arXiv subjects

B. Jamieson

Publications and source records attributed to B. Jamieson.

At least 19 recordsLinked to original sources

arXiv2026

A New High-Intensity Source for Ultracold Neutrons

The TRIUMF UltraCold Advanced Neutron (TUCAN) collaboration has completed a new superthermal source for ultracold neutrons (UCNs) at TRIUMF. It uses neutrons from a spallation target driven by TRIUMF's %520-MeV main cyclotron. Heavy water and liquid deuterium serve as neutron moderators, and inelastic scattering inside superfluid $^4$He at around \qty{1.1}{\kelvin} slows the neutrons down to become ultracold. During commissioning runs with the completed source, including the deuterium moderator, up to $1.47(2)\times 10^7$ UCNs were detected in the experimental area after irradiating the target and accumulating UCNs in the source for \qty{60}{\second}. Up to \qty{6.75(3)e5} UCN/s were detected during continuous operation, more than at any other source in the world.

physics.ins-det↗

arXiv2025

Ultracold Neutron Guide-Coating Facility at U.Winnipeg

We report the construction and commissioning of a new ultracold neutron (UCN) guide-coating facility at the University of Winnipeg. The facility employs pulsed laser deposition (PLD) to produce diamond-like carbon (DLC) coatings on cylindrical UCN guides up to 1 m in length with a 200 mm outer diameter. DLC is a promising material for UCN transport and storage due to its high real component of the optical potential, low neutron absorption cross section, and low depolarization probabilities. First coating attempts on a full length aluminum UCN guide and matching blank flange were successfully coated with a carbon film with density of 2.3 g/cm$^3$, corresponding to optical potentials of 200 neV, as measured by X-ray reflectometry (XRR). Coating thicknesses were measured to be 90 nm for the UCN guide and 180 nm for the flange with no evidence of delamination. The implementation of a plasma plume collimator and plasma feed back control via a time of flight in vacuum ion probe produced a film with an XRR measured density of 2.8 g/cm$^3$, corresponding to an optical potential of 240 neV. This 80 nm thick film had poor adhesion to the aluminum tube substrate. These results establish a baseline for the coating facility. Ongoing and future work focuses on improving the diamond content of films and adhesion through plasma plume collimation, TOF ion probe feed back, and pre/post treatment methods with the goal of providing high quality DLC UCN guides for the TUCAN experiment at TRIUMF.

physics.ins-det↗

arXiv2025

Initial results of the TRIUMF ultracold advanced neutron source

We report the first results on ultracold neutron production from a new spallation-driven superfluid $^4$He (He-II) source at TRIUMF, which is being prepared for a new, precise measurement of the neutron electric dipole moment. A total of $(9.3 \pm 0.8)\times 10^{5}$ ultracold neutrons were observed at a proton beam current of \SI{37}{\uA}, when the target was irradiated for a period of \SI{60}{\s}. The results are in fair agreement with expectations based on a detailed simulation of neutron transport and ultracold neutron source cryogenics. There is some indication that the new source might not be as limited by the conduction of heat through the He-II as originally expected. The results indicate that the source is likely to make its ultimate production goals, once the liquid deuterium cold moderator system is completed, with the expectation that $5.7\times 10^7$~UCNs would be detected in the same experiment with full liquid levels. This would, for example, correspond to delivery of $1.4\times 10^6$~UCNs delivered to each of two nEDM measurement cells, and a statistical uncertainty of $1\times 10^{-27}~e$cm on the neutron EDM in 280 days of running.

nucl-ex↗

arXiv2025

Neutron EDM Experiment with an Advanced Ultracold Neutron Source at TRIUMF

The TRIUMF Ultracold Advanced Neutron (TUCAN) collaboration has been developing a high-intensity ultracold neutron (UCN) source aimed at searching for the neutron electric dipole moment (EDM) with a sensitivity goal of $10^{-27}\ e{\rm cm}$. This article reports on recent progress in commissioning of the UCN source and in the development of the neutron EDM spectrometer. In its final configuration, the accelerator-driven super-thermal UCN source will enable a neutron EDM experiment with two orders of magnitude improved statistics compared to the current best experiment. Substantial progress in 2024 allowed the collaboration to operate the complete source system, with the exception of the liquid deuterium cold moderator, resulting in the first production of UCNs. The status of the EDM spectrometer is also presented, with emphasis on UCN handling components and magnetic subsystems relevant to field control, shielding, and magnetometry.

