First ultracold neutrons produced at TRIUMF

Ahmed, S.; Altiere, Emily; Andalib, T.; Bell, B.; Bidinosti, Chris; Cudmore, E; Das, Mala; Davis, Charles A.; Franke, B.; Gericke, Michael; Giampa, P.; Gnyp, Patricia; Hansen-Romu, S.; Hatanaka, K.; Hayamizu, T.; Jamieson, B.; Jones, David P.H.; Kawasaki, S.; Kikawa, T.; Kitaguchi, Masaaki; Klassen, W.; Konaka, A.; Korkmaz, E.; Kuchler, F.; Lang, Μ.; Lee, L.; Lindner, T.; Madison, Kirk W.; Makida, Y.; Mammei, J.; Mammei, R.; Martin, J. W.; Matsumiya, R.; Miller, Eric K.; Mishima, Kenji; Momose, Takamasa; Okamura, Takahiro; Page, S. L.; Picker, R.; Pierre, E.; Ramsay, W. D.; Rebenitsch, L.; Rehm, Frank; Schreyer, W.; Shimizu, Hirohiko M.; Sidhu, S.; Sikora, A.; Smith, J. K.; Tanihata, I.; Thorsteinson, B.; Vanbergen, S.; Oers, W. T. H. van; Watanabe, Yutaka

doi:10.1103/physrevc.99.025503

Cited by 36 publications

(29 citation statements)

References 33 publications

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“…During the Fall 2017 campaign [8], we also confirmed that the number of UCN extracted from the UCN source is proportional to the calculated beam current (Fig. 21).…”

Section: Implementation and Experiencessupporting

confidence: 73%

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Fast-switching magnet serving a spallation-driven ultracold neutron source

Ahmed¹,

Altiere²,

Andalib³

et al. 2019

Phys. Rev. Accel. Beams

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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 µA 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 µs 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, lowinductance 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.

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“…During the Fall 2017 campaign [8], we also confirmed that the number of UCN extracted from the UCN source is proportional to the calculated beam current (Fig. 21).…”

Section: Implementation and Experiencessupporting

confidence: 73%

“…A prototype UCN source was installed directly above the target in 2017 and first results from the commissioning of the UCN source were reported in Ref. [8]. Table I shows the specifications for the kicker magnet system.…”

Section: Beamline Layoutmentioning

confidence: 99%

Fast-switching magnet serving a spallation-driven ultracold neutron source

Ahmed¹,

Altiere²,

Andalib³

et al. 2019

Phys. Rev. Accel. Beams

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“…We benchmarked this simulation model against the prototype source currently in operation at TRIUMF and achieved a good match between the simulated and measured UCN yield [22]. However, large uncertainties in the simulations of UCN storage and transport could potentially mask under-or over-estimations in UCN production of as much as 30 %.…”

Section: Simulation Modelmentioning

confidence: 93%

“…[21] demonstrated that with a 3 He fridge it is possible to reach the low temperature required for a superfluidhelium source close to a neutron spallation target. This source was later moved to a new spallation target with up to 50 times more beam power (40 µA, 483 MeV, 19.3 kW) at TRIUMF [22,23]. Thanks to a fast kicker magnet [24], this spallation target can be irradiated for arbitrary durations, allowing to optimally match the irradiation time to experimental requirements and reducing the heat load whenever no UCN production is required.…”

Section: Introductionmentioning

confidence: 99%

Optimizing neutron moderators for a spallation-driven ultracold-neutron source at TRIUMF

Schreyer

Davis

Kawasaki

et al. 2020

Nuclear Instruments and Methods in Physics Research Section A:

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We report on our efforts to optimize the geometry of neutron moderators and converters for the TRIUMF UltraCold Advanced Neutron (TUCAN) source using MCNP simulations. It will use an existing spallation neutron source driven by a 19.3 kW proton beam delivered by TRIUMF's 520 MeV cyclotron. Spallation neutrons will be moderated in heavy water at room temperature and in liquid deuterium at 20 K, and then superthermally converted to ultracold neutrons in superfluid, isotopically purified 4 He. The helium will be cooled by a 3 He fridge through a 3 He-4 He heat exchanger.The optimization took into account a range of engineering and safety requirements and guided the detailed design of the source. The predicted ultracold-neutron density delivered to a typical experiment is maximized for a production volume of 27 L, achieving a production rate of 1.4 · 10 7 s −1 to 1.6 · 10 7 s −1 with a heat load of 8.1 W. At that heat load, the fridge can cool the superfluid helium to 1.1 K, resulting in a storage lifetime for ultracold neutrons in the source of about 30 s. The most critical performance parameters are the choice of cold moderator and the volume, thickness, and material of the vessel containing the superfluid helium.The source is scheduled to be installed in 2021 and will enable the TUCAN collaboration to measure the electric dipole moment of the neutron with a sensitivity of 10 −27 e cm.

