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A truly monster-sized CCD detector (charged coupled device) for ultra low light level
astronomy has been designed, built and successfully installed in a new AIP-dewar vessel
and performed just flawlessly in its first scientific-grade laboratory tests.
The detector is the
largest of its kind ever built and consists of 10560 by 10560 pixels, each 9 times 9
micrometer (9/1000th of a millimetre) in size, totalling to approximately 112 million pixels over
an area of 95mm times 95mm. It must be operated in a nearly perfect vacuum and at a
temperature of -130°C to suppress the natural molecular and atomic motions of the material
it is made of. Two of these devices will work simultaneously in the Potsdam Echelle
Polarimetric and Spectroscopic Instrument (PEPSI) where they will detect a photon stream
as small as a few photons per second per wavelength bin, a billion times less than the naked
eye could register. PEPSI will be installed at the 2 x 8.4m Large Binocular Telescope (LBT)
in Arizona in 2011 and then comprises the most powerful spectrograph available for its
astronomers.
The heart of its eyes was designed by Richard Bredthauer and his team at
Semiconductor Technology Associates (STA) in southern California and was prepared for its
low light level sensitivity in Michael Lesser's Imaging Technology Laboratory (ITL) of the
University of Arizona by thinning the light sensitive area. This process took two years and
takes off one atomic layer after the other from the silicon wafer surface until only a few
hundred atomic levels of silicon remain. Thereby the detector gained a peak quantum
efficiency of 96% at 450nm, i.e. it misses only 4% of all incoming photons (an excellent
astronomical photographic plate missed up to 98% of the incoming photons).
The AIP labs in
Potsdam manufactured the dewar vessel and the CCD camera head with its delicate cold
finger. "The requirements on the vacuum tightness and mechanical stiffness were particularly
high for this device due its shear size with its 16 amplifiers and its complex thermal behaviour
across the CCD surface" explains Professor Klaus G. Strassmeier, P.I. of the PEPSI and the
10k-CCD project and one of the two scientific directors of the AIP in Potsdam. "One must
imagine that the peak-to-valley precision of such an oversized CCD surface is still just a
hundreds of a millimetre from edge to edge". "This is if you stick 112 million toothpicks into
the ground to cover the surface of a soccer field to better than a few millimetres across its
diagonal, and you have only one trial per toothpick", says Prof. Strassmeier. Once it sees
starlight from the LBT, PEPSI and its two 10k CCDs are designed to measure cosmic
magnetic fields and characterize Earth-sized exoplanets.
Science contacts
Prof. Dr. Klaus G. Strassmeier (Astrophysikalisches Institut Potsdam)
Astrophysikalisches Institut Potsdam
An der Sternwarte 16
D-14482 Potsdam
+49 331 7499-295
Dr. Michael Lesser (Imaging Technology Laboratory)
+1 520 628-2078
Dr. Richard Bredthauer (Semiconductor Technology Associates Inc.)
+1 949 481-1595
Press contact
Madleen Köppen
+49 0331 7499-469
The Astrophysical Institute Potsdam (AIP) is a research organization of the Leibniz-association and is located in
Potsdam/Babelsberg at the south-western border to Berlin. About 140 personnel work on a variety of
astrophysical and astro-engineering topics. The AIP is partner of the Large Binocular Telescope (LBT) in
southern Arizona.
Imaging Technology Laboratory (ITL) is dedicated
to advancing scientific and industrial imaging science by developing enabling technologies for the
University of Arizona and worldwide research sponsors.
Semiconductor Technology Associates Inc. (STA) is dedicated to providing the highest quality custom Charge
Coupled Devices to the commercial and scientific communities. Their expertise lies in the design, fabrication,
packaging and characterization of the finest CCDs available in the world.
[Press release]
[PEPSI web pages]
[AIP home page]
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Torr
during lab acceptance tests. [Foto: Emil Popow, AIP]
