Characterization of a gamma-backscattering imaging device.
N. González 1*, E. Fajardo 2, W. Blanco 1,2, F. Cristancho 1,2
1 Departamento de Física, Universidad Nacional de Colombia, Bogotá, Colombia.
2 Centro Internacional de Física, Bogotá, Colombia.
The gamma-ray backscattering technique is a nondestructive method for the location of buried materials in soil. It is based on the dependence of the number of backscattered photons with the electron density of the medium. To obtain images using this technique we use a device known as the Compton Camera [1,2], whose main parts are a 22Na source placed in a conical lead shielding and two geometrically opposing CsI detectors, one position-sensitive detector in charge of building the image and a backscattering detector in charge of triggering the recollection of data.
In order to evaluate the factors that affect the quality of images obtained with the Compton Camera we have performed experiments in which the electronic parameters like bias voltage and also geometric parameters such as camera-soil and camera-object distances were varied. Other set of experiments were carried out to determine the response of the Compton Camera to materials like water, sand, paraffin, paper, lead, polystyrene and air. We develope mathematical methods that strive to give a numerical value to the image quality and to the device’s capability of distinguishing different materials.
[1] J. Gerl, Nucl. Phys. A752 (2005), 688c.
[2] E.Fajardo et al. AIP Conf. Proc. 1265 (2010),449.