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Aerosol samples on polycarbonate filters were collected daily for several years in the Southern High Plains region of western Texas. Selected samples representing a variety of size modes, locations, and air quality conditions were analyzed by PIXE. Silicon and other crustal elements dominated during dust storms and in the coarse mode; sulfur dominated during anthropogenic pollution episodes and in the fine mode. A mixture of both aerosol types was present even during “clear” conditions. The Al/Si ratio in dust events increases with wind speed. These data provide an initial assessment of aerosol chemistry in the West Texas plains.

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was used to quantitatively determine deuterium (D) concentration in pulsed‐laser deposited (PLD) zinc oxide (ZnO) thin films on Al2O3 substrates. Dual‐beam analysis technique was applied, where the sputtering ion source was Cs+ and the analysis ion source was Bi3+. Standard samples were prepared by implanting D+ ions into a high purity ZnO single crystal. Detection limit of ToF‐SIMS instrument for D atoms in ZnO film was studied, and it was found to be about 5×1016 atoms/cm3. In addition, our data show that it is very difficult to characterize low concentration of H atoms by normal ToF‐SIMS due to H background interference.

We have investigated atomic and molecular anion production from singly charged atomic and molecular hydrogen, deuterium, and mixed isotope beams during grazing interactions with large area KBr, KCl, and LiF single crystal targets in the incident energy range 4–22.5 keV. Electron capture and, in the case of incident molecular ions, dissociation occur during the grazing interactions without appreciable angular straggling or change in velocity. As a result, atomic and molecular cation and anion interaction products are strongly peaked in the specular reflection direction, and, in case of dissociation products, at the fractional kinetic energies determined by the product fragment mass to incident mass ratios. A large‐acceptance electrostatic analysis and detection system is used to collect the charged scattering products with high efficiency. Of particular interest is the production of metastable molecular ions H2−, HD−, and D2−. By comparing molecular anion yields obtained from incident hydrogen, deuterium a...

Real time radiation dose measurements are challenging in high dose rate environments such as those used for testing electronic devices or biological agents. Dosimetry needs in pulsed reactor fields and particle accelerator facilities require development of dosimeters with fast (10 s of picoseconds) response to pulsed radiation, linear response over a wide range of dose rates (up to 1011 Gy/s), high resistance to radiation damage, and successful operation in mixed gamma and neutron environments. Gallium arsenide photoconductive detectors (GaAs PCD) have been shown to exhibit many of these desirable characteristics, especially fast time response. Less than 50 ps time resolution has been demonstrated when previously irradiated by fission neutrons. We have conducted a study of the response‐time dependence on neutron fluence, starting with fluences at ∼1014 n/cm2. A 23‐MeV electron beam was used to produce photoneutrons in a tungsten target for irradiation of a GaAs wafer from which PCDs were made. The process was modeled using MCNPX computer code and the simulation results were compared to the experimental measurements. GaAs PCDs were fabricated from both neutron‐irradiated and non‐irradiated GaAs samples. The results of the preliminary tests of these devices in accelerator‐produced pulses of electron and bremsstrahlung radiation of various energies (13 to 35 MeV) and pulse lengths (100 ps to 4 μs) are presented together with an overview of the future plans of continuing GaAs PCD research at Idaho State University.

Current advances in technology have enabled dramatic improvements to the performance of multi‐detector arrays within the last 10 years. FAUST is a forward array of 68 Si‐CsI(Tl) detector telescopes that has been in use since 1996. To take full advantage of current technology, FAUST has undergone an overhaul installing new preamplifiers from Zepto Systems and modifications to allow for Dual‐Axis Dual‐Lateral position sensitive detectors to be installed. A new calibration software package has also been developed utilizing a novel linearization algorithm. The combination of these upgrades has led to isotopic identification for elements in the Z = 1–13 range and has greatly increased the angular resolution of the array.

The gadolinium isotopes are interesting for reactor applications as well as for medicine and astrophysics. The gadolinium isotopes have some of the largest neutron capture cross sections. As a consequence they are used in the control rod in reactor fuel assembly. From the basic science point of view, there are seven stable isotopes of gadolinium with varying degrees of deformation. Therefore they provide a good testing ground for the study of deformation dependent structure such as the scissors mode. Decay gamma rays following neutron capture on Gd isotopes are detected by the DANCE array, which is located at flight path 14 at the Lujan Neutron Scattering Center at Los Alamos National Laboratory. The high segmentation and close packing of the detector array enable gamma‐ray multiplicity measurements. The calorimetric properties of the DANCE array coupled with the neutron time‐of‐flight technique enables one to gate on a specific resonance of a specific isotope in the time‐of‐flight spectrum and obtain the...

