is divided in two insulated halves, thus information of particle entrance position is derived from charges induced at the right and left halves. ERDA and energy detection of recoiled sample atoms ERDA in transmission geometry, where only the energy of the recoiling sample atoms is measured, was extensively used for contamination analysis of target foils for nuclear physics experiments. This technique is excellent for discerning different contaminants of foils used in sensitive experiments, such as carbon contamination. Using 127I ion beam, a profile of various elements can be obtained and the amount of contamination can be determined. High levels of carbon contamination could be associated with beam excursions on the support, such as a graphite support. This could be corrected by using a different support material. Using a Mo support, the carbon content could be reduced from 20-100 at.% to 1-2 at.% level of the oxygen contamination probably originating from residual gas components. For nuclear experiments, high carbon contamination would result in extremely high background and the experimental results would be skewed or less differentiable with the background. With ERDA and heavy ion projectiles, valuable information can be obtained on the light element content of thin foils even if only the energy of the recoils is measured. ERDA and particle identification Generally, the energy spectra of different recoil elements overlap due to finite sample thickness, therefore particle identification is necessary to separate the contributions of different elements. Common examples of analysis are thin films of TiNxOy-Cu and BaBiKO. TiNxOy-Cu films were developed at the University of Munich and are used as tandem solar absorbers. Figure 8 shows the various components to the film. The copper coating and the glass substrate was also identified. Not only is ERDA is also coupled to Rutherford backscattering spectrometry, which is a similar process to ERDA. Using a solid angle of 7.5 mrs, recoils can be detected for this specific analysis of TiNxOy-Cu. It is important when designing an experiment to always consider the geometry of the system as to achieve recoil detection. In this geometry and with Cu being the heaviest component of the sample, according to eq. 2, scattered projectiles could not reach the detector. To prevent pileup of signals from these recoiled ions, a limit of 500 Hz needed to be set on the count rate of ΔΕ pulses. This corresponded to beam currents of lass than 20 particle pA. Another example