Neutron absorption in supermirror coatings: Effects on shielding

Kolevatov, R.; Schanzer, Christian; Böni, P.

doi:10.1016/j.nima.2018.12.069

Cited by 10 publications

(19 citation statements)

References 22 publications

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“…The fast neutron shielding load decreases as R −3 [17], so even the straight guide shielding gets thinner with distance. On the other hand, increasing the supermirror m value increases the prompt gamma shielding requirement [18], so whilst the table shows the ranges the precise number must be calculated in each case.…”

Section: Summary Of Shielding Costsmentioning

confidence: 99%

Instrument suite cost optimisation in a science megaproject

Bentley¹

2020

J. Phys. Commun.

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This article presents a cost optimisation study of neutron scattering instrumentation at the European Spallation Source (ESS) in Lund, Sweden. This is done by focusing on the main cost drivers for almost half of the instrument hardware-optics and shielding -and trading detailed cost functions against beam transmission functions in a multi-dimensional, yet simple, parameter space. A cost saving of almost 30% is identified. The method is demonstrated in a worked example on a mature instrument design, and there are no reductions in performance. The proposed solution is shown to correspond to a Nash equilibrium of simultaneous shielding and optics strategies, versus the baseline which is trapped by working through sequential strategies. Finally, this cost analysis is bench-marked against, and found to be in agreement with, the costs of operational facilities of a similar class. and optimised simultaneously, around an architectural concept. This is somewhat similar to Brooks' idea of conceptual integrity in software development [4].Achieving this requires co-located personnel, using a common set of tools, and with thorough crosschecking in place, performed by a dedicated team. The suggestion to do this is not taken without a solid basis in existing excellence, since the NIST Center for Neutron Research [5] at NIST (USA) and SINQ [6] at the Paul Scherrer Institut (PSI, Switzerland) both followed this model to some degree.One might expect that a cost reduction carries some sacrifice of scope or performance. This idea is reinforced by many public 'austerity' measures that have taken place since the financial crisis in 2008, but these were often achieved not via efficiency gains but instead from huge budget cuts in critical areas, with proportional reductions in scope. Instead, a simultaneous and architectural shielding and optics strategy will be derived to reduce the costs of these main areas without reducing performance. The other four main cost drivers-choppers, staff, detectors and 'other' that covers admin and overheads, review meetings etc-these are not completely fixed, but they are somewhat less easily optimised architecturally compared to optics and shielding.The savings in the present study come from an expert understanding of the interplay between neutron optics and shielding, and taking a holistic, architectural approach to designing both of those systems in harmony, according to best current practice. As the ESS is an in-kind project, with 15 instruments contributed by foreign partner laboratories, the status-quo approach would be to design each system independently on each project. This would create a duplication of labour, and unnecessary interfaces in the project: both internally between the groups working on optics and shielding, who in some projects are physically located in different countries, and between the project's and its neighbours' shielding activities. Shielding design interfaces in a regulated, nuclear setting are a major risk to any project, let alone a facility attempting to reach new heigh...

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Section: Summary Of Shielding Costsmentioning

confidence: 99%

Instrument suite cost optimisation in a science megaproject

Bentley¹

2020

J. Phys. Commun.

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“…Results of a recent calculation of neutron absorption in supermirror coatings [6,7], together with consideration of guide substrate waviness effects on shielding [8], allow to single out the two contributions upon data recorded by the Logger. This opens an opportunity for rigorous calculations of the neutron capture in particular materials and, given the prompt gamma spectra, evaluation of the dose rates and shielding requirements directly from running a ray-tracing model of the neutron instrument.…”

Section: R Kolevatov / Mcstas and Scatter Logger Driven Calculationsmentioning

confidence: 99%

“…In Section 2, an overview of results of the studies [6,7] and [8] is given while Section 3 contains details of their implementation in McStas components. In Section 4, we illustrate the use for the particular case of shielding of the ESS BIFROST [9] instrument.…”

Section: R Kolevatov / Mcstas and Scatter Logger Driven Calculationsmentioning

confidence: 99%

“…In [6,7] capture probabilities in the multilayer coatings per incident neutron were calculated for multilayer compositions used in commercial production of supermirrors (m = 1.6 . .…”

Section: Reflection With Q > Q Ni Cmentioning

confidence: 99%

“…At reflection with low momentum transfer neutrons typically don't penetrate beyond the outermost nickel layer of the coating and the parametric dependencies given by (1) and (2) don't hold [7]. For momentum transfer at reflection below critical value q Ni c and a perfectly even layer surface, the reflection loss is typically below 0.01%.…”

Section: Low Angle Reflection Effect Of Wavinessmentioning

confidence: 99%

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McStas and Scatter Logger driven calculations of prompt gamma shielding for neutron guides

Kolevatov

2020

JNR

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McStas ScatterLogger component bundle was adapted for evaluating a contribution to dose rate around neutron guides arising from prompt gamma radiation accompanying neutron capture in the supermirror guide coating upon specular reflection. Thickness of typical shielding materials needed to reduce this contribution to the desired level can be now evaluated directly from running a ray-tracing simulation of the instrument in McStas. An overview of the corresponding modifications to the existing McStas components and description of the newly written supplementary ones is given together with examples and use instructions.

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