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Low energy sputtering of cobalt by cesium ions

An experimental facility to investigate low energy (less than 500 eV) sputtering of metal surfaces with ions produced by an ion gun is described. Results are reported on the sputtering yield of cobalt by cesium ions in the 100 to 500 eV energy range at a pressure of 1 times 10(exp -6) Torr. The target was electroplated on a copper substrate. The sputtered atoms were collected on a cobalt foil surrounding the target. Co-57 was used as a tracer to determine the sputtering yield.

Handoo, A.

Demonstration of closed shell breeding of cesium ions with an electron beam ion source

An electron beam ion source serves as a charge breeder for the Californium Rare Isotope Breeder Upgrade (CARIBU) at the Argonne Tandem Linac Accelerator System (ATLAS). The source accepts radioactive beams of 1+ or 2+ ions and raises their charge state for post-acceleration by ATLAS. The efficiency of this process impacts the length of each experiment and, hence, the type and number of experiments that can be run in each program cycle. Recent efforts to improve the charge breeding efficiency for the 80 < A < 160 species typical of CARIBU have focused on utilizing the closed shell breeding technique. Here, with this technique, the electron beam energy is manipulated to take advantage of the large gap in ionization energies at shell closures and selectively populate a single charge state. Charge breeding studies with stable cesium ions have demonstrated an absolute efficiency of 72% for Cs 27+ and a total efficiency of 93%. The Cs 27+ efficiency result represents a factor of 3 improvement over the previous best charge breeding result of 23% for Cs 27+ .

Vondrasek, R. [Argonne National Laboratory (ANL),

Investigations of negative and positive cesium ion species

A direct test is provided of the hypothesis of negative ion creation at the anode or collector of a diode operating under conditions simulating a cesium thermionic converter. The experimental technique involves using direct ion sampling through the collector electrode with mass analysis using a quadrupole mass analyzer. Similar measurements are undertaken on positive ions extracted through the emitter electrode. Measurements were made on a variety of gases including pure cesium, helium-cesium mixtures and cesium-hydrogen as well as cesium-xenon mixtures. The gas additive was used primarily to aid in understanding the negative ion formation processes. Measurements were conducted using emitter (cathode) temperatures up to about 1000 F. The major negative ion identified through the collector was Cs(-) with minor negative ion peaks tentatively identified as H(-), H2(-), H3(-), He(-) and a mass 66. Positive ions detected were believed to be Cs(+), Cs2(+) and Cs3(+).

Chanin, L. M.

Negative and positive cesium ion studies

Mass spectrometric analyses have been performed on the positive and negative species from discharges in Cs, He-Cs, and He-H2-Cs mixtures. Sampling was conducted through the electrodes of normal glow discharges and from close-spaced heated-cathode conditions, which approximate a cesium thermionic converter. No negative Cs ions were observed for Cs pressures less than .01 torr. Identified species included Cs(+), Cs2(+), Cs(-), and what appeared to be multiply charged ions. Low-mass negative and positive ions attributed to H2 were observed when an He-H2 mixture was also present in the discharge region.

Kuehn, D. G.

A study of environmental effects caused by cesium from ion thrusters

The ATS-F satellite will carry two cesium ion thrusters. Cesium is a material that is not present in the upper atmosphere, and there is concern that the introduction of this material may result in some unexpected behavior. A study has been conducted to assess the magnitude of the effects that are to be expected. No observable effects were found as a result of the study. Consideration was given to the origin and destination of the material and the various reactions that could occur. The origin was considered to be anywhere in space from altitudes of about 100 km upward. The probable short term destination is in the form of cesium ions trapped in the earth's magnetic field or as ions and atoms in the heterosphere. The maximum possible number of cesium atoms in the field of view of an earth based observer is of the order of one million per square centimeter, far too few to be observable by visible, near-visible, or radio-frequency means. Further, no phenomena could be found that would result in the occurance of an observable event.

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