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M. Williams

Publications and source records attributed to M. Williams.

At least 19 recordsLinked to original sources
arXiv2026

Position- and Temperature-Dependent Responsivity in a KID-Based Phonon-Mediated Detector

We report on the position- and temperature-dependent response of a kinetic inductance phonon-mediated (KIPM) detector. To study position-dependence, we used a controllable mirror attached to a micro-electromechanical system (MEMS) to steer optical light with a 100 $μ$m spot size over the backside of the cryogenic detector. With both pulsed and continuous operation of the LED, we observe features of the detector housing and find that the signal is strongest when the LED is pointed directly at the KID. The "off-KID" response is measured to be 34% of the "on-KID" response and is largely independent of direction. We model phonon propagation and collection in the KIPM detector with G4CMP and assert that the isotropic angular dependence is unlikely to be due to discrete phonon absorption "sinks", such as the microwave feedline or the device mounting points, but can be explained instead by an isotropic energy loss in the crystal. We furthermore utilize the temperature flexibility of the MEMS and KIPM detector system to investigate temperature-dependent responsivity, both at the sensor level (i.e., frequency shifts in the KID) and at the detector level (i.e., position dependence). We fit the KID's response to a two-component heat capacity and present the model as an alternative way to understand the KID's response to absorbed energy. We show on- and off-KID data at a range of temperatures and show that the phonon dynamics are not temperature dependent. We comment on the resulting implication for KID dynamics and design improvements.

physics.ins-det↗
arXiv2026

{DEMAND}: {A}n organic glass scintillator array for direct measurements of $(α,n)$ and $(p,n)$ reactions in inverse kinematics

We have developed an array of up to 20 organic glass scintillator detectors, each consisting of a $3~\mathrm{cm}\times3~\mathrm{cm}\times3~\mathrm{cm}$ scintillator cube coupled to a photomultiplier tube. Sensitive to neutrons from a few hundred keV to several tens of MeV, the array was designed for use with recoil separators in inverse-kinematics measurements of astrophysical $(α,n)$ and $(p,n)$ reactions. It provides a prompt start signal for identifying recoil-neutron coincidences from the recoil time of flight. We characterize eight detectors used in an inverse-kinematics measurement of $^{22}\mathrm{Ne}(α,n)^{25}\mathrm{Mg}$, using source and in-beam data. From the widths of $γ$-ray Compton-edge peaks at 311, 341, 477, and 1062 keVee, we find an energy resolution described by $\mathrm{FWHM}(E)/E=\sqrt{A^2/E+B^2/E^2+C^2}$, with $A=0.00(7)$, $B=0.0618(54)$, and $C=0.135(5)$. The time-difference spectrum of nearest-neighbor $γ$-$γ$ coincidences from a $^{22}\mathrm{Na}$ source (250--600 keVee) gives a FWHM coincidence timing resolution of $910(40)$ ps, corresponding to a single-detector resolution of $640(30)$ ps. Mixed neutron-$γ$ fields from the in-beam reaction and a $^{241}\mathrm{AmBe}$ source show pulse-shape discrimination with an $n$-$γ$ figure of merit $>1$ down to about 100 keVee. Below 100 keVee, the total neutron yield can still be extracted using two-Gaussian fits to energy-gated pulse-shape discrimination spectra. Monte Carlo simulations of the present $^{22}\mathrm{Ne}(α,n)^{25}\mathrm{Mg}$ measurement give a neutron singles detection efficiency of $1.56(45)%$, with uncertainty dominated by systematic effects in the simulation inputs.

physics.ins-det↗
arXiv2026

Direct measurement of the ${}^{23}\mathrm{Mg}(p, γ){}^{24}\mathrm{Al}$ reaction using the DRAGON recoil separator and a hybrid array of $γ$-ray detectors

Background: The $^{23}$Mg$(p,γ)^{24}$Al reaction plays a key role in nova nucleosynthesis, serving as a bridge between the Ne-Na and Mg-Al cycles and impacting synthesis of a wide variety of nuclides. It is crucial that the rate of this reaction be well constrained by experimental data, in particular the properties of the key resonance at $E_{\mathrm{cm}}\approx480$ keV, which dominates the rate at nova temperatures. Purpose: Our study aims to improve experimental constraints on the energy and strength of the key $E_{\mathrm{cm}}\approx480$ keV $^{23}$Mg$(p,γ)^{24}$Al resonance through a new direct measurement of its strength and energy. Methods: We used a $^{23}\mathrm{Mg}$ radioactive beam to directly observe capture into the $E_{\mathrm{cm}}\approx480$ keV resonance in inverse kinematics. The $^{24}\mathrm{Al}$ recoils were selected by the DRAGON recoil separator, and coincident $γ$ rays were measured in a hybrid $\mathrm{LaBr}_3/\mathrm{CeBr}_3/\mathrm{BGO}$ scintillator array. The $^{24}\mathrm{Al}$ singles yield was used to determine the resonance strength, while the time difference between the coincident $γ$ rays and the incident beam was used to determine the resonance energy. Results: We obtained a strength of $ωγ=38(7)$ meV and an energy of $E_{\mathrm{cm}}=478.8(26)$ keV for the key astrophysical $^{23}\mathrm{Mg}(p,γ)^{24}\mathrm{Al}$ resonance. Conclusions: Our reported strength is in excellent agreement with the previously reported direct measurement, as well as shell model calculations. Our energy is in good agreement with earlier indirect measurements. Reaction rate calculations incorporating our results indicate that the $^{23}\mathrm{Mg}(p,γ)^{24}\mathrm{Al}$ rate is constrained to a $1σ$ up/down factor of 1.5 or smaller in the nova temperature range of 0.2--0.4 GK.

nucl-ex↗
arXiv2026

First strength measurements of low-energy resonances in the $^{45}$Sc($p,γ$)$^{46}$Ti reaction and its astrophysical implications

The $^{45}$Sc($p,γ$)$^{46}$Ti reaction plays an important role in both hydrostatic and explosive nucleosynthesis. During hydrostatic oxygen and silicon burning in massive stars, including dynamic processes such as convective carbon-oxygen (C-O) shell mergers, it acts as a bottleneck that regulates the reaction flow in the Sc-Ti mass region. In oxygen-neon (ONe) novae, the ejecta indicate the production of elements up to the Fe group, as observed in V1974 Cygni, and the $^{45}$Sc($p,γ$)$^{46}$Ti reaction links nuclei above Ca to the Fe region. In core-collapse supernovae (CCSNe), it influences the production of the radioactive isotope $^{47}$Sc. At present, the thermonuclear reaction rate is based on statistical model calculations. In this work, we report on measurements of the $^{45}$Sc($p,γ$)$^{46}$Ti reaction performed using the 5~MV accelerator at the Nuclear Science Laboratory, University of Notre Dame, over a laboratory proton energy range of 526--1275~keV. We present the first direct measurements of the resonance strengths for six resonances at $E^{\rm lab}_{\rm R} = 917.4$, 1026.0, 1031.1, 1049.7, 1059.4 and 1257.5~keV, together with integrated resonance strengths at $E^{\rm lab} = 555$, 630, 700, 761 and 871~keV. For resonance energies below the lowest directly measured energy, available transfer-reaction data were used to estimate the resonance strengths. An updated thermonuclear reaction rate is derived, and its astrophysical implications are discussed.

nucl-ex↗
arXiv2026

$l$-forbidden $\mathbf{M1}$ strengths near $^{100}$Sn from knockout reactions in Cd and Sn

Neutron knockout reactions on beams of $^{104,102}$Cd, and $^{104}$Sn are presented. States in the residual $^{103,101}$Cd and $^{103}$Sn nuclei are populated, including low-lying $7/2^+$ states of $νg_{7/2}$ character. These states have half-lives $\approx 400$ ps due to their low energy and hindered $B(M1; 7/2^+ \rightarrow 5/2^+)$ strengths. The excited-state half-lives were measured using their Doppler-shifted lineshapes, and the resulting $B(M1)$ strengths are compared to Valence Space In Medium Similarity Renormalization Group (VS-IMSRG) calculations. The VS-IMSRG calculations under-predict the $l$-forbidden $M1$ strengths in the $^{100}$Sn region, as well as in other regions of the nuclear chart near $^{40}$Ca and $^{208}$Pb.

nucl-ex↗
arXiv2026

Transmission Efficiency of the Recoil Mass Spectrometer EMMA at TRIUMF

The mean transmission efficiency of the EMMA recoil mass spectrometer at TRIUMF has been measured with 6 different angular apertures at 17 kinetic energy/charge deviations with respect to the central, reference trajectory. Measurements performed using a 148Gd alpha source installed at the target position of the spectrometer are compared to ion-optical calculations and Monte Carlo simulations. The transmission efficiency as a function of angle and kinetic energy/charge is described empirically using piecewise Gaussian functions whose parameters are fit to the data.

