Imaging

The two primary techniques used on IMBL are planar radiography and computed tomography.

Imaging can be performed using a monochromatic or polychromatic x-ray beam. The poly chromatic beam is used in situations which require high photon energies, above the upper limit of the monochromator.

Typical maximum beam sizes are: 50 mm wide by ~3 mm high in hutch 2B, and 300 mm wide by 30 mm high in hutch 3B. We have recently integrated a beam expander which will increase the height of the beam in 3B to 80 mm over a limited range of energies. Further information on this is available on request.

The beamline was designed for large scale imaging, where samples are several centimetres cubed. The maximum spatial resolution achievable is ~10 microns FWHM PSF. Detector pixel sizes are described below. The smallest available is 6 microns, with 100 microns and higher available on the flat panel detectors.

Detectors

The IMBL beamline employs several imaging detectors. The choice is made depending on: spatial resolution required, sensitivity, and speed.

Ruby

Our workhorse imaging detector is nicknamed Ruby. It uses a PCO.edge optical sensor with a high speed CameraLink interface to a readout computer, to capture images of an x-ray phosphor plates, through a zoom lens system.
The full image size from the sensor is 2560 by 2160 pixels. An image pixel size can be set from 6.5 microns to 50 microns with a commensurate change in the field of view (16.6 mm x 14.0 mm, 128 mm x 108 mm).
The fastest full frame rate is 100 fps (10 msecs per frame). However, the frame rate can be increased by reducing the number of pixels that are read out. For instance, an image of only 1280 x 1024 pixels will read out at 212 fps.

Xineos

For capturing larger images, we use a Teledyne Dalsa Xineos flat panel detector This uses an array of photodiodes to detect scintillation from a thick CsI plate. The array and the plate are directly coupled so the image pixel size is fixed at 99 microns. An array of 2994 x 2997 pixels provides almost 30 cm x 30 cm of active area. Full frame readout rate uses a progressive scan at 30 fps (33 msec per frame)

Spectrum Logic 1410

The proximity coupled detectors are higher sensitivity than Ruby. For dose sensitive collections using smaller images with a finer image pixel size, we use a Spectrum Logic 1410 flat panel detector. Like the Xineos it uses an array of CMOS integrated photodetectors coupled to a thin CsI plate. The pixel size is fixed at 50 microns in an array of 2802 x 2400. This provides an active area of 14 x 12 cm.

Dectris Eiger2 3MW

For low dose medical imaging we use a photon counting detector with a 750 micron CdTe converter. This provides optimum efficiency at typical radiography energies. The sensitive area is 233 mm x 80 mm sampled with 75 micron pixels (3110 x 1064). The maximum full frame readout rate is 200 fps.

Notes on our detectors

The limitations on the active area of the detector is not a limit to the collected image size. Our experiment control system can automatically patch and stitch images to provide very large fields of view.
All detectors are read out using EPICS Area Detector software. This provides an abstracted detector interface which can be controlled through custom made graphical interfaces and experiment control software.