TRIUMF

Non-destructive beam diagnostics are essential for low-energy medical cyclotrons, where even thin interceptive devices can severely degrade beam quality. We investigate an external fiber monitor (EFM) based on Ce-doped silica scintillating fibers that detects secondary radiation generated at existing beamline components of the 18 MeV Bern Medical Cyclotron beam transfer line (BTL). Three use cases were studied: (i) beam intensity monitoring around an electrically isolated, water-cooled beam dump; (ii) beam-loss monitoring around a 10 mm collimator under varying the beam focusing; and (iii) by steering a 6×6 mm beam spot on a beam dump. For case (i), the summed EFM signal exhibits a linear dependence on the current on target over nearly three orders of magnitude. In case (ii), a normalized EFM-based beam-loss proxy scales monotonically with an electrical loss proxy across several focusing settings. Furthermore, opposing-fiber signal ratios provide decoupled, monotonic sensitivity to horizontal and vertical beam displacements.

Objective.High-energy proton irradiation of232Th produces both225Ac and its precursor225Ra, the latter being underexplored despite its potential applicability at relevant facilities. This study aims to provide a theoretical basis for232Th-based225Ra production by modeling the associated yields and radioisotopic impurity levels.Approach.Production yields of225Ra and levels of228Ra impurity were calculated using Monte Carlo simulations for proton energies of 100-800 MeV, total232Th target thicknesses of 0.125-8 mm, and an irradiation time of 15 d. A theoretical model was developed for predicting the cumulative yield of225Ac eluates from a225Ra yield. The levels of228Ra-derived228Ac impurity in225Ac eluates and the postelution decay times required to suppress228Ac to acceptable thresholds were modeled and computed.Main results.The calculated225Ra yields at the end of bombardment for a 15 d irradiation ranged from 2.3 ± 0.3 MBq µA-1at 100 MeV to 563.1 ± 12.3 MBq µA-1at 700 MeV. Increases in225Ra yield were most pronounced when the proton energy was raised from 100 to 200 MeV, with diminishing returns at higher energies. The cumulative yield of225Ac eluates was about 29.1% of a225Ra yield under combined conditions of hypothetical and empirical settings. Postelution times of at least 25.1-30.1 h should be allowed to reduce228Ac impurity levels to below 0.1%.Significance.The developed models provide a quantitative basis for evaluating and optimizing225Ra production via proton irradiation of232Th. This study quantitatively predicted the presence of228Ac in225Ac eluates under various conditions and showed how228Ac can be suppressed by introducing minimal postelution decay times.

Abstract The DarkSide-20k dark matter direct detection experiment will employ a $${21}\,\hbox {m}^{2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>21</mml:mn> <mml:mspace/> <mml:msup> <mml:mtext>m</mml:mtext> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:math> silicon photomultiplier (SiPM) array, instrumenting a dual-phase 50 tonnes liquid argon Time Projection Chamber (TPC). SiPMs are arranged into modular photosensors called Tiles , each integrating 24 SiPMs onto a printed circuit board (PCB) that provides signal amplification, power distribution, and a single-ended output for simplified readout. $$16$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>16</mml:mn> </mml:mrow> </mml:math> Tiles are further grouped into Photo-Detector Units (PDUs). This paper details the production of the Tiles and the Quality Assurance and Quality Control (QA-QC) protocol established to ensure their performance and uniformity. The production and QA-QC of the Tiles are carried out at Nuova Officina Assergi (NOA), an ISO-6 clean room facility at LNGS. This process includes wafer-level cryogenic characterisation, precision die attaching, wire bonding, and extensive electrical and optical validation of each Tile. The overall production yield exceeds 83.5%, matching the requirements of the DarkSide-20k production plan. These results validate the robustness of the Tile design and its suitability for operation in a cryogenic environment.

Since its first observation in the 1970s, neutrino-induced neutral-current single positive pion production (NC1π^{+}) has remained an elusive and poorly understood interaction channel. This process is a significant background in neutrino oscillation experiments and studying it further is critical for the physics program of next-generation accelerator-based neutrino oscillation experiments. In this Letter, we present the first double-differential cross-section measurement of NC1π^{+} interactions using data from the ND280 detector of the T2K experiment collected in ν-beam mode. The measured flux-averaged integrated cross section is σ=(6.07±1.22)×10^{-41} cm^{2}/nucleon. We compare the results on a hydrocarbon target to the predictions of several neutrino interaction generators and final-state-interaction models. While model predictions agree with the differential results, the data show a weak preference for a cross-section normalization approximately 30% higher than predicted by most models studied in this Letter.

