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The possibility of isomer depletion, an externally induced transfer of population from long-lived nuclear isomers to shorter-lived states, has been investigated for many years, motivated by questions of science and the potential for applications. This review surveys the history and outcomes of such investigations as an entry point to this topic and looks toward further research in this field. [ABSTRACT FROM AUTHOR]

The high spin structure of 108Ag nucleus has been studied using the reaction 11B + 100Mo at 39 MeV with Indian National Gamma Array (INGA) at TIFR-BARC accelerator facility. From the two- and higher-fold coincidence analysis of the emitted γ-rays, the level structure of the nucleus is built, with addition of around ∼ 60 new transitions. A new positive parity dipole band has been observed and significant additions have been made in the low spin region. A pair of nearly degenerate, negative parity, dipole bands is established, which is studied using the triaxial projected shell model (TPSM).

We have performed a theoretical study concerning the analysis of the nuclear and atomic resonance conditions for 110mAg isomer depletion through nuclear excitation by electron capture (NEEC). This analysis includes selection of the relevant fusion-evaporation reaction for 110mAg isomer production and calculation of its cross section. Moreover, using the relativistic multiconfiguration Dirac-Fock method, calculations of the dependence of the energy released by electron capture into specific atomic subshells (N, O and P) on the 110mAg ion charge state have been carried out. In addition, the potentially possible kinetic energy of the NEEC resonance and predictions of the mean equilibrium charge state for the 110mAg recoil ions as a function of its kinetic energy in the C stopping medium have been evaluated. [ABSTRACT FROM AUTHOR]

We present theoretical research on the optimal atomic resonance conditions for long-lived (T1=2 ~ 6.85 h) 93mMo isomer depletion via nuclear excitation by electron capture (NEEC) in a beam-based scenario. Analysis of potentially possible NEEC-resonance kinetic energy and predictions of the mean equilibrium charge state for the 93mMo recoil ion as a function of its kinetic energy in the He, C, Mg, and Al stopping media have been performed. We have found for the solid targets the high probability of observing the NEEC process for electron capture into M subshells for q = +33 charge state, and also significant probability for electron capture into N subshells for q = +34. Moreover, we have concluded that, for the studied solid targets, the occurrence of NEEC seems to be more probable than for a He gas target. The results of our study should be an important step toward the controlled release of energy stored in the nuclear isomer of some elements and may also be useful in the development of a new class of nuclear energy sources. [ABSTRACT FROM AUTHOR]

For a better understanding of the nature of isomer depletion via the nuclear excitation by electron capture (NEEC) process, we have presented here, for the long-lived (T1/2 ~ 6.85 h) 93mMo isomer, the results of highprecision multiconfiguration Dirac-Fock calculations concerning the dependence of the energy released by electron capture into different atomic subshells of the N, M, and L shells on the specific charge state. These energy values can be understood as benchmarks, i.e., reference parameters, which are crucial for implementations of the proposed beam-based scenario approach for different stopping targets. The authors believe that this detailed analysis of the atomic conditions for the NEEC process should be a first step to applied research, which aims to allow the controlled release of energy stored in the nuclear isomer of selected elements. The presented studies may contribute to the development of the concept of new, unconventional, and ultra-energy-dense nuclear power sources. [ABSTRACT FROM AUTHOR]

The third-order reaction, H + O2 + M - -> HO2 + M, is measured near the low-pressure limit at room temperature for M = He, Ne, Ar, Kr, O2, N2, and H2O and over an extended range of temperatures in a shock tube for M = Ar, O2, and N2. The measurements are consistent with the available experimental record and, in particular, confirm the exceptionally high recombination rate constant when M = H2O.

A comprehensive study of the low-lying states of 108Ag, near the isomeric state at Ei = 110 keV with Jπ = 6+ and T1/2 = 438 y, has been presented. Spectroscopy of these states has been carried out using the reaction 100Mo(11B, 3nγ)108Ag at 39 MeV beam energy using INGA. The multipolarities and electromagnetic nature of the transitions have been assigned based on the angular correlation and polarization measurements. The experimentally identified states have been compared to the results of the Projected Hartree-Fock calculations to understand the configurations involved in these states. [ABSTRACT FROM AUTHOR]

The scattering of thermal neutrons from isomeric nuclei may include events in which the outgoing neutrons have increased kinetic energy. This process has been called inelastic neutron acceleration, or INNA, and occurs when the final nucleus, after emission of the neutron, is left in a state with lower energy than that of the isomer. The result, therefore, is an induced depletion of the isomer to the ground state. A cascade of several γ's must accompany the neutron emission to release the high angular momentum of the initial isomeric state. INNA was previously observed in a few cases, and the measured cross sections were only in modest agreement with theoretical estimates. The most recent measurement of an INNA cross section was σINNA=258±58 b for neutron scattering by 177Lum. In the present work, an INNA cross section of σINNA=168 ± 33 b was deduced from measurements of the total burnup of the high-spin, four-quasiparticle isomer 178Hfm2 during irradiation by thermal neutrons. Statistical estimates for the probability of different reaction channels past neutron absorption were used in the analysis, and the deduced σINNA was compared to the theoretically predicted cross section. [ABSTRACT FROM AUTHOR]

