A refined Monte Carlo code for low-energy electron emission from gold material irradiated with sub-keV electrons

Considering the significance of low-energy electrons(LEEs;0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles(AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been suggested. In this study, a track-structure Monte Carlo simulation code using the dielectric theory was developed to simulate the transport of electrons below 50 keV in gold. In this code, modifications, particularly for elastic scattering, are implemented for a more precise description of the LEE emission in secondary electron emission. This code was validated using the secondary electron yield and backscattering coefficient. To ensure dosimetry accuracy, we further verified the code for energy deposition calculations using the Monte Carlo toolkit, Geant4. The development of this code provides a basis for future studies regarding the role of AuNPs in targeted radionuclide radiotherapy.

Radiation-hardened property of single-walled carbon nanotube film-based field-effect transistors under low-energy proton irradiation

Strong C-C bonds,nanoscale cross-section and low atomic number make single-walled carbon nanotubes(SWCNTs)a potential candidate material for integrated circuits(ICs)applied in outer space.However,very little work combines the simulation calculations with the electrical measurements of SWCNT field-effect transistors(FETs),which limits further understanding on the mechanisms of radiation effects.Here,SWCNT film-based FETs were fabricated to explore the total ionizing dose(TID)and displacement damage effect on the electrical performance under low-energy proton irradiation with different fluences up to 1×1015 p/cm2.Large negative shift of the threshold voltage and obvious decrease of the on-state current verified the TID effect caused in the oxide layer.The stability of the subthreshold swing and the off-state current reveals that the displacement damage caused in the CNT layer is not serious,which proves that the CNT film is radiation-hardened.Specially,according to the simulation,we found the displacement damage caused by protons is different in the source/drain contact area and channel area,leading to varying degrees of change for the contact resistance and sheet resistance.Having analyzed the simulation results and electrical measurements,we explained the low-energy proton irradiation mechanism of the CNT FETs,which is essential for the construction of radiation-hardened CNT film-based ICs for aircrafts.

Measurement of the Low-Energy Rb+-Rb Total Collision Rate in an Ion-Neutral Hybrid Trap

An ion-neutral hybrid trap is built to study low-energy ion-atom collisions. The ion-neutral hybrid trap is combined with two spatially concentric traps: a linear Paul trap for the ionic species and a magneto-optical trap(MOT) for the neutral species. The total ion atom collision rate coefficient k_(ia)between^(87)Rb atoms and optically dark ^(87)Rb^+ ions is measured by monitoring the reduction of the steady-state MOT atoms by sequentially introducing various mechanisms, namely photoionization and ion-atom collisions. In contrast to other experiments, a concise experimental procedure is devised to obtain the loss rates of the MOT atoms due to photoionization and ion atom collisions in one experimental cycle, and then the collision rate k_(ia) of cold ^(87)Rb atoms with ^(87)Rb^+ ions is deduced to 0.94(±0.24)× 10^(-13) m^3/s with T_i= 3770(±100) K measured by the time of fligt of the ion signal.The measurements show good agreement with the collision rate derived from the Langevin model.

A segmented conical electric lens for optimization of the beam spot of the low-energy muon facility at PSI: a Geant4 simulation analysis

The low-energy muon facility at PSI provides nearly fully polarized positive muons with tunable energies in the ke V range to carry out muon spin rotation(LE-μSR)experiments with nanometer depth resolution on thin films,heterostructures, and near-surface regions. The low-energy muon beam is focused and transported to the sample by electrostatic lenses. In order to achieve a minimum beam spot size at the sample position and to enable the steering of the beam in the horizontal and vertical direction, a special electrostatic device has been implemented close to the sample position. It consists of a cylinder at ground potential followed by four conically shaped electrodes,which can be operated at different electric potential. In LE-μSR experiments, an electric field at the sample along the beam direction can be applied to accelerate/decelerate muons to different energies(0.5–30 keV). Additionally, a horizontal or vertical magnetic field can be superimposed for transverse or longitudinal field μSR experiments. The focusing properties of the conical lens in the presence of these additional electric and magnetic fields have been investigated and optimized by Geant4 simulations. Some experimental tests were also performed and show that the simulation well describes the experimental setup.

Unusual thermodynamics of low-energy phonons in the Dirac semimetal Cd_(3)As_(2)

By studying the thermal conductivity,specific heat,elastic modulus,and thermal expansion as a function of temperature for Cd_(3)As_(2),we have unveiled a couple of important thermodynamic features of the low-energy phonons strongly interacting with Dirac electrons.The existence of soft optical phonons,as inferred from the extremely low thermal conductivity,is unambiguously confirmed by low-temperature specific heat revealing significant deviation from Debye's description.The estimated Debye temperature is small in the range of 100-200 K and varies significantly depending upon the measurement used in its experimental determination.The thermodynamic Gr¨uneisen ratioγreveals a remarkable reduction below about 100 K,an energy scale that is highly relevant to the Dirac states,towards negative values below about 10 K that are indicative of lattice instability.

Low-energy electronic states of carbon nanocones in an electric field

The low-energy electronic states and energy gaps of carbon nanocones in an electric field are studied using a single-?-band tight-binding model. The analysis considers five perfect carbon nanocones with disclination angles of 60°, 120°, 180°, 240° and 300°, respectively. The numerical results reveal that the low-energy electronic states and energy gaps of a carbon nanocones are highly sensitive to its geometric shape(i.e. the disclination angle and height), and to the direction and magnitude of an electric field. The electric field causes a strong modulation of the state energies and energy gaps of the nanocones, changes their Fermi levels, and induces zero-gap transitions. The energy-gap modulation effect becomes particularly pronounced at higher strength of the applied electric field, and is strongly related to the geometric structure of the nanocone.

