No description available.

No description available.

A new technique is presented for measuring the spatial and momentum distributions of a buffer-gas cooled ion cloud in a Paul trap by extracting it from the trap and fitting the time profile of the extracted ion signal. A thermodynamic model based on the Gibbs distribution has been developed which describes the initial ion cloud phase space volume and fits the measured time distributions of the extracted cloud using only one parameter: temperature. A time-of-flight system has been built to systematically vary the ion extraction conditions and compare predictions of the model to various measurements of the ion cloud time profile. A new numerical method using a multipole expansion was developed to compute the extraction fields. Agreement between the ion simulations and the time-of-flight data is better than 2% of the total flight time. / Ion cloud temperatures were measured for seven different trap loadings of potassium ions and four loadings of sodium ions, in both cases down to clouds of about 1000 ions. This is the first time that temperature measurements have been made for such small numbers of buffer-gas cooled ions. The results show that the temperature of the ions above the buffer gas temperature appears to be proportional to the two-thirds power of the number of ions in the cloud. / Dynamic manipulation of the extracted ion cloud phase space volume was also accomplished using a time-varying acceleration voltage to change the ion cloud energy spread in flight. / A concept is also outlined to measure the detailed phase space area of the extracted cloud using the projection-slice theorem of tomographic imaging. / These measurements have applications for the use of ion traps as beam collectors for nuclear physics experiments at isotope separator facilities and possibly for nano-circuit fabrication.

A system for mass-selective capture of ions by a Paul trap was designed and tested. / An Paul trap and associated electronics have been assembled and tested, selectively trapping the ionic clusters C$ sp{+} sb2$ and C$ sp{+} sb3$ from a pulsed laser ion source. The ions were injected at 90 eV, trapped, extracted and detected, several parameters related to these processes were investigated. Simple models of the injection mechanism employed and for evaluating the pseudo-potential well depth of the ion trap are proposed. The overall efficiency of the ion injection system has been evaluated and compared to other methods of ion capture by an RFQ trap from an external source.

The buffer gas cooling process and the properties of the cooled beam in a novel rf quadrupole ion beam guide with axial field was studied. The operation principle of the axial field quadrupole ion beam guide is similar to the quadrupole mass filter operating in AC only mode but the rods were segmented and differential DC biases were applied to produce the axial field. It was operated in buffer gas. / A Monte Carlo simulation was developed and the simulation results were compared with the experimental results. The beam distribution in a thermal equilibrium was assumed as the thermal equilibrium distribution in a simple harmonic motion with rf distortion and the assumption was confirmed by the Monte Carlo simulation. / The temperature of the cooled beam was measured with a beam profile, measurement system which consists of a miniature quadrupole ion beam guide aid a rotating semi-circular Faraday plate. The temperature of the cooled beam was measured to be 0.0424 +/- 0.0026 eV in the experiment while that of the simulated beam was 0.0372 +/- 0.0009 eV. The variation of beam temperature with beam current was 0.0153 +/- 0.0026 eV/nA. The maximum achieved ion transmission was 80%. The transmitted ion beam's energy spread was measured with a retarding potential energy analyzer to be less than 0.1 eV. The cooling time was 0.7 ms with 1V/ cm axial field and was observed to be very dependent on the ion current when there was no axial field.

Here a temperature stable optical fiber current sensor based on the Sagnac loop interferometer and a cavity formed from two Faraday rotation mirrors is developed and tested. To the best of the author's knowledge a cavity composed of two Faraday rotation mirrors has never been used for the measurement of alternating currents. For the first time, it is shown that the maximum Faraday rotation angle for a long, static optical fiber is input polarization insensitive. Also, linear birefringence is shown to quench this angle in long optical fiber. The polarization dynamics in an optical ground wire network, for a summer period and a fall period, are reported for the first time. The highest-speed polarization changes are attributed to the high-voltage power line, i.e., the electrical current. A novel spectral analysis polarization optical time domain reflectometry method, that uses an induced birefringent event, is shown to work in long optical fiber.

Abstract not available.

Weakly electric fish use a unique sensory modality in order to help them communicate, navigate and find prey. These fish emit electric discharges that are monitored by electroreceptors located in the fish's skin. Surrounding objects perturb these baseline transdermal potentials and create electric images. The study of these images has led to a better understanding of general sensory processing principles; however, many aspects of these fish's natural electrosensory environment remain unknown. To this end, a two-dimensional finite element model of Apteronotus leptorhynchus was created. Using this model, we suggest new ways by which electric fish are able to locate objects and propose that it is possible for these fish to extract useful information from their environment using their natural scanning behaviour. Our results also reveal important limitations in standard experimental paradigms that aim to mimic the effects of conspecifics. Alternative paradigms that will enable more realistic stimulation are suggested.

No description available.

No description available.