When used for the production of an x-ray imaging backlighter source on Sandia National Laboratories' 20 MA, 100 ns rise-time Z accelerator [M. K. Matzen et al., Phys. Plasmas 12, 055503 (2005)], the terawatt-class, multikilojoule, 526.57 nm Z-Beamlet laser (ZBL) [P. K. Rambo et al., Appl. Opt. 44, 2421 (2005)], in conjunction with the 6.151 keV, Mn-He-alpha curved-crystal imager [D. B. Sinars et al., Rev. Sci. Instrum. 75, 3672 (2004)], is capable of providing a high quality x radiograph per Z shot for various high-energy-density physics experiments. Enhancements to this imaging system during 2005 have led to the capture of inertial confinement fusion capsule implosion and complex hydrodynamics images of significantly higher quality. The three main improvements, all leading effectively to enhanced image plane brightness, were bringing the source inside the Rowland circle to approximately double the collection solid angle, replacing direct exposure film with Fuji BAS-TR2025 image plate (read with a Fuji BAS-5000 scanner), and generating a 0.3 -0.6 ns, similar to 200 J prepulse 2 ns before the 1.0 ns, similar to 1 kJ main pulse to more than double the 6.151 keV flux produced compared with a single 1 kJ pulse. It appears that the 20 +/- 5 mu m imaging resolution is limited by the 25 mu m scanning resolution of the BAS-5000 unit, and to this end, a higher resolution scanner will replace it. ZBL is presently undergoing modifications to provide two temporally separated images ("two-frame") per Z shot for this system before the accelerator closes down in summer 2006 for the Z-refurbished (ZR) upgrade. In 2008, after ZR, it is anticipated that the high-energy petawatt (HEPW) addition to ZBL will be completed, possibly allowing high-energy 11.2224 and 15.7751 keV K alpha(1) curved-crystal imaging to be performed. With an ongoing several-year project to develop a highly sensitive multiframe ultrafast digital x-ray camera (MUDXC), it is expected that two-frame HEPW 11 and 16 keV imaging and four-frame ZBL 6.151 keV curved-crystal imaging will be possible. MUDXC will be based on the technology of highly cooled silicon and germanium photodiode arrays and ultrafast, radiation-hardened integrated circuitry. (c) 2006 American Institute of Physics.

Year after year the Dosimetry and Facilities Session has been a fixture in the Nuclear Space and Radiation Conference (NSREC). As well as being home to subjects absolutely fundamental to dosimetry such as radiation transport, energy deposition, and X-ray photoemission, this session often included newly introduced topics such as hardness assurance and experimental techniques. This review paper describes the 40-year history of this session, whose title changed constantly over the years to reflect new developments. We have attempted to follow the logical chronological development and simultaneously give the reader a pedagogical tour through the main technical areas. Because of the wide variety of subjects in this session, this review covers first the context and background, and then four major subcategories as follows: the development of dosimetry devices and techniques; the basic physics of dosimetry and electron-photon/material interactions; neutron dosimetry and reactor facilities; and bremsstrahlung sources and other radiation facilities.

Silicon-on-insulator (SOI) and bulk-silicon transistors were irradiated using X-ray, Co-60 gamma, and proton radiation sources. Co-60 gamma irradiation generates larger radiation-induced threshold voltage shifts (by a factor of two) in SOI buried oxides and in parasitic field oxides under low-field conditions than X-ray or proton irradiation. For all devices examined, the radiation-induced threshold voltage shifts generated by X-ray irradiation were equal to, within experimental uncertainty, the radiation-induced threshold voltage shifts generated by proton irradiation. The differences in threshold voltage shifts, for the different radiation sources are attributed to differences in stopping power and consequently charge yield. The results suggest that for simulating proton-rich space environments, X-ray laboratory radiation sources are better suited for hardness assurance testing than Co-60 gamma radiation sources. Using Co-60 gamma sources for hardness assurance testing will result in more conservative estimates of device failure levels. Thus, our results do not preclude the use of Co-60 gamma radiation sources for hardness assurance testing for proton-rich environments. For electron-rich space environments, Co-60 gamma radiation sources may be better suited for hardness assurance testing.

In the previous sections Len Lorence has described the need, theory, and types of radiation codes that can be applied to model the results of radiation effects tests or working environments for electronics. For the rest of this segment, the author will concentrate on the specific ways the codes can be used to predict device response or analyze radiation test results. Regardless of whether one is predicting responses in a working or test environment, the procedures are virtually the same. The same can be said for the use of 1-, 2-, or 3-dimensional codes and Monte Carlo or discrete ordinates codes. No attempt is made to instruct the student on the specifics of the code. For example, the author will not discuss the details, such as the number of meshes, energy groups, etc. that are appropriate for a discrete ordinates code. For the sake of simplicity, he will restrict himself to the 1-dimensional code CEPXS/ONELD. This code along with a wide variety of other radiation codes can be obtained form the Radiation Safety Information Computational Center (RSICC) for a nominal handling fee.

This report contains the notes from the second session of the 1997 IEEENuclear and Space Radiation Effects Conference Short Course on ApplyingComputer Simulation Tools to Radiation Effects Problems. Part A discussesthe physical phenomena modeled in radiation transport codes and varioustypes of algorithmic implementations. Part B gives examples of how thesecodes can be used to design experiments whose results can be easily analyzedand describes how to calculate quantities of interest for...

