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C. Y. Liu

Publications and source records attributed to C. Y. Liu.

17 recordsLinked to original sources
arXiv2025

Dynamics of Magnetic Evaporative Beamline Cooling for Preparation of Cold Atomic Beams

The most sensitive direct neutrino mass searches today are based on measurement of the endpoint of the beta spectrum of tritium to infer limits on the mass of the unobserved neutrino. To avoid the smearing associated with the distribution of molecular final states in the T-He molecule, the next generation of these experiments will need to employ atomic (T) rather than molecular (T$_{2}$) tritium sources, at currents of at least 10$^{15}$ atoms per second. Following production, atomic T can be trapped in gravitational and/or magnetic bottles for beta spectrum experiments, if and only if it can first be cooled to millikelvin temperatures. Accomplishing this cooling presents substantial technological challenges. The Project 8 collaboration is developing a technique based on magnetic evaporative cooling along a beamline (MECB) for the purpose of cooling T to feed a magneto-gravitational trap that also serves as a cyclotron radiation emission spectroscope. Initial tests of the approach are planned in a pathfinder apparatus using atomic Li. This paper presents a method for analyzing the dynamics of the MECB technique, and applies these calculations to the design of systems for cooling and slowing of atomic Li and T. A scheme is outlined that could provide a current of T at the millikelvin temperatures required for the Project 8 neutrino mass search.

physics.ins-det↗
arXiv2025

Fundamental Nuclear and Particle Physics At Neutron Sources

Fundamental neutron and neutrino physics at neutron sources, combining precision measurements and theory, can probe new physics at energy scales well beyond the highest energies probed by the LHC and possible future high energy collider facilities. The European Spallation Source (ESS) will in the not too far future be a most powerful pulsed neutron source and simultaneously the world's brightest pulsed neutrino source. The ESS, and neutron sources in general, can provide unprecedented and unique opportunities to contribute to the search for the missing elements in the Standard Model of particle physics. Currently there are no strong indications where hints of the origin of the new physics will emerge. A multi-pronged approach will provide the fastest path to fill the gaps in our knowledge and neutron sources have a pivotal role to play. To survey the ongoing and proposed physics experiments at neutron sources and assess their potential impact, a workshop was held at Lund University in January, 2025. This report is a summary of that workshop and has been prepared as input to the European Strategy Update.

nucl-ex↗
arXiv2025

Role of nuclear and electromagnetic fragmentation in the charge-changing reactions of 18O on carbon and lead targets at around 370 MeV/nucleon

Charge-changing cross sections (CCCSs) of 18O on carbon (C) and lead (Pb) targets have been measured with an uncertainty of less than 4% at around 370MeV/nucleon. We evaluate the contributions of nucleon-nucleon (NN) and electromagnetic (EM) interactions to CCCSs by considering the direct proton removal process, the charged particle evaporation (CPE) after neutron removal, and the EM excitation. We conclude that the CPE accounts for 12.3% and 5% of CCCSs on C and Pb, respectively. Only less than 1% of CCCSs of 18O is attributed to the EM excitation. Further investigation of projectiles from 18O to 197Au on C, silver (Ag) and Pb targets at 300 and 900MeV/nucleon show that the contribution of EM to CCCSs on Ag and Pb increases with projectile mass numbers and incident energies, and can reach 10% for 197Au on Pb at 900MeV/nucleon. In contrast, the EM contribution to CCCS is negligible for all projectiles on C at both energies.

nucl-ex↗
arXiv2024

Charge radii of $^{11-16}$C, $^{13-17}$N and $^{15-18}$O determined from their charge-changing cross-sections and the mirror-difference charge radii

