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A novel real-time optical fibered dosimetry system based on optically stimulated luminescence (OSL) of SrS:Ce,Sm phosphor was developed and is presented. The advantages of this system are the combination of OSL and optical fibers, immediate readout, simplicity of use, low cost, reliability, flexibility, and robustness. Experimental results show an excellent linearity with the dose (0.01 to 6 Gy), repeatability better than 2%, radiation sensitivity up to 80 mV x c[Gy.sup.-1] and accuracy since error on dose is less than 5%. The applications targeted are the measurement of the dose delivered during a treatment in radiation therapy and the monitoring of the dose or dose-rate around or in nuclear reactor and accelerator facilities in high energy physics. Further experiments are still to be conducted in order to fully characterize the system and evaluate the feasibility of each application mentioned. Index Terms--Optical fiber, optically stimulated luminescence, OSL, radiation dosimetry, real-time dosimetry.

The low-dose-rate response of five bipolar integrated circuits is evaluated on the basis of switching experiments. Such experiments consist of performing first a high-dose-rate irradiation followed by a low-dose-rate irradiation. Based on these experiments, a time-saving method to predict the low-dose-rate degradation of bipolar linear microcircuits is proposed. This approach provides a good estimate of the low-dose-rate degradation. Index Terms--Bipolar technology, dose rate, enhanced low-dose-rate sensitivity (ELDRS), integrated circuit, switching experiment, total dose.

A new approach for assessing the risk of upsetting digital optocouplers due to the propagation of single event transients (SETs) is proposed. The optocoupler's input current ([I.sub.f]) and propagation time ([t.sub.pHL]) are found to be the most critical parameters for this approach. A case study using the 6N140 optocoupler and SETs measured at the output of the National Semiconductor LM139 is detailed to validate the concept. Index Terms--Analog single event transients (SETs), optocouplers, radiation hardness assurance, SET propagation.

A series of proton irradiations of GaAs/GaAlAs vertical cavity surface emitting lasers (VCSELs) has been carried out for the purpose of assessing the suitability of these devices for space applications. The irradiations were performed on biased and unbiased devices at energies of 30, 40, 50, and 60 MeV. Both current versus voltage (I–V) and optical power versus current (P–I) characteristics were measured before and after each irradiation phase. A simple circuit equivalent model for the VCSEL has been developed to analyze proton damage effects through the extraction of electrical parameters. The current threshold of VCSEL is shown to be the only important parameter modified by a high fluence (up to 10[sup 12] protons/cm[sup 2]) irradiation. Changes in the threshold current show radiation generated recombination centers to be the main cause of degradation. Due to carrier injection annealing related effects, we observed that unbiased devices show the greatest relative threshold increase (between 15% and 20% at 10[sup 13] protons/cm[sup 2]). The threshold current damage factor was also calculated. The analysis of the I–V characteristics shows that in the range of low fluences (10[sup 10]–10[sup 12] protons/cm[sup 2]) radiation induced ordering effects may compete with the usual radiation degradation that we observed at higher fluences. Consequently, the nonionizing energy loss approach, which is extensively used to predict the degradation of electronic devices under a full spectrum of energetic particles, is deemed to be not yet applicable for prediction of end-of-life performances of VCSELs. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Proton irradiations of GaAs/GaAlAs vertical cavity surface emitting lasers (VCSELS) were carried out to assess their suitability for space applications. The nonionizing energy loss approach is not found to be applicable for prediction of end-of-life performances of VCSELS.

A new methodology for understanding single-event transient (SET) phenomena in analog circuits is described. Device and circuit simulation techniques are coupled in order to reproduce experimental data obtained from the National Semiconductor LM124 operational amplifier and to determine the most sensitive parts of the integrated circuit. Experimental data obtained at the Physical Nuclear Institute from a low-power voltage regulator that uses the LM124 are also used to illustrate the method.