In this work, the isoscaling for the 40Ca+112,124Sn reactions at the beam energy of 45 MeV/A was investigated as a function of the excitation energy of reconstructed quasi‐projectiles. The excitation energy dependence of the isoscaling parameter obtained from the intra‐system isoscaling was investigated and is expected to provide information for the determination of the symmetry energy coefficient of highly excited nuclei.

Neutron‐induced gamma‐ray reactions are extensively used in the nondestructive analysis of materials and other areas where the information about the chemical composition of a substance is crucial. The common technique to find the intensity of the gamma ray is to fit gamma‐ray line shape with an analytical function, for example, a Gaussian. However, the Gaussian fitting may fail if the gamma‐ray peak is Doppler‐broadened since this leads to the miscalculation of the area of the peak and, therefore, to misidentification of the material. Due to momentum considerations, Doppler‐broadening occurs primarily with gamma rays from neutron‐induced inelastic scattering reactions with light nuclei. The recoiling nucleus of interest must have excited states whose lifetimes are much smaller than the time of flight in the material. We have examined various light nuclei bombarded by 14 MeV neutrons to predict when the peak shape of a neutron‐induced gamma ray emitted from these nuclei will be Doppler‐broadened. We have f...

Hybridization and thermal evolution of the Ni+C60 composites, deposited on Si(001) at room temperature, were studied using Scanning Electron Microscopy, μ‐Raman spectroscopy and Rutherford Backscattering. As‐deposited, the hybrid films exhibited a granular nano‐structure with Ni nano‐particles encapsulated in C60 polymerized rinds. The Ni and C (C60) distributions in a top layer were found homogeneous with a stable Ni/C (C60) ratio; in the larger depth the distributions were inhomogeneous and their ratio dramatically varied. At elevated temperatures, all structural parameters were changed. In the subsurface layer Ni—and C (C60)—rich zones were formed (due to the induced phase separation), C60—molecules decayed and their fragments were transformed into amorphous carbon (a‐C). The free volume distribution of the stressed hybrid matter was analyzed by the Hg marker that (in a form of vapors) in‐diffused in to the samples. The RBS analysis showed that the Hg distribution of the as‐deposited films followed the...

The uniformity of rubber‐carbon black composite materials has been investigated with positron Doppler Broadening Spectroscopy (DBS). The number of grams of carbon black (CB) mixed into one hundred grams of rubber, phr, is used to characterize a sample. A typical concentration for rubber in tires is 50 phr. The S parameter measured by DBS has been found to depend on the phr of the sample as well as the type of rubber and carbon black. The variation in carbon black concentration within a surface area of about 5 mm diameter can be measured by moving a standard Na‐22 or Ge‐68 positron source over an extended sample. The precision of the concentration measurement depends on the dwell time at a point on the sample. The time required to determine uniformity over an extended sample can be reduced by running with much higher counting rate than is typical in DBS and correcting for the systematic variation of S parameter with counting rate. Variation in CB concentration with mixing time at the level of about 0.5% has been observed.The uniformity of rubber‐carbon black composite materials has been investigated with positron Doppler Broadening Spectroscopy (DBS). The number of grams of carbon black (CB) mixed into one hundred grams of rubber, phr, is used to characterize a sample. A typical concentration for rubber in tires is 50 phr. The S parameter measured by DBS has been found to depend on the phr of the sample as well as the type of rubber and carbon black. The variation in carbon black concentration within a surface area of about 5 mm diameter can be measured by moving a standard Na‐22 or Ge‐68 positron source over an extended sample. The precision of the concentration measurement depends on the dwell time at a point on the sample. The time required to determine uniformity over an extended sample can be reduced by running with much higher counting rate than is typical in DBS and correcting for the systematic variation of S parameter with counting rate. Variation in CB concentration with mixing time at the level of about 0.5% ha...

Time projection chambers (TPC) are powerful devices for studying charged particles produced in nuclear collisions. The high resolution and large angular acceptances of these devices permit 4π event reconstruction providing ample event characterization for nuclear structure and reaction experiments. In conjunction with a magnetic field, TPC’s can be used to identify diverse particle species ranging from pions to light charged fragments in intermediate energy collisions. This particle identification capability is suitable for nuclear reactions studies of the density dependence of the symmetry energy in the nuclear equation of state. By varying the gas with which the detector chamber is filled, a TPC can be used as an active target in which the fill gas acts as both the target and detector. This will allow low threshold processes relevant to nuclear structure, fission and nuclear astrophysics to be studied in inverse kinematics. The scientific and technical plans for implementing an active target time projec...

