MedOptics Dectector - Characteristics

Detlef Smilgies, CHESS

the "more than you ever wanted to know" page

The D1 area detector (MedOptics) is a fibercoupled CCD camera

i.e. there is an optical fiber bundle connecting the fluorescent screen (that coverts x-rays into optical light) to the CCD chip - thats's the same electronic device capturing the images as in your digital camera

with a pixel size of 46.9 microns x 46.9 microns

note: this value was obtained recently when we recalibrated the camera (Oct. 2007). The value from the previous calibration was 47.2 microns. Since we modified the image correction mode a bit to the current state of the art, this small correction of less than 1% is reasonable. However, to be self-consistent, the images before re-calibration should be evaluated using the old pixel size.

and a total of 1024 x 1024 pixels with a 14-bit dynamical range per pixel.

i.e. min value is 1, max value per pixel is 16,383.

Typical read-out time per image is below 5 sec.

The read-out time may be further reduced using 2x2 (about 3 sec) or 4x4 binning (about 2 sec) at the cost of lower resolution.

The images are background corrected,

the read-out noise level is about 200 units

distortion-corrected,

to account for imperfections in the fiber optics bundle

and flat-field corrected.

accounting for variation in sensitivity of the fluorescent screen and the pixels in the CCD

A pedestal value of 20 was added to the images to avoid negative values.

recommended viewing range in fit2d is 15 to 15,000 (log scale)

Reference: Sol M. Gruner, Mark W. Tate, Eric F. Eikenberry. Charge-coupled device area x-ray detectors. Rev Scientific Instruments, 73, 2002, 2815-2842

note: all CHESS CCD detectors follow the calibration protocol described by Gruner et al., as closely as possible.