A broad beam describes a radiation shielding situation in which the beam impinging on a barrier surface is laterally extensive including scattered radiation.

A calibration is a correction procedure that determines the relationship between the measured output of a system and the reference standard. Calibration procedures include scanning air or an appropriate test phantom.
The calibration of a CT system takes account of variations in beam intensity or detector efficiency in order to achieve best homogeneity within the field of view and the accuracy of CT numbers.

See also Calibration Factor and Acceptance Checking.

A computed tomography (CT) scanner is used to create cross-sectional slices of different objects. The medical version of CT system scans the human body for tumors or other abnormalities, other versions are used for non-destructive testing in the industry.
The CT imaging system includes the moveable gantry and patient table or couch. The gantry is a frame that contains the x-ray source, collimators, filters, detectors, a data acquisition system (DAS), rotational components including slip ring systems and all associated electronics. The x-ray tube and detector system are mounted opposite each other, allowing a rapid and synchronous rotation around the patient table.
In older CT scanners a small generator supplied power to the x-ray tube and the rotational components via cables for operation. Up to the 4th generation the CT tube and detectors rotate together around the patient for each slice. CT systems with slip ring technology (the x-ray tube rotates around a stationary ring of detectors) operate without cables and provides continuous rotation of the gantry components without interference of cables. Spiral CT scanners work with a continuous table movement while the x-ray tube is rotating around the patient.

Overview about CT scanner generations:
See also Contrast Media Injector, Dual-Head CT Power Injector, Syringeless CT Power Injector.

A sample is placed into a concentrated beam of neutrons. Through neutron-capture heavier nuclei become frequently unstable. This artificial radiation decays with a characteristic half-live consisting of alpha- and beta-particles and gamma-rays.

See Neutron Activation Analysis

Air KERMA (Kinetic Energy Released per unit MAss of air) measures the amount of radiation energy in air, unit is J/kg. This include the initial kinetic energy of the primary ionizing particles such as photoelectrons, Compton electrons, positron//negatron pairs from photon radiation, and scattered nuclei from fast neutrons, when for example air is irradiated by an x-ray beam. J/kg (gray) is also the unit of the radiation quantity 'Absorbed Dose'.