The photodisintegration cross section of radioactive 241Am has been obtained for the first time using monoenergetic γ‐ray beams from the HIγS facility. The induced activity of 240Am produced via the 241Am(γ,n) reaction in the γ‐ray energy range from 9.5 to 16 MeV was measured by the activation technique utilizing high resolution HPGe detectors. The 241Am(γ,n) cross section was determined both by measuring the absolute γ‐ray flux and by comparison to the 197Au(γ,n) and 58Ni(γ,n) cross section standards. The experimental data for the 241Am(γ,n) reaction in the giant dipole resonance energy region is compared with statistical nuclear‐model calculations.

A novel apparatus constructed at IFIN‐HH is described for automated synthesis of radiopharmaceuticals labeled with 18F for use in positron emission tomography (PET) investigations. [18 F] fluoride was produced at the IFIN‐HH cyclotron by irradiation of H2O enriched 97% in 18O with 13 MeV deuterons, or 8 MeV protons. The irradiated H2O was transferred (injected) into the radiochemical fully‐automated processing systems which ensured the separation of 18F from H2O, the labeling with 18F, and finally purified by filtration with selective absorbants. The system is easy to operate and contains a programmable logical controller that manages the entire operation program stored in its internal memory. The computer is used to assist the operator during the different steps of synthesis and to allow visualization of the process and printing the report. The device was used for used for the production of 2‐[18 F] FLUORO‐2‐DEOXY‐D‐GLUCOSE at the IFIN‐HH cyclotron, one of the most used radiopharmaceutical in PET investi...

Controlatron neutron generators are used for testing neutron detection systems at Sandia National Laboratories. To provide for increased tube lifetimes for the moderate neutron flux output of these generators, metal hydride (ZrT2) target fabrication processes have been developed. To provide for manufacturing quality control of these targets, ion beam analysis techniques are used to determine film composition. The load ratios (i.e. T/Zr concentration ratios) of ZrT2 Controlatron neutron generator targets have been successfully measured by simultaneously acquiring RBS and ERD data using a He++ beam energy of 10 MeV. Several targets were measured and the film thicknesses obtained from RBS measurements agreed within ±2% with Dektak profilometer measurements. The target fabrication process and ion beam analysis techniques will be presented.

Carbon‐based nanocrystals, formed in silica by low‐energy carbon implantation and subsequent thermal annealing, have been previously reported, but ambiguities as to the equilibrium morphology and its relationship to the source of photo luminescence. In our study, silica samples were implanted with 2.0×1017 atoms/cm2 C− ions at energies of 8.5 keV, 40 keV and 70 keV. Samples were annealed for 15, 30, 60, 120, 240 minutes at 1100° C in a forming gas (4%H2+96%Ar). Rutherford backscattering (RBS), particle induced x‐ray emission (PIXE), and photoluminescence (PL) were used to characterize the nanocrystals formed by these conditions. The resulting photoluminescence analysis indicated that the size distribution of the nanocrystals could be tailored to yield a broad spectral output between 2.0–2.8 eV by controlling the formation parameters. Also a few notable factors, such as liberation of oxygen in the silica during implantation, as well as uptake of ambient oxygen in the annealing furnace, will be shown to pla...

The classical trajectory Monte Carlo method is used to calculate total and state selective nl‐electron capture cross sections for highly charged ions Z = 4–10, 14, 18 and 26 colliding with water. The initialization for the 1B1 and 3A1 orbitals of the water molecule is based on a Slater orbital expansion. The Z‐dependence of the calculated total cross sections is in reasonable agreement with recent data. The K‐shell x‐ray emission cross sections are determined from the calculated state‐selective electron capture results.

We report the results of dissociation dynamics of multiply charged acetylene molecules formed in collision with 1.2 MeV Ar8+ projectiles. Using the coincidence map, we found the evidence for molecular deformation due to a vibrationally active transition state of multiply charged C2H2 under the impact of low energy projectiles. ‘Butterfly‐like’ structures are observed in the coincidence spectra between hydrogen and carbon ionic fragments. Such structures can be generated by numerical simulations and are found to originate from the bending motion of the dissociating molecule. From the measured slopes of the coincidence islands for carbon atomic fragments and theoretical values determined from the charge and momentum distribution of the correlated particles, we observe a diatom‐like behavior of the C‐C charged complex during dissociation of multiply charged acetylene. This is a signature of sequentiality in the breakup dynamics of this multiply charged molecular species.

The neutralization energy carried by highly charged ions (HCIs) provides an alternative method for localizing energy on a target’s surface, producing features and modifying surfaces with fluences and kinetic energy damage that are negligible compared to singly ionized atoms. Since each HCI can deposit an enormous amount of energy into a small volume of the surface (e.g., Xe44+ delivers 51 keV of neutralization energy per HCI), each individual HCI’s interaction with the target can produce a nanoscale feature. Many studies of HCI‐surface features have characterized some basic principles of this unique ion‐surface interaction, but the activity reported here has been focused on studying ensembles of HCI features in ultra‐thin insulating films by fabricating multi‐layer tunnel junction devices. The ultra‐thin insulating barriers allow current to flow by tunneling, providing a very sensitive means of detecting changes in the barrier due to highly charged ion irradiation and, conversely, HCI modification provide...

