Monte Carlo of Trapped Ultracold Neutrons in the UCNτ Trap

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

Esquireite, BaSi_6O_(13)·7H_2O, a New Layer Silicate from the Barium Silicate Deposits of California

Esquireite, BaSi_6O_(13)·7H_2O, is a new mineral from the Esquire #1 claim along Rush Creek, eastern Fresno County, California, USA, and a Ba-silicate lens on the NW slope of Trumbull Peak, Mariposa County, California, USA. Esquireite is a low-temperature hydrothermal alteration product of sanbornite and is found on surfaces of sanbornite. The mineral occurs as colorless rectangular blades, elongated and striated parallel to [010] and flattened on {001}. The streak is white, the luster is vitreous to pearly, and the crystals are transparent. The Mohs hardness is about 2. The tenacity is somewhat flexible, but not elastic, with brittle failure. The fracture is irregular and there are two cleavages: perfect on {001} and fair on {100}. The measured and calculated densities are 2.18(2) g/cm^3 and 2.237 g/cm^3, respectively. Esquireite is biaxial (+), with α 1.477(1), β 1.481(1), γ 1.492 (calc.) (white light); 2V_(meas) = 63.8(6)°; no dispersion or pleochroism; optical orientation: Y = b; Z ^ c ≈ 22° in obtuse β. Six electron-microprobe analyses gave the following empirical formula, based on 20 O apfu: Ba_(0.95)Si_(6.00)O_(20)H_(14.10). Esquireite is monoclinic, space group C2, with cell parameters a 13.601(4), b 4.9222(10), c 15.092(5) Å, β 111.578(19)°, V 939.6(4) Å^3, and Z = 2. The eight strongest lines in the X-ray powder diffraction patterns are [d_(obs) Å(I)(hkl)]: 7.02(38)(002), 5.11(33)(201), 4.649(66)(003,203), 4.191(100)(111), 3.339(65)(402,311,312), 2.967(32)(205,114,311), 2.343(33)(multiple), and 2.261(35)(multiple). The crystal structure (R_1 = 10.8% for 323 reflections with F_o > 4σ F) contains four-tetrahedra-thick [Si_6O_(13)]^(2–) silicate layers with Ba(H_2O)_8^(2+) polyhedra between the layers

Devitoite, a new heterophyllosilicate mineral with astrophyllite-like layers from eastern Fresno County, California

Devitoite, [Ba_6(PO_4)_2(CO_3)] [Fe^(2+)_7Fe^(3+)_2(Si_4O_(12))_2O_2(OH)_4], is a new mineral species from the Esquire #8 claim along Big Creek in eastern Fresno County, California, U.S.A. It is also found at the nearby Esquire #7 claim and at Trumbull Peak in Mariposa County. The mineral is named for Alfred (Fred) DeVito (1937–2004). Devitoite crystallized very late in a sequence of minerals resulting from fluids interacting with a quartz–sanbornite vein along its margin with the country rock. The mineral occurs in subparallel intergrowths of very thin brown blades, flattened on {001} and elongate and striated parallel to [100]. The mineral has a cream to pale brown streak, a silky luster, a Mohs hardness of approximately 4, and two cleavages: {001} perfect and {010} good. The calculated density is 4.044 g/cm^3. It is optically biaxial (+), α 1.730(3), β 1.735(6), γ 1.755(3); 2V_(calc) = 53.6°; orientation: X ≈ b, Y ≈ c, Z ≈ α; pleochroism: brown, Y >>> X > Z. Normalized electron-microprobe analyses provided: BaO 38.83, CaO 0.50, MgO 0.75, FeO 22.02, Fe_2O_3 6.08, Al_2O_3 1.50, SiO_2 20.97, TiO_2 0.80, P_2O_5 4.84, H_2O 1.67, CO_2 2.04, total 100.00 wt%, with FeO and Fe_2O_3 assignments and H_2O and CO_2 based on the structure. The empirical formula is [(Ba_(5.45) Ca_(0.19))_(∑5.64)(PO_4)_(1.47)O_(0.30)(CO_3)] [(Fe^(2+)_(6.60)Mg_(0.40))_(∑7)(Fe^(3+)_(1.64)Ti^(4+)_(0.22)Al^(3+)0.14)_(∑2)(Si_(7.51)Al_(0.49))_(∑8)O_(26)(OH)_4]. Devitoite is triclinic, Pl, α 5.3437(7), b 11.6726(15), c 14.680(2) Å, α91.337(4), β 96.757(4), y 103.233(4)°, V 884.0(2) Å^3 and Z = 1. The crystal-structure determination (R_1 = 9.56% for 1370 F_o > 4σF) shows the mineral to be a heterophyllosilicate with astrophyllite-type HOH layers in which five-coordinated Fe^(3+) takes the place of Ti^(4+). The interlayer region contains Ba atoms, PO_4 groups and CO_3 groups. The configuration of the Ba and PO_4 in the interlayer region is similar to that found in the structure of yoshimuraite