Publications

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Lasing on the D1 transition (62P1/2 → 62S1/2) of cesium can be reached in both diode and excimer pumped alkali lasers. The first uses D2 transition (62S1/2 → 62P3/2) for pumping, whereas the second is pumped by photoexcitation of ground state Cs-Ar collisional pairs and subsequent dissociation of diatomic, electronically-excited CsAr molecules (excimers). Despite lasing on the same D1 transition, di erences in pumping schemes enables chemical pathways and characteristic timescales unique for each system. We investigate unavoidable plasma formation during operation of both systems side by side in Ar/C2H6/Cs.

Abstract not provided.

The excimer-pumped alkali laser (XPAL) system has recently been demonstrated in several different mixtures of alkali vapor and rare gas. Without special preventive measures, plasma formation during operation of XPAL is unavoidable. Recent advancements in the availability of reliable data for electron impact collisions with atoms and molecules have enabled development of a complete reaction mechanism to investigate XPAL-induced plasmas. We report on pathways leading to plasma formation in an Ar∕C2H6∕Cs XPAL sustained at different cell temperatures. We find that depending on the operating conditions, the contribution of electron impact processes can be as little as bringing the excitation of Cs(2P) states to higher level Cs states, and can be as high as bringing Cs(2P) excited states to a full ionization. Increasing the input pumping power or cell temperature, or decreasing the C2H6 mole fraction leads to electron impact processes dominating in plasma formation over the energy pooling mechanisms previously reported in literature.

Abstract not provided.

This report is an outcome of the ASC ATDM Level 2 Milestone 6015: Asynchronous Many-Task Software Stack Demonstration. It comprises a summary and in depth analysis of DARMA and a DARMA-compliant Asynchronous Many-Task (AMT) runtime software stack. Herein performance and productivity of the over- all approach are assessed on benchmarks and proxy applications representative of the Sandia ATDM applications. As part of the effort to assess the perceived strengths and weaknesses of AMT models compared to more traditional methods, experiments were performed on ATS-1 (Advanced Technology Systems) test bed machines and Trinity. In addition to productivity and performance assessments, this report includes findings on the generality of DARMAs backend API as well as findings on interoperability with node- level and network-level system libraries. Together, this information provides a clear understanding of the strengths and limitations of the DARMA approach in the context of Sandias ATDM codes, to guide our future research and development in this area.

Abstract not provided.

Atomic microsystems have the potential of providing extremely accurate measurements of timing and acceleration. However, atomic microsystems require active maintenance of ultrahigh vacuum in order to have reasonable operating lifetimes and are particularly sensitive to magnetic fields that are used to trap electrons in traditional sputter ion pumps. This paper presents an approach to trapping electrons without the use of magnetic fields, using radio frequency (RF) fields established between two perforated electrodes. The challenges associated with this magnet-less approach, as well as the miniaturization of the structure, are addressed. These include, for example, the transfer of large voltage (100-200 V) RF power to capacitive loads presented by the structure. The electron trapping module (ETM) described here uses eight electrode elements to confine and measure electrons injected by an electron beam, within an active trap volume of 0.7 cm3. The operating RF frequency is 143.6 MHz, which is the measured series resonant frequency between the two RF electrodes. It was found experimentally that the steady state electrode potentials on electrodes near the trap became more negative after applying a range of RF power levels (up to 0.15 W through the ETM), indicating electron densities of ≈3 × 105cm-3 near the walls of the trap. The observed results align well with predicted electron densities from analytical and numerical models. The peak electron density within the trap is estimated as ∼1000 times the electron density in the electron beam as it exits the electron gun. This successful demonstration of the RF electron trapping concept addresses critical challenges in the development of miniaturized magnet-less ion pumps.

Abstract not provided.

Abstract not provided.

Abstract not provided.