The general guidelines for the design of the full-field microtomography setup focus on modularity and flexibility of use in the sample manipulation and detection system. The ability to perform in situ studies of materials processes under particular environments requires temporal resolution down to 1 s or better for a single tomography scan. Having flexibility to study different sample sizes or regions of interest within the same sample, with different spatial resolution, requires similar flexibility in the configuration of the detection system for changing the field-of-view and pixel size in an efficient manner. Details of the setup for full-field microtomography in terms of the specific equipment are listed below.
ForMAX is equipped with a high-resolution full-field microtomography detection system consisting of two main components, an optical microscope and a sCMOS camera (detector). The X-ray image formed by the transmission (and refraction) of the X-ray beam through the sample is converted by a scintillator into visible light. This visible light image is then magnified by the optical microscope. The magnified image is recorded digitally by a high sensitivity visible light sCMOS camera.
The ForMAX endstation features a high-resolution white-beam optical microscope from Optique Peter, with a triple objective lens configuration allowing the selection of three different magnifications by motorised switching of the objective heads. The microscope can accommodate 2X, 5X, 7.5X, 10X and 20X magnification objectives, as listed in the table below together with details of field-of-view and effective pixel sizes. These are calculated for the Andor Zyla 5.5 camera with a pixel size of 6.5 µm.
|Magnification||Field-of-view (h x v, mm2)||Pixel size (µm2)|
|2X *||8.3 x 7.0||3.25 x 3.25|
|5X *||3.3 x 2.8||1.30 x 1.30|
|7.5X *||2.2 x 1.9||0.87 x 0.87|
|10X||1.7 x 1.4||0.65 x 0.65|
|20X||0.8 x 0.7||0.33 x 0.33|
* Note: The field-of-view given by these objective magnifications will be achieved with the installation of compound refractive lenses for producing a larger beam at the sample position.
Two different sCMOS cameras are available for use at ForMAX, the Andor Zyla 5.5 and the Hamamatsu ORCA Lightning. Both cameras are coupled to the optical microscope via a dual camera port configuration, allowing the selection of either camera by motorised switching of the camera port. The choice of camera depends principally on the requirements of the experiment in terms of the desired field-of-view and the achievable pixel size, in relation to the objective magnification, and acquisition speed. The principal specifications of each camera are as follows:
|Camera||Andor Zyla 5.5||Hamamatsu ORCA Lightning|
|Number of pixels||5.5M||12M|
|Sensor size (h x v)||2560 x 2160 pixels||4608 x 2592 pixels|
|Pixel size (h x v)||6.5 x 6.5 µm2||5.5 x 5.5 µm2|
|Maximum frame rate (full frame)||75 Hz @ 16-bit; 100 Hz @ 12-bit||30 Hz @ 16-bit; 121 Hz @ 12-bit|
ForMAX is equipped with a modular configuration of sample stages from LAB Motion Systems, consisting of the following specific stages from top to bottom in the stack:
- 2-axis horizontal (X–Z) sample alignment stage (+/- 6 mm translation range for each axis)
- Air bearing rotary stage, model RT150ST (maximum rotation speed: 725 rpm; maximum load capacity: 43 kg)
- Slip ring, to pass through power and electrical control signals from stages mounted on top of the rotary stage
- Rotary union module
- Vertical (Y) stage, model 5103.A20-40 from Huber (+/- 20 mm translation range)
- Linear (Z) stage, from Föhrenbach (375 mm full travel range)
Fluid slip ring
The rotary union module of the sample stage configuration allows passage of fluids (gases, liquids, dispersions) through the rotary axes to the sample environment on top.