physics.ins-det↗

arXiv2025

Cryogenic systems for the TUCAN EDM experiment

The TUCAN (TRIUMF UltraCold Advanced Neutron) Collaboration is completing a new ultracold neutron (UCN) source. The UCN source will deliver UCNs to a neutron electric dipole moment (EDM) experiment. The EDM experiment is projected to be capable of an uncertainty of $1\times 10^{-27}~e$cm, competitive with other planned projects, and a factor of ten more precise than the present world's best. The TUCAN source is based on a UCN production volume of superfluid helium (He-II), held at 1~K, and coupled to a proton-driven spallation target. The production rate in the source is expected to be in excess of $10^7$~UCN/s; since UCN losses can be small in superfluid helium, this should allow us to build up a large number of UCNs. The spallation-driven superfluid helium technology is the principal aspect making the TUCAN project unique. The superfluid production volume was recently cooled, for the first time, and successfully filled with superfluid helium. The design principles of the UCN source are described, along with some of the challenging cryogenic milestones that were recently passed.

physics.ins-det↗

arXiv2023

Characterization of electroless nickel-phosphorus plating for ultracold-neutron storage

Electroless nickel plating is an established industrial process that provides a robust and relatively low-cost coating suitable for transporting and storing ultracold neutrons (UCN). Using roughness measurements and UCN-storage experiments we characterized UCN guides made from polished aluminum or stainless-steel tubes plated by several vendors. All electroless nickel platings were similarly suited for UCN storage with an average loss probability per wall bounce of $2.8\cdot10^{-4}$ to $4.1\cdot10^{-4}$ for energies between 90 neV and 190 neV, or a ratio of imaginary to real Fermi potential $η$ of $1.7\cdot10^{-4}$ to $3.3\cdot10^{-4}$. Measurements at different elevations indicate that the energy dependence of UCN losses is well described by the imaginary Fermi potential. Some special considerations are required to avoid an increase in surface roughness during the plating process and hence a reduction in UCN transmission. Increased roughness had only a minor impact on storage properties. Based on these findings we chose a vendor to plate the UCN-production vessel that will contain the superfluid-helium converter for the new TRIUMF UltraCold Advanced Neutron (TUCAN) source, achieving acceptable UCN-storage properties with ${η=3.5(5)\cdot10^{-4}}$.

nucl-ex↗

arXiv2021

A measurement of proton-carbon forward scattering in a proof-of-principle test of the EMPHATIC spectrometer

The next generation of long-baseline neutrino experiments will be capable of precision measurements of neutrino oscillation parameters, precision neutrino-nucleus scattering, and unprecedented sensitivity to physics beyond the Standard Model. Reduced uncertainties in neutrino fluxes are necessary to achieve high precision and sensitivity in these future precise neutrino measurements. New measurements of hadron-nucleus interaction cross sections are needed to reduce uncertainties of neutrino fluxes. We report measurements of the differential cross-section as a function of scattering angle for proton-carbon interactions with a single charged particle in the final state at beam momenta of 20, 30, and 120 GeV/c. These measurements are the result of a beam test for EMPHATIC, a hadron-scattering and hadron-production experiment. The total, elastic and inelastic cross-sections are also extracted from the data and compared to previous measurements. These results can be used in current and future long-baseline neutrino experiments, and demonstrate the feasibility of future measurements by an upgraded EMPHATIC spectrometer.

physics.ins-det↗

arXiv2021

Improved constraints on neutrino mixing from the T2K experiment with $\mathbf{3.13\times10^{21}}$ protons on target

The T2K experiment reports updated measurements of neutrino and antineutrino oscillations using both appearance and disappearance channels. This result comes from an exposure of $14.9~(16.4) \times 10^{20}$ protons on target in neutrino (antineutrino) mode. Significant improvements have been made to the neutrino interaction model and far detector reconstruction. An extensive set of simulated data studies have also been performed to quantify the effect interaction model uncertainties have on the T2K oscillation parameter sensitivity. T2K performs multiple oscillation analyses that present both frequentist and Bayesian intervals for the PMNS parameters. For fits including a constraint on \ssqthonethree from reactor data and assuming normal mass ordering T2K measures $\sin^2θ_{23} = 0.53^{+0.03}_{-0.04}$ and $Δm^2_{32} = (2.45 \pm 0.07) \times 10^{-3}$ eV$^{2}$c$^{-4}$. The Bayesian analyses show a weak preference for normal mass ordering (89% posterior probability) and the upper $\sin^2θ_{23}$ octant (80% posterior probability), with a uniform prior probability assumed in both cases. The T2K data exclude CP conservation in neutrino oscillations at the $2σ$ level.

hep-ex↗

arXiv2021

First T2K measurement of transverse kinematic imbalance in the muon-neutrino charged-current single-$π^+$ production channel containing at least one proton

