Neutron radiation hardness of aluminum gallium nitride UV LEDs at various wavelengths.

Radiation hard diagnostics are critical to the success of nuclear fusion at National Ignition Facility, Z, ITER, and prolonged space explorations. We have first demonstrated the exceptional proton radiation hardness of initial GaN devices and qualified their space flight and deployment for missions such as the Laser Interferometer Space Antenna and International Space Station. We have further conducted neutron radiation hardness experiments at Los Alamos Neutron Science Center by opening a new high fluence beam station. During 2014-2016, we irradiated multiple Aluminum Gallium Nitride (AlGaN) LEDs with a maximum fluence of 2.4 × 1013 neutrons/cm2 in 3 years and generated 54 161 current-voltage (I-V) scan traces. Our data processing program analyzes each and all I-V traces. In addition, we retrieved local temperature records to analyze and remove temperature effects in the outdoor environment. The I-V curve families of AlGaN UV LEDs with emitting wavelengths of 265, 275, and 310 nm were compared. The I-V curves of 265 nm AlGaN UV LEDs have the smallest deviations from the average value, while the I-V curves for 310 nm AlGaN LEDs showed the largest deviations from the average value. We have reached another important recommendation for the optimal use of multiple AlGaN optoelectronic devices or imaging arrays for inertially confined fusion diagnostics: Shorter wavelength devices at 265 nm exhibit more consistent radiation hardness performance than the 310 nm devices. Higher aluminum content LEDs or AlxGa1-xN devices with higher mole fraction x for generating shorter wavelengths have better radiation hardness for fusion diagnostics.

Gallium nitride (GaN) devices as a platform technology for radiation hard inertial confinement fusion diagnostics.

Inertial Confinement Fusion (ICF) is undergoing more detailed research to increase neutron yield and will require high resolution imaging near the target. Neutron damage to diagnostics remains a serious issue in understanding and achieving ICF. We have demonstrated that Gallium Nitride (GaN) optoelectronic devices have exceptional neutron radiation hardness, by systematic testing of neutron radiation effects in GaN devices and materials with elevated neutron fluence levels and a broad neutron energy spectrum. During the 2013-2017 run cycles at Los Alamos Neutron Science Center (LANSCE), we irradiated various GaN materials and devices with fast and thermal plus resonance neutrons at several beamlines. This paper presents a radiation hardness study for Aluminum Gallium Nitride and Gallium Nitride (AlGaN/GaN) deep UV LEDs irradiated at the LANSCE 4FP60R beamline. The fluence level was up to 2.4 × 1013 neutrons/cm2 for neutrons with energies greater than 0.1 MeV. The device performance was monitored in real time. After three years of irradiation studies, we found that the GaN devices maintained operation in the forward active region. The current and voltage relation (I-V curves) varied insignificantly in the linear region. Our results demonstrate the radiation hardness needed for laser fusion diagnostics at least up to 1017 neutron yield per shot, if the diagnostics is placed 1 m away from the target, where the neutron fluence per shot is approximately 8 × 1011 n/cm2. The GaN devices can operate for multiple shots.

Comparison of polystyrene scintillator fiber array and monolithic polystyrene for neutron imaging and radiography.

The neutron imaging diagnostic at the National Ignition Facility has been operating since 2011 generating neutron images of deuterium-tritium (DT) implosions at peak compression. The current design features a scintillating fiber array, which allows for high imaging resolution to discern small-scale structure within the implosion. In recent years, it has become clear that additional neutron imaging systems need to be constructed in order to provide 3D reconstructions of the DT source and these additional views need to be on a shorter line of sight. As a result, there has been increased effort to identify new image collection techniques that improve upon imaging resolution for these next generation neutron imaging systems, such as monolithic deuterated scintillators. This work details measurements performed at the Weapons Neutron Research Facility at Los Alamos National Laboratory that compares the radiographic abilities of the fiber scintillator with a monolithic scintillator, which may be featured in a future short line of sight neutron imaging systems.

Neutron multiplicity in the fission of 238U and 235U with neutrons up to 200 MeV.

Prompt-fission-neutron multiplicities were measured for 238U(n,f) and 235U(n,f) from 0.4 to 200 MeV. The data are of great importance in connection with accelerator-coupled nuclear reactor systems incinerating actinides. We report that fission induced by 200 MeV neutrons produces approximately 10 more prompt neutrons than fission induced by reactor neutrons. Most neutrons are evaporated from the fission fragments and the prefission compound nucleus, as the preequilibrium emission of energetic neutrons accounts for a maximum of 15% of the prompt neutrons at 200 MeV.

The effectiveness of activity scheduling and relaxation training in the treatment of spasmodic dysmenorrhea.

