RDI’s CMOS_1M system uses a single large CMOS sensor to create a continuous image area 147 mm x 94 mm with 1.39 million pixels. Each pixel has an active area of 100 mm2. Scattered x-rays from the sample are converted into visible light with a Gd2O2S:Tb phosphor screen and the light is then transferred to the CMOS sensor with a thin fiber optic plate.
A special feature of CMOS sensors compared to CCD detectors is that individual pixels of the sensor can be readout while all the other pixels are acquiring data. The total read time for the detector is only 0.033 seconds. This allows the imaging system to be used for shutter-less crystallography where a series of images are collected as the crystal sample is smoothly rotated through 180 (or 360) deg. Usually each frame is taken with a 0.1 deg rotation of the crystal and an exposure time of 0.1 - 5 seconds. Therefore, a complete dataset of 1800 (or 3600) frames is collected in 3 minutes at an x-ray synchrotron or in about ½ to one hour with a laboratory source.
With our system images frames are acquired every 0.1 deg with a short exposure time while with most CCD systems images are acquired with an oscillation range of 0.5 -1.0 deg with longer exposure times per frame. When images from the CMOS system are added to simulate the data from a CCD system the data quality and dynamic range are as good or better than that from a CCD system. However, the CMOS images are usually used directly by analysis programs to give improved positioning accuacy of the diffraction peaks which results in higher resolution of the final crystal structure.
The detector is read out using a standard 1Gig Ethernet cable into a standard Intel PC system running Windows 7. Diffraction data collected with this system can be directly analyzed with standard analysis programs (XDS, HKL2000, MOSFLM, D*Trek, etc.). The detector control software can be configured to also control an x-ray goniometer and an x-ray generator or a device driver can be provided to allow control of the detector with other software.
Here are the detailed specifications for the CMOS_1M system.
|Active area (mm2)||147.6 x 94.4|
|Image size in pixels||1476 x 944 pixels (1.39 x 106 pixels)|
||100.1 x 100.1|
|Phosophor (optimized for 1 Angstrom)||Gd2O2S:Tb phosophor plate|
|Detector window||Aluminized mylar or Beryllium|
|Spatial Resolution (FWHM) microns||100|
|Dark current (e/pixel/sec)||1|
|Read noise (electrons)||175|
|Signal from one
12 keV photon (electrons)
temperature (deg C)
with external water chiller|
|Readout time (sec)
readout and acquisition)|
||20 wide x 18 high
x 10 thick|
|Detector to PC
||1 GigE Ethernet
interface using TCP/IP|
|PC Computer system
||8 Gybyte Intel
system using Windows 7|
Front view of system Rear view of system