X-ray spectroscopy discrepancies at measured energies below 50 keV are shown through ITS detector response calculations to be caused by germanium K edge escape peak losses. Accounting for this detector response, CEPXS/ONELD transport calculations through silicon agree well with measurements.

CEPXS/ONELD code predictions of dose enhancement in a 1-D geometry were examined. Relative dose calculations at Co-60 energies were compared with ionization chamber data of Wall and Burke for 54 different cases. Excellent agreement was found.

A dual-dielectric pMOS dosimeter (RADFET) has been recently designed at Sandia. The RADFET consists of a thermally grown oxide and a CVD deposited nitride. With a negatively applied bias, holes are generated in the SiO/sub 2/ transport and are trapped at the SiO/sub 2//Si/sub 3/N/sub 4/ interface producing a measurable threshold-voltage shift. Because holes are trapped away from the Si/SiO/sub 2/ interface, hole neutralization by tunneling and interface-trap buildup are minimized resulting in little fade or annealing of the RADFET output response. RADFETs were irradiated at dose rates from 0.002 to 50 rad(Si)/s with biases from -5 to -20 V. RADFETs were also annealed for times up to 10/sup 7/ s at temperatures up to 100/spl deg/C. Within experimental uncertainty, no difference in RADFET output response at a given bias was observed over the dose rate range examined and for 25/spl deg/C anneals. At an anneal temperature of 100/spl deg/C only a 20% decrease in RADFET output response was observed. These results show that Sandia's RADFETs exhibit little or no fade of their output characteristics and are ideal for low dose rate space applications.

Measurements of energy deposition from bremsstrahlung production as a function of angle and beam energy (5-25 MeV) are shown to be in excellent agreement with Monte Carlo predictions. Dosimetry measurements are made and predicted in both equilibrated and underequilibrated radiation environments. In the latter case the quality of the agreement requires an accurate prediction of both the photon and electron spectra produced by the primary electron beam. An improved empirical equation for predicting bremsstrahlung production is also presented. This empirical relation can be used to estimate doses without resorting to expensive calculational efforts. It also gives an analytical relationship for dose as a function of energy and angle for a converter optimized for bremsstrahlung production using 15.5 MeV electrons. >

It is demonstrated that the thermal generation rate in the bulk depletion regions of GaAs p-n junctions can be as much as three-orders-of-magnitude greater for samples metallized in e-beam evaporators as compared to thermal evaporators. This degradation is unexpected because the low-energy radiation present in such e-beam evaporation systems is unable by itself to cause atomic displacement responsible for defect creation in GaAs. Results derived from samples metallized in the e-beam evaporator indicate, however, that low-energy electrons are somehow involved in the formation of the defects responsible for the increased generation rate. Experiments performed in controlled-radiation environments have clearly demonstrated that neither simple radiation damage from electrons or from x-rays is sufficient to degrade these GaAs devices. Likewise,, the simple diffusion of impurity ions in the absence of a high fluence of low-energy electrons is also insufficient. Therefore, the experimental results suggest a damaging mechanism in which the presence of both low-energy electrons and impurity ions is necessary to cause the increase in generation rates observed in bulk GaAs.

Dose attenuation with depth in an absorber of on-axis bremsstrahlung generated from an electron target is measured. It is shown to agree within +or-9% with Monte Carlo predictions as a function of absorber material (Al, Fe, Pb) and incident electron-beam energy (5.5-25.1 MeV). For this on-axis bremsstrahlung, 1 to 5 g/cm/sup 2/ of upstream and 0.2 to 1 g/cm/sup 2/ of downstream Al buffer are sufficient to provide electron equilibration for CaF/sub 2/:Mn thermoluminescent dosimeters (TLDs) over the measured energy range of 5.5 to 25.1 MeV. Once effective equilibration has been established, an expression is given that can be used to predict the dose-area product per absorbed beam charge at a given incident beam energy in TLDs as a function of depth in absorbers, within a fixed solid angle centered about the beam axis. This expression is quantified for the measurements presented here. >

The relationship between dose in TLDs and dose in packaged microelectronic devices as a function of electron beam energy is calculated using the CEPXS/ONELD radiation transport code. The effects of adjacent materials, including TLDs, upon the energy deposition in the device are also discussed. The calculations indicate that dosimetry errors for linac electron beam environments (electron energies >12 MeV) can be made less than 5% if appropriate materials and geometries are used. The CEPXS/ONELD code provides a powerful tool for dosimetry analysis in electron-beam environments. >

The radiation field from an intense reusable source of flash x-rays that delivers a measured peak dose and dose rate of 370 +/- 60 krad (CaF2) and (3.5 +/- 0.7) X 10(13) rad (CaF2)/s over a useful area of 80 cm2 is characterized. CaF2:Mn TLDs (thermoluminescent dosimeters), which are used to measure the dose field, are shown to be dose-rate independent within +/- 15% up to this level. Energy deposition in the CaF2 TLD chip was analyzed according to the origin of the electrons responsible for that deposition with a new computational tool.

The radiation field from an intense reusable source of flash X-rays that delivers a measured peak dose and dose rate of 370+or-60 krad (CaF/sub 2/) and (3.5 +or-0.7)*10/sup 13/ rad (CaF/sub 2/)/s over a useful area of 80 cm/sup 2/ is characterized. CaF/sub 2/:Mn TLDs (thermoluminescent dosimeters), which are used to measure the dose field, are shown to be dose-rate independent within +or-15% up to...