Charge-changing cross-sections of $^{11-16}$C, $^{13-17}$N and $^{15-18}$O on a carbon target have been determined at energies around 300 MeV/nucleon. A nucleon separation energy-dependent correction factor has been introduced to the Glauber model calculation for extracting the nuclear charge radii from the experimental CCCSs. The charge radii of $^{11}$C, $^{13,16}$N and $^{15}$O thus were determined for the first time. With the new radii, we studied the experimental mirror-difference charge radii ($ΔR_{\text {ch}}^{\text {mirror}}$) of $^{11}$B-$^{11}$C, $^{13}$C-$^{13}$N, $^{15}$N-$^{15}$O, $^{17}$N-$^{17}$Ne pairs for the first time. We find that the $ΔR_{\text {ch}}^{\text {mirror}}$ values of $^{13}$C-$^{13}$N and $^{15}$N-$^{15}$O pairs follow well the empirical relation to the isospin asymmetry predicted by the $ab$ $initio$ calculations, while $ΔR_{\text {ch}}^{\text {mirror}}$ of $^{11}$B-$^{11}$C and $^{17}$N-$^{17}$Ne pairs deviate from such relation by more than two standard deviations.

nucl-ex↗
arXiv2024

Suppression and excitation condition of collision on instabilities of electrostatic plasmas

Two-stream (TS) and Bump-On-Tail (BOT) electron distributions can induce instabilities in collisionless plasmas, which is closely related to phenomena in space and fusion plasmas. Collisions can lead to unexpected plasma behavior, especially in dense and/or low temperature plasmas. In this work, the Vlasov-Poisson system with Krook collisions are used to study the effect of collisions. Normally, the collision can dissipate the system energy which causes the suppression of the instabilities. Against the traditional suppression effect of collision on the instability, it is found in our simulation that the collision can also excite the instability even in the forbidden beam velocity range predicted by the cold-beam theory. With collision, the beam velocity range can be divided into suppression area [vth/2, vc + vth], transition area [vc - vth, vc + vth], excitation area [vc + vth, 2vc] and forbidden area [2vc, +infinity] for TS instability. where vc is the critical velocity from cold-beam theory and vth is thermal velocity or the beam width in our simulation. The collision dissipation effect and the excitation of beam instability can compete with each other, which evoked the excitation of collision on TS instability. The collision can change the suppression and excitation condition from beam theory. However, for BOT instability, there is only suppression effect of collision on the instability. These results can expand the view of collision effect on instability of electrostatic plasmas.

physics.plasm-ph↗
arXiv2023

Isospin-dependence of the charge-changing cross-section shaped by the charged-particle evaporation process

We present the charge-changing cross sections (CCCS) of $^{11-15}$C, $^{13-17}$N, and $^{15,17-18}$O at around 300 MeV/nucleon on a carbon target, which extends to $p$-shell isotopes with $N < Z$ for the first time. The Glauber model, which considers only the proton distribution of projectile nuclei, underestimates the cross sections by more than 10\%. We show that this discrepancy can be resolved by considering the contribution from the charged-particle evaporation process (CPEP) following projectile neutron removal. Using nucleon densities from the deformed relativistic Hartree-Bogoliubov theory in continuum, we investigate the isospin-dependent CPEP contribution to the CCCS for a wide range of neutron-to-proton separation energy asymmetry. Our calculations, which include the CPEP contribution, agree well with existing systematic data and reveal an ``evaporation peak" at the isospin symmetric region where the neutron-to-proton separation energy is close to zero. These results suggest that analysis beyond the Glauber model is crucial for accurately determining nuclear charge radii from CCCSs.

nucl-ex↗
arXiv2023

Demonstration of Sub-micron UCN Position Resolution using Room-temperature CMOS Sensor

High spatial resolution of ultracold neutron (UCN) measurement is of growing interest to UCN experiments such as UCN spectrometers, UCN polarimeters, quantum physics of UCNs, and quantum gravity. Here we utilize physics-informed deep learning to enhance the experimental position resolution and to demonstrate sub-micron spatial resolutions for UCN position measurements obtained using a room-temperature CMOS sensor, extending our previous work [1, 2] that demonstrated a position uncertainty of 1.5 microns. We explore the use of the open-source software Allpix Squared to generate experiment-like synthetic hit images with ground-truth position labels. We use physics-informed deep learning by training a fully-connected neural network (FCNN) to learn a mapping from input hit images to output hit position. The automated analysis for sub-micron position resolution in UCN detection combined with the fast data rates of current and next generation UCN sources will enable improved precision for future UCN research and applications.

