An optional focusing SELENE extension to conventional neutron guides: A case study for the ESS instrument BIFROST

TY - JOUR

T1 - An optional focusing SELENE extension to conventional neutron guides

T2 - A case study for the ESS instrument BIFROST

AU - Hansen, Ursula Bengård

AU - Bertelsen, Mads

AU - Stahn, Jochen

AU - Lefmann, Kim

PY - 2017/4/21

Y1 - 2017/4/21

N2 - The high brilliance at the European Spallation Source (ESS) will allow for performing experiments with much smaller samples than at present neutron facilities and in much more complex sample environments. However the higher flux also results in higher background from unwanted neutrons not originating from scattering of the sample. We here present a new design idea for beam delivery, where a 165 m ballistic guide system with good transport properties is followed by a 4–8 m SELENE guide system similar to Montel optics used for X-ray optics. We have investigated the system by detailed Monte-Carlo simulations using McStas. We show that under certain conditions, this set-up works surprisingly well, with a brilliance transfer of 20–60% for neutrons of wavelength 4 Å and above. We demonstrate that the guide system is able to focus the beam almost perfectly onto samples sizes in the range of 0.1–2 mm. We furthermore show that our SELENE system is insensitive to gravity and to realistic values of guide waviness. We argue that this guide system can be useful as an optional guide insert when small samples are used in the vicinity of bulky sample environment, e.g. for high-field or high-pressure experiments.

AB - The high brilliance at the European Spallation Source (ESS) will allow for performing experiments with much smaller samples than at present neutron facilities and in much more complex sample environments. However the higher flux also results in higher background from unwanted neutrons not originating from scattering of the sample. We here present a new design idea for beam delivery, where a 165 m ballistic guide system with good transport properties is followed by a 4–8 m SELENE guide system similar to Montel optics used for X-ray optics. We have investigated the system by detailed Monte-Carlo simulations using McStas. We show that under certain conditions, this set-up works surprisingly well, with a brilliance transfer of 20–60% for neutrons of wavelength 4 Å and above. We demonstrate that the guide system is able to focus the beam almost perfectly onto samples sizes in the range of 0.1–2 mm. We furthermore show that our SELENE system is insensitive to gravity and to realistic values of guide waviness. We argue that this guide system can be useful as an optional guide insert when small samples are used in the vicinity of bulky sample environment, e.g. for high-field or high-pressure experiments.

U2 - 10.1016/j.nima.2017.01.075

DO - 10.1016/j.nima.2017.01.075

M3 - Journal article

SN - 0168-9002

VL - 852

SP - 46

EP - 56

JO - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

JF - Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

ER -