Laboratory Studies of Thermal Energy Charge Transfer of Silicon and Iron Ions in Astrophysical Plasmas

The laser ablation/ion storage facility at the UNLV Physics Department is dedicated to the study of atomic processes in low temperature plasmas. Our current program is directed to the study of charge transfer of multiply charged ions and neutrals that are of importance to astrophysics at energies less than 1 eV (about 10(exp 4) K). Specifically, we measure the charge transfer rate coefficient of ions such as N(2+), Si(3+), Si(3+), with helium and Fe(2+) with molecular and atomic hydrogen. All these ions are found in a variety of astrophysical plasmas. Their electron transfer reactions with neutral atoms can affect the ionization equilibrium of the plasma

Laboratory Studies of Thermal Energy Charge Transfer of Silicon and Iron Ions in Astrophysical Plasmas

Charge transfer at electron-volt energies between multiply charged atomic ions and neutral atoms and molecules is of considerable importance in astrophysics, plasma physics, and in particular, fusion plasmas. In the year covered by this report, several major tasks were completed. These include: (1) the re-calibration of the ion gauge to measure the absolute particle densities of H2, He, N2, and CO for our current measurements; (2) the analysis of data for charge transfer reactions of N(exp 2 plus) ion and He, H2, N2, and CO; (3) measurement and data analysis of the charge transfer reaction of (Fe(exp 2 plus) ion and H2; (4) charge transfer measurement of Fe(exp 2 plus) ion and H2; and (5) redesign and modification of the ion detection and data acquisition system for the low energy beam facility (reflection time of flight mass spectrometer) dedicated to the study of state select charge transfer

Charge Transfer Between Ground-State N(2+) and H2, N2, and CO at Electron-Volt Energies

The charge-transfer rate coefficients for reactions of N(2+)(2 S(sup 2)2p(sup 2)P(sup 0)) with H2, N2, and CO are measured using ion storage. A cylindrical rf ion trap was used to store N(2+) ions produced by laser ablation of a solid titanium nitride target. The rate coefficients were derived from the decay rate of the ion signal. The rate coefficients for the above three reactions are 3.38(0.35) x 10(exp -11)sq sm/s at T(sub equiv.)=2.9 x 10(exp 3) K, 2.10(0.18) x 10(exp -9)sq sm/s at T(sub equiv.) = 1.3 x 10(exp 4) K, and 3.37(0.29) x 10(exp -9)sq cm/s at T(sub equiv.) = 1.3 x 10(exp 4) K, respectively. No theoretical or other experimental values are available at this energy range

Measurement of Charge Transfer Rate Coefficient Between Ground-State N(2+) Ion and He at Electron-Volt Energies

The charge transfer rate coefficient for the reaction N(2+)(2p(sup 2)P(sup 0)) + He yields products is measured by recording the time dependence of the N(2+) ions stored in an ion trap. A cylindrical radio-frequency ion trap was used to store N(2+) ions produced by laser ablation of a solid titanium nitride target. The decay of the ion signals was analyzed by single exponential least-squares fits to the data. The measured rate coefficient is 8.67(0.76) x 10(exp -11)sq cm/s. The N(2+) ions were at a mean energy of 2.7 eV while He gas was at room temperature, corresponding to an equivalent temperature of 3.9 x 10(exp 3) K. The measured value is in good agreement with a recent calculation

Experimental determination of the stable boundary for a cylindrical ion trap

The first radio frequency (rf) quadrupole ion traps were designed with hyperbolic trapping electrodes and had the advantage of a working theoretical model with an analytical solution for the equation of motion for an ion. This came at the cost of a difficult fabrication process by the nature of the hyperbolic design. Cylindrical designs were found to be an easily constructed and functional alternative for ion trapping, but a sound theoretical model for this geometry has yet to emerge. While the hyperbolic theory yields approximate parameters for stable ion trapping, experiments conducted near the stable/unstable boundary require an experimental determination of this boundary

Real-Time Image Processing Using A Self-Pumped Phase Conjugate Mirror

Real-time 'exclusive or' operation obtained with an interferometer using a self-pumped phase conjugate mirror is reported. Also, results of image subtraction, intensity inversion and image differentiation are shown. Methods of extending the operation to higher order differentiation and of obtaining the Laplacian are discussed

Optimization of MVAC systems for energy management by evolutionary algorithm

Energy management in existing building services installations is an essential focus of contemporary facilities management. The subway company that is one of the major utilities services in Hong Kong Special Administrative Region (HKSAR) has considered better energy management schemes in its subway stations to reduce the running cost. In the past few years, in order to achieve energy saving in the stations, some feasible measures in the Mechanical Ventilation and Air Conditioning (MVAC) systems were implemented, however the engineering decisions were supported by the trial-and-error or imprecise estimation. Improvement to this process would be possible if numerical optimization methods were to be used. Evolutionary algorithm coupled with external plant simulation programme was applied to determine the optimum conditions of the essential parameters of the MVAC systems, in order to provide a holistic energy management approach. For the centralized MVAC systems of the 5 subway stations under studies, the developed optimization and simulation model was found useful to appraise the energy management opportunities for effective design and facilities management

Measurement of Thermal-Energy Charge-Transfer Rate Coefficient of Mo6+ and Argon

The charge-transfer rate coefficient of Mo6+ and argon has been measured at mean ion energies of 8.8 and 1.4 eV using a laser-ablation ion source and an ion trap. The rate coefficient deduced from these measurements is 1.02(0.10)×10-10 cm3 s-1 and appears to be independent of the mean ion energy at this energy range. However, the measured value is an order of magnitude smaller than the Langevin rate coefficient

Fully-Passive Quantum Key Distribution

Passive implementations of quantum key distribution (QKD) sources are highly desirable as they eliminate side-channels that active modulators might introduce. Up till now, passive decoy-state and passive encoding BB84 schemes have both been proposed. Nonetheless, passive decoy-state generation and passive encoding have never been simultaneously implemented with linear optical elements before, which greatly limits the practicality of such passive QKD schemes. In this work, we overcome this limitation and propose a fully-passive QKD source with linear optics that eliminates active modulators for both decoy-state choice and encoding. This allows for highly practical QKD systems that avoid side-channels from the source modulators. The passive source we propose (combined with the decoy-state analysis) can create any arbitrary state on a qubit system and is protocol-independent. That is, it can be used for various protocols such as BB84, reference-frame-independent QKD, or the six-state protocol. It can also in principle be combined with e.g. measurement-device-independent QKD, to build a system without side-channels in either detectors or modulators