric map of the SZ effect that was obtained by
Pointecouteau et al. (2001) on RXJ1347-1145, the non-detection of a millimetric
counterpart to the radio decrement towards PC1643+4631 and 2 mm number count
upper limits. We discuss limitations in ground-based single-dish millimetre
observations, namely sky noise and the number of detectors. We advocate the use
of fully sampled arrays of (100 to 1000) bolometers as a big step forward in
the millimetre continuum science. Efforts in France are briefly mentionned.Comment: 7 pages, 6 figures, to appear in the Proceedings of the 2K1BC
``Experimental Astronomy at millimeter wavelengths'', Breuil-Cervinia (AO)
Italy - July 9 - 13, 2001, Eds. M. De Petris et a
Calibration and First light of the Diabolo photometer at the Millimetre and Infrared Testa Grigia Observatory
We have designed and built a large-throughput dual channel photometer,
Diabolo. This photometer is dedicated to the observation of millimetre
continuum diffuse sources, and in particular, of the Sunyaev-Zel'dovich effect
and of anisotropies of the 3K background. We describe the optical layout and
filtering system of the instrument, which uses two bolometric detectors for
simultaneous observations in two frequency channels at 1.2 and 2.1 mm. The
bolometers are cooled to a working temperature of 0.1 K provided by a compact
dilution cryostat. The photometric and angular responses of the instrument are
measured in the laboratory. First astronomical light was detected in March 1995
at the focus of the new Millimetre and Infrared Testa Grigia Observatory (MITO)
Telescope. The established sensitivity of the system is of 7 mK_RJ s^1/2$. For
a typical map of at least 10 beams, with one hour of integration per beam, one
can achieve the rms values of y_SZ ~ 7 10^-5 and the 3K background anisotropy
Delta T/T ~ 7 10^-5, in winter conditions. We also report on a novel bolometer
AC readout circuit which allows for the first time total power measurements on
the sky. This technique alleviates (but does not forbid) the use of chopping
with a secondary mirror. This technique and the dilution fridge concept will be
used in future scan--modulated space instrument like the ESA Planck mission
project.Comment: 10 pages, LaTeX, 12 figures, accepted for publication in Astronomy
and Astrophysics Supplement Serie