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Nuclear Pumping of the Atomic Carbon Laser
Prelas, Mark Antonio
Department of Study
Degree Granting Institution
University of Illinois at Urbana-Champaign
Experiments which led to the discovery of five new nuclear pumped laser systems and the kinetic modeling of one of these systems were accomplished in this study. (Energy was derived from the n(,th) + 10(,B) (--->) (alpha) + ('7)Li + 2.35 MeV reaction). The five systems oscillated upon the same transition of atomic carbon: C(3p ('1)P(,1))(--->)C(3s ('1)P(,1) ) + 1.454 (mu)m. However, the systems utilized 5 types of mixtures to achieve lasing; He + CO, He + CO(,2), Ne + CO, Ne + CO(,2), and Ar + CO(,2).
Several unique features were evident in the atomic carbon nuclear pumped laser (NPL) systems. First, the systems required an extremely low power deposition in comparison to their electrically pumped laser (EPLs) counterpart: He + CO, CO(,2) - NPL (TURN)1.0 W/cm('3), EPL (TURN)90 W/cm('3)-, Ne + CO, CO(,2) - NPL (TURN)9.0 W/cm('3), EPL (TURN)900 W/cm('3). Secondly, the Ar + CO(,2) system oscillated with the nuclear pumping source but had not oscillated with the electrical pumping source. Finally, delays between the laser signal and the excitation pulse (i.e., thermal neutron pulse from the U of Ill TRIGA reactor) of up to 5 ms were observed.
The delays were evident only in mixtures which required multiple stops to populate the upper laser level (ULL). Since the main method of transferring energy to the carbon donor species (e.g., CO and CO(,2)) in the NPL is through the rare gas metastable, the delay was observed only in mixtures where the metastable energy was insufficient to dissociate the carbon donor and directly populate the ULL (He + CO(,2), Ne + CO, Ne + CO(,2) and Ar + CO(,2)).
A theoretical and experimental program was undertaken to demonstrate the cause of the delays observed in the He + CO(,2) system. It was found that recombination was not a dominant mechanism by observing both cascading transitions to the ULL and the laser. Thus a direct method of populating the ULL, such as that shown to be dominant in the atomic carbon EPL with mixtures of He + CO in previous studies, occurs:
He* + CO (--->) C(3p ('1)P(,1)) + 0 + He
The delay in He + CO(,2) mixtures was determined to be caused by a series of slow processes and long lived states which eventually lead to the production of CO: