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Development of a robust, thin, hole-blocking ( n+) contact on high purity germanium (HPGe) has been the main challenge in the development of Ge-based radiation sensors. Yttrium has been reported to be a viable hole-blocking contact on HPGe, and detectors with low leakage have been fabricated. Niobium has also been considered as a potential hole-blocking contact due to its low work function. Here, we investigate interface chemistry and the Schottky barrier height of Y and Nb, as well as electron-blocking contacts Au and Pt, on Ge(100) surfaces using hard x-ray photoelectron spectroscopy. We find a barrier height of 1.05 ± 0.10 eV for Y/HPGe, confirming the formation of a hole-blocking barrier. For Nb/HPGe, the barrier height of 0.13 ± 0.10 eV demonstrates that the interface is not hole-blocking. The Schottky barrier of Au and Pt was found to be 0.45 ± 0.10 and 0.51 ± 0.10 eV, respectively.

Annalen der Physik OF, 2100285 (2022). doi:10.1002/andp.202100285, For photon energies from several 10 keV up to a few MeV Compton polarimetry is an indispensable tool to gain insight into subtle details of fundamental atomic radiative processes. Within the SPARC collaboration several segmented semiconductor detectors are developed that are well suited for application as efficient Compton polarimeters. In this report, these recent developments are reviewed and it is discussed how Compton polarimetry can be employed at the upcoming Gamma Factory., Published by Barth, Leipzig

Methane (CH4) impacts climate as the second strongest anthropogenic greenhouse gas and air quality by influencing tropospheric ozone levels. Space-based observations have identified the Four Corners region in the Southwest United States as an area of large CH4 enhancements. We conducted an airborne campaign in Four Corners during April 2015 with the next-generation Airborne Visible/Infrared Imaging Spectrometer (near-infrared) and Hyperspectral Thermal Emission Spectrometer (thermal infrared) imaging spectrometers to better understand the source of methane by measuring methane plumes at 1- to 3-m spatial resolution. Our analysis detected more than 250 individual methane plumes from fossil fuel harvesting, processing, and distributing infrastructures, spanning an emission range from the detection limit [Formula: see text] 2 kg/h to 5 kg/h through [Formula: see text] 5,000 kg/h. Observed sources include gas processing facilities, storage tanks, pipeline leaks, and well pads, as well as a coal mine venting shaft. Overall, plume enhancements and inferred fluxes follow a lognormal distribution, with the top 10% emitters contributing 49 to 66% to the inferred total point source flux of 0.23 Tg/y to 0.39 Tg/y. With the observed confirmation of a lognormal emission distribution, this airborne observing strategy and its ability to locate previously unknown point sources in real time provides an efficient and effective method to identify and mitigate major emissions contributors over a wide geographic area. With improved instrumentation, this capability scales to spaceborne applications [Thompson DR, et al. (2016) Geophys Res Lett 43(12):6571-6578]. Further illustration of this potential is demonstrated with two detected, confirmed, and repaired pipeline leaks during the campaign.

Localized anthropogenic sources of atmospheric CH4 are highly uncertain and temporally variable. Airborne remote measurement is an effective method to detect and quantify these emissions. In a campaign context, the science yield can be dramatically increased by real-time retrievals that allow operators to coordinate multiple measurements of the most active areas. This can improve science outcomes for both single- and multiple-platform missions. We describe a case study of the NASA/ESA CO2 and MEthane eXperiment (COMEX) campaign in California during June and August/September 2014. COMEX was a multi-platform campaign to measure CH4 plumes released from anthropogenic sources including oil and gas infrastructure. We discuss principles for real-time spectral signature detection and measurement, and report performance on the NASA Next Generation Airborne Visible Infrared Spectrometer (AVIRIS-NG). AVIRIS-NG successfully detected CH4 plumes in real-time at Gb s−1 data rates, characterizing fugitive releases in concert with other in situ and remote instruments. The teams used these real-time CH4 detections to coordinate measurements across multiple platforms, including airborne in situ, airborne non-imaging remote sensing, and ground-based in situ instruments. To our knowledge this is the first reported use of real-time trace-gas signature detection in an airborne science campaign, and presages many future applications. Post-analysis demonstrates matched filter methods providing noise-equivalent (1σ) detection sensitivity for 1.0 % CH4 column enhancements equal to 141 ppm m.

