ERDAS

Forward recoil spectrometry (FRS) [33], also known as elastic recoil detection analysis (ERDA), is fiindamentally the same as RBS with the incident ion hitting the nucleus of one of the atoms in the sample in an elastic collision. In this case, however, the recoiling nucleus is detected, not the scattered incident ion. RBS and FRS are near-perfect complementary teclmiques, with RBS sensitive to high-Z elements, especially in the presence of low-Z elements. In contrast, FRS is sensitive to light elements and is used routinely in the detection of Ft at sensitivities not attainable with other techniques [M]- As the teclmique is also based on an incoming ion that is slowed down on its inward path and an outgoing nucleus that is slowed down in a similar fashion, depth infonuation is obtained for the elements detected. 

Sweeney R J, Prozesky V M, Churms C L, Padayaohee J and Springhorn K 1998 Appiioation of a A E-E teiesoope for sensitive ERDA measurement of hydrogen Nucl. Instrum. Methods B 136-138 685... 

Behrisoh R, Prozesky V M, Huber H and Assmann W 1996 Hydrogen desorption induoed by heavy-ions during surfaoe anaiysis with ERDA Nucl. Instrum. Methods B 118 262... 

R. H. Essenhigh, "Energy Use, Efficiency, and Conservation in Industry," Proceedings of the EPA/ERDA Symposium on Environment and Energy Conservation, Denver, Colo., Nov. 1975, EPA-600/2-76-212, ERDA-47. 

T. W. Newton, The Kinetics of the Oxidation Reduction Reactions of Uranium, Neptunium, Plutonium, andMmericium inMqueous Solution, TlD-26506, U.S. Energy, Research, and Development Administration (ERDA) Technical Information Center, Washington, D.C., 1975. 

S. N. Rea, Texas Instruments Incorporated Monthly Technical Progress Report, No. 03-76-31, ERDA/JPL 954475-76-11, Texas Instmments, Dallas, May 1976. 

A National Plan for Energy Research, Development, and Demonstration Creating Energy Choicesfor the Future, Vol. 1 ERDA, (1976). 

Engineering, McGraw-Hill, New York, 1955. Standiford, Chem. Eng., 70, 158-176 (Dec. 9, 1963). Testing Frocedure for Evaporators, American Institute of Chemical Engineers, 1979. Upgrading Evaporators to Reduce Energy Consumption, ERDA Technical Information Center, Oak Ridge, Tenn., 1977. 

Biirchsted et al.. Nuclear Air Cleaning Handbook, ERDA 76-21, Oak Ridge, Term., 1976. 

ERDA, Study on feasibility of upgrading the operating temperature of A1 busbars without plating . 

A, A , A ESD ESDIAD SIMS SNMS GDMS FARMS RBS LEIS ERDA NRA ... 

ERDA, like RBS, is based on the following physical concepts ... 

In ERDA, different regimes have been developed with a broad range of projectiles and energies, which can roughly be separated into three groups ... 

The sensitivity and depth resolution of ERDA depend on the type of projectile, on the type of particle, and on energy measurement. Because of the broad range of particles and methods used, general statements about sensitivity and depth resolution are hardly possible. Recent reviews of ERDA techniques are available [3.152-3.154]. 

For atomic masses M2 4 Mj the recoil cross-section is almost independent of the atomic number, because the cross-section becomes proportional to (Z2/M2) and the ratio Z2/M2 is close to 0.5 for all elements. ERDA with heavy projectiles thus has the advantage of almost constant sensitivity for all elements. Only for hydrogen the ratio Z2/M2 is equal to 1, hence the intensity of hydrogen recoils is enhanced by roughly a factor of four. 

For quantitative evaluation of ERDA energy spectra considerable deviations of recoil cross-sections from the Rutherford cross-section (Eq. 3.51) must be taken into account. Light projectiles with high energy can penetrate the Coulomb barrier of the recoil atom the nuclear interaction generally leads to a cross-section that is larger than ctr, see Eq. (3.51). For example, the H recoil cross-section for MeV He projec-... 

For ERDA arrangements using high-energy heavy projectiles, mainly gas telescope detectors, are used for AF and F measurements [3.153, 3.165, 3.166]. In an ionization... 

Reasonable estimates of ultimate sensitivity and depth resolution in ERDA can hardly be given because of the large range of projectiles and energies (from He ions of several MeV up to 200-MeV Au ions), and the use of different detection systems. In addition, stability of the sample under irradiation (which, of course, depends on the target material) is also important in the discussion of sensitivity and detection limits. The sensitivity is mainly determined by the recoil cross-section, the solid an-... 

The depth resolution of ERDA is mainly determined by the energy resolution of the detector system, the scattering geometry, and the type of projectiles and recoils. The depth resolution also depends on the depth analyzed, because of energy straggling and multiple scattering. The relative importance of different contributions to the depth resolution were studied for some specific ERDA arrangements [3.161, 3.163]. 

As a second example, results from a TOP ERDA measurement for a multi-element sample are shown in Fig. 3.65 [3.171]. The sample consists of different metal-metal oxide layers on a boron silicate glass. The projectiles are 120-MeV Kr ions. It can be seen that many different recoil ions can be separated from the most intense line, produced by the scattered projectiles. Figure 3.66 shows the energy spectra for O and Al recoils calculated from the measured TOF spectra, together with simulated spectra using the SIMNRA code. The concentration and thickness of the O and Al layers are obtained from the simulations. 

Because the cross-sections for nuclear reaction are usually lower than the cross-sections for elastic scattering of projectiles used in RBS or in elastic recoil detection analysis (ERDA), higher currents must be used to obtain comparably high intensity in... 

NRA as in RBS or ERDA, and possible modification of the target composition as a result of irradiation must be considered. Nuclear reaction cross-sections are also usually not available in analytical form for direct evaluation of measured data. Concentrations are, therefore, often obtained by comparison of the measured data with results from standard samples of known concentration. 

Eor a non-resonant nuclear reaction with emission of an ion, a depth scale can be obtained from the measured energy of the emitted ions. If ions emitted from a depth x are lower in energy by AE than ions emitted from the surface, a relationship between AE and x can be found, similarly to RBS and ERDA analysis ... 

---