This paper reports the first T2K measurement of the transverse kinematic imbalance in the single-$π^+$ production channel of neutrino interactions. We measure the differential cross sections in the muon-neutrino charged-current interaction on hydrocarbon with a single $π^+$ and at least one proton in the final state, at the ND280 off-axis near detector of the T2K experiment. The extracted cross sections are compared to the predictions from different neutrino-nucleus interaction event generators. Overall, the results show a preference for models which have a more realistic treatment of nuclear medium effects including the initial nuclear state and final-state interactions.

hep-ex↗

arXiv2020

T2K measurements of muon neutrino and antineutrino disappearance using $3.13\times 10^{21}$ protons on target

We report measurements by the T2K experiment of the parameters $θ_{23}$ and $Δm^2_{32}$ which govern the disappearance of muon neutrinos and antineutrinos in the three-flavor PMNS neutrino oscillation model at T2K's neutrino energy and propagation distance. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, muon-like events from each beam mode are used to measure these parameters separately for neutrino and antineutrino oscillations. Data taken from $1.49 \times 10^{21}$ protons on target (POT) in neutrino mode and $1.64 \times 10^{21}$ POT in antineutrino mode are used. The best-fit values obtained by T2K were $\sin^2\left(θ_{23}\right)=0.51^{+0.06}_{-0.07} \left(0.43^{+0.21}_{-0.05}\right)$ and $Δm^2_{32}=2.47^{+0.08}_{-0.09} \left(2.50^{+0.18}_{-0.13}\right)$\evmass for neutrinos (antineutrinos). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed. An analysis using an effective two-flavor neutrino oscillation model where the sine of the mixing angle is allowed to take non-physical values larger than 1 is also performed to check the consistency of our data with the three-flavor model. Our data were found to be consistent with a physical value for the mixing angle.

hep-ex↗

arXiv2020

Search for $hep$ solar neutrinos and the diffuse supernova neutrino background using all three phases of the Sudbury Neutrino Observatory

A search has been performed for neutrinos from two sources, the $hep$ reaction in the solar $pp$ fusion chain and the $ν_e$ component of the diffuse supernova neutrino background (DSNB), using the full dataset of the Sudbury Neutrino Observatory with a total exposure of 2.47 kton-years after fiducialization. The $hep$ search is performed using both a single-bin counting analysis and a likelihood fit. We find a best-fit flux that is compatible with solar model predictions while remaining consistent with zero flux, and set a one-sided upper limit of $Φ_{hep} < 30\times10^{3}~\mathrm{cm}^{-2}~\mathrm{s}^{-1}$ [90% credible interval (CI)]. No events are observed in the DSNB search region, and we set an improved upper bound on the $ν_e$ component of the DSNB flux of $Φ^\mathrm{DSNB}_{ν_e} < 19~\textrm{cm}^{-2}~\textrm{s}^{-1}$ (90% CI) in the energy range $22.9 < E_ν< 36.9$~MeV.

hep-ex↗

arXiv2019

EMPHATIC: A proposed experiment to measure hadron scattering and productioncross sections for improved neutrino flux predictions

Hadron scattering and production uncertainties are a limiting systematic on accelerator and at-mospheric neutrino flux predictions. New hadron measurements are necessary for neutrino fluxpredictions with well-understood and reduced uncertainties. We propose a new compact experimentto measure hadron scattering and production cross sections at beam energies that are inaccessibleto currently operating experiments. These measurements can reduce the current 10% neutrino fluxuncertainties by an approximate factor of two.

hep-ex↗

arXiv2019

Cosmogenic Neutron Production at the Sudbury Neutrino Observatory

Neutrons produced in nuclear interactions initiated by cosmic-ray muons present an irreducible background to many rare-event searches, even in detectors located deep underground. Models for the production of these neutrons have been tested against previous experimental data, but the extrapolation to deeper sites is not well understood. Here we report results from an analysis of cosmogenically produced neutrons at the Sudbury Neutrino Observatory. A specific set of observables are presented, which can be used to benchmark the validity of GEANT4 physics models. In addition, the cosmogenic neutron yield, in units of $10^{-4}\;\text{cm}^{2}/\left(\text{g}\cdotμ\right)$, is measured to be $7.28 \pm 0.09\;\text{stat.} ^{+1.59}_{-1.12}\;\text{syst.}$ in pure heavy water and $7.30 \pm 0.07\;\text{stat.} ^{+1.40}_{-1.02}\;\text{syst.}$ in NaCl-loaded heavy water. These results provide unique insights into this potential background source for experiments at SNOLAB.