Segmented γ -scanning (SGS) is the most widely applied technique to non-destructively reconstruct the isotope specific activity content in radioactive waste drums. Around 25% of all radioactive waste drums at the Forschungszentrum Julich exhibit a homogeneous matrix distribution and activity distribution. Due to these conditions, a numerical method is derived, which largely enhances the accuracy and reliability of the activity reconstruction in comparison to the common analytical method by avoiding various simplifications in the calculations. The numerical method is validated with GEANT4 simulations of reference drums containing the isotopes 137 Cs and 60 Co. The activities, which are reconstructed with the numerical method in waste matrices with a density range from 0.5 g cm −3 to 2.3 g cm −3 show systematic deviations of around −2.1% and 4.0% in case of 137 Cs and 60 Co, respectively. These results show a significant improvement in accuracy compared to the analytical method revealing systematic deviations of around 14.8% and 23.2%, respectively. These results are confirmed by the reconstruction of the activity content in a reference drum from SGS measurements. Uncertainties calculated in the numerical method are halved in comparison to the analytical method. Thus, the reliability of the reconstructed activities is enhanced.

Fugitive emissions from waste disposal sites are important anthropogenic sources of the greenhouse gas methane (CH4). As a result of the growing world population and the recognition of the need to control greenhouse gas emissions, this anthropogenic source of CH4 has received much recent attention. However, the accurate assessment of the CH4 emissions from landfills by modeling and existing measurement techniques is challenging. This is because of inaccurate knowledge of the model parameters and the extent of and limited accessibility to landfill sites. This results in a large uncertainty in our knowledge of the emissions of CH4 from landfills and waste management. In this study, we present results derived from data collected during the research campaign COMEX (CO2 and Methane EXperiement) in late summer 2014 in the Los Angeles (LA) Basin. The objective of COMEX, which comprised aircraft observations of methane by the remote sensing Methane Airborne MAPper (MAMAP) instrument and a Picarro greenhouse gas in-situ analyser, was the quantitative investigation of CH4 emissions. Enhanced CH4 concentrations or "CH4 plumes" were detected downwind of landfills by remote sensing aircraft surveys. Subsequent to each remote sensing survey, the detected plume was sampled within the atmospheric boundary layer by in-situ measurements of atmospheric parameters such as wind information and dry gas mixing ratios of CH4 and carbon dioxide (CO2) from the same aircraft. This was undertaken to facilitate the independent estimation of the surface fluxes for the validation of the remote sensing estimates. During the COMEX campaign, four landfills in the LA Basin were surveyed. One landfill has repeatedly shown a clear emission plume. This landfill, the Olinda Alpha Landfill, was observed on four days during the last week of August and first days of September 2014. Emissions were estimated for all days using a mass balance approach. The derived emissions are between 13.0 and 18.2 kt CH4/yr with related uncertainties in the range of 17 % to 46 %. The comparison of the remote sensing and in-situ based CH4 emission rate estimates reveals good agreement within the error bars with an average absolute difference of around 2.3 kt CH4/yr. The US Environmental Protection Agency (EPA) reported inventory value is 11.5 kt CH4/yr in 2014, on average 3.0 kt CH4/yr (±1.5 kt CH4/yr) lower than our estimates acquired in late Summer 2014. This difference may in part be explained by a possible leak located on the south-western slope of the landfill, which we identified in the observations of the Airborne Visible/Infrared Imaging Spectrometer – Next Generation (AVIRIS-NG) instrument, flown contemporaneously aboard a second aircraft on one day.

