A multilayer surface detector for ultracold neutrons

Wang, ‪Zhehui; Hoffbauer, Mark A.; Morris, C. L.; Callahan, Nathan; Adamek, E.; Bacon, Jeffrey; Blatnik, M.; Brandt, Aaron; Broussard, L. J.; Clayton, S. M.; Cude-Woods, C.; Currie, Scott; Dees, Eric; Ding, X.; Gao, Jianbo; Gray, F.; Hickerson, K. P.; Holley, A. T.; Ito, T. M.; Liu, C. Y.; Makela, M.; Ramsey, J.; Pattie, R. W.; Salvat, Daniel; Saunders, Alexander; Schmidt, Darren; Schulze, R.; Seestrom, S.J.; Sharapov, E.I.; Sprow, Aaron; Tang, Z.; Wei, Wanchun; Wexler, J.; Womack, Tanner L.; Young, A. R.; Zeck, B. A.

doi:10.1016/j.nima.2015.07.010

Cited by 23 publications

(18 citation statements)

References 17 publications

(16 reference statements)

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“…Additionally, a holding field everywhere perpendicular to the trapping field is provided to ensure that there are no regions of vanishing magnetic field inside the trapping volume and depolarization losses are negligible [9,10]. An in-situ neutron detector, using 10 B coated ZnS scintillating sheets [11] (shown in Fig. 1C), can be moved into the trap to count the surviving neutrons.…”

Section: Overviewmentioning

confidence: 99%

Monte Carlo simulations of trapped ultracold neutrons in the UCNτ experiment

Callahan¹,

Liu²,

González³

et al. 2019

Phys. Rev. C

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In the UCNτ experiment, ultracold neutrons (UCN) are confined by magnetic fields and the Earth's gravitational field. Field-trapping mitigates the problem of UCN loss on material surfaces, which caused the largest correction in prior neutron experiments using material bottles. However, the neutron dynamics in field traps differ qualitatively from those in material bottles. In the latter case, neutrons bounce off material surfaces with significant diffusivity and the population quickly reaches a static spatial distribution with a density gradient induced by the gravitational potential. In contrast, the field-confined UCN-whose dynamics can be described by Hamiltonian mechanics-do not exhibit the stochastic behaviors typical of an ideal gas model as observed in material bottles. In this report, we will describe our efforts to simulate UCN trapping in the UCNτ magneto-gravitational trap. We compare the simulation output to the experimental results to determine the parameters of the neutron detector and the input neutron distribution. The tuned model is then used to understand the phase space evolution of neutrons observed in the UCNτ experiment. We will discuss the implications of chaotic dynamics on controlling the systematic effects, such as spectral cleaning and microphonic heating, for a successful UCN lifetime experiment to reach a 0.01% level of precision.

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Section: Overviewmentioning

confidence: 99%

Monte Carlo simulations of trapped ultracold neutrons in the UCNτ experiment

Callahan¹,

Liu²,

González³

et al. 2019

Phys. Rev. C

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“…UCN leaving the pinhole on the downstream side of the guide transit through a 2.54 cm diameter outlet port to a 10 B coated ZnS:Ag foil detector [38]. UCN are captured in a 100 nm layer of 10 B coated on the ZnS:Ag substrate.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of commercial nickel–phosphorus coating for ultracold neutron guides using a pinhole bottling method

Pattie

Adamek

Brenner

et al. 2017

Nuclear Instruments and Methods in Physics Research Section A:

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We report on the evaluation of commercial electroless nickel phosphorus (NiP) coatings for ultracold neutron (UCN) transport and storage. The material potential of 50 µm thick NiP coatings on stainless steel and aluminum substrates was measured to be V F = 213(5.2) neV using the time-of-flight spectrometer ASTERIX at the Lujan Center. The loss per bounce probability was measured in pinhole bottling experiments carried out at ultracold neutron sources at Los Alamos Neutron Science Center and the Institut Laue-Langevin. For these tests a new guide coupling design was used to minimize gaps between the guide sections. The observed UCN loss in the bottle was interpreted in terms of an energy independent effective loss per bounce, which is the appropriate model when gaps in the system and upscattering are the dominate loss mechanisms, yielding a loss per bounce of 1.3(1) × 10 −4 . We also present a detailed discussion of the pinhole bottling methodology and an energy dependent analysis of the experimental results.

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“…1), and a UCN detector (D) after the gas scattering cell. Both of these detectors use a technology recently developed at Los Alamos [4] and are constructed using a plastic sheet coated with a ZnS scintillator powder whose surface is coated with approximately 80 nm of 10 B. Neutrons that reach the 10 B layer of the detector have a near 100% probability of being captured via 10 B(n,α) 7 Li * .…”

Section: Description Of Experimentsmentioning

confidence: 99%

“…Since hydrocarbon gases are a potential contaminant in gas systems because of their use in wire chambers, these measurements can be used to predict cross sections for a wide variety of gases. Our improved measurement uses a newly developed UCN [4] detector that can be mounted directly on our gas scattering cell.…”

Section: Introductionmentioning

confidence: 99%

Total cross sections for ultracold neutrons scattered from gases

Seestrom¹,

Adamek²,

Barlow³

et al. 2017

Phys. Rev. C

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Abstract.We have followed up on our previous measurements of upscattering of ultracold neutrons (UCN) from a series of gases by making measurements of total cross sections on the following gases hydrogen, ethane, methane, isobutene, n-butane, ethylene, water vapor, propane, neopentane, isopropyl alcohol, and 3 He. The values of these cross sections are important for estimating the loss rate of trapped neutrons due to residual gas and are relevant to neutron lifetime measurements using UCN. The effects of the UCN velocity and path-length distributions were accounted for in the analysis using a Monte Carlo transport code. Results are compared to our previous measurements and with the known absorption cross section for 3 He scaled to our UCN energy. We find that the total cross sections for the hydrocarbon gases are reasonably described by a function linear in the number of hydrogen atoms in the molecule.

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A multilayer surface detector for ultracold neutrons

Abstract: A multilayer surface detector for ultracold neutrons (UCNs) is described. The top10 B layer is exposed to vacuum and directly captures UCNs. The ZnS:Ag layer beneath the 10 B layer is a few microns thick, which is sufficient to detect the charged particles from the 10 B(n,α)

Cited by 23 publications

References 17 publications

Monte Carlo simulations of trapped ultracold neutrons in the UCNτ experiment

Monte Carlo simulations of trapped ultracold neutrons in the UCNτ experiment

Evaluation of commercial nickel–phosphorus coating for ultracold neutron guides using a pinhole bottling method

Total cross sections for ultracold neutrons scattered from gases

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