The 171,173Yb(d,pγ) reactions have been measured to determine the efficacy of this reaction as a surrogate for neutron capture on radioactive nuclei. Preliminary results for the surrogate cross section ratios, with gating conditions that best mimic the spin distribution of neutron capture, reproduce the Wisshak et al., (n,γ) cross section ratios within 15%.

The NEG‐coating, composed of ZrTiV with a lower temperature of activation, has been developed as a large surface getter pump for the aluminum (Al) chamber of small aperture and long length with a very poor conductance. However, the outgas of discharged gases, Ar or Kr, as well as the hydrocarbon molecules inside the NEG‐coated Al chamber has been observed. The desorption of the so‐called inert gases with heavier atomic mass residing inside the chamber results in the potential problem of higher cross section of scattering with the traveling beam hence reduces the life time seriously. To verify the outgas source of CH4, the NEG‐coated Al‐chamber exposed with heavy water (D2O) has been investigated. It shows the D2O and methane are the only outgases from the non‐coated Al chamber exposed with D2O. However, more outgas of CDxHy, CD4, and the C2DxHy complexes have been measured in the case of NEG‐coated Al chamber. Desorption of C2DxHy molecules can be reduced by exposing the NEG‐coated surface with synchrotro...

Irradiation induced random displacements of atoms and replacement collision sequences are possible mechanisms for phase transformations as well as other physical properties changes as grain size variation and hardness increase or decrease. In this study Ni4Mo alloy samples were subject to low‐flux bombardment by ion beams. This alloy has similar structure to the Hastelloy‐C used in industry and to U3Si that is used as nuclear fuel. Sample regions were irradiated while the energy density of the bombarding beams was carefully controlled and the non‐irradiated regions were kept close to room temperature. This way the irradiation induced temperature increase was highly localized creating “quench‐like” conditions. After the irradiation, the samples were annealed at low temperature. Due to irradiation conditions there was a high density of nucleation sites favoring the formation of finer grain structures as well as localized phase transformations. The results showed that with the appropriate fluence and post‐ir...

Total cross section measurements of electron capture processes are being studied for low‐energy, Aq++H(D) collisions using the Ion‐Atom Merged‐Beams apparatus at the Multicharged Ion Research Facility (MIRF) at Oak Ridge National Laboratory (ORNL). On this apparatus, a modified Faraday cup detector is used to measure the intensity of the neutral beam. The conversion of the measured electrical current to the true neutral particle beam current is necessary to accurately determine the true cross section values. Inherent in this conversion process is the number of secondary electrons (γ) emitted from the surface of the detector upon impact of an atom. The method employed to determine γ and its role in the absolute electron capture measurements at ORNL‐MIRF are presented. With a recent upgrade to the apparatus, the neutral beam H(D) production technique has been improved and is discussed in detail in this paper.

We have experimentally explored laser‐induced dissociation and ionization of diatomic molecular ions, such as H2+, N2+, CO+ and ND+, using coincidence 3D momentum imaging. The vibrationally excited molecular‐ion beam (5–10 keV) is crossed by an ultrafast intense laser beam (typically 7–50 fs, 1013–1016 W/cm2 at 790 and 395 nm). The resulting fragments, including neutral fragments, are recorded in coincidence by a time‐ and position‐sensitive detector. Complete angular and kinetic energy release (KER) distributions are reconstructed from the measured momentum vectors of the fragments. For example, this experimental method enabled the observation of a surprising high KER component in N2+ dissociation despite its overlap in KER with the ionization channel.

Al0.49Ga0.51N (12 nm)/GaN (13 nm) Multi Quantum Wells of 15 periods are grown on sapphire by MOCVD technique. GaN/AlN, each of thickness 200 nm and 20 nm respectively, are used as buffer layers between substrate and epilayer to incorporate the strain in epilayers. It is a well established technique to engineer the band gap in AlxGa1−xN by adjusting alloy composition. These samples are used in visible & UV light emitters. In the present study, we employ a photoluminescence technique to estimate the composition and luminescence peak positions of AlGaN and GaN. Crystallinity and quality of interfaces have been studied by Rocking curve scan. The Threading Dislocations formed at the GaN buffer layer travel across the entire layers to the surface to form good quality films. Photo‐luminescence results show a very sharp GaN peak at 3.4 eV, as observed and reported by others, which shows that samples are free from point defects.

