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Mezei, J. Zs.; Roos, Johanna Brinne; Shilyaeva, Ksenia; Elander, Nils; Larson, Åsa

doi:10.1103/physreva.84.012703

Cited by 20 publications

(32 citation statements)

References 25 publications

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“…One can crudely estimate V opt as follows: if one assumes that the 10 MeV potential energy of a neutron in the nucleus of radius 1 fm is averaged over the volume of a material made of atoms whose size is larger than the nucleus by a factor of 10 5 , then the average potential energy V opt ∼ 100 neV. For a non-relativistic neutron of kinetic energy of a few meV one can therefore get total external reflection for angles of incidence of a few mrad. Since this ILL experiment multilayer coatings of alternating materials with large neutron optical potential differences with a graded distribution of separations called "supermirrors" [123] have been developed which greatly increase the range of transverse momenta which can be reflected with high probability and therefore the transverse phase space acceptance from the source by exploiting coherent interference of scattering from the different layers (diffraction) over the full spectrum of neutron wavelengths from the cold source. Supermirror performance is roughly classified by a parameter m defined by p T = mp T,N i which measures the increase of the critical angle of reflection relative to nickel of natural isotopic abundance where specular reflection still occurs.…”

Section: Neutron Opticsmentioning

confidence: 99%

“…We do not include in our estimate the various methods by which the initial cold neutron brightness might be increased which are the subjects for ongoing research. Examples include neutronics techniques such as a reentrant moderator designs [133], strategic use of neutron reflector/filters [134], supermirror reflectors [123], and non-specular, high-albedo materials such as diamond nanoparticle composites [135][136][137]. Some of these techniques are not suitable for use at multipurpose spallation sources serving a materials science user community, where sharply defined neutron pulses in time may be required.…”

Section: Design Considerations For An Improved N −N Oscillation Searcmentioning

confidence: 99%

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Neutron-antineutron oscillations: Theoretical status and experimental prospects

et al. 2016

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The observation of neutrons turning into antineutrons would constitute a discovery of fundamental importance for particle physics and cosmology. Observing the n−n transition would show that baryon number (B) is violated by two units and that matter containing neutrons is unstable. It would provide a clue to how the matter in our universe might have evolved from the B = 0 early universe. If seen at rates observable in foreseeable next-generation experiments, it might well help us understand the observed baryon asymmetry of the universe. A demonstration of the violation of B − L by 2 units would have a profound impact on our understanding of phenomena beyond the Standard Model of particle physics.Slow neutrons have kinetic energies of a few meV. By exploiting new slow neutron sources and optics technology developed for materials research, an optimized search for oscillations using free neutrons from a slow neutron moderator could improve existing limits on the free oscillation probability by at least three orders of magnitude. Such an experiment would deliver a slow neutron beam through a magnetically-shielded vacuum chamber to a thin annihilation target surrounded by a low-background antineutron annihilation detector. Antineutron annihilation in a target downstream of a free neutron beam is such a spectacular experimental signature that an essentially background-free search is possible. An authentic positive signal can be extinguished by a very small change in the ambient magnetic field in such an experiment. It is also possible to improve the sensitivity of neutron oscillation searches in nuclei using large underground detectors built mainly to search for proton decay and detect neutrinos. This paper summarizes the relevant theoretical developments, outlines some ideas to improve experimental searches for free neutron oscillations, and suggests avenues both for theoretical investigation and for future improvement in the experimental sensitivity.

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Section: Neutron Opticsmentioning

confidence: 99%

Section: Design Considerations For An Improved N −N Oscillation Searcmentioning

confidence: 99%

Neutron-antineutron oscillations: Theoretical status and experimental prospects

et al. 2016

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“…Because ab initio treatments must consider many excited states out to large internuclear distances, only systems with few electrons and few degrees of freedom are practical to calculate. 16,[27][28][29][30][31][32][33] It is then sensible to validate theoretical methods by comparison to experimental MN results of atom-atom systems. To date, there is limited overlap between systems that have received both theoretical and experimental treatments.…”

Section: Introductionmentioning

confidence: 99%

Reactions of C+ + Cl−, Br−, and I−—A comparison of theory and experiment

Sawyer

Hedvall

Miller

et al. 2019

The Journal of Chemical Physics

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Rate constants for the reactions of C " + Cl & , Br & , and I & were measured at 300 K using the variable electron and neutral density electron attachment mass spectrometry technique in a flowing afterglow Langmuir probe apparatus. Upper bounds of < 10 -8 cm 3 s -1 were found for reaction of C + with Br & and I & , and a rate constant of 4.2 ± 1.1 × 10 &= cm @ s &B was measured for reaction with Cl & . The C + + Clmutual neutralization reaction was studied theoretically from first principles and a rate constant of 3.9 × 10 -10 cm 3 s -1 , an order of magnitude smaller than experiment, was obtained with spin-orbit interactions included using a semi-empirical model. The discrepancy between the measured and calculated rate constants could be explained by the fact that in the experiment the total loss of C + ions was measured, while the theoretical treatment did not include the associative ionization channel. The charge transfer was found to take place at small internuclear distances and the spin-orbit interaction was found to have a minor effect on the rate constant.

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“…Due to the ongoing progress in neutron optical developments it is now possible to use supermirror guides with different shape or tapering designs and rather large angles of reflection of the supermirror coatings [16][17][18][19][20]. Together with the virtual source concept [2,21] and large focusing monochromator arrays [22][23][24][25][26] the intensity at the sample position can be enhanced significantly.…”

Section: Introductionmentioning

confidence: 99%

Parabolic versus elliptic focusing – Optimization of the focusing design of a cold triple-axis neutron spectrometer by Monte-Carlo simulations

Komarek

Böni

Braden

2011

Nuclear Instruments and Methods in Physics Research Section A:

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We present Monte-Carlo simulations for the focusing design of a novel cold-neutron triple-axis spectrometer to be installed at the end position of the cold guide NL-1 of the research reactor FRM-II in Munich, Germany. Our simulations are of general relevance for the design of triple-axis spectrometers at end positions of neutron guides. Using the McStas program code we performed ray trajectories to compare parabolic and elliptic focusing concepts. In addition the design of the monochromator was optimized concerning crystal size and mosaic spread. The parabolic focusing concept is superior to the elliptic alternative in view of the neutron intensity distribution as a function of energy and divergence. In particular, the elliptical configuration leads to an inhomogeneous divergence distribution.

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Mutual neutralization in low-energyH++F−collisions

Cited by 20 publications

References 25 publications

Neutron-antineutron oscillations: Theoretical status and experimental prospects

Neutron-antineutron oscillations: Theoretical status and experimental prospects

Reactions of C+ + Cl−, Br−, and I−—A comparison of theory and experiment

Parabolic versus elliptic focusing – Optimization of the focusing design of a cold triple-axis neutron spectrometer by Monte-Carlo simulations

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