Exploring performance of neutron guide systems using pinhole beam extraction

TY - JOUR

T1 - Exploring performance of neutron guide systems using pinhole beam extraction

AU - Bertelsen, Mads

AU - Jacobsen, Henrik

AU - Hansen, Ursula Bengård

AU - Carlsen, H.H.

AU - Lefmann, Kim

PY - 2013/11/21

Y1 - 2013/11/21

N2 - We perform an optimization of pinhole neutron guide systems under systematically varying conditions. It is investigated how neutron guide systems consisting of a parabolic feeder inside the biological shielding followed by a pinhole and an elliptical guide perform with different pinhole sizes and divergence requirements. We have clarified in which situations such a guide system is a viable choice and when the parabolic feeder is necessary in terms of neutron transport. The advantage of this design is the reduction of background from fast thermal neutrons compared to a system without a pinhole, hence the smallest possible pinhole is of interest. It is found that instruments with divergence requirements of ±1.0 will have excellent neutron transport with a 3×3 cm2 pinhole, while lower divergence requirements of ±0.5 can do with a smaller pinhole of 2×2 cm2. The feeder effectively reduces the necessary pinhole size, and is especially beneficial for short instruments. In addition to these qualities, a feeder will often smoothen the divergence profile, mostly for longer instruments.

AB - We perform an optimization of pinhole neutron guide systems under systematically varying conditions. It is investigated how neutron guide systems consisting of a parabolic feeder inside the biological shielding followed by a pinhole and an elliptical guide perform with different pinhole sizes and divergence requirements. We have clarified in which situations such a guide system is a viable choice and when the parabolic feeder is necessary in terms of neutron transport. The advantage of this design is the reduction of background from fast thermal neutrons compared to a system without a pinhole, hence the smallest possible pinhole is of interest. It is found that instruments with divergence requirements of ±1.0 will have excellent neutron transport with a 3×3 cm2 pinhole, while lower divergence requirements of ±0.5 can do with a smaller pinhole of 2×2 cm2. The feeder effectively reduces the necessary pinhole size, and is especially beneficial for short instruments. In addition to these qualities, a feeder will often smoothen the divergence profile, mostly for longer instruments.

U2 - 10.1016/j.nima.2013.07.062

DO - 10.1016/j.nima.2013.07.062

M3 - Journal article

SN - 0168-9002

VL - 729

SP - 387

EP - 398

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 -