mechanically support

So, to make it short I'm working on implementing a food control device. whether they are contaminated or not. (see Attachment).
Within the device (rack) there are: racket rays tube, a Detector reader (Amptek) and a laser that indicates the presence of food (Libelle), so as a result, give way to the tube to shoot rays that are then read from detector.
The position taken by the tube and the final one is fixed. while the angle will vary for the detector.
for the laser the position you see in the step file is the definitive one. its surface will be at the level of the top floor surface
How do you suggest me mechanically fix them?