Cesium ion sputter source

The measurements that have been made at Rochester and the experience that has been gathered over the years on the operation of sputter ion sources [38] indicate that an analytical tool of unprecedented sensitivity and accuracy for isotopic ratio determinations can be constructed by coupling SIMS technology with the new accelerator technique. The only difference in principle between the experiments that have been conducted to date and the technique as it would be applied in secondary ion mass spectrometry is that the primary beam of cesium would be focussed to a fine probe of pm dimensions rather than the spot diameters of approximately 1 mm that have been used to date. 

All carbon samples could easily be oxidized to C02, a form of the sample greatly preferred by most users, for many reasons. Neither the on-line or dedicated electrostatic accelerators under construction have succeeded in overcoming the problem of too much memory of C02 gas. Consequently, the sample presented to the cesium sputter beam source will probably have to be a solid. The cesium sputter source is the most likely to be used because it can produce negative ions of carbon in microampere beams. 

During the search for 36C1 at Rochester, 5-13 pA of Cl ions were produced from silver chloride in the cesium sputter source. The detection techniques were basically similar to those discussed for 14C. The samples and the results obtained are given in Table 2. 

R. Middleton, J. Klein, Production of metastable negative ions in a cesium sputter source Verification of the existence of N2 and CO. Phys. Rev. A 60, 3786-3799 (1999)... 

The detection sensitivity for carbon hydrogen the electronegative elements—F, Cl, O, S, etc.—and certain metals with low work functions (such as Au and Pt) is greatly enhanced by analyzing their negative secondary ions, sputtered by a Cs+ ion beam. Most cesium ion sources use heated metal to provide vapor to... 

SNICS (Source of Negative Ions hy Cesium Sputtering)... 

In this ion source the cesium atoms used to cause sputtering, are ionized in an inert-gas discharge. The cathode containing a small amount of the material whose beam is to be produced, is inserted in the chamber through the air lock. The ionized cesium then sputters the solid cathode material to produce negative ions. This ion-source is used to produce the negative ions of almost all the solid materials. 

The ion source produces a beam of ions from a few milligrams of solid material. The element is first chemically extracted from the sample (e.g., a rock, rain water, a meteorite) and then loaded into a sample holder and inserted into the ion source through a vacuum lock. Atoms are sputtered from the sample by cesium ions (using multicathode SNICS ion source), which are produced on a hot spherical ionizer and focused to a small spot on the sample. Negative ions produced on the surface of the sample are extracted from the ion source and sent down the evacuated beam-line toward the first magnet. At this point the beam current is about 10 pA (mostly due to the stable isotopes), which corresponds to 10 ions per second. 

In an analogous way to the measurement of the electronic absorption spectra of cations, those of anions can be obtained. A sputter source has been used to generate the pure carbon anions. In this, a graphite rod is bombarded with cesium ions. The carbon species are formed by sputtering and gas phase processes and the ions produced are extracted for mass-selection. Sufficient ion concentrations have been attained for the spectroscopic studies of carbon anions in the C4 to CJo range. The carbon species are unusual among anions in that they have large... 

---