Positron Annihilation Spectroscopy (PAS) techniques can be utilized as a sensitive probe of defects in materials. Studying these microscopic defects is very important for a number of industries in order to predict material failure or structural integrity. We have been developing gamma‐induced pair‐production techniques to produce positrons in thick samples (∼4–40 g/cm2, or ∼0.5–5 cm in steel). These techniques are called ‘Accelerator‐based Gamma‐induced Positron Annihilation Spectroscopy’ (AG‐PAS). We have begun testing the capabilities of this technique for imaging of defect densities in thick structural materials. As a first step, a linear accelerator (LINAC) was employed to produce photon beams by stopping 15 MeV electrons in a 1 mm thick tungsten converter. The accelerator is capable of operating with 30–60 ns pulse width, up to 200 mA peak current at 1 kHz repetition rate. The highly collimated bremsstrahlung beam impinged upon our steel tensile specimens, after traveling through a 1.2 m thick concre...

The demand of highly charged ions of isotopes from all mass regions of the nuclear chart for low energy experiment or for the post acceleration has driven the development of different charge breeding methods. Charge state breeder employ high charge state ion sources like the Electron Beam Ion Source/Trap (EBIS/T) and the Electron Cyclotron Resonance Ion Source (ECRIS). Existing radioactive beam facilities like REX‐ISOLDE or ISAC (TRIUMF) are already using charge state boosters for the post acceleration of radioactive ions. Upcoming facilities like the MSU re‐accelerator project, SPIRAL II, SPES, EURISOL and MATS within FAIR have identified the need of a breeding system, because of the demand for highly charged ions at low energies and due to the available budget. Charge state breeding with EBIS/T devices requires several steps, which need to be optimized. A beam of singly charged ions must be prepared prior to injection into an EBIS/T in order to match the acceptance of the electron beam. An efficient injection and short breeding times are required as well as a high abundance in one specific charge state, which can be manipulated in EBIS/T devices. Further issues of charge breeder development are extraction and purification of the wanted highly charged ion species. The present paper will review the efforts of the EBIS/T community and will give an overview of the planned and running facilities.

Displacement cascades in zirconia have been studied using classical molecular dynamics simulations. Polycrystalline zirconia with nano‐meter grains were created using Voronoi polyhedra construction and studied in comparison with single crystalline zirconia. The results show that displacement cascades with similar kinetic energy generated larger number of displaced atoms in polycrystalline than in the single crystal structure. The fraction of atoms with coordination number change was also higher in polycrystalline zirconia that was explained to be due to the diffusion of oxygen and relaxation at grain boundaries.

Neutron activation analysis using Au foil is a common and important method for measurement of thermal neutron fluence. To determine the activity of Au foil experimentally, Kawada et al. proposed 2{pi}{beta}+2{pi}{beta}-{gamma} coincidence counting. This method is based on 4{pi}{beta}-{gamma} coincidence counting but a 4{pi}{beta} detector is divided into two 2{pi}{beta} detectors those are independently operated in the method. In this research the correction factors in 2{pi}{beta}+2{pi}{beta}-{gamma} coincidence counting were obtained by measurement and simulation. The activities obtained by these correction factors were in good agreement.

Photon activation analysis (PAA) was introduced about contemporarily with the other activation analysis methods (neutron, NAA, and charged particle activation, CPAA). Nonetheless, for different reasons, PAA has been applied less frequently than the other techniques mentioned. The incident photon energy should exceed about 12 MeV (except in some special rare applications) so as to obtain appreciably high activity yields of the product nuclides. Thus, cyclic electron accelerators (LINACs or microtrons) are used for activation preferably. The predominant photonuclear reaction is of the (γ,n)‐type. Thus, normally neutron‐deficient nuclides are produced. These usually emit gamma rays, annihilation quanta and characteristic X‐ray fluorescence, all of whom can be used for analytical evaluation. The spectrometry equipment is the same as used for the other activation techniques (semiconductor detectors, sodium iodide crystals in coincidence geometry). Being uncharged high energy photons have a large penetration po...

Several tests have been done with the neutron generator incorporated inside a small submarine equipped also with a few other sensors like video cameras and a magnetometer. Following the detection of an anomaly on the sea bottom a neutron sensor is requested to check for the presence of explosives. In the experiment, the TNT explosive was measured behind an iron shield. Comparison was made with similar measurements when the TNT explosive was replaced by stones. By measuring the C/O ratio the TNT explosive was successfully identified. All the measurements were done first in air and after that repeated in freshwater and in sea water.

We are building the SOPHI experiment in Saclay, which is a device based on a small 5 MeV electron linac [1] to produce positrons via pair production on a tungsten target. This device should provide 108 slow e+/s, i.e. a factor 300 greater than the strongest activity Na22 based setup. The SOPHI system has been finalized at the end of 2006 and the main components have been studied and built during 2007 [2]. The experiment is currently being assembled and first results are expected for autumn 2008. The electron linac, positron beam production and transport system will be presented, and expected positron production rate reported.

