TUCAN

Overview (from the Momose website)

In fall 2017, the Japanese-Canadian TUCAN (TRIUMF Ultra Cold Advanced Neutron) collaboration succeeded for the first time in producing ultracold neutrons (UCN). This was a major milestone towards the search for the elusive neutron electric dipole moment (nEDM). UCN move so slowly, about 5 meters per second compared to about 500 meters per second for air molecules, and with such low energy that they can be contained and observed. Thus, UCN are ideal for determining the neutron electric dipole moment (nEDM), which TUCAN aims to measure with the highest-ever precision. The nEDM is predicted to be vanishingly small, but if it is measured to be larger than expected, the TUCAN results could aid in solving a key cosmic puzzle: why there is much more matter than antimatter in the universe.
TRIUMF’s UCN facility is aiming to be the world’s highest-density source of ultracold neutrons. High density is critical to the research because most ultracold neutron experiments are statistics limited—the experiments require enormous numbers of individual measurements to arrive at a statistically reliable result. To support this effort, the Madison and Momose groups are developing atomic magnetometers based on the optical pumping of 199Hg and 129Xe isotopes, which will cohabit with UCN inside the nEDM experimental chamber, and will measure fluctuations of the magnetic field on the ppb scale.  We have succeeded in producing laser-polarized 199Hg with orders of magnitude greater polarization than that obtained in a commercial NMR machine.  We are now working to identify sources of systematic error, and push the measurement precision to its ultimate limit.
For an overview of TUCAN visit an overview of TUCAN and the project page.

Long term goal : develop precision magnetometers for the TUCAN experiment

    • Develop vapor-based atomic magnetometers (using 199Hg and 129Xe isotopes) that are co-located with the neutrons
    • Develop a suite of vapor-based atomic magnetometers (using Cs atoms) that can be used to precisely measure the magnetic field gradient just outside the neutron vacuum cell.

 

  • Recent work

    • Development of a high-power, narrow-linewidth continuous-wave UV laser.
    • Doppler-free spectroscopy of Xe 5p-6p two-photon transition hyperfine splitting and isotope shifts.
    • Production of hyperpolarized 129Xe via Spin-exchange optical pumping (SEOP).
    • Characterization of the Cs magnetometer elements for the field gradient array sensor

  • Current status

    • Laser-based production of polarized 199Hg vapour and characterization of low-field magnetic resonance
    • Characterizing VUV lamp-based production & detection of polarized 129Xe.

Associated publications

B. Algohi et al.,
Initial results of the TRIUMF ultracold advanced neutron source
Phys. Rev. C 114, L012501 (2026); arXiv:2509.02916

K. Abe et al.,
A New High-Intensity Source for Ultracold Neutrons
arXiv:2607.03033

T. Hepworth et al.,
Ultracold neutron guide-coating facility at U. Winnipeg
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1092, 171841 (2026); arXiv:2510.06289

T. Higuchi et al.,
Neutron EDM Experiment with an Advanced Ultracold Neutron Source at TRIUMF
CPT and Lorentz Symmetry, pp. 177-185 (2026); arXiv:2507.05278

J. W. Martin et al.,
Cryogenic systems for the TUCAN EDM experiment
arXiv:2506.09064

W. Klassen, S. Ahmed, K. Pond Grehan, C. Hovde, K.W. Madison, R.R. Mammei, J.W. Martin, M. McCrea, T. Mohammadi, T. Momose, P. Opsahl, D. Ostapchuk
A magnetically silent optically pumped magnetometer for a neutron electric dipole moment experiment
The European Physical Journal C, xxxxx (2024), arXiv:2405.08696

R. Matsumiya et al.,
The Precision nEDM Measurement with UltraCold Neutrons at TRIUMF
https://arxiv.org/abs/2207.09880

S. Ahmed et al.
Fast-switching magnet serving a spallation-driven ultracold neutron source
Phys. Rev. Accel. Beams 22, 102401 || https://arxiv.org/abs/1905.08857

S. Ahmed et al.
A beamline for fundamental neutron physics at TRIUMF
Nucl. Instr. Meth. Phys. Res. Sec. A: Accel., Spectr., Detect. Assoc. Equip. (2019). || https://arxiv.org/abs/1810.01001

S. Ahmed et al.
First ultracold neutrons produced at TRIUMF
Phys. Rev. C 99, 025503 (2019) || https://arxiv.org/abs/1809.04071

Emily Altiere, Eric R. Miller, Tomohiro Hayamizu, David J. Jones, Kirk W. Madison, and Takamasa Momose
High-resolution two-photon spectroscopy of a 5p^5 6p <- 5p^6 transition of xenon
Phys. Rev. A 97, 012507 (2018)

Joshua Nikolai Wienands
Coils, Fields and Xenon Towards Measuring Xenon Spin Precession in a Magnetic Field for the UCN Collaboration
Master of Science, Thesis – August 2016 || UBC-Circle Link to dissertation