Bi-spectral extraction through elliptic neutron guides
نویسندگان
چکیده
In this article we present the results of investigating a suggested guide extraction system utilizing both a thermal and a cold moderator at the same time, the so-called bi-spectral extraction. Here, the thermal moderator has line of sight to the sample position, and the neutrons from the cold source are reflected by a supermirror towards the sample. The work is motivated by the construction of the European Spallation Source (ESS) but the results are general and can be used at any neutron source. Due to the long pulse structure, most instruments at ESS will be long, often exceeding 50 m from moderator to detector. We therefore investigate the performance of bi-spectral extraction for instrument lengths of 30 m, 56 m, 81 m and 156 m. In all these cases, our results show that we can utilize both moderators (and thus high intensity in a wide wavelength band) in the same instrument at a cost of flux of 5-25 % for neutrons with wavelength larger than 1 Å. In general, the divergence distribution is smooth at the sample position for all wavelengths.
منابع مشابه
The dependence of the gravity effect in elliptic
8 Elliptic neutron guides are expected to be widely used for construction of long neutron 9 beamlines at the future European Spallation Source and other facilities due to their superiour 10 transmission properties compared to conventional straight guides. At the same time, neutrons 11 traveling long distances are subject to the action of gravity that can significantly modify their 12 flight pat...
متن کاملAn improved elliptic guide concept for a homogeneous neutron beam without direct line of sight
Ballistic neutron guides are efficient for neutron transport over long distances, and in particular elliptically shaped guides have received much attention lately. However, elliptic neutron guides generally deliver an inhomogeneous divergence distribution when used with a small source, and do not allow kinks or curvature to avoid a direct view from source to sample. In this article, a kinked do...
متن کاملBi-spectral beam extraction in combination with a focusing feeder
Bi-spectral beam extraction combines neutrons from two different kind of moderators into one beamline, expanding the spectral range and thereby the utilization of an instrument. This idea can be realized by a mirror that reflects long wavelength neutrons from an off-axis colder moderator into a neutron guide aligned with another moderator emitting neutrons with shorter wavelengths which will be...
متن کاملOn the Spectral Properties of Degenerate Non-selfadjoint Elliptic systems of Differential Operators
متن کامل
New variants of the global Krylov type methods for linear systems with multiple right-hand sides arising in elliptic PDEs
In this paper, we present new variants of global bi-conjugate gradient (Gl-BiCG) and global bi-conjugate residual (Gl-BiCR) methods for solving nonsymmetric linear systems with multiple right-hand sides. These methods are based on global oblique projections of the initial residual onto a matrix Krylov subspace. It is shown that these new algorithms converge faster and more smoothly than the Gl-...
متن کامل