physics.ins-det↗
arXiv2020

Characterization of magnetic field noise in the ARIADNE source mass rotor

ARIADNE is a nuclear-magnetic-resonance-based experiment that will search for novel axion-induced spin-dependent interactions between an unpolarized source mass rotor and a nearby sample of spin-polarized $^3$He gas. To detect feeble axion signals at the sub-atto-Tesla level, the experiment relies on low magnetic background and noise. We measure and characterize the magnetic field background from a prototype tungsten rotor. We show that the requirement is met with our current level of tungsten purity and demagnetization process. We further show that the noise is dominantly caused by a few discrete dipoles, likely due to a few impurities trapped inside the rotor during manufacturing. This is done via a numerical optimization pipeline which fits for the locations and magnetic moments of each dipole. We find that under the current demagnetization, the magnetic moment of trapped impurities is bounded at $10^{-9} \mathrm{A}\mathrm{m}^2$.

physics.ins-det↗
arXiv2019

A New Cryogenic Apparatus to Search for the Neutron Electric Dipole Moment

A cryogenic apparatus is described that enables a new experiment, nEDM@SNS, with a major improvement in sensitivity compared to the existing limit in the search for a neutron Electric Dipole Moment (EDM). It uses superfluid $^4$He to produce a high density of Ultra-Cold Neutrons (UCN) which are contained in a suitably coated pair of measurement cells. The experiment, to be operated at the Spallation Neutron Source at Oak Ridge National Laboratory, uses polarized $^3$He from an Atomic Beam Source injected into the superfluid $^4$He and transported to the measurement cells as a co-magnetometer. The superfluid $^4$He is also used as an insulating medium allowing significantly higher electric fields, compared to previous experiments, to be maintained across the measurement cells. These features provide an ultimate statistical uncertainty for the EDM of $2-3\times 10^{-28}$ e-cm, with anticipated systematic uncertainties below this level.

physics.ins-det↗
arXiv2019

Improvement of charge resolution for radioactive heavy ions at relativistic energies using a hybrid detector system

In typical nuclear physics experiments with radioactive ion beams (RIBs) selected by the in-flight separation technique, Si detectors or ionization chambers are usually equipped for the charge determination of RIBs. The obtained charge resolution relies on the performance of these detectors for energy loss determination, and this affects the particle identification capability of RIBs. We present an approach on improving the resolution of charge measurement for heavy ions by using the abundant energy loss information from different types of existing detectors along the beam line. Without altering the beam line and detectors, this approach can improve the charge resolution by more than 12\% relative to the multiple sampling ionization chamber of the best resolution.

physics.ins-det↗
arXiv2018

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

The ultracold neutron (UCN) source at Los Alamos National Laboratory (LANL), which uses solid deuterium as the UCN converter and is driven by accelerator spallation neutrons, has been successfully operated for over 10 years, providing UCN to various experiments, as the first production UCN source based on the superthermal process. It has recently undergone a major upgrade. This paper describes the design and performance of the upgraded LANL UCN source. Measurements of the cold neutron spectrum and UCN density are presented and compared to Monte Carlo predictions. The source is shown to perform as modeled. The UCN density measured at the exit of the biological shield was $184(32)$ UCN/cm$^3$, a four-fold increase from the highest previously reported. The polarized UCN density stored in an external chamber was measured to be $39(7)$ UCN/cm$^3$, which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of $σ(d_n) = 3\times 10^{-27}$ $e\cdot$cm.

physics.ins-det↗
arXiv2017

Evaluation of commercial nickel-phosphorus coating for ultracold neutron guides using a pinhole bottling method

We report on the evaluation of commercial electroless nickel phosphorus (NiP) coatings for ultracold neutron (UCN) transport and storage. The material potential of 50~$μ$m thick NiP coatings on stainless steel and aluminum substrates was measured to be $V_F = 213(5.2)$~neV using the time-of-flight spectrometer ASTERIX at the Lujan Center. The loss per bounce probability was measured in pinhole bottling experiments carried out at ultracold neutron sources at Los Alamos Neutron Science Center and the Institut Laue-Langevin. For these tests a new guide coupling design was used to minimize gaps between the guide sections. The observed UCN loss in the bottle was interpreted in terms of an energy independent effective loss per bounce, which is the appropriate model when gaps in the system and upscattering are the dominate loss mechanisms, yielding a loss per bounce of $1.3(1) \times 10^{-4}$. We also present a detailed discussion of the pinhole bottling methodology and an energy dependent analysis of the experimental results.