An anomalous ratio between Kα and Kβ fluorescence interpreted with plasma radiation modeling can be a useful diagnostic in laser-produced plasmas. In cold tungsten there exists a similar but as yet undocumented anomaly: for 2 MeV end point bremsstrahlung in the forward direction Kβ/Kα1≃1, while this ratio is closer to 0.5 for bremsstrahlung in reflection and for an isolated atom. As in the laser-produced plasma, the anomalous ratio reflects a localized source of fluorescence inside the material combined with differential attenuation of the fluorescence photons on their way out. To measure the ≃60 keV fluorescence lines, a Cauchois transmission crystal spectrograph that works well for laser-produced plasmas must suppress the intense bremsstrahlung that accompanies the fluorescence, by beefing up marginal shielding and avoiding extraneous scatter sources. [ABSTRACT FROM AUTHOR]

In a material, a beam of x rays is accompanied by various kinds of secondary radiation, including Compton electrons from collisions between the x rays and the material’s electrons. For megavoltage bremsstrahlung in air, many of these Compton electrons are forward-directed and fast enough to be deflected outside the beam’s edge by a magnetic field perpendicular to the beam. At the beam’s edge, the dose from the deflected Compton electrons has a pattern that depends on the radiation’s end point energy. Dose patterns measured with radiochromic film on a nominally 1 and 2 MV linear accelerator agree reasonably well with the corresponding Monte Carlo computations. With further development, the dose pattern produced outside the beam by such a sweeper magnet could become a noninvasive way to monitor megavoltage bremsstrahlung, when the end point energies are difficult to determine with other methods. [ABSTRACT FROM AUTHOR]

Radial inhomogeneity scale lengths for radial electric field, ion density, and magnetic-field-aligned (parallel) electron-drift velocity have been measured and interpreted in magnetized, low-temperature, collisionless plasma. The effect of a narrow layer of inhomogeneity in these parameters on the excitation of electrostatic ion-cyclotron waves is investigated. When the ion Larmor radius ρi is on the order of, or larger than, the half-width at half-maximum σr{Er} of the Gaussian-like, radially localized, radial electric-field profile Er(r), the radial profile of the azimuthal ion rotation velocity, measured using laser-induced fluorescence (LIF), has a peak that, because of finite-Larmor-radius effects, is significantly lower than the peak of the combined radial profile of the E×B and diamagnetic drift velocities. Results of an experimentally validated test-particle simulation are presented and applied using experimentally relevant electric-field profiles. Two experimental configurations are explored for which the ions enter into the electric field at different rates. In one configuration, the ions experience an effectively adiabatic increase in electric-field strength. In the other configuration, the increase in electric-field strength is effectively instantaneous. The simulation reproduces both the main features of the radial profile of LIF-measured ion flow and the observed density depletion in regions of relatively high plasma potential for experimental conditions in which no waves were observed. The density depletion is interpreted as resulting from the finite-Larmor-radius ion orbits in the presence of an inhomogeneous electric field with radial scale length σr{Er}≈ρi. [ABSTRACT FROM AUTHOR]

Presents an experiment using a large laser facility to simulate young supernova remnants. Component of the laboratory system; Use of x-ray radiography; Provision of energy for explosion by hohlraum.

A segmented disk electrode is described that produces and controls both relative drift parallel to the magnetic field and localized flow perpendicular to the magnetic field in a Q machine plasma. Measurements of the electron drift velocity va with respect to the ions, and the electric field E for many bias-voltage combinations are used to demonstrate the controllability of the ratio v[sub E]/v[sub d], where v[sub E]=E×B/B², in a narrow channel between the regions that magnetically map to the segments. Radial electric fields of magnitudes ranging from 0 to ± 3 V/cm localized within a current channel with parallel electron drift velocities up to half the electron thermal velocity have been produced with the segmented disk electrode. [ABSTRACT FROM AUTHOR]

A method of obtaining absolute, direct measurements of the spatial and spectral characteristics of bremsstrahlung is discussed. This technique, called x-ray activation of nuclei (XAN) is based on the use of well-known photonuclear reactions which populate long-lived nuclear isomers. These populations sample incident photon continua at discrete excitation energies and effectively store this information for convenient retrieval following the irradiation of gram-sized targets. Recently a series of experiments has been conducted which has significantly expanded the available data for the photoexcitation of a wide range of isomers at higher energies. Thus it has become feasible to extend the use of XAN to energies approaching 4 MeV. The utility of this technique is demonstrated by the characterization of bremsstrahlung from the newly installed research linac at the University of Texas at Dallas. [ABSTRACT FROM AUTHOR]