physics.ins-det↗
arXiv2025

Direct measurement of $^{59}$Cu($p$,$α$)$^{56}$Ni precludes a strong NiCu cycle in Type-I X-ray bursts

Model-observation comparisons of type-I X-ray bursts (XRBs) can reveal the properties of accreting neutron star systems, including the neutron star compactness. XRBs are powered by nuclear burning and a handful of reactions have been shown to impact the model results. Reactions in the NiCu cycles, featuring a competition between $^{59}$Cu($p$,$γ$)$^{60}$Zn and $^{59}$Cu($p$,$α$)$^{56}$Ni, have been shown to be among the most important reactions as they are a critical checkpoint in $rp$-process flow and significantly impact the light curves and burst ashes. We report a direct measurement of $^{59}$Cu($p$,$α$)$^{56}$Ni bringing stringent constraints on this reaction rate. New results rule out a strong NiCu cycle in XRBs, with a negligible degree of recycling, $\leq$5\% up to 1.5 GK. The new reaction rate, when varied within new uncertainty limits, shows no impact on one-zone XRB model light-curves tailored for clocked-burster $\tt{GS 1826-24}$, hence removing an important nuclear physics uncertainty in the model-observation comparison.

astro-ph.HE↗
arXiv2025

First In-Beam Demonstration of a hybrid LaBr3/CeBr3/BGO array to measure radiative capture resonance energies in an extended gas target using a novel time of flight technique

We have deployed a new hybrid array of LaBr3, CeBr3, and BGO scintillators for detecting $γ$ rays at the DRAGON recoil separator at TRIUMF. The array was developed to improve $γ$-ray timing resolution over the existing BGO array. This allows the average position of resonant capture in an extended gas target to be determined with $\sim$15 mm precision or better, even with five or fewer detected capture events. This, in turn, allows determination of resonant capture energies with statistical uncertainties below ${\sim} 1\%$. Here we report the results of a first in-beam demonstration of the array, measuring the $E_{cm} = 0.4906(3)$ MeV resonance in the ${}^{23}\mathrm{Na}(p,γ){}^{24}\mathrm{Mg}$ reaction, focusing on the timing properties of the array and its anticipated performance in future experiments with radioactive beams.

physics.ins-det↗
arXiv2023

Searching for resonance states in $^{22}$Ne($p,γ$)$^{23}$Na

Background: Globular clusters show strong correlations between different elements, such as the well-known sodium-oxygen anticorrelation. One of the main sources of uncertainty in this anticorrelation is the $^{22}$Ne($p,γ$)$^{23}$Na reaction rate, due to the possible influence of an unobserved resonance state at $E_\mathrm{x} = 8862$ keV ($E_\mathrm{r, c.m.} = 68$ keV). The influence of two higher-lying resonance states at $E_\mathrm{x} = 8894$ and $9000$ keV has already been ruled out by direct $^{22}$Ne($p,γ$)$^{23}$Na measurementsPurpose: To study excited states in $^{23}$Na above the proton threshold to determine if the unconfirmed resonance states in $^{23}$Na exist. Methods: The non-selective proton inelastic scattering reaction at low energies was used to search for excited states in $^{23}$Na above the proton threshold. Protons scattered from various targets were momentum-analysed in the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratorium, Munich, Germany. Results: The resonance states previously reported at $E_\mathrm{x} = 8862$, $8894$ and $9000$ keV in other experiments were not observed in the present experiment at any angle. This result, combined with other non-observations of these resonance states in most other experiments, results in a strong presumption against the existence of these resonance states. Conclusions: The previously reported resonance states at $E_\mathrm{x} = 8862$, $8894$ and $9000$ keV are unlikely to exist and should be omitted from future evaluations of the $^{22}$Ne($p,γ$)$^{23}$Na reaction rates. Indirect studies using low-energy proton inelastic scattering are a simple and yet exceptionally powerful tool in helping to constrain astrophysical reaction rates by providing non-selective information of the excited states of nuclei.

nucl-ex↗
arXiv2023

Structure Studies of $^{13}\text{Be}$ from the $^{12}$Be(d,p) reaction in inverse kinematics on a solid deuteron target

