Event by event energy sensitive imaging with TimePix pixel detector and its application for gamma photon tracking

The semiconductor pixel detector TimePix is a newly developed successor of the Medipix2 device. Each TimePix pixel is provided with a preamplifier, a discriminator and a counter. Each counter can be configured to work in one of three principal operation modes: 1. counting of detected particles; 2. measurement of particle energy; 3. measurement of time of interaction. All these features can be advantageously exploited in the field of medical and material sensitive imaging using various radiographic techniques. Regardless of the high performance of the TimePix device, its quality suffers from the charge sharing effect which derogates the detector’s energy sensitivity and decreases its spatial resolution. Nevertheless, it has been already demonstrated that the influence of this effect can be not only effectively suppressed but even utilized to gain more complex information from the measurement. The technique consists in the independent processing of each event of particle detection separately (event-by-event mode). The TimePix device can be operated in triggered mode and, moreover, it can also generate the trigger (using so called back-side pulse). All these features allow the construction of an enhanced multilayered Compton Gamma Camera with very high detection efficiency of about 10% which is several orders of magnitude higher than the efficiency of collimator (pin hole) based systems. Such camera has great applicability in the fields of nuclear medicine (SPECT) and homeland security. This article presents in its introduction a summary of experimental results verifying the potential of the TimePix device operated in event-by-event mode applied in several imaging techniques (material sensitive X-ray transmission radiography, X-ray fluorescence imaging). In the second part, a proposal of a new multilayered Compton Gamma Camera (Tracker) will be showed together with its Monte-Carlo simulations as well as results of preliminary experiments verifying its functiona- - lity.