INTRODUCTION Although the carbon budget is often presented in terms of global-scale fluxes, many of the contributing processes occur through localized point sources, which have been challenging to measure from space. Persistent anthropogenic carbon dioxide (CO 2 ) emissions have altered the natural balance of Earth’s carbon sources and sinks. These emissions are driven by a multitude of individual mobile and stationary point sources that combust fossil fuels, with urban areas accounting for more than 70% of anthropogenic emissions to the atmosphere. Natural point-source emissions are dominated by wildfires and persistent volcanic degassing. RATIONALE Comprehensive global measurements from space could help to more completely characterize anthropogenic and natural point-source emissions. In global carbon cycle models, anthropogenic point-source information comes from bottom-up emission inventories, whereas natural point-source information comes from a sparse in situ measurement network. Whereas clusters of urban CO 2 point-source plumes merge together, isolated point sources (e.g., remote power plants, cement production plants, and persistently degassing volcanoes) create localized plumes. Because turbulent mixing and diffusion cause rapid downwind dilution, they are challenging to detect and analyze. Point-source detection from space is complicated by signal dilution: The observed values of Δ X CO 2 (enhancement of the column-averaged dry-air CO 2 mole fraction) correspond to in situ CO 2 enhancements of 10-fold or higher. Space-based sensors that detect and quantify CO 2 in plumes from individual point sources would enable validation of reported inventory fluxes for power plants. These sensors would also advance the detectability of volcanic eruption precursors and improve volcanic CO 2 emission inventories. RESULTS Spaceborne measurements of atmospheric CO 2 using kilometer-scale data from NASA’s Orbiting Carbon Observatory-2 (OCO-2) reveal distinct structures caused by known anthropogenic and natural point sources, including megacities and volcanoes. Continuous along-track sampling across Los Angeles (USA) by OCO-2 at its ~2.25-km spatial resolution exposes intra-urban spatial variability in the atmospheric X CO 2 distribution that corresponds to the structure of the urban dome, which is detectable under favorable wind conditions. Los Angeles X CO 2 peaks over the urban core and decreases through suburban areas to rural background values more than ~100 km away. Enhancements of X CO 2 in the Los Angeles urban CO 2 dome observed by OCO-2 vary seasonally from 4.4 to 6.1 parts per million (ppm). We also detected isolated CO 2 plumes from the persistently degassing Yasur, Ambrym, and Aoba volcanoes (Vanuatu), corroborated by near-simultaneous sulfur dioxide plume detections by NASA’s Ozone Mapping and Profiler Suite. An OCO-2 transect passing directly downwind of Yasur volcano yielded a narrow filament of enhanced X CO 2 ( Δ X CO 2 ≈ 3.4 ppm), consistent with plume modeling of a CO 2 point source emitting 41.6 ± 19.7 kilotons per day (15.2 ± 7.2 megatons per year). These highest continuous volcanic CO 2 emissions are collectively dwarfed by about 70 fossil fuel–burning power plants on Earth, which each emit more than 15 megatons per year of CO 2 . CONCLUSION OCO-2’s sampling strategy was designed to characterize CO 2 sources and sinks on regional to continental and ocean-basin scales, but the unprecedented kilometer-scale resolution and high sensitivity enables detection of CO 2 from natural and anthropogenic localized emission sources. OCO-2 captures seasonal, intra-urban, and isolated plume signals. Capitalizing on OCO-2’s sensitivity, a much higher temporal resolution would capture anthropogenic emission signal variations from diurnal, weekly, climatic, and economic effects, and, for volcanoes, precursory emission variability. Future sampling strategies will benefit from a continuous mapping approach with the sensitivity of OCO-2 to systematically and repeatedly capture these smaller, urban to individual plume scales of CO 2 point sources. OCO-2 detects urban CO 2 signals with unprecedented detail over Los Angeles. Individual “footprints” of OCO-2 X CO 2 data from early fall 2014 and summer 2015 over the city of Los Angeles strongly contrast with values over the distant, rural Antelope Valley. X CO 2 is the averaged dry-air molar CO 2 concentration between the spacecraft and Earth’s surface.