The low-lying structure of $^{13}$Be has remained an enigma for decades. Despite numerous experimental and theoretical studies, large inconsistencies remain. Being both unbound, and one neutron away from $^{14}$Be, the heaviest bound beryllium nucleus, $^{13}$Be is difficult to study through simple reactions with weak radioactive ion beams or more complex reactions with stable-ion beams. Here, we present the results of a study using the $^{12}$Be(d,p)$^{13}$Be reaction in inverse kinematics using a 9.5~MeV per nucleon $^{12}$Be beam from the ISAC-II facility. The solid deuteron target of IRIS was used to achieve an increased areal thickness compared to conventional deuterated polyethylene targets. The Q-value spectrum below -4.4~MeV was analyzed using a Bayesian method with GEANT4 simulations. A three-point angular distribution with the same Q-value gate was fit with a mixture of $s$- and $p$-wave, $s$- and $d$-wave, or pure $p$-wave transfer. The Q-value spectrum was also compared with GEANT simulations obtained using the energies and widths of states reported in four previous works. It was found that our results are incompatible with works that revealed a wide $5/2^+$ resonance but shows better agreement with ones that reported a narrower width.

nucl-ex↗
arXiv2023

Artificial Intelligence for the Electron Ion Collider (AI4EIC)

The Electron-Ion Collider (EIC), a state-of-the-art facility for studying the strong force, is expected to begin commissioning its first experiments in 2028. This is an opportune time for artificial intelligence (AI) to be included from the start at this facility and in all phases that lead up to the experiments. The second annual workshop organized by the AI4EIC working group, which recently took place, centered on exploring all current and prospective application areas of AI for the EIC. This workshop is not only beneficial for the EIC, but also provides valuable insights for the newly established ePIC collaboration at EIC. This paper summarizes the different activities and R&D projects covered across the sessions of the workshop and provides an overview of the goals, approaches and strategies regarding AI/ML in the EIC community, as well as cutting-edge techniques currently studied in other experiments.

physics.acc-ph↗
arXiv2023

Cross Sections of the $^{83}$Rb(p,$γ)^{84}$Sr and $^{84}$Kr(p,$γ)^{85}$Rb Reactions at Energies Characteristic of the Astrophysical $γ$ Process

We have measured the cross section of the $^{83}$Rb(p,$γ)^{84}$Sr radiative capture reaction in inverse kinematics using a radioactive beam of $^{83}$Rb at incident energies of 2.4 and $2.7 A$ MeV. Prior to the radioactive beam measurement, the $^{84}$Kr(p,$γ)^{85}$Rb radiative capture reaction was measured in inverse kinematics using a stable beam of $^{84}$Kr at an incident energy of $2.7 A$ MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the $γ$ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be $0.17-0.42$ times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the $p$ nucleus $^{84}$Sr, caused by the reduced rate of the $^{84}$Sr($γ$,p)$^{83}$Rb reaction derived from the present measurement.

nucl-ex↗
arXiv2022

First application of Markov Chain Monte Carlo-based Bayesian data analysis to the Doppler-Shift Attenuation Method

Motivated primarily by the large uncertainties in the thermonuclear rate of the $^{30}$P$(p,γ)^{31}$S reaction that limit our understanding of classical novae, we carried out lifetime measurements of $^{31}$S excited states using the Doppler Shift Lifetimes (DSL) facility at the TRIUMF Isotope Separator and Accelerator (ISAC-II) facility. The $^{31}$S excited states were populated by the $^{3}$He$(^{32}$S$,α)^{31}$S reaction. The deexcitation $γ$ rays were detected by a clover-type high-purity germanium detector in coincidence with the $α$ particles detected by a silicon detector telescope. We have applied modern Markov chain Monte Carlo-based Bayesian methods to perform lineshape analyses of Doppler-shift attenuation method $γ$-ray data for the first time. We have determined the lifetimes of the two lowest-lying $^{31}$S excited states. First experimental upper limits on the lifetimes of four higher-lying states have been obtained. The experimental results were compared to shell-model calculations using five universal $sd$-shell Hamiltonians. Evidence for $γ$ rays originating from the astrophysically important $J^π=3/2^+$, 260-keV $^{30}$P$(p,γ)^{31}$S resonance has also been observed, although strong constraints on the lifetime will require better statistics.

nucl-ex↗
arXiv2022

Snowmass Computational Frontier: Topical Group Report on Experimental Algorithm Parallelization