The feasibility of using TANDEM electrostatic particle accelerators as a linear TOF analyzer for molecular ions (TOF‐AMS) is reported in this work. A specific ion source, based on a soft ionization technique commonly used in modern mass spectrometry, employing a pulsed UV‐laser to desorb molecular ions from the solid state, was built for that purpose. The current instrumentation has been used to analyze samples of CsI and C60 using the whole accelerator as a linear Time of Flight spectrometer. From the point of view of basic studies on molecular collisions, the apparatus has some unique features that allow the simultaneous discrimination of various fragmentation and charge exchange channels for different types of molecular ions. From the point of view of applied studies, the TOF‐AMS technique may be able to overcome some difficulties encountered in mass spectrometry of biomolecules.

A scanning system has been designed for portal protection applications, with the capability of detecting explosive materials after an initial scan of 30 seconds. The scanner operates using the principle of neutron induced return gamma‐ray spectrometry. This system utilizes high purity germanium detectors, a neutron generator based on deuterium‐tritium fusion and a unique neutron reflector and guide design. The neutron reflector amplifies the flux and alters the energy spectrum of neutrons produced by the generator. A depleted uranium reflector is shown to perform 7.3 times better than no reflector, and is found to perform 1.5 times better than a tungsten reflector using MCNP simulation. This improvement is due to neutron knockout and induced fission occurring in depleted uranium. The system is capable of detecting 300 g of explosives with 90% detection probability, which includes a 15% rescan rate after a 30 second initial scan.

National security programs have expressed interest in developing systems to isotopically map shipping containers, fuel assemblies, and waste barrels for various materials including special nuclear material (SNM). Current radiographic systems offer little more than an ambiguous density silhouette of a container’s contents. In this paper we will present a system being developed at LLNL to isotopically map containers using the nuclear resonance fluorescence (NRF) method. Recent experimental measurements on NRF strengths in SNM are discussed.

Hydrogen is a ubiquitous contaminant that is known to have dramatic effects on the electrical, chemical, and mechanical properties of many types of materials in even minute quantities. Thus, the detection of hydrogen in materials is of major importance. Nuclear Reaction Analysis (NRA) is a powerful technique for nondestructive profiling hydrogen in materials. However, NRA has found only limited use in many applications because of poor sensitivity due to cosmic ray background (CSRB). Most attempts to eliminate CSRB to achieve ppm detection levels using higher energy nuclear reactions or tons of passive shielding are not compatible with commercial ion beam analysis space and equipment requirements Zimmerman, et al. have previously reported upon a coincidence detector that meets IBA space requirements and reduces the cosmic ray background, but the detector suffers from lower detection efficiency and small sample size. We have replaced the BGO well detector in the Zimmerman coincidence detection scheme with a larger Nal well detector and used faster timing electronics to produce a detector that can handle larger samples with higher detection efficiency, and still eliminate cosmic ray background.

Carbon was implanted into sapphire at various temperatures as part of a study of the different defect structures produced by a series of light ions. Implantations were made with 150 keV ions to fluences of 1×1016 and 1×1017 ions/cm2 at room temperature (RT) and 1000° C. The defect structures were characterized using Rutherford backscattering‐channeling (RBS‐C) and transmission electron microscopy (TEM). The RBS‐C spectra indicated low residual disorder for RT implantation at 1×1016 C+/cm2. The de‐channeling approached the random value at 1×1017 C+/cm2 and the TEM examination revealed a buried amorphous layer containing embedded sapphire nanocrystals. Damaged layers containing planar defects generally aligned parallel to the surface surrounded this layer. The RBS‐C spectra for the sample implanted at 1000° C with 1×1017 C+/cm2 suggested a highly damaged but crystalline surface that was confirmed by TEM micrographs.

In a previous work, the measurement of radiative vacancy transfer probabilities from the K shell to the L sub‐shells were measured, when rare earth elements were irradiated with 3 MeV–4 MeV protons. It was found that those probabilities did not depend on the ion energy and there was a close agreement with theoretical predictions. Therefore, in this work the K‐shell X‐ray intensity ratios for rare‐earth elements have been measured following irradiation with 12C4+ and 16O5+ ion beams, with incident energies between 12 MeV and 15 MeV. From the X‐ray intensity ratios, the radiative vacancy transfer probabilities from the shell K to the L sub‐shells were determined. The experimental data were compared to theoretical predictions, such as the Scofield theoretical predictions for these probabilities. The results showed a good agreement between theory and experiment, and did not show dependence with the ion incident energy.