Reliable techniques to infer greenhouse gas emission rates from localised sources require accurate measurement and inversion approaches. In this study airborne remote sensing observations by the MAMAP instrument and airborne in-situ measurements are used to infer emission estimates of carbon dioxide released from a cluster of coal fired power plants. For the analysis of in-situ data, a mass balance approach is described and applied. Whereas for the remote sensing observations an inverse Gaussian plume model is used in addition to a mass balance technique. A comparison between methods shows that results for all methods agree within a few percent for cases where in-situ measurements were made for the complete vertical plume extent. Even though the power plants are partly in close proximity and the associated carbon dioxide plumes are overlapping it is possible to derive emission rates from remote sensing data for individual power plants that agree well with results derived from emission factors and energy production data for the time of the overflight.

Radioactive waste must be characterized in order to verify its conformance with national regulations for intermediate storage or its disposal. Segmented gamma scanning (SGS) is a most widely applied non-destructive analytical technique for the characterization of radioactive waste drums. The isotope specific activity content is generally calculated assuming a homogeneous matrix and activity distribution for each measured drum segment. However, real radioactive waste drums exhibit non-uniform isotope and density distributions most affecting the reliability and accuracy of activities reconstruction in SGS. The presence of internal shielding structures in the waste drum contributes generally to a strong underestimation of the activity and this in particular for radioactive sources emitting low energy gamma-rays independently of their spatial distribution. In this work we present an improved method to quantify the activity of spatially concentrated gamma-emitting isotopes (point sources or hot spots) in heterogeneous waste drums with internal shielding structures. The isotope activity is reconstructed by numerical simulations and fits of the angular dependent count rate distribution recorded during the drum rotation in SGS using an analytical expression derived from a geometric model. First results of the improved method and enhancements of this method are shown and are compared to each other as well as to the conventional method which assumes a homogeneous matrix and activity distribution. It is shown that the new model improves the accuracy and the reliability of the activity reconstruction in SGS and that the presented algorithm is suitable with respect to the framework requirement of industrial application.

Improved methods for the reconstruction of the isotope specific activity content in nuclear waste drums with data obtained by a gamma scanning system developed at Shanghai Jiao Tong University require an analytical function of the detector response. In this work we derive an analytical detector response function for a collimated HPGe detector with a square collimation window. The model is based on a purely geometric model respecting the configuration of the collimated detector system, the positions of radioactive point sources and the absorption of γ-rays in the matrix as well as in the HPGe crystal. We show that the derived analytical detector response function is in good agreement with data simulated by MCNP5.

This work improves the reliability and accuracy in the reconstruction of the total isotope activity content in heterogeneous nuclear waste drums containing point sources. The method is based on χ 2 ‐ fits of the angular dependent count rate distribution measured during a drum rotation in segmented gamma scanning. A new description of the analytical calculation of the angular count rate distribution is introduced based on a more precise model of the collimated detector. The new description is validated and compared to the old description using MCNP5 simulations of angular dependent count rate distributions of Co-60 and Cs-137 point sources. It is shown that the new model describes the angular dependent count rate distribution significantly more accurate compared to the old model. Hence, the reconstruction of the activity is more accurate and the errors are considerably reduced that lead to more reliable results. Furthermore, the results are compared to the conventional reconstruction method assuming a homogeneous matrix and activity distribution.