The first purpose of this study was to examine the effectiveness of activity scheduling as a treatment for spasmodic dysmenorrhea, compared to relaxation training (a treatment of demonstrated effectiveness) and to a waiting-list control condition. The second purpose was to examine the differential effectiveness of these treatments on different measures. Forty women suffering from spasmodic dysmenorrhea completed six individualized treatment sessions or remained on the waiting list. Results showed that both activity scheduling and relaxation training were effective treatments for spasmodic dysmenorrhea, with both treatments producing improvements on general measures of dysmenorrhea, a symptom severity measure, and an activity measure.

Situational-specificity of motivational differences between depressed and nondepressed subjects.

Performance on an easy or a difficult coding task for 4 90-sec. repetitions by 15 college women who showed depressive symptoms on the Beck Depression Inventory and the MMPI-Depression Scale and 15 who did not indicated no support for a psychological or motivational deficit in depression. Replication with clinically depressed persons is recommended.

Self-instruction: An analysis of the differential effects of instruction and reinforcement.

This study investigated the impact of training 9 first- and second-grade children to use a full self-instructional regimen, and then differentially reinforced the use of self-instruction only, accuracy only, or both self-instruction and accuracy. Three comparison children received no training in self-instruction and were reinforced for accuracy only. Children improved dramatically in academic accuracy subsequent to self-instructional training, independent of the use of self-instruction and of the specific behavior consequated. Children who were reinforced for using self-instruction did use self-instruction, and those who were not, did not. Comparison group children showed little improvement until training in problem-solving strategies was given after 9 days of reinforcement for accuracy. Self-instructional training is discussed as one type of event that increases the likelihood of accurate performance. Its effectiveness may be explained in terms of a teaching strategy rather than in terms of modifying cognitive processes.

Behavioral measures of multiple personality: the case of Margaret.

This report concerns the systematic study of a 28-year-old subject diagnosed as multiple personality. The purpose of this study was to examine similarities and differences in three of her distinct personalities, utilizing behavioral measures. Three tasks were presented to the personalities: a memory task; a perceptual-motor task; and an attention task utilizing event-related potentials. The memory task and perceptual-motor task indicated that the three personalities shared information and that learning extended from one personality to the next. The attention task indicated that the three personalities were differentially processing the stimuli that were presented to them, as measured by the ERPs. The results are discussed in the context of the individual case and of the phenomena of multiple personality.

Psychological treatments of dysmenorrhea: differential effectiveness for spasmodics and congestives.

Two studies are reported, examining the effectiveness of psychological treatments for dysmenorrhea. In Experiment 1, 33 women with spasmodic dysmenorrhea were treated with relaxation alone, or relaxation plus imagery, or assigned to a waiting-list control condition; and 29 women with congestive dysmenorrhea were treated with relaxation alone, or assigned to a waiting-list control condition. In Experiment 2, 18 additional congestives were treated with a coping skills package, or this package plus relaxation; these two groups were compared with the two congestive groups from Experiment 1. The dependent measures were reports of symptom severity, general discomfort, resting time, and medication use. Consistent with the literature, the main findings of the present studies are: (a) relaxation training (alone or with imagery) effectively reduces resting time for spasmodics; and (b) none of the treatments was shown to be effective for congestive sufferers.

Equivalence class formation in language-able and language-disabled children.

Stimulus equivalence seems to have relevance to the study of semantics and of language more generally. If so, there may be a relation between language use and the demonstration of stimulus equivalence. This was examined in three groups of children ranging in chronological age and matched on a conventional measure of mental age: normally developing preschoolers, retarded children who used speech or signs spontaneously and appropriately, and retarded children who did not. All children were taught a series of four related discriminations and were then tested to determine if classes of equivalent stimuli had formed. All of the language-able children (retarded and normal) formed equivalence classes, whereas none of the language-disabled children did so. Although the exact nature of the relation between stimulus equivalence and language remains to be clarified, these results support the view that stimulus equivalence is a phenomenon with relevance to language.

The effects of instructions and calculation procedures on observers' accuracy, agreement, and calculation correctness.

Although the quality of observational data is generally evaluated by observer agreement, measures of both observer agreement and accuracy were available in the present study. Videotapes with a criterion protocol were coded by 16 observers. All observers calculated agreement scores both on their own and their partner's data and on a contrived data set misrepresented as data collected by other observers. Compared with agreement scores calculated by the experimenter, observers erroneously inflated their own agreement scores and deflated the agreement scores on the contrived data. Half of the observers (n = 8) had been given instructions emphasizing the importance of accuracy during observation while the other half had been given instructions emphasizing interobserver agreement. Accuracy exceeded agreement for the former group, whereas agreement exceeded accuracy for the latter group. The implications are that agreement should be calculated by the experimenter and that the accuracy-agreement relationship can be altered by differential observer instructions.