Nuclear Resonance Fluorescence Research Articles

Transmission nuclear resonance fluorescence measurements of 238U in thick targets

Transmission nuclear resonance fluorescence measurements were made on targets consisting of Pb and depleted U with total areal densities near 86 g / cm 2 . The 238U content in the targets varied from 0% to 8.5% (atom fraction). The experiment demonstrates the capability of using transmission measurements as a non-destructive technique to identify and quantify the presence of an isotope in samples with thicknesses comparable to the average thickness of a nuclear fuel assembly. The experimental data also appear to demonstrate the process of notch refilling with a predictable intensity. Comparison of measured spectra to previous backscatter 238U measurements indicates general agreement in observed excited states. Evidence of two new 238U excited states and possibly a third state have also been observed.

Nondestructive inspection of explosive materials using linearly polarized two-colored photon beam

A nondestructive inspection method for screening explosive materials that are hidden in passenger vehicles, trucks, and cargo containers with radiation shielding was presented. The method was examined experimentally using linearly polarized two-colored photon beam . A sample object was irradiated with the photon beam, followed by an emission of gamma-rays in nuclear resonance fluorescence . The gamma-rays from oxygen and nitrogen emitted through nuclear resonance fluorescence were measured using high-purity germanium detectors. We were able to evaluate the element concentration ratio.

Nondestructive isotope detection of hidden materials by using nuclear resonance fluorescence

Nondestructive isotope detection of hidden materials by using nuclear resonance fluorescence

Nuclear Resonance Fluorescence Excitations Measured by LaBr3(Ce) Scintillators

Nuclear Resonance Fluorescence Excitations Measured by LaBr3(Ce) Scintillators

Plant pentacyclic triterpenic acids as modulators of lipid membrane physical properties

Free triterpenic acids (TTPs) present in plants are bioactive compounds exhibiting multiple nutriceutical activities. The underlying molecular mechanisms have only been examined in part and mainly focused on anti-inflammatory properties, cancer and cardiovascular diseases, in all of which TTPs frequently affect membrane-related proteins. Based on the structural characteristics of TTPs, we assume that their effect on biophysical properties of cell membranes could play a role for their biological activity. In this context, our study is focused on the compounds, oleanolic (3β-hydroxy-12-oleanen-28-oic acid, OLA), maslinic (2α,3β-dihydroxy-12-oleanen-28-oic acid, MSL) and ursolic ((3β)-3-hydroxyurs-12-en-28-oic acid, URL) as the most important TTPs present in orujo olive oil. X-ray diffraction, differential scanning calorimetry, 31P nuclear magnetic resonance and Laurdan fluorescence data provide experimental evidence that OLA, MSL and URL altered the structural properties of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and DPPC-Cholesterol (Cho) rich membranes, being located into the polar-hydrophobic interphase. Specifically, in DPPC membranes, TTPs altered the structural order of the Lβ′, phase without destabilizing the lipid bilayer. The existence of a nonbilayer isotropic phase in coexistence with the liquid crystalline Lα phase, as observed in DPPC:URL samples, indicated the presence of lipid structures with high curvature (probably inverted micelles). In DPPC:Cho membranes, TTPs affected the membrane phase properties increasing the Laurdan GP values above 40°C. MSL and URL induced segregation of Cho within the bilayer, in contrast to OLA, that reduced the structural organization of the membrane. These results strengthen the relevance of TTP interactions with cell membranes as a molecular mechanism underlying their broad spectrum of biological effects.

Nuclear resonance fluorescence ofNp237

Identification and characterization of fissile material is of international concern because of the possibility of proliferation. For safeguards applications, techniques providing isotopic information are necessary [1]. However, few techniques can distinguish between fissile isotopes. Nuclear resonance fluorescence is one technique that can be used in applications to identify and quantify isotopic content. NRF has also been proposed in several detector systems as a viable way to identify fissile material in cargo containers [2, 3]. It is necessary to measure the characteristic resonances of each isotope that is to be distinguished in identification and assay applications.

Photoexcitation of astrophysically important states inMg26. II. Ground-state-transition partial widths

The level structure of $^{26}\mathrm{Mg}$ near the neutron-separation energy, which is of interest for s-process nucleosynthesis, was studied at the High Intensity Gamma-Ray Source of the Triangle Universities Nuclear Laboratory using the method of nuclear resonance fluorescence. A nearly monoenergetic and linearly polarized $\ensuremath{\gamma}$-ray beam was used to scan the excitation energy range from $10.5$ to $11.7$ MeV. For the five states observed, the total widths and partial widths are determined. Precise measurement of these widths is necessary for the prediction of neutron production for the s-process.

