ABSTRACT
Nuclear weapons generate massive amounts of radiation as neutrons, gamma rays, X-rays, visible light and infrared. The resulting radiation doses can cause sickness or death in hours to months. X-rays are classified as an ionizing radiation; the photon energy is sufficient to ionize atoms and disrupt molecular bonds, and therefore is harmful to living tissue at high doses. Detection of the nuclear materials needs to overcome potential attenuation and shielding effects. Various techniques for X-rays, gamma rays and neutrons are being utilized in the security applications. The pitch of X-ray and gamma-ray imaging systems currently ranges from about 100 um to 1 mm. For small pixel pitches bump bonding is used to connect the detector pixels to the application specific integrated circuits. Conventional X-ray radiograph, double-energy and color X-ray techniques provide a two-dimensional view of the object under investigation. A three-dimensional view can be obtained using Computed Tomography approach.
