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15
Chapter 2
System Component Descriptions
PI-SCX Camera
CCD Array: PI-SCX currently offers three CCD formats: the 1340x1300 array with
20x20 µm pixels, the 2084x2084 array with 24x24 µm pixels, and the 4096x4096 array
with 15x15 µm pixels. All are scientific grade full-frame arrays with MPP. The
application of indium tin oxide (ITO) technology to the PI-SCX:4300 array provides a
QE of approximately 65% to 550 nm. When used with an x-ray scintillator screen and a
software-programmable, high-capacity or high-sensitivity amplifier, these systems can
effectively provide x-ray photon-counting capability with up to 16-bit dynamic range.
CCD Chamber: The vacuum-sealed CCD chamber protects the CCD from
contamination as well as insulates it from the warmer air in the camera body. The
inherent low humidity prevents condensation on the cooled surface of the array. The
thermal barrier provided by the fiberoptic prevents the condensation from forming on the
front of the fiberoptic .
PI-SCX cameras are normally shipped with a vacuum level of ~10 mTorr or better.
Because this vacuum may deteriorate over time due to outgassing of electrical
components, some PI-SCX cameras are designed with a built-in vacuum port that can be
used to restore the vacuum to its original level. Instructions for repumping the vacuum
are provided in Appendix C.
Fiber Optic: The PI-SCX fiberoptic tapers are bonded to the face of the CCD arrays
with Princeton Instruments' patented fiberoptic-coupling technology. The direct bonding
to the face of the array eliminates the need for an intermediate fiberoptic faceplate or an
oil layer between surfaces, thereby increasing sensitivity. The PI-SCX:1300 is bonded to
a 1:1 or 1.5:1 fiberoptic taper which extends outside the vacuum for a resolution of
25 lp/mm for the 1:1 taper or 16 lp/mm for the 1.5:1 taper. The PI-SCX:4096 is available
with either a 1:1 fiberoptic taper (31 lp/mm, 61x61 mm field of view) or a 1.9:1
fiberoptic taper (120x120 mm field of view). The PI-SCX:4300 is available with either a
1:1 fiberoptic taper (20 lp/mm) or a 2.4:1 taper (120x120 mm field of view).
Thermoelectric Cooler: While the CCD accumulates charge, thermal activity releases
electrons, generating dark current. Cooling the CCD enhances the low-light sensitivity by
reducing thermally generated charge. With forced-air assistance, the PI-SCX:1300
camera’s thermoelectric cooler is capable of cooling the CCD to -30°C with ±0.05°C
stability at temperature lock. With 25°C water for water-assisted cooling, the
PI-SCX:1300 camera can reach -35°C. With +5°C water, the PI-SCX:4096 (≤1.5:1 fiber
ratio) and the PI-SCX:4300 are designed to reach -50°C. With +0°C water, the
PI-SCX:4096 (>1.5:1 fiber ratio) is designed to reach -45°C
Cooling is accomplished by mounting the CCD on a cold finger, which in turn is seated
on a thermoelectric (Peltier-effect) cooler. With air-cooling, the heat is transferred
through the Peltier stages to internal fins and is removed by forced air. With water-
cooling, a 50:50 ethylene glycol-water coolant is circulated through a heatsink thermally