|
Illustration of
CCD
(illustrations: CXC/S. Lee)
|
|
ACIS Schematic
ACIS schematic layout overhead view to illustrate the location of the
imaging (ACIS-I) and spectroscopic (ACIS-S) arrays of CCD ships. Chips
S1 and S3 are back-illuminated chips; all of the other chips are
front-illuminated.
|
|
High-Resolution Camera
(HRC)
The HRC accurately records the position, number, and energy of X-rays.
The camera consists of two clusters of 69 x 06 lead oxide (PbO2) glass
tubes, 1.2 mm long and 10m in diameter (1/8th the diameter of a human
hair.) The X-rays strike the tubes and release electrons that are
accelerated down the tubes at high voltage. The electrons trigger the
release of other electrons, and at the end of the tubes millions of
electrons strike a grid and produce a finely detailed map of the source
which emitted the X-rays.
|
|
Chandra
spacecraft
Schematic of the Chandra spacecraft with an exploded view of the
science instruments.
|
|
CCD Imaging Spectrometer
(ACIS) Illustration
A diagram of Chandra CCD Imaging Spectrometer (ACIS), which is used for
studying the temperature variation across X-ray sources such as vast
clouds of hot gas in intergalactic space.
|
|
High Energy Transmission
Gratings
There are two instruments aboard Chandra dedicated to high resolution
spectroscopy: the High Energy Transmission Grating Spectrometer (HETGS)
and the Low Energy Transmission Grating Spectrometer (LETGS). Each
spectrometer is activated by swinging an assembly into position behind
the mirrors. The assembly holds hundreds of gold transmission gratings:
when in place behind the mirrors, the gratings intercept the X-rays
reflected from the mirrors.
|
|
Grating Cross
Section
Two types of gratings are in the HETG, in order to distinguish between
them, the HEG and MEG gratings are oriented at slightly different
angles, so that the X-rays are diffracted in an "X" pattern on the
detector. The HETG grating facets are made of bars which are spaced
closer together than a wavelength of visible light; it would take
hundreds of bars to equal the thickness of a sheet of paper. The bars
are supported by plastic membranes which are as thin as a soap bubble,
yet can withstand the trauma of a shuttle launch. The gratings take
advantage of the fact that the gold bars are partially transparent to
X-rays, so that the diffraction is more efficient, and more X-rays are
captured in the high resolution spectrum.
|