Precise experimental control and interrogation of molecules and calculations of their structure are enriching the investigation of nuclear and particle physics phenomena. Molecules containing heavy, octupole-deformed nuclei, such as radium, are of particular interest. Here, we report precision laser spectroscopy measurements and theoretical calculations of the structure of the radioactive radium monofluoride molecule 225Ra19F. Our results reveal fine details of the short-range electron-nucleus interaction, indicating the high sensitivity of this molecule to the distribution of magnetization, within the radium nucleus. These results provide a stringent test of the description of the electronic wave function inside the nuclear volume, highlighting the suitability of these molecules for investigating subatomic phenomena.

Abstract A search for a pseudoscalar a produced in association with a top-quark pair, or in association with a single top quark plus a W boson, with the pseudoscalar decaying into b -quarks ( $$a\rightarrow b\bar{b}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>a</mml:mi> <mml:mo>→</mml:mo> <mml:mi>b</mml:mi> <mml:mover> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> </mml:math> ), is performed using the full Run 2 data sample using a dileptonic decay mode signature. The search covers pseudoscalar boson masses between 12 and 100 GeV and involves both the kinematic regime where the decay products of the pseudoscalar are reconstructed as two standard b -tagged small-radius jets, or merged into a large-radius jet due to its Lorentz boost. No significant excess relative to expectations is observed. Assuming a branching ratio $$\text {BR}(a\rightarrow b\bar{b})=100\% $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>BR</mml:mtext> <mml:mo>(</mml:mo> <mml:mi>a</mml:mi> <mml:mo>→</mml:mo> <mml:mi>b</mml:mi> <mml:mover> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> <mml:mo>)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>100</mml:mn> <mml:mo>%</mml:mo> </mml:mrow> </mml:math> , the range of pseudoscalar masses between 50 and 80 GeV is excluded at 95% confidence level for a coupling of the pseudoscalar to the top quark of 0.5, while a coupling of 1.0 is excluded at 95% confidence level for the masses considered, with the coupling defined as the strength modifier of the Standard Model Yukawa coupling.

Background: Lithium plays an important role in nuclear astrophysics, fusion energy generation, and nuclear technology. From a theoretical point of view, the nucleus $^7$Li presents a remarkable challenge, as its bound states and resonances can be understood as being formed by a $^4$He and $^3$H pair, or simultaneously, a single neutron/proton coupled to a $^6$Li/$^6$He core. In light of this complexity, a consistent description of $^7$Li bound-state and continuum properties in a unified model presents a significant advancement towards a predictive theory of nuclear structure and reactions. Purpose: Towards achieving such a predictive description, we carry out calculations for $^7$Li within an ab initio framework, taking into account the mass/charge partitions $^6$Li + $n$ and $^6$He + $p$ in a single coupled-channel calculation. This approach allows us to both investigate the effects of the coupling between partitions on the spectrum of $^7$Li, and calculate the cross sections for the $^6$Li($n,p)^6$He and $^6$He($p,n)^6$Li reactions. Method: We use the no-core shell model with continuum, which is capable of describing both bound and scattering states in a unified framework. Results: Our calculation reproduces all the experimentally observed states of $^7$Li in the correct order and predicts new resonances. We also calculated the cross section of the reaction $^6$He($p,n)^6$Li and differential cross sections of the elastic scattering of protons on $^6$He to provide theoretical results for comparison with planned experiments. Conclusions: The overall shape of the cross section of the reaction $^6$Li$(n,p)^6$He as a function of energy is reproduced, although the absolute magnitude is overestimated due to omission of the ($n,\alpha$) reaction channel. A more accurate description of the cross section is achieved by phenomenological adjustmenting the energies of resonances.

The $^{46}$Ar($^3$He,d)$^{47}$K reaction was performed in inverse kinematics using a radioactive $^{46}$Ar beam produced by the SPIRAL1 facility at GANIL and a cryogenic $^{3}$He target. The AGATA-MUGAST-VAMOS setup allowed the coincident measurement of the $\gamma$ rays, deuterons and recoiling $^{47}$K isotopes produced by the reaction. The relative cross sections towards the proton-addition states in $^{47}$K point towards a depletion of the $\pi s_{1/2}$ shell. The experimental findings are in good agreement with ab initio calculations, which predict that $^{46}$Ar exhibits a charge density bubble associated with a pronounced proton closed-shell character.