Carbon dioxide (CO2) is the most important anthropogenic greenhouse gas (GHG) causing global warming. The atmospheric CO2 concentration increased by more than 30% since pre-industrial times – primarily due to burning of fossil fuels – and still continues to increase. Reporting of CO2 emissions is required by the Kyoto protocol. Independent verification of reported emissions, which are typially not directly measured, by methods such as inverse modeling of measured atmospheric CO2 concentrations is currently not possible globally due to lack of appropriate observations. Existing satellite instruments such as SCIAMACHY/ENVISAT and TANSO/GOSAT focus on advancing our understanding of natural CO2 sources and sinks. The obvious next step for future generation satellites is to also constrain anthropogenic CO2 emissions. Here we present a promising satellite remote sensing concept based on spectroscopic measurements of reflected solar radiation and show, using power plants as an example, that strong localized CO2 point sources can be detected and their emissions quantified. This requires mapping the atmospheric CO2 column distribution at a spatial resolution of 2×2 km2 with a precision of 0.5% (2 ppm) or better. We indicate that this can be achieved with existing technology. For a single satellite in sun-synchronous orbit with a swath width of 500 km, each power plant (PP) is overflown every 6 days or more frequent. Based on the MODIS cloud mask data product we conservatively estimate that typically 20 sufficiently cloud free overpasses per PP can be achieved every year. We found that for typical wind speeds in the range of 2–6 m/s the statistical uncertainty of the retrieved PP CO2 emission due to instrument noise is in the range 1.6–4.8 MtCO2/yr for single overpasses. This corresponds to 12–36% of the emission of a mid-size PP (13 MtCO2/yr). We have also determined the sensitivity to parameters which may result in systematic errors such as atmospheric transport and aerosol related parameters. We found that the emission error depends linearly on wind speed, i.e., a 10% wind speed error results in a 10% emission error, and that neglecting enhanced aerosol concentrations in the PP plume may result in errors in the range 0.2–2.5 MtCO2/yr, depending on PP aerosol emission. The discussed concept has the potential to contribute to an independent verification of reported anthropogenic CO2 emissions and therefore could be an important component of a future global anthropogenic GHG emission monitoring system. This is of relevance in the context of Kyoto protocol follow-on agreements but also allows detection and monitoring of a variety of other strong natural and anthropogenic CO2 and CH4 emitters. The investigated instrument is not limited to these applications as it has been specified to also deliver the data needed for global regional-scale CO2 and CH4 surface flux inverse modeling.

In this paper we present our results on using electromyographic (EMG) sensor arrays for finger gesture recognition. Sensing muscle activity allows to capture finger motion without placing sensors directly at the hand or fingers and thus may be used to build unobtrusive body-worn interfaces. We use an electrode array with 192 electrodes to record a high-density EMG of the upper forearm muscles. We present in detail a baseline system for gesture recognition on our dataset, using a naive Bayes classifier to discriminate the 27 gestures. We recorded 25 sessions from 5 subjects. We report an average accuracy of 90% for the within-session scenario, showing the feasibility of the EMG approach to discriminate a large number of subtle gestures. We analyze the effect of the number of used electrodes on the recognition performance and show the benefit of using high numbers of electrodes. Cross-session recognition typically suffers from electrode position changes from session to session. We present two methods to estimate the electrode shift between sessions based on a small amount of calibration data and compare it to a baseline system with no shift compensation. The presented methods raise the accuracy from 59% baseline accuracy to 75% accuracy after shift compensation. The dataset is publicly available.

Recent developments of large-area Si(Li) orthogonal-strip detectors have revealed their capability for applications in Compton-effect-based instruments. Some inherent advantages of silicon such as the dominance of Compton scattering in photon interactions and operation at room or somewhat lower temperature combined with the availability of large-volume Si(Li) detectors could stimulate the development of powerful Compton instruments. Several diodes 10 mm in thickness with a diameter of 102 mm were fabricated. Two 10 mm thick diodes were cut to form a 74 mmtimes74 mm square with slightly rounded corners. The same position-sensitive structure, 32 strips with a pitch of 2 mm, was produced on the thin Li-diffused n-contact and boron-implanted p+-contact by means of photolithography and plasma etched grooves. The position-sensitive area of 64 mmtimes64 mm is surrounded by a 5 mm wide guard-ring. One of these 10 mm thick Si(Li) orthogonal-strip detectors has been mounted in a cryostat prepared at Lawrence Livermore National Laboratory (LLNL). The detector will be extensively tested there with the goal of being integrated into the Compact Si+Ge Compton camera system consisting of this Si(Li) and a HPGe orthogonal-strip detector

