Systematic performance study of common neutron guide geometries

Klenø, Kaspar Hewitt; Lieutenant, K.; Andersen, K.H.; Lefmann, Kim

doi:10.1016/j.nima.2012.08.027

Cited by 55 publications

(34 citation statements)

References 19 publications

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“…Gaps in the divergence distribution were also observed when we positioned the focal point closer to the source [7]. The divergence anomaly in this case, however, is caused by a discontinuous connection of different geometry mirrors as was reported on a similar truncated geometry in a former study [10]. Actually, the glancing angle from the sample area (20 mm in height) to the region connecting the straight and the elliptical sections is 0.3-0.5…”

Section: -P2 Qens/wins 2014supporting

confidence: 65%

Beam-transport optimization for cold-neutron spectrometer

Nakajima

Ohira‐Kawamura

Kikuchi

et al. 2015

EPJ Web of Conferences

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Abstract. We report the design of the beam-transport system (especially the vertical geometry) for a cold-neutron disk-chopper spectrometer AMATERAS at J-PARC. Based on the elliptical shape, which is one of the most effective geometries for a ballistic mirror, the design was optimized to obtain, at the sample position, a neutron beam with high flux without serious degrading in divergence and spacial homogeneity within the boundary conditions required from actual spectrometer construction. The optimum focal point was examined. An ideal elliptical shape was modified to reduce its height without serious loss of transmission. The final result was adapted to the construction requirements of AMATERAS. Although the ideas studied in this paper are considered for the AMATERAS case, they can be useful also to other spectrometers in similar situations.

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Section: -P2 Qens/wins 2014supporting

confidence: 65%

Beam-transport optimization for cold-neutron spectrometer

Nakajima

Ohira‐Kawamura

Kikuchi

et al. 2015

EPJ Web of Conferences

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“…Another possibility for guide design is the combination parabolic-straightparabolic, where the straight section can be curved. This combination transmists almost as well as an elliptical guide 24 .…”

Section: The Guide Systemsmentioning

confidence: 96%

“…For instruments of 60 m and longer, and for the 40 m triple-axis instruments, we have employed elliptical guides for beam transport, since recent experiments and simulations has shown this design to be strongly superior over traditional curved guides 6,24 . For the values of guide reflectivities, we have everywhere used recent information from one supplier 25 .…”

Section: The Guide Systemsmentioning

confidence: 99%

“…On the other hand, with modern ballistic-type guides, the transport of neutrons represents no essential problem 24 , while the instrument space becomes less restricted at the same time as the general background level decreases. In addition, certain combinations of T and τ may result in instruments with lengths which allow them to be grouped together in common instrument halls, rather than requiring separate buildings.…”

Section: Considerations Beyond a Simple Figure-of-meritmentioning

confidence: 99%

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Simulation of a suite of generic long-pulse neutron instruments to optimize the time structure of the European Spallation Source

Lefmann

Klenø

Birk

et al. 2013

Review of Scientific Instruments

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We here describe the result of simulations of 15 generic neutron instruments for the long-pulsed European Spallation Source (ESS). All instruments have been simulated for 20 different settings of the source time structure, corresponding to pulse lengths between 1 ms and 2 ms; and repetition frequencies between 10 Hz and 25 Hz. The relative change in performance with time structure is given for each instrument, and an unweighted average is calculated. The performance of the instrument suite is proportional to a) the peak flux and b) the duty cycle to a power of approx. 0.3. This information is an important input to determining the best accelerator parameters. In addition, we find that in our simple guide systems, most neutrons reaching the sample originate from the central 3-5 cm of the moderator. This result can be used as an input in later optimization of the moderator design. We discuss the relevance and validity of defining a single Figure-ofMerit for a full facility and compare with evaluations of the individual instrument classes.

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“…With the addition of the super-mirror coating in the seventies [4,5], another vital step in the improvement of neutron guides was taken, increasing dramatically the reflection angle and thus the divergence and intensity transported by the guide. In recent years ballistic guides with straight tapering [6,7], parabolic tapering [8,9] and full elliptical [8][9][10][11] geometries have been investigated and implemented with the aim of reducing transport losses and improving divergence profiles in guide systems.…”

Section: Introductionmentioning

confidence: 99%