Design and operation of a tunable MeV-level Compton-scattering-basedγ-ray source

A monoenergetic gamma-ray (MEGa-ray) source based on Compton scattering, targeting nuclear physics applications such as nuclear resonance fluorescence, has been constructed and commissioned at Lawrence Livermore National Laboratory. In this paper, the overall architecture of the system, as well as some of the design decisions (such as laser pulse lengths and interaction geometry) made in the development of the source, are discussed. The performances of the two laser systems (one for electron production, one for scattering), the electron photoinjector, and the linear accelerator are also detailed, and initial $\ensuremath{\gamma}$-ray results are presented.

Characterization and applications of a tunable, laser-based, MeV-class Compton-scatteringγ-ray source

A high peak brilliance, laser-based Compton-scattering $\ensuremath{\gamma}$-ray source, capable of producing quasimonoenergetic photons with energies ranging from 0.1 to 0.9 MeV has been recently developed and used to perform nuclear resonance fluorescence (NRF) experiments. Techniques for characterization of $\ensuremath{\gamma}$-ray beam parameters are presented. The key source parameters are the size ($0.01\text{ }\text{ }{\mathrm{mm}}^{2}$), horizontal and vertical divergence ($6\ifmmode\times\else\texttimes\fi{}10\text{ }\text{ }{\mathrm{mrad}}^{2}$), duration (16 ps), and spectrum and intensity (${10}^{5}\text{ }\text{ }\mathrm{photons}/\mathrm{shot}$). These parameters are summarized by the peak brilliance, $1.5\ifmmode\times\else\texttimes\fi{}{10}^{15}\text{ }\text{ }\mathrm{photons}/{\mathrm{mm}}^{2}/{\mathrm{mrad}}^{2}/\mathrm{s}/0.1%$ bandwidth, measured at 478 keV. Additional measurements of the flux as a function of the timing difference between the drive laser pulse and the relativistic photoelectron bunch, $\ensuremath{\gamma}$-ray beam profile, and background evaluations are presented. These results are systematically compared to theoretical models and computer simulations. NRF measurements performed on $^{7}\mathrm{Li}$ in LiH demonstrate the potential of Compton-scattering photon sources to accurately detect isotopes in situ.

Compton ring for nuclear waste management

This paper describes an intense gamma-ray source based on the Compton scattering of laser photons by the electrons circulating in the storage ring. Gamma-ray energies fall in the range from 1 to 5MeV. This source is an ideal tool for nuclear waste management by the nuclear resonance fluorescence method. The Compton ring is also a very promising tool for application in novel technologies for express cargo inspection to prevent nuclear terrorism. A crab-crossing scheme in the ring lattice can be expected to permit a gamma-beam intensity of up to 5×1013gammas/s with the latest laser and accelerator technologies.

Preparation of functional spherical polysilsesquioxane/gold nanoparticle composites and their applications in DNA assay

Functional spherical solid and hollow particles of polysilsesquioxanes (PSQs) containing amine, thiol, and vinyl groups were prepared by polymerizing organotrialkoxysilanes (OTASs) containing corresponding chemical groups. Fluorescent PSQ particles were prepared by physically entrapping Rhodamine 6G, Coumarin 7, and Fluoresceine sodium salts. The intensity of fluorescent light increased initially with increasing amount of entrapped fluorophores and then leveled off or decreased slightly after reaching a maximum value. PSQ particles containing gold nanoparticles (GNPs), both inside and on the surface, were prepared by the in situ reduction of gold ions by the PSQ particles. When the reduction reaction was carried out for extended periods of time, the GNP that had formed inside the poly(3-mercaptopropyl)silsesquioxane (PMPSQ) and polyvinylsilsesequioxane (PVSQ) particles underwent interesting morphological changes. PSQ particles containing amine and thiol groups fixed the GNPs on the surface, which could be utilized further in binding amine-modified oligo-DNA strands. The aggregation of PSQ/GNP particles combined with complementary oligo-DNA strands was examined to demonstrate that these particles could be applied to DNA assays and isolation. The particles were characterized by scanning electron microscopy, transmission electron microscopy, solid state nuclear magnetic resonance spectroscopy, ultraviolet/visible spectroscopy, and fluorescence microscopy.