The established technique for producing position-sensitive structures by means of photolithography and subsequent plasma etching of grooves through detector contacts was applied for amorphous germanium contacts (a-Ge contacts). A simple 50-strip structure with a pitch of 615 /spl mu/m was produced. Charge sharing between two adjacent strips (33 mm length) was investigated with the aid of 60-keV photons and 5.8-MeV /spl alpha/-particles. No charge losses were detected when irradiating the structured a-Ge contact of the 16-mm-thick detector with 60-keV photons. The same was concluded for /spl alpha/-particles hitting the unstructured p/sup +/-contact made by boron implantation. Moreover, excellent position information for /spl alpha/-particles, with an accuracy of about 30 /spl mu/m, could be extracted in this case. Surprising results were obtained for /spl alpha/-particles impinging on the structured a-Ge contact. No coincident signals from the two adjacent strips caused by /spl alpha/-particles were observed. But a normally positive signal from one of the strips occasionally coincided with a negative signal from the other strip and vice versa. Using a cooled FET assembly mounted near a strip, an energy resolution of 0.78 keV [FWHM] for 60-keV photons was achieved and a slightly better resolution for lower energies. Even better energy resolutions will probably be possible, because the measuring setup was far from being optimized.

Both a pH-sensitive thin-film sensor and a thick-film reference electrode have been integrated into a hybrid sensor module that is suitable for (bio-)chemical analysis in aqueous solutions. The pH-sensitive thin-film sensor consists of a capacitive layer structure of Al/p-Si/SiO2/Al2O3 and is prepared by semiconductor-compatible process steps. The thick-film reference electrode of p-Si/Ag/AgCl is printed by conventional screen-printed technique onto the same silicon substrate. Such combination of the thin-film sensor and the thick-film reference allows the realization of a miniaturized sensor hybrid without an external macroscopic reference electrode. Due to its set-up, the sensor hybrid shows a response characteristic to both H+- and Cl−-ions and can be employed in well-defined analytes, like for biomedical applications. The utility of the new thin-film / thick-film sensor hybrid is demonstrated for the determination of the H+- and Cl−-ion concentration in aqueous solutions.

The applicability of LaBr3-detectors for the non destructive characterization of radioactive waste drums is evaluated by comparing their performance with those of HPGe-detectors. It is shown, that relevant easy-to-measure key-nuclides are identified as well as quantified with a LaBr3-detector even in complex spectra at nearly the same level of precision and reliability than with HPGe-detectors.

New Mexico State University, Las Cruces, NM 88003-8001, USA* Author to whom correspondence should be addressed.Received: 28 September 2001 / Accepted: 10 October 2001 / Published: 2 November 2001Abstract: A reference electrode fabricated by means of thick-film technique is depositedonto a silicon substrate and combined with a thin-film pH sensor to a “hybrid” chip system.To evaluate the suitability of this combination, first investigations were carried out. Thecharacteristics of the thin-film pH sensor were studied towards the thick-film Ag/AgClreference electrode. Measurements were performed in the capacitance/voltage (C/V) andconstant capacitance (Concap) mode for different pH values keeping the concentration ofchloride ions constant. No difference of the sensor behaviour could be found whencomparing the results to measurements, obtained versus a conventional macroscopicAg/AgCl reference electrode.Keywords: Hybrid sensor chip, Thick-film reference electrode, Thin-film pH sensor.IntroductionThe requirement of continuous monitoring for environmental and medical applications has beentaken place in a main interest of developing a variety of miniaturised sensors for chemical andbiological analytes in aqueous solutions [1-7]. In combination with the possibility of using siliconplanar technology, some miniaturised potentiometric sensors have been developed and are nowavailable [8]. The advantage of such sensors is their process compatibility with integrated circuittechnology. Furthermore, they are appropriate for on-line monitoring, where small analyte volumes areneeded. However, these miniaturised sensors still suffer from the drawback of an integrated reference

