ORNL Oxygen Broomstick Experiment: MCNP model and evaluation results for SINBAD entry NEA-1517/59

The existing entry NEA-1517/59 (SDT2) of the SINBAD database comprises the results of measurement of the neutron transmission spectra through the liquid oxygen broomstick of the length 60” (152.4 cm). The experiment was performed in 1965 at the Tower Shielding Facility located in Oak Ridge National Laboratory and was designed to measure the neutron total cross sections in the range of 1.9 – 8.6 MeV. The purpose of the present work was to assemble the MCNP input deck for the Monte Carlo code MCNP, perform the sample calculations of the radiation transport and sensitivities with evaluated neutron reaction cross section from ENDF/B-VIII.0 and JEFF-3.3, to show the impact on the (n,tot) and (n,α) cross sections and thus to demonstrate the value of this benchmark for the validation of the modern evaluated data. The impact of validation benchmark on $^{16}O(n,α$_0$) cross section was shown do agree with the thick target neutron yield induced by α-particles with energies up to 5 - 6 MeV in carbon. An attempt was also made to find the missing measured data for other ORNL O-broomsticks of length 24” (60.96 cm), 36” (91.44 cm) and probably 72” (182.88 cm)

KFK γ-ray leakage Iron sphere benchmark with Cf source: entry for SINBAD and analysis

An information necessary for the new entry in the SINBAD database was collected and thoroughly analyzed. It covers the measurement of the γ-ray leakage spectra from three iron spheres of diameter 20, 25 and 35 cm with a Cf source in the center. The experiment was performed at Kernforschungszentrum Karlsruhe (KFK) around 1977 and was an extension of measurements of the neutron leakage spectra, the latter were already compiled in SINBAD. This report includes the detailed description of the KFK experiment, the numerical γ-ray leakage spectra and other information necessary for the nuclear data validation. The MCNP input deck was assembled and used for the sample calculations of the radiation transport and sensitivities with the ENDF/B-VIII.0 neutron reaction cross section data. The spontaneous fission of $^{252}$Cf was modelled as a source of neutrons and gammas, both prompt and delayed. If the neutron emission data are rather well established, the knowledge of the γ-ray data is much poorer. In the present work the prompt γ-ray spectrum and multiplicities were combined from known measurements and theoretical calculations. The knowledge of the delayed gamma-ray multiplicities and spectra from $^{252}$Cf(s.f.) are still relying on the old and scarce measurements or compilations. The KFK experiment was compared with similar measurements performed at IPPE a few years later. Agreement between them, confirmed by direct comparison and similar conclusions derived from Monte-Carlo analysis, proves the reliability of both experiments

Scalable quantum error correction code on a ring topology of qubits

Quantum error correction is an important ingredient for scalable quantum computing. Stabilizer codes are one of the most promising and straightforward ways to correct quantum errors, since they do not require excessive complexity of physical qubits, are convenient for logical operations, and improve performance with increasing the involved qubits number. Here, we propose a linear scalable code of the permutative stabilizers for small distances on the ring architecture, which takes into account the topological features of the superconducting platform. We present the way to construct the quantum circuit of the code and provide numerical simulation that demonstrate the exponential logical error rate suppression.Comment: 6 pages, 4 figure

Noise induced oscillations and coherence resonance in a generic model of the nonisothermal chemical oscillator

Oscillating chemical reactions are common in biological systems and they also occur in artificial non-biological systems. Generally, these reactions are subject to random fluctuations in environmental conditions which translate into fluctuations in the values of physical variables, for example, temperature. We formulate a mathematical model for a nonisothermal minimal chemical oscillator containing a single negative feedback loop and study numerically the effects of stochastic fluctuations in temperature in the absence of any deterministic limit cycle or periodic forcing. We show that noise in temperature can induce sustained limit cycle oscillations with a relatively narrow frequency distribution and some characteristic frequency. These properties differ significantly depending on the noise correlation. Here, we have explored white and colored (correlated) noise. A plot of the characteristic frequency of the noise induced oscillations as a function of the correlation exponent shows a maximum, therefore indicating the existence of autonomous stochastic resonance, i.e. coherence resonance

Thermal noise of folding mirrors

Current gravitational wave detectors rely on the use of Michelson interferometers. One crucial limitation of their sensitivity is the thermal noise of their optical components. Thus, for example fluctuational deformations of the mirror surface are probed by a laser beam being reflected from the mirrors at normal incidence. Thermal noise models are well evolved for that case but mainly restricted to single reflections. In this work we present the effect of two consecutive reflections under a non-normal incidence onto mirror thermal noise. This situation is inherent to detectors using a geometrical folding scheme such as GEO\,600. We revise in detail the conventional direct noise analysis scheme to the situation of non-normal incidence allowing for a modified weighting funtion of mirror fluctuations. An application of these results to the GEO\,600 folding mirror for Brownian, thermoelastic and thermorefractive noise yields an increase of displacement noise amplitude by 20\% for most noise processes. The amplitude of thermoelastic substrate noise is increased by a factor 4 due to the modified weighting function. Thus the consideration of the correct weighting scheme can drastically alter the noise predictions and demands special care in any thermal noise design process