Modeling and Reconstruction Strategy for Compton Scattering Tomography with Scintillation Crystals

The recent development of energy-resolved scintillation crystals opens the way to build novel imaging concepts based on the variable energy. Among them, Compton scattering tomography (CST) is one of the most ambitious concepts. Akin to Computerized Tomography (CT), it consists in probing the attenuation map of an object of interest using external ionizing sources but strives to exploit the scattered radiation as an imaging agent. For medical applications, the scattered radiation represents 70 to 80% when the energy of the source is larger than 100 keV and results from the Compton effect. This phenomenon stands for the collision of a photon with an electron and rules the change of course and loss of energy undergone by the photon. In this article, we propose a modeling for the scattered radiation assuming polychromatic sources such as 60Co and scintillation crystals such as LBC:Ce. Further, we design a general strategy for reconstructing the electron density of the target specimen. Our results are illustrated for toy objects.

‘Seeing with one's own eyes’ and speaking to the mind: a history of the Wilson cloud chamber in the teaching of physics

In 1911 the Wilson cloud chamber opened new possibilities for physics pedagogy. The instrument, which visualized particles’ tracks as trails of condensed vapour, was adopted by physicists to pursue frontier research on the Compton effect, the positron and the transmutation of atomic nuclei. But as the present paper will show, Wilson's instrument did not just open up new research opportunities, but the possibility of developing a different kind of teaching. Equipped with a powerful visualization tool, some physicists–teachers employed Wilson's instrument to introduce their students to a wide range of phenomena and concepts, ranging from the behaviour of clouds to Einstein's photon, the wave–particle duality and the understanding of the nucleus. This paper uses the notes, books and prototypes of these pioneering physicists–teachers to compose a pedagogical history of the Wilson cloud chamber, documenting an episode of immense ingenuity, creativity and scientific imagination.

Theoretical and Experimetal Hints to a Flux of Doppler-Transformation-Energies during processes with Energy Conservation

In a microscopic model of the photoelectric effect it becomes clear that the conservation of energy is exclusively determined by Doppler shift processes, i.e., the whole energy of the pho-ton vanishes by means of Doppler redshifts. Accordingly, if a photon is generated, the energy is won by Doppler blueshifts. This is supposed to be valid for all processes with energy con-servation. An experiment is carried out to make this Doppler energy flow visible by means of interactions with probes. The result of this experiment is that a weak force is measurable in the vicinity of processes with energy conservation. With the aid of a twisted rubber driven low-power device ( ), accelerations of about 10-6 m/s2 are measurable. In the close vicinity of the device, accelerations with values up to 10-3 m/s2 can be concluded. The conse-quences which result from this force are discussed. Keywords: Compton-Effect, Doppler-Effect, energy- momentum conservation, flywheel

Nonlinear dynamics of a charged particle in a strong non-null knot wave background

In this paper, we study the dynamics of a charged particle interacting with the non-null electromagnetic knot wave background. We analyze the classical system in the Hamilton–Jacobi formalism and find the action, the linear momentum and the trajectory of the particle. Also, we calculate the effective mass and the emitted radiation along the knot wave. Next, we quantize the system in the classical strong knot wave background by using the strong-field QED canonical formalism. We explicitly construct the Furry picture and calculate the Volkov solutions of the Dirac equation. As an application, we discuss the one-photon Compton effect where we determine the general form of the S-matrix. Also, we discuss in detail the first partial amplitudes in the transition matrix in two simple backgrounds and show that there is a pair of states for which these amplitudes are identical.