Radioactive waste has to undergo a process of quality checking in order to check its conformance with national regulations prior to its transport, intermediate storage and final disposal. Within the quality checking of radioactive waste packages non-destructive assays are required to characterize their radio-toxic and chemo-toxic contents. The Institute of Energy and Climate Research - Nuclear Waste Management and Reactor Safety of the Forschungszentrum Jülich develops in the framework of cooperation nondestructive analytical techniques for the routine characterization of radioactive waste packages at industrial-scale. During the phase of research and development Monte Carlo techniques are used to simulate the transport of particle, especially photons, electrons and neutrons, through matter and to obtain the response of detection systems. The radiological characterization of low and intermediate level radioactive waste drums is performed by segmented γ-scanning (SGS). To precisely and accurately reconstruct the isotope specific activity content in waste drums by SGS measurement, an innovative method called SGSreco was developed. The Geant4 code was used to simulate the response of the collimated detection system for waste drums with different activity and matrix configurations. These simulations allow a far more detailed optimization, validation and benchmark of SGSreco, since the construction of test drums covering a broad range of activity and matrix properties is time consuming and cost intensive. The MEDINA (Multi Element Detection based on Instrumental Neutron Activation) test facility was developed to identify and quantify non-radioactive elements and substances in radioactive waste drums. MEDINA is based on prompt and delayed gamma neutron activation analysis (P&DGNAA) using a 14 MeV neutron generator. MCNP simulations were carried out to study the response of the MEDINA facility in terms of gamma spectra, time dependence of the neutron energy spectrum, neutron flux distribution. The validation of the measurements simulations with Mont-Carlo transport codes for the design, optimization and data analysis of further P&DGNAA facilities is performed in collaboration with LMN CEA Cadarache. The performance of the prompt gamma neutron activation analysis (PGNAA) for the nondestructive determination of actinides in small samples is investigated. The quantitative determination of actinides relies on the precise knowledge of partial neutron capture cross sections. Up to today these cross sections are not very accurate for analytical purpose. The goal of the TANDEM (Trans-uranium Actinides’ Nuclear Data – Evaluation and Measurement) Collaboration is the evaluation of these cross sections. Cross sections are measured using prompt gamma activation analysis facilities in Budapest and Munich. Geant4 is used to optimally design the detection system with Compton suppression. Furthermore, for the evaluation of the cross sections it is strongly needed to correct the results to the self-attenuation of the prompt gammas within the sample. In the framework of cooperation RWTH Aachen University, Forschungszentrum Jülich and the Siemens AG will study the feasibility of a compact Neutron Imaging System for Radioactive waste Analysis (NISRA). The system is based on a 14 MeV neutron source and an advanced detector system (a-Si flat panel) linked to an exclusive converter/scintillator for fast neutrons. For shielding and radioprotection studies the codes MCNPX and Geant4 were used. The two codes were benchmarked in processing time and accuracy in the neutron and gamma fluxes. Also the detector response was simulated with Geant4 to optimize components of the system.

In the II–VI compounds ZnS, CdS, ZnSe, CdSe, ZnTe and CdTe doped with In, the formation of In M -V M pairs in shown to occur using the radioactive dopant 111 In along with the perturbed γγ angular correlation technique. For CdS and ZnSe, the migration energy of the metallic vacancy defect V M and its binding energy to the donor In is determined. The creation of V M defects under different experimental conditions is investigated, such as stoichiometry, temperature, electron irradiation and doping with Li atoms.

At Lawrence Livermore National Laboratory, we are pursuing the development of a gamma-ray imaging system using the Compton effect. We have built our first generation hybrid Compton imaging system, and we have conducted initial calibration and image measurements using this system. In this paper, we present the details of the hybrid Compton imaging system and initial calibration and image measurements