physics.ins-det↗
arXiv2016

Distributed Data-Processing Pipeline for Mingantu Ultrawide Spectral Radioheliograph

The Chinese Spectral RadioHeliograph (CSRH) is a synthetic aperture radio interferometer built in Inner Mongolia, China. As a solar-dedicated interferometric array, CSRH is capable of producing high quality radio images at frequency range from 400 MHz to 15 GHz with high temporal, spatial, and spectral resolution.To implement high cadence imaging at wide-band and obtain more than 2 order higher multiple frequencies, the implementation of the data processing system for CSRH is a great challenge. It is urgent to build a pipeline for processing massive data of CSRH generated every day. In this paper, we develop a high performance distributed data processing pipeline (DDPP) built on the OpenCluster infrastructure for processing CSRH observational data including data storage, archiving, preprocessing, image reconstruction, deconvolution, and real-time monitoring. We comprehensively elaborate the system architecture of the pipeline and the implementation of each subsystem. The DDPP is automatic, robust, scalable and manageable. The processing performance under multi computers parallel and GPU hybrid system meets the requirements of CSRH data processing. The study presents an valuable reference for other radio telescopes especially aperture synthesis telescopes, and also gives an valuable contribution to the current and/or future data intensive astronomical observations.

astro-ph.IM↗
arXiv2016

A Possible 55-day X-ray Period of the Ultraluminous Accreting Pulsar M82 X-2

We report a possible detection of a 55-day X-ray modulation for the ultraluminous accreting pulsar M82 X-2 from archival Chandra observations. Because M82 X-2 is known to have a 2.5-day orbital period, if the 55-day period is real, it will be the superorbital period of the system. We also investigated variabilities of other three nearby ultraluminous X-ray sources in the central region of M82 with the Chandra data and did not find any evidence of periodicities. Furthermore, we re-examined the previously reported 62-day periodicity near the central region of M82 by performing a systematic timing study with all the archival Rossi X-Ray Timing Explorer and Swift data. Using various dynamic timing analysis methods, we confirmed that the 62-day period is not stable, suggesting that it is not the orbital period of M82 X-1 in agreement with previous work.

astro-ph.HE↗
arXiv2014

New charge radius relations for atomic nuclei

We show that the charge radii of neighboring atomic nuclei, independent of atomic number and charge, follow remarkably very simple relations, despite the fact that atomic nuclei are complex finite many-body systems governed by the laws of quantum mechanics. These relations can be understood within the picture of independent-particle motion and by assuming neighboring nuclei having similar pattern in the charge density distribution. A root-mean-square (rms) deviation of 0.0078 fm is obtained between the predictions in these relations and the experimental values, i.e., a comparable precision as modern experimental techniques. Such high accuracy relations are very useful to check the consistence of nuclear charge radius surface and moreover to predict unknown nuclear charge radii, while large deviations from experimental data is seen to reveal the appearance of nuclear shape transition or coexsitence.

nucl-th↗
arXiv2014

Long-term optical and radio variability of BL Lacertae

Well-sampled optical and radio light curves of BL Lacertae in B, V, R, I bands and 4.8, 8.0, 14.5 GHz from 1968 to 2014 were presented in this paper. A possible $1.26 \pm 0.05$ yr period in optical bands and a $7.50 \pm 0.15$ yr period in radio bands were detected based on discrete correlation function, structure function as well as Jurkevich method. Correlations among different bands were also analyzed and no reliable time delay was found between optical bands. Very weak correlations were detected between V band and radio bands. However, in radio bands the variation at low frequency lagged that at high frequency obviously. The spectrum of BL Lacertae turned mildly bluer when the object turned brighter, and stronger bluer-when-brighter trends were found for short flares. A scenario including a precessing helical jet and periodic shocks was put forward to interpret the variation characteristics of BL Lacertae.

astro-ph.HE↗