Nondestructive assay of plutonium and minor actinide in spent fuel using nuclear resonance fluorescence with laser Compton scattering [formula omitted

We propose a new nondestructive assay method for 235U, 239Pu, and minor actinides in spent nuclear fuel assembly in a water pool. Nuclear fuel materials are detected using nuclear resonance fluorescence (NRF) with laser Compton scattering (LCS) γ-rays. The NRF assay can provide a finger print of each isotope since the NRF γ-ray energy is characteristic of a specific nuclide. We design a high-flux LCS γ-ray source, in which γ-rays are generated by collision of laser photons provided from Yb-doped fiber laser and electrons from energy recovery linac. This system has following advantages; this can detect isotopes of most elements behind heavy materials such as uranium of a thickness of several centimeters, and analyze the fuel assembly in a water pool. A simulation calculation shows that we can detect 1% fraction 239Pu in all the fuel rods with statistical error lower than 2% using the high flux LCS γ-ray source and the measurement time of 4000s.

SU‐GG‐I‐159: In‐Vivo Iron Measurement through Nuclear Resonance Fluorescence

In‐vivo quantitative measurement of iron has been the focus of several studies related to iron disorders in the human body. Techniques such as SQUID and MRI have been used to detect liver iron stores in patients afflicted with hemochromatosis and thalassemia. Here we present a gamma‐stimulated spectroscopy method to detect iron in an aqueous sample through nuclear resonance fluorescence. A high‐energy tuned gamma‐ray beam was used to excite characteristic gamma emission from an iron sample suspended in water. The gamma‐beam was generated using the free‐electron‐laser source at Duke University and tuned to 6.93 MeV to resonate with the 6926 keV energy state in natural iron (56‐Fe). The beam was collimated and focused onto a sample of natural iron immersed in water corresponding to an iron concentration of 180 mg/g. An identical phantom of copper immersed in water was used to obtain an estimate of the background noise from the spectroscopic acquisition setup. Emitted gamma spectra were generated for each sample using a high‐purity germanium (HPGe) detector and background corrected using time‐of‐flight techniques. The resulting spectrum showed a strong gamma line at 6926 keV originating from 56‐Fe in the sample. This experiment demonstrates the ability to selectively stimulate and quantify a specific energy level in iron through nuclear resonance gamma‐stimulated spectroscopy. Through tomographic imaging the technique can be expanded to obtain three‐dimensional quantitative maps of iron stores in the liver or other organs in the body in a manner that is both non‐invasive and in‐vivo.

Ionic perylene-3,4-dicarboximide as chromonic mesogens and the use of a fluorescence technique in determining phase-transition temperatures

We report a study of the chromonic liquid-crystalline properties of 2-(N,N-diethyl-N-methylammonium)ethylperylene-3,4-dicarboximide formate (1) in aqueous solution by polarised optical microscopy (POM), 2H nuclear magnetic resonance (NMR) spectroscopy and fluorescence spectroscopy. Compound 1 shows chromonic liquid-crystalline properties at concentrations higher than 4 wt% at room temperature. We showed that fluorescence spectroscopy could be used to determine the concentration-dependent, phase-transition temperatures of this chromonic liquid crystal. The values determined by fluorescence spectroscopy are consistent with the values determined by 2H NMR spectroscopy and POM.

Mössbauer Spectroscopy: Elegance and versatility in chemical diagnostics

Dedicated to Professor Rudolf Ludwig Mössbauer on the occasion of his 80th birthday.Soon after the discovery of the recoilless nuclear resonance fluorescence by Rudolf L. Mössbauer some fifty years ago a new spectroscopic technique developed quickly on the basis of this resonance phenomenon as an excellent tool for the investigation of materials through electric and magnetic hyperfine interactions between electrons and suitable Mössbauer nu-clides. Many disciplines of solid state research have benefited from applications of the new tool for non-destructive phase analysis. Chemists in particular have recognized the information that can be derived from Mössbauer spectra regarding oxidation and spin state, molecular symmetry, bonding properties, magnetism, dynamic phenomena such as spin state switching, electronic transfer processes and other phase fluctuations to name a few. This Keynote Lecture presents highlights of chemical applications of Mössbauer spectroscopy selected from work during the past five decades which will demonstrate the elegance and versatility of the technique in the hands of (not only) chemists, but materials scientists in the broadest sense. The retrospect begins with studies in the early sixties on simple oxides and coordination compounds, where Mössbauer spectroscopy played a decisive role in solving unanswered questions, and concludes with fascinating current discoveries on the Planet Mars and most recent developments in the use of synchrotron radiation for nuclear resonance scattering (NFS, NIS).