The next generation of radiobiology research requires increasingly more complex radiation sources to address questions ranging from the effects of space‐based radiation to the influence of dose rate on biological systems. The Idaho Accelerator Center (IAC) has developed a radiobiology research facility to address some of these questions. The irradiation challenge is to deliver stable and reproducible conditions of high dose rate with well‐controlled beam uniformity, dose, and dose rate under controlled temperature. In this work, we used a 25 MeV modified medical grade linear accelerator (LINAC) to obtain a high and adjustable electron dose rate. To overcome electron beam drift we used a collimator that both assisted the LINAC operator to steer the beam and ensured that regardless of beam drift, only the fixed collimated beam would irradiate the specimens. In addition, we utilized a beam flattener to keep the beam variation as low as 3% at 2.5 cm from the beam’s center, and 1% variation between the simultaneously irradiated sample tubes. We also demonstrated that a segmented Faraday “cup” (FC) array provides a useful real‐time beam scanning and monitoring system, and is promising for implementing real‐time dosimetry and control.

Compact active interrogation sources are being developed that use low‐energy (kilovolt) nuclear reactions to produce high‐energy (megavolt) neutrons or gamma‐rays. We are evaluating target materials for these interrogation sources by performing rapid thermal load and high power density tests that reach conditions expected during source operation. Following the tests, the targets are analyzed with low and high resolution microscopes to assess whether any physical or structural damage has occurred. This paper presents results of the examinations of LiF, Li2O, LiNbO3, CaF2, B4C, and LaB6 target materials following rapid thermal and electron beam heating tests.

Active interrogation, a measurement technique which uses a radiation source to probe materials and generate unique signatures useful for characterizing those materials, is a powerful tool for assaying special nuclear material. The most commonly used technique for performing active interrogation is to use an electronic neutron generator as the probe radiation source. Exploiting the unique operating characteristics of these devices, including their monoenergetic neutron emissions and their ability to operate in pulsed modes, presents a number of options for performing prompt and delayed signature analyses using both photon and neutron sensors. A review of literature in this area shows multiple applications of the active neutron interrogation technique for performing nuclear nonproliferation measurements. Some examples include measuring the plutonium content of spent fuel, assaying plutonium residue in spent fuel hull claddings, assaying plutonium in aqueous fuel reprocessing process streams, and assaying nuclear fuel reprocessing facility waste streams to detect and quantify fissile material. This paper discusses the historical use of this technique and examines its context within the scope and challenges of next‐generation nuclear fuel cycles and advanced concept nuclear fuel cycle facilities.

We have shown that, clioquinol (CQ) (5‐chloro‐7‐iodo‐8 hydroxy quinoline) can be radioiodinated and has rapid brain uptake and fast clearance from the blood and brain in normal mice. In order to enhance its brain uptake and retard the fast brain clearance, we incorporated it into butylpolycyanoacrylate (BCA) nanoparticles (NP). Selective localization of 125I CQ BCA nanoparticles was observed in autoradiograph of Alzheimer’s Disease (AD) patient’s postmortem brain sections. We studied its biodistribution in normal mice and experimental AD mice. AD lesions were created by administration of preformed aggregates of A‐beta peptide (A□42) into hippocampus of mice using a stereotactic device. Biodistribution and ex‐vivo autoradiography of the brains of mice injected with 125I CQ BCA nanoparticles showed that: 1. nanoparticles enhanced (1.5–2 times) the brain delivery of the 125I‐CQ 2. Autoradiograph of AD brain sections showed localized uptake of the radiotracer and 3. experimental animal brains had positive aut...

To make measurements with the intense (but often contaminated) radioactive beams available today, one often needs to identify the reaction products to determine the events of interest. The low energies required for many astrophysics measurements make impossible the use of traditional energy loss techniques, and additional constraints are required. We demonstrate a simple technique to measure the risetimes of silicon strip‐detector signals and show partial discrimination can be obtained even at energies below 1 MeV/u.

Unbalanced magnetron sputtering deposition of C‐H films has been performed with various levels of negative substrate bias and with a fixed flow rate of hydrogen. Argon was used as a sputtering gas and formed the majority of the gas in the plasma. The effect of hydrogenation on the final concentration of trapped elements and their thermal stability with respect to hydrogen content is studied using ion beam analysis (IBA) techniques. The elemental concentrations of the films were measured in the films deposited on silicon substrates with a 2.5 MeV of H+ beam, which is used to perform Rutherford Backscattering Spectrometry (RBS) and Non‐Rutherford Backscattering spectrometry (NRBS) and with 16 MeV of O5+ beam, used to perform Elastic Recoil Detection Analysis (ERDA). Effect of bias on the thermal stability of trapped hydrogen in the films has been studied. As the films were heated in‐situ in vacuum using a non‐gassy button heater, hydrogen was found to be decreasing around 400° C.