The substantial increase in data volume and complexity expected from future experiments will require significant investment to prepare experimental algorithms. These algorithms include physics object reconstruction, calibrations, and processing of observational data. In addition, the changing computing architecture landscape, which will be primarily composed of heterogeneous resources, will continue to pose major challenges with regard to algorithmic migration. Portable tools need to be developed that can be shared among the frontiers (e.g., for code execution on different platforms) and opportunities, such as forums or cross-experimental working groups, need to be provided where experiences and lessons learned can be shared between experiments and frontiers. At the same time, individual experiments also need to invest considerable resources to develop algorithms unique to their needs (e.g., for facilities dedicated to the experiment), and ensure that their specific algorithms will be able to efficiently exploit external heterogeneous computing facilities. Common software tools represent a cost-effective solution, providing ready-to-use software solutions as well as a platform for R\&D work. These are particularly important for small experiments which typically do not have dedicated resources needed to face the challenges imposed by the evolving computing technologies. Workforce development is a key concern across frontiers and experiments, and additional support is needed to provide career opportunities for researchers working in the field of experimental algorithm development. Finally, cross-discipline collaborations going beyond high-energy physics are a key ingredient to address the challenges ahead and more support for such collaborations needs to be created. This report targets future experiments, observations and experimental algorithm development for the next 10-15 years.

hep-ex↗
arXiv2022

Direct measurement of resonances in $^7$Be($α,γ$)$^{11}$C relevant to $νp$-process nucleosynthesis

We have performed the first direct measurement of two resonances of the $^7$Be($α,γ$)$^{11}$C reaction with unknown strengths using an intense radioactive $^7$Be beam and the DRAGON recoil separator. We report on the first measurement of the 1155 and 1110 keV resonance strengths of $1.73 \pm 0.25(stat.) \pm 0.40(syst.)$ eV and $125 ^{+27}_{-25}(stat.) \pm 15(syst.)$ meV, respectively. The present results have reduced the uncertainty in the $^7$Be($α,γ$)$^{11}$C reaction rate to $\sim$ 9.4-10.7% over T = 1.5-3 GK, which is relevant for nucleosynthesis in the neutrino-driven outflows of core-collapse supernovae ($νp$-process). We find no effect of the new, constrained reaction rate on $νp$-process nucleosynthesis.

nucl-ex↗
arXiv2022

First inverse kinematics measurement of resonances in $^7$Be($α,γ$)$^{11}$C relevant to neutrino-driven wind nucleosynthesis using DRAGON

A possible mechanism to explain the origin of the light $p$-nuclei in the Galaxy is the nucleosynthesis in the proton-rich neutrino-driven wind ejecta of core-collapse supernovae via the $νp$-process. However this production scenario is very sensitive to the underlying supernova dynamics and the nuclear physics input. As far as the nuclear uncertainties are concerned, the breakout from the $pp$-chains via the $^7$Be($α,γ$)$^{11}$C reaction has been identified as an important link which can influence the nuclear flow and therefore the efficiency of the $νp$-process. However its reaction rate is poorly known over the relevant temperature range, T = 1.5-3 GK. We report on the first direct measurement of two resonances of the $^7$Be($α,γ$)$^{11}$C reaction with previously unknown strengths using an intense radioactive $^7$Be beam from the ISAC facility and the DRAGON recoil separator in inverse kinematics. We have decreased the $^7$Be($α,γ$)$^{11}$C reaction rate uncertainty to $\sim$ 9.4-10.7% over the relevant temperature region.

nucl-ex↗
arXiv2022

Single neutron transfer on 23Ne and its relevance forthepathway ofnucleosynthesis in astrophysical X-ray bursts

We present new experimental measurements of resonance strengths in the astrophysical 23Al(p, γ)24Si reaction, constraining the pathway of nucleosynthesis beyond 22Mg in X-ray burster scenarios. Specifically, we have performed the first measurement of the (d, p) reaction using a radioactive beam of 23Ne to explore levels in 24Ne, the mirror analog of 24Si. Four strong single-particle states were observed and corresponding neutron spectroscopic factors were extracted with a precision of {\sim}20{\%}. Using these spectroscopic factors, together with mirror state identifications, we have reduced uncertainties in the strength of the key {\ell} = 0 resonance at Er= 157 keV, in the astrophysical 23Al(p, γ) reaction, by a factor of 4. Our results show that the 22Mg(p, γ)23Al(p, γ) pathway dominates over the competing 22Mg(α, p) reaction in all but the most energetic X-ray burster events (T>0.85GK), significantly affecting energy production and the preservation of hydrogen fuel.

nucl-ex↗