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“…Optimizing a UCN source design to allow sufficient heat removal from the UCN converter, or to allow optical or pumping access, while maintaining low UCN transport loss is a common problem, in particular for He-II based sources under high heat loads. 28,29,31,32 The heat exchanger (also due to materials typically used) will need to be in a low radiation area so unwanted heating due to activation is reduced. Sufficient space between the heat exchanger and the tungsten target will be required for shielding.…”

Section: A Heat Removal With Ucn Extraction Guidementioning

confidence: 99%

A next-generation inverse-geometry spallation-driven ultracold neutron source

Leung

Muhrer

Hügle

et al. 2019

Journal of Applied Physics

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The concept of a next-generation spallation-driven ultracold neutron (UCN) source capable of delivering an integrated flux of ∼ 10 9 UCN s −1 is presented. A novel "inverse geometry" design is used with 40 liters of superfluid 4 He (He-II) as converter cooled with state-of-the-art sub-cooled cryogenic technology to ∼ 1.6 K. Our source design is optimized for a 100 W maximum thermal heat load constraint on the He-II and its vessel. In this paper, we first explore a modified Lujan-Center Mark-3 target for UCN production as a benchmark. We then present the baseline concept of our inverse geometry source design that gives a total UCN production rate in the converter of P UCN = 2.4 × 10 8 s −1 . In our inverse geometry, the spallation target is wrapped symmetrically around the cryogenic UCN converter to permit raster scanning the proton beam over a relatively large volume of tungsten spallation target to reduce the demand on the cooling requirements, which makes it reasonable to assume that water edge-cooling only is sufficient. Our design is refined in several steps to reach P UCN = 2.1 × 10 9 s −1 under our other restriction of 1 MW maximum available proton beam power. We then study effects of the He-II scattering kernel used as well as reductions in P UCN due to pressurization to reach a estimate of P UCN = 1.8 × 10 9 s −1 . Finally, we provide an estimate for the UCN extraction efficiency to show that the total extracted UCN rate out of the converter can be as large as R ex ≈ 6 × 10 8 s −1 for the He-II at 1.6 K out of a 18 cm diameter guide. The UCN extraction loss is dominated by upscattering in the He-II so that if the He-II can be cooled further to 1.4 K, R ex ≈ 8 × 10 8 s −1 can be attained. These extracted UCN rates are around an order of magnitude higher than the strongest proposed sources so far, and is around three orders of magnitude stronger than existing sources.He-II offers much higher thermal conductivities and a UCN upscattering time constant given by τ up ≈ (100 s K 7 )/T 7 (see Sec. VI), resulting in UCN loss times 3 s for a He-II bath at a temperature T = 1.6 K. At these temperatures, the total scattering mean-free-path for 8.9 Å (1 meV) neutrons, the primary UCN producing CN component, is ≈ 18 m. 25 This permits the design of a simple, large volume source where the converter material also serves as the coolant.There are two "in-pile" He-II sources currently under construction. One is at TRIUMF, Canada, where the source is coupled to a 500 MeV proton beam with 20 kW incident beam power. [26][27][28][29] The next generation version of this source will have an expected R ex ∼ 10 6 s −1 and UCN density deliverable to an experimental volume of ∼ 6, 000 cm −3 (both polarized).

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First ultracold neutrons produced at TRIUMF

Cited by 36 publications

References 33 publications

Fast-switching magnet serving a spallation-driven ultracold neutron source

Fast-switching magnet serving a spallation-driven ultracold neutron source

Optimizing neutron moderators for a spallation-driven ultracold-neutron source at TRIUMF

A next-generation inverse-geometry spallation-driven ultracold neutron source

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