54516854
Derivation and quantitative analysis of the differential self-interrogation Feynman-alpha method
A stochastic theory for a branching process in a neutron population with two energy levels is used to assess the applicability of the differential self-interrogation Feynman-alpha method by numerically estimated reaction intensities from Monte Carlo simulations. More specifically, the variance to mean or Feynman-alpha formula is applied to investigate the appearing exponentials using the numerically obtained reaction intensities.
21278706
Submillimeter-resolution radiography of shielded structures with laser-accelerated electron beams
We investigate the use of energetic electron beams for high-resolution radiography of flaws embedded in thick solid objects. A bright, monoenergetic electron beam (with energy >100 MeV) was generated by the process of laser-wakefield acceleration through the interaction of 50-TW, 30-fs laser pulses with a supersonic helium jet. The high energy, low divergence, and small source size of these beams make them ideal for high-resolution radiographic studies of cracks or voids embedded in dense materials that are placed at a large distance from the source. We report radiographic imaging of steel with submillimeter resolution.
117722455
Neutron-induced 235 U fission spectrum measurements using liquid organic scintillation detectors
Measurements have been performed at Los Alamos Neutron Science Center to acquire neutron fission spectra of ${}^{235}$U in the energy range between 0.5 and 10 MeV. These new data complement the currently available experimental data, which are not well known in the energy range below 1 and above 5 MeV. Organic liquid scintillation detectors (EJ-309s) were used together with a digital data-acquisition system. The EJ-309 detectors show excellent pulse shape discrimination capabilities and this is vital for identifying only neutron pulses and rejecting $\ensuremath{\gamma}$-ray pulses. The measurement data show the dependence of average fission neutron energy as a function of the inducing neutron energy. The data agree well with previously published measurements and Watt spectra fits for energies up to tens of MeV. At high fission-inducing neutron energies the spectrum deviates from Watt-spectra fits. The increased energy deposited in higher energy neutron-induced fissions does not significantly increase emitted fission neutron energies for up to 10 MeV. A significant decrease in neutron energy around second-chance fission cannot be observed beyond the current measurement uncertainties.
41048114
Application of a laser-wakefield driven monochromatic photon source to nuclear resonance fluorescence
Nuclear resonance fluorescence is of particular interest to the detection of special nuclear material (SNM) where isotopic characterization is paramount. In addition to photons emitted by resonance de-excitation, there will also be a significant amount of backscattered photons that will distort the NRF signal. The backscattered spectra must be characterized in order to design a detection system that maximizes the material identification probability. However, to our knowledge the cross-sections for nuclear resonance absorption do not exist in any version MCNP. Therefore, a novel method is applied here to reproduce the measured results from Bertozzi et al. using bremsstrahlung X-rays. The NRF signal this source was compared with the response from the University of Nebraska (UNL) quasi-monochromatic X-ray source to compare the performance on a per source photon basis. An absolute comparison of each source is left for future work. The results of the simulations show that the UNL source would have a higher efficiency on a per source photon basis by a factor of approximately 170.
10071539
MeV-energy x rays from inverse compton scattering with laser-wakefield accelerated electrons.
We report the generation of MeV x rays using an undulator and accelerator that are both driven by the same 100-terawatt laser system. The laser pulse driving the accelerator and the scattering laser pulse are independently optimized to generate a high energy electron beam (>200  MeV) and maximize the output x-ray brightness. The total x-ray photon number was measured to be ∼1×10(7), the source size was 5  μm, and the beam divergence angle was ∼10  mrad. The x-ray photon energy, peaked at 1 MeV (reaching up to 4 MeV), exceeds the thresholds of fundamental nuclear processes (e.g., pair production and photodisintegration).
122721397
Analysis of Neutron and Photon Detection Position for the Calibration of Plastic (BC-420) and Liquid (BC-501) Scintillators
This report presents the results of the neutron and photon calibration of a Bicron BC-420 plastic scintillator and a BC-501 liquid scintillator using a set of reference gamma sources and a Cf-252 source. The position of neutron and photon detection inside the scintillators as a function of energy is investigated by Monte Carlo simulation.
34636075
The LHCb Muon detector alignment
The Muon detector of the LHCb experiment is used in both trigger steps (Level-0 and High Level Trigger) and provides also the off-line Muon Identification. Therefore the proper alignment of the detector is needed and it should be monitored during the data taking. In this document the methods used for the alignment of the Muon detector and the results obtained are presented. Two sets of data have been analyzed: a sample of Monte Carlo tracks simulated from the interaction point, and, for a first check with real data on the survey measurements, the cosmic rays acquired during the commissioning in September and October 2008.