IMBL Detectors

There are two broad types of x-ray detector for our kind of work: Indirect detection involves converting the x-ray energy to optical photons, then detecting those with silicon based optical sensor arrays. In direct detection detectors the x-ray energy is directly converted to charge, which is then amplified and digitised under each pixel. IMBL has examples of both types.

Ruby

Our primary ‘work horse’ detector is the in-house designed Ruby imager. It uses a low noise scientific CMOS sensor to view optical light emission from a converter screen. The standard converter is a 25 micron thick Gadox powder (Gd2O2S:Tb), which emits light in the green part of the spectrum.

The sensor has 2560 horizontal by 2160 vertical pixels (5.5 MPix). The maximum frame rate is 100 fps (10 ms exposure).

Ruby can accept various lenses. The sensor to screen distance is variable allowing for a range of view fields. The finest resolution and smallest field of view is 16 mm by 14 mm, 6.3 micron pixels. With Ruby zoomed out it will view 110 mm horizontal by 93 mm vertical at 43 micron pixels.

Flat panel detectors

Indirect detectors which use the close proximity of a converter and the sensor are popular in clinical imaging. They provide moderate spatial resolution but very good efficiency. IMBL has two such devices. A Hamamatsu C10900D which has a 122 mm horizontal by 123 mm vertical field of view. The pixels are 100 microns. The full field frame rate is 35 fps with an ability to switch to a 122 mm horizontal by 7 mm vertical region readout at 70 fps.

The second flat panel is a Teledyne-Dalsa Xineos 3030HR. This has a large field of view (296 mm horizontal by 296 mm vertical) with 99 micron pixels. In this full field mode the readout speed is 31 fps. The Xineos can also be run with alternative regions. For instance a 148 mm horizontal by 148 mm vertical mode again with 99 micron pixels will readout at 57 fps.

Both these flat panel detectors use an amorphous silicon photodiode array to detect optical light from a CsI:Tl converter.

Direct conversion detectors

Only one direct conversion detector is in operation. This is a Dectris Eiger2 3MW, used for our clinical program. The sensitive array is made from 75 micron pixels, 3110 wide by 1064 high. Due to it’s critical use for clinical studies access to this detector is on request only.