The detector solid angle has to be closed, but the thick sample can take more current without heating, which decreases sample degradation. Once the ion beam has ionized target sample atoms, the sample ions are recoiled toward the detector. The beam ions are scattered at an angle that does not permit them to reach the detector. The sample ions pass through an entrance window of the detector, and depending on the type of detector used, the signal is converted into a spectrum. In elastic recoil detection analysis, a silicon diode is the most common detector. This type of detector is commonly used, however, there are some major disadvantages when using this type of detector. For example, the energy resolution decreases significantly with a Si detector when detecting heavy recoiled ions. There is also a possibility of damage to the detector by radiation exposure. These detectors have a short functional lifetime (5–10 years) when doing heavy ion analysis. One of the main advantages of silicon detectors is their simplicity. However, they have to be used with a so-called “range foil” to range out the forward scattered heavy beam ions. Therefore, the simple range foil ERD has two major disadvantages: first, the loss of energy resolution due to the energy straggle and second, thickness inhomogeneity of the range foil, and the intrinsic indistinguishability of the signals for the various different recoiled target elements. Aside from the listed disadvantages, ERDA range foils with silicon detectors is still a powerful method and is relatively simple to work with. Another method of detection for ERDA is time of flight (TOF)-ERD. This method does not present the same issues, as those for the silicon detector. However, the throughput of TOF detectors is limited; the detection is performed in a serial fashion (one ion in the detector at a time). The longer the TOF for ions, the better the time resolution (equivalent to energy resolution) will be. TOF spectrometers that have an incorporated solid state detector must be confined to small solid angles. When performing HI-ERDA, TOF detectors are often used and/or "∆E/E" detectors-such as ionization chambers. These types of detectors usually implement small solid angles for higher depth resolution. Figure 6, on the left, shows a Time-of-Flight detector commonly used in ERDA. Heavier ions have a longer flight time than the lighter ions. Detectors in modern time-of-flight instruments have improved sensitivity, temporal and spatial resolution, and lifetimes.