Anfange: Unter A. versteht man die Nutzung groser landwirtschaftlicher Flachen bei intensiver Bodenbearbeitung zur Gewinnung von Pflanzenertragen fur Nahrung, Kleidung und Futtermittel. Er nimmt mit der Seshaftwerdung spatmesolithischer Kulturen seinen Anfang: Alteste Pflanzenreste, die auf A. schliesen lassen, sind in Vorderasien im Gebiet des ›Fruchtbaren Halbmondes‹ aus der Zeit 8000 bis 6000 v.Chr. gefunden worden. Spater verfugten die mesopotamischen und agyptischen Hochkulturen schon uber einen entwickelten und spezialisierten A. Im griechisch-romischen Bereich schlieslich wird die Einfuhrung des A. durch die Sage in die Vorgeschichte (Geschenk der Demeter o. a. Gotter) verlegt, ist aber wohl im 4. Jahrtausend v.Chr. erfolgt. Die ersten archaologischen Befunde fur A. im griechischen Raum stammen jedoch aus der minoisch-mykenischen Epoche. In historischer Zeit ist der A. schlieslich unbestritten die wichtigste Grundlage der antiken Wirtschaft.

During the development of double-sided microstructured Si(Li) detectors thin Li-doped contacts with effective thicknesses below 10 /spl mu/m could be created. The effective thickness was determined by evaluating the measured energy loss of /spl alpha/-particles entering the detector through the Li-doped contact. Extensive examinations have been performed to find the correlation between the effective thicknesses determined with the help of /spl alpha/-particles and the thicknesses based on the measured distribution of the Li-ions in the Li-diffused layers. Pronounced discrepancies were found in the relation between the effective thicknesses and the thicknesses of the removed layer during the thinning process. In any case, the effective thickness was considerably smaller than the thickness estimated from the distribution of the Li-ions. The dependence of the effective thickness on the bias voltage and the temperature was studied. A possible explanation of the relatively small effective thicknesses based on the internal electric field inside the Li-doped layer caused by the concentration gradient is presented. The technique to create Li-doped layers with an effective thickness smaller than 5 /spl mu/m is described. In this way, the transmission Si(Li) detectors with the effective dead layers being smaller than 0.1% of their thickness can be realized (patent is filed).

The functional change of the Venetian villa a cultural-geographical analysis The aim of this contribution is to analyse the develop ment of the Venetian villa, which has become one of the most intrinsic elements of the landscape in north-eastern Italy since the 15th century. In comparison with the Tuscan villa-fattoria system, which developed during the 13th century around the urban republics like Florence, Lucca and Pistoia, the Venetian villa is historically a late pheno menon. It began to flourish only since the 16th century after the decline of oriental trade, when the Venetians were oblig ed to obtain political control over their hinterland territories (terra ferma). The ideological justification for the colonization of the terra ferma was based on numerous articles by A. Cornaro, L. B. Alberti and A. Palladio in recollection and reinter

This article intends to describe the social situation and living conditions of the drought refugees living in the periphery of Mopti. The complex phenomenon of ‘poverty’ and of social discrimination is explained by different indicators (kind of ‘informal economy’, kind of dwelling, composition of food, hygienic situation). In contemporary Africa hunger has become a problem of those people who have lost their original social and economic roots. This holds expecially true for the drought refugees. The transformation of nomads and peasants into proletarian and dependent outcasts will be demonstrated.

Recent developments of large-area Si(Li) orthogonal-strip detectors have revealed their capability for applications in Compton effect based instruments. Some inherent advantages of silicon like dominance of Compton scattering in photon interactions and operation at room or somewhat lower temperature combined with the availability of large-volume Si(Li) detectors could stimulate the development of powerful Compton instruments. Several 10 and 20 mm thick diodes with a diameter of 102 mm were fabricated. Two 10 mm thick diodes were cut to form a 74 mm /spl times/ 74 mm square with slightly rounded corners. The same position-sensitive structure, 32 strips with a pitch of 2 mm, was produced on the thin Li-diffused n-contact and boron implanted p/sup +/-contact by means of photolithography and plasma etched grooves. The position-sensitive area of 64 mm /spl times/ 64 mm is surrounded by a 5 mm wide guard-ring. One of these 10 mm thick Si(Li) orthogonal-strip detectors will be mounted in a cryostat prepared at LLNL. There, the detector will be extensively tested with the goal to be integrated into the compact Compton camera system consisting of double-sided strip Si(Li) and HPGe detectors.