hep-ex↗

arXiv2019

A fast-switching magnet serving a spallation-driven ultracold neutron source

A fast-switching, high-repetition-rate magnet and power supply have been developed for and operated at TRIUMF, to deliver a proton beam to the new ultracold neutron (UCN) facility. The facility possesses unique operational requirements: a time-averaged beam current of 40~$μ$A with the ability to switch the beam on or off for several minutes. These requirements are in conflict with the typical operation mode of the TRIUMF cyclotron which delivers nearly continuous beam to multiple users. To enable the creation of the UCN facility, a beam-sharing arrangement with another facility was made. The beam sharing is accomplished by the fast-switching (kicker) magnet which is ramped in 50~$μ$s to a current of 193~A, held there for approximately 1~ms, then ramped down in the same short period of time. This achieves a 12~mrad deflection which is sufficient to switch the proton beam between the two facilities. The kicker magnet relies on a high-current, low-inductance coil connected to a fast-switching power supply that is based on insulated-gate bipolar transistors (IGBTs). The design and performance of the kicker magnet system and initial beam delivery results are reported.

physics.acc-ph↗

arXiv2019

Measurement of neutron production in atmospheric neutrino interactions at the Sudbury Neutrino Observatory

Neutron production in GeV-scale neutrino interactions is a poorly studied process. We have measured the neutron multiplicities in atmospheric neutrino interactions in the Sudbury Neutrino Observatory experiment and compared them to the prediction of a Monte Carlo simulation using GENIE and a minimally modified version of GEANT4. We analyzed 837 days of exposure corresponding to Phase I, using pure heavy water, and Phase II, using a mixture of Cl in heavy water. Neutrons produced in atmospheric neutrino interactions were identified with an efficiency of $15.3\%$ and $44.3\%$, for Phase I and II respectively. The neutron production is measured as a function of the visible energy of the neutrino interaction and, for charged current quasi-elastic interaction candidates, also as a function of the neutrino energy. This study is also performed classifying the complete sample into two pairs of event categories: charged current quasi-elastic and non charged current quasi-elastic, and $ν_μ$ and $ν_e$. Results show good overall agreement between data and Monte Carlo for both phases, with some small tension with a statistical significance below $2σ$ for some intermediate energies.

hep-ex↗

arXiv2019

Tests of Lorentz invariance at the Sudbury Neutrino Observatory

Experimental tests of Lorentz symmetry in systems of all types are critical for ensuring that the basic assumptions of physics are well-founded. Data from all phases of the Sudbury Neutrino Observatory, a kiloton-scale heavy water Cherenkov detector, are analyzed for possible violations of Lorentz symmetry in the neutrino sector. Such violations would appear as one of eight possible signal types in the detector: six seasonal variations in the solar electron neutrino survival probability differing in energy and time dependence, and two shape changes to the oscillated solar neutrino energy spectrum. No evidence for such signals is observed, and limits on the size of such effects are established in the framework of the Standard Model Extension, including 40 limits on perviously unconstrained operators and improved limits on 15 additional operators. This makes limits on all minimal, Dirac-type Lorentz violating operators in the neutrino sector available for the first time.

hep-ex↗

arXiv2018

A beamline for fundamental neutron physics at TRIUMF

This article describes the new primary proton beamline 1U at TRIUMF. The purpose of this beamline is to produce ultracold neutrons (UCN) for fundamental-physics experiments. It delivers up to 40 microA of 480 MeV protons from the TRIUMF cyclotron to a tungsten spallation target and uses a fast kicker to share the beam between the Center for Molecular and Materials Science and UCN. The beamline has been successfully commissioned and operated with a beam current up to 10 microA, facilitating first large-scale UCN production in Canada.

physics.ins-det↗

arXiv2018

First ultracold neutrons produced at TRIUMF

We installed a source for ultracold neutrons at a new, dedicated spallation target at TRIUMF. The source was originally developed in Japan and uses a superfluid-helium converter cooled to 0.9$\,$K. During an extensive test campaign in November 2017, we extracted up to 325000 ultracold neutrons after a one-minute irradiation of the target, over three times more than previously achieved with this source. The corresponding ultracold-neutron density in the whole production and guide volume is 5.3$\,$cm$^{-3}$. The storage lifetime of ultracold neutrons in the source was initially 37$\,$s and dropped to 24$\,$s during the eighteen days of operation. During continuous irradiation of the spallation target, we were able to detect a sustained ultracold-neutron rate of up to 1500$\,$s$^{-1}$. Simulations of UCN production, UCN transport, temperature-dependent UCN yield, and temperature-dependent storage lifetime show excellent agreement with the experimental data and confirm that the ultracold-neutron-upscattering rate in superfluid helium is proportional to $T^7$.

physics.ins-det↗