rior SEE performance as compared to a Si diode [Mars94]. Dark current damage factors were measured as a function of proton energy and were found to agree very well with the calculated InGaAs NIEL [Mars92], as shown in figure 21. The dark current damage factors (and corresponding responsivity damage factors) were combined with proton environment spectra using the formalism presented in section 2.4 to predict the on orbit performance of the detector as a function of orbit altitude and shielding. The dark current results are shown in [Mars92] for a particular orbit. The responsivity results are shown in figure 22 for a wide range of circular orbits. These results further illustrate the breadth of useful results that can be obtained using the displacement damage analysis tools described in this course. IV-88 DARK CURRENT DAMAGE FACTORS Ino.53Ga0.47 As PIN DIODE VR = -5V AND T = 25 C PROTON ENERGY (MeV) Figure 21 The calculated NIEL for InGaAs exhibits the same energy dependence as measured dark current damage factors. The two are scaled by the constant of 1.4x10 10 uAg/MeV, which relates device leakage to calculated displacement damage. After [Mars92]. 300 mils Al 150 mils Al 40 mils Al InGaAs PIN PHOTODIODES CIRCULAR ORBIT ALTITUDE (X 10 km) Figure 22 Predicted proton induced responsivity changes for an InGaAs photodiode. Note the shift in the position of the minimum to higher altitudes as the shielding is reduced. This is a result of the increased low energy component of the proton spectra at higher altitudes, which stopped in the thicker shields. After [Dale92a]. IV-89 A recent short course treated radiation effects in infrared (IR) detectors [Pick93]. Additional information can also be found in [Hopk97] and past IEEE Transactions on Nuclear Science (TNS) journals from this conference [e.g., Wate87, Hopk94a]. Very little work on proton effects appears in the open literature, but as new civilian programs (such as NASA's Hubble Space Telescope, Next Generation Space Telescope, ESA's High Resolution Imaging Spectrome