On the Search for Nuclear Resonance Fluorescence Signatures of $^{235}{\rm U}$ and $^{238}{\rm U}$ Above 3 MeV

Nuclear resonance fluorescence is a physical process that provides an isotope-specific signature that could be used for the identification and characterization of materials. The technique involves the detection of prompt discrete-energy photons emitted from a sample that is exposed to photons in the MeV energy range. Potential applications of the technique range from detection of high explosives to characterization of special nuclear materials such as 235U. Pacific Northwest National Laboratory and Passport Systems have collaborated to conduct a a pair of measurements to search for a nuclear resonance fluorescence response of 235U above 3 MeV and of 238U above 5 MeV using an 8 g sample of highly enriched uranium and a 90 g sample of depleted uranium. No new signatures were observed. The minimum detectable integrated cross section for 235U is presented.

Isotope-specific detection of low-density materials with laser-based monoenergetic gamma-rays

What we believe to be the first demonstration of isotope-specific detection of a low-Z and low density object shielded by a high-Z and high-density material using monoenergetic gamma rays is reported. The isotope-specific detection of LiH shielded by Pb and Al is accomplished using the nuclear resonance fluorescence line of L7i at 478 keV. Resonant photons are produced via laser-based Compton scattering. The detection techniques are general, and the confidence level obtained is shown to be superior to that yielded by conventional x-ray and gamma-ray techniques in these situations.

Photoactivation of the p-nucleus 92Mo with bremsstrahlung at ELBE

In nuclear network calculations especially the p-nucleus 92Mo is frequently underproduced. Since experimental data of the photodisintegration of 92Mo so far do not exist, it was necessary to measure the reaction yields with the photoactivation method using the brems-strahlung facility ELBE at FZ Dresden-Rossendorf. Also the reaction 100Mo(γ,n) could be tested while irradiating Mo samples of natural composition. The photon fluence was measured with nuclear resonance fluorescence (NRF) of strong and well-known transitions in 11B. As a normalization standard the photoactivation reaction 197Au(γ,n) was used. For the 65 s half-life of 91mMo a fast pneumatic delivery was used. The photoactivation yields of the (γ,p) and (γ,n) reactions are compared to yield integrals of the bremsstrahlung spectral shape folded with the cross sections derived from Hauser-Feshbach nuclear model calculations using the TALYS program and cross sections from earlier experiments.

Spin and parity assignments to dipole excitations of the odd-mass nucleus 207Pb from nuclear resonance fluorescence experiments with linearly-polarized γ-ray beams

Pb(γ⃗,γ′) photon scattering reactions were studied [1] with the nearly monochromatic, linearly polarized photon beams at the High Intensity γ-ray Source (HIγS) at the DFELL. Azimuthal scattering intensity asymmetries measured with respect to the polarization plane of the beam have been used for the first time to assign both the spin and parity quantum numbers of dipole excited states of 206,207,208Pb at excitation energies in the vicinity of 5.5 MeV. Evidence for dominant particle-core coupling is deduced from these results along with information on excitation energies and electromagnetic transition matrix elements.

Photoexcitation of astrophysically important states inMg26

We performed a nuclear resonance fluorescence experiment to determine the energy and quantum numbers of excited states in {sup 26}Mg. Spin-parity ambiguities of excited states in {sup 26}Mg, the compound nucleus for the s-process neutron source {sup 22}Ne({alpha},n){sup 25}Mg, result in large uncertainties in the reaction rates. The present work uses the monoenergetic {gamma}-ray beam from the High-Intensity {gamma}-ray Source to probe states in the excitation energy range of E{sub x}=10.8 to 11.4 MeV. Five excited states were observed and unambiguous quantum numbers were assigned at E{sub x}=10 573.3(8) keV (J{sup {pi}}=1{sup -}), E{sub x}=10 647.3(8) keV (J{sup {pi}}=1{sup +}), E{sub x}=10 805.7(7) keV (J{sup {pi}}=1{sup -}), E{sub x}=10 949.1(8) keV (J{sup {pi}}=1{sup -}), and E{sub x}=11 153.5(10) keV (J{sup {pi}}=1{sup +}). The two natural parity states, located between the {alpha}-particle and neutron thresholds, are expected to significantly influence the rate of the competing {sup 22}Ne({alpha},{gamma}){sup 26}Mg reaction. An important finding of this work is that the E{sub x}=11 154 keV level has unnatural parity, contrary to previous results, and thus does not contribute to the {sup 22}Ne+{alpha} reaction rates.