A gas cluster ion beam (GCIB) technology was successfully applied to surface treatment of Cu, stainless steel, Ti, and Nb samples and to Nb rf‐cavities by using accelerated cluster ion beams of Ar, O2 and combinations of them, with accelerating voltages up to 35 kV. DC field emission (dark current) measurements and electron microscopy were used to investigate metal surfaces treated by GCIB. The experimental results showed that GCIB technique can significantly reduce the number of field emitters and can change the structure of the Nb oxide layer on the surface. The RF tests of the GCIB‐treated Nb rf‐cavities showed improvement of the quality factor Q at 4.5 K. The superconducting gap was also enhanced by using the oxygen GCIB irradiation exposure.

The proton induced inner‐shell vacancy decay process is comprised of radiative and non‐radiative transitions. It is characterized by fluorescence, Auger and Coster‐Kronig yields. These studies have been evolving over the last four decades, resulting in close and stringent comparisons of the measured values with the predictions of theoretical models. In view of the present scenario, we report in this paper the role of these atomic parameters for W (tungsten) and their energy dependence. Their role in understanding this phenomenon and current progress in this regard will be highlighted. Requirements and opportunities for further effort will also be discussed.

Dipole‐strength distributions in the stable even‐mass molybdenum isotopes up to the neutron‐separation energies have been studied in photon‐scattering experiments with bremsstrahlung at the superconducting electron accelerator ELBE at the Research Center Dresden‐Rossendorf, Germany, and with mono‐energetic photon beams at the High Intensity Gamma‐ray Source facility at Triangle Universities Nuclear Laboratory. In order to determine the dipole‐strength distribution, statistical methods were developed for the analysis of the measured spectra. The data obtained for the stable even‐mass molybdenum isotopes from the present (γ,γ’) experiments are combined with (γ,n) cross sections from the literature resulting in a photoabsorption cross section covering the full range from about 4 to 15 MeV, which is of interest for nuclear structure as well as for nuclear astrophysics network calculations. Novel information about the low‐energy tail of the Giant Dipole Resonance and the energy spreading of its strength is der...

Clinical Trials are under way to evaluate agents labeled with the nuclide 225Ac and its decay product 213Bi, in targeted alpha‐immuno‐therapy [1]. 225Ac can be produced on a medium‐energy cyclotron via the nuclear reaction 226Ra(p,n)225Ac. To demonstrate proof‐of‐principle, a vintage AEG cyclotron, Model E33 [2], with an internal target, had been employed in a pilot production program at the Technical University of Munich (TUM). To enhance production capability and further support the clinical studies, the TUM facility has recently been refurbished and upgraded, adding a new external beam‐line, automated target irradiation and transport systems, new laboratories, hot cells, etc. [3]. An improved high‐power rotating target has been built and installed [4]. The AEG cyclotron itself has also been modified and upgraded to accelerate and extract H− ions. We have designed, built, and tested a new axial Penning‐type ion source which is optimized for the production of H− ions. The ion source has continued to evol...

Laser Compton Scattered (LCS) X‐rays are produced as a result of the interaction between accelerated electrons and a laser beam. The yield of LCS X‐rays is dependent on the laser power, angle of collision between interacting particles, and the electron linear accelerator’s (linac) electron beam energy and its current. One of our research goals at the Idaho Accelerator Center (IAC) focuses on applications such as detection and imaging of fissionable isotopes for nuclear non‐proliferation, safeguards and homeland security. Quasi monochromatic LCS X‐rays offer much better signal‐to‐noise ratios for such applications. The energy of LCS X‐rays is tunable, that enable element‐specific analysis. Two sharp 36.5 keV and 98.4 keV LCS peaks were observed in two separate experiments based on electron beams tuned at 32 MeV and 37 MeV, that were brought in collision with the (Power)peak = 4 GW Nd.YAG laser operating at 532 nm and 266 nm wavelengths. The linac was operating at 60 Hz with an electron beam pulse length of...

We have used 300 keV Al+‐irradiation and 1 MeV proton‐irradiation to obtain vacancy‐migration enhanced phase transformation of FePt nanoparticles at lower temperatures (∼200° C). SRIM‐2006 computer code was used to estimate the irradiation parameters and the defect concentrations. Low temperature annealing showed promising results, but further annealing at higher temperatures gave detrimental effects due to lattice strain produced by larger defect clusters. These effects are more prominent in proton‐irradiation and the effects of vacancy clusters seem to remain stronger even at higher temperatures. The magnetization results indicate dissociation of vacancy clusters above 600° C. The magnetization studies of 700° C and 800° C annealed particles aged for one year at room temperature showed defect strain release over time.