Analyses of Low-Energy <i>π</i>^--¹²C Elastic Scattering Data

A new updated simple local optical potential is proposed for analyzing low-energy π--12C elastic scattering data at 80 MeV and below. This potential is composed of two real terms and an imaginary term. The nature of the real part of the potential is repulsive at smaller radii and attractive at larger ones. In fact, the height of the repulsive term is found to change linearly with the incident pion kinetic energy. On the other hand, the imaginary part of the potential is attractive, shallow and non-monotonic with a dip at about 1.6 fm. Such a nature of the potential makes it feasible to predict π--12C cross sections at other energies in the energy region considered herein. Coulomb effects are incorporated by following Stricker’s prescription. This study will serve positively in studying both pionic atoms and the role of negative pions in radiotherapy.

1-2 Nuclear Fragmentation in Low-energy Antiproton Induced Reactions

The dynamics of antiproton-nucleus collisions is complicated, which is associated with the mean-field potentials of hadrons in nuclear medium, and also with a number of reaction channels, i.e., the annihilation channels, chargeexchange reaction, elastic and inelastic collisions. Larger yields of strange particles in antiproton induced reactions are favorable to form hypernuclei in comparison to proton-nucleus and heavy-ion collisions.

ACHIEVEMENT OF LOW-ENERGY HEAVY-ION BIOLOGY

Generally,the interaction of low-energy ions with matter used to attract less attention than that of high-energy ions.In the 1980s,when the study of ion beam modification of materials was prosperous both at home and abroad,a new biological effect caused by ion beam implantation was discovered by Prof. Yu Zengliang and his postgraduates at CAS institute of Plasma Physics.In their research into the interaction between low energy ions and organism,they put forward and developed some new concepts,such as the bio damage model of mass-deposition and cell itching processing with ion beam.And they applied those principles in breeding new cultivars and made sig-

Early-life famine exposure,adulthood obesity patterns,and risk of low-energy fracture

Malnutrition in early life increases the risk of osteoporosis,but the association of early-life undernutrition combined with adulthood obesity patterns with low-energy fracture remains unknown.This study included 5323 community-dwelling subjects aged⩾40 years from China.Early-life famine exposure was identified based on the participants’birth dates.General obesity was assessed using the body mass index(BMI),and abdominal obesity was evaluated with the waist-to-hip ratio(WHR).Low-energy fracture was defined as fracture occurring after the age of⩾40 typically caused by falls from standing height or lower.Compared to the nonexposed group,the group with fetal,childhood,and adolescence famine exposure was associated with an increased risk of fracture in women with odds ratios(ORs)and 95%confidence intervals(CIs)of 3.55(1.57–8.05),3.90(1.57–9.71),and 3.53(1.05–11.88),respectively,but not in men.Significant interactions were observed between fetal famine exposure and general obesity with fracture among women(P for interaction=0.0008).Furthermore,compared with the groups with normal BMI and WHR,the group of women who underwent fetal famine exposure and had both general and abdominal obesity had the highest risk of fracture(OR,95%CI:3.32,1.17–9.40).These results indicate that early-life famine exposure interacts with adulthood general obesity and significantly increases the risk of low-energy fracture later in life in women.

Influence of low-energy supersymmetric vector-like quirk particles on W mass increment and muon g–2 anomaly

In the low energy realization of the quirk assisted Standard Model,the couplings between the exotic particles"quirks"and gauge bosons may contribute to the W mass and muon g−2 anomaly reported by FermiLab.We calculate the contributions from supersymmetric quirk particles as an example.By imposing the theoretical constraints,we determined that the CDF II W-boson mass increment strictly constrains the mixing and coupling parameters and the quirk mass mF,while the muon g−2 anomaly cannot be solely attributed to the involvement of exotic particles,considering their significantly large masses.

A low-energy ion spectrometer with half-space entrance for three-axis stabilized spacecraft

A low-energy ion spectrometer(LEIS) for use aboard three-axis stabilized spacecraft has been developed to measure ion energy per charge distribution in three-dimensional space with good energy-, angular-and temporal-resolutions. For the standard top-hat electrostatic analyzer used widely in space plasma detection, three-axis stabilized spacecraft makes it difficult to obtain complete coverage of all possible ion arrival directions. We have designed angular scanning deflectors supplementing to a cylindrically symmetric top-hat electrostatic analyzer to provide a half-space field of view as 360°×90°(–45°–+45°), and fabricated the LEIS flight model for detecting magnetospheric ions in geosynchronous orbit. The performance of this payload has been evaluated in detail by a series of simulation and environmental tests, and the payload has also been calibrated through laboratory experiments using a low-energy ion source. The results show that capabilities of the LEIS payload are in accordance with the requirements of a magnetospheric mission.

Research on Improved Low-Energy Adaptive Clustering Hierarchy Protocol in Wireless Sensor Networks

In wireless sensor networks(WSNs), due to the limited battery power of the sensor nodes, the communication energy consumption is the main factor to affect the lifetime of the networks. A reasonable design of the communication protocol can effectively reduce the energy consumption of the network system. Based on low-energy adaptive clustering hierarchy(LEACH), an improved LEACH protocol in WSNs is proposed. In order to optimize the cluster head(CH) election in the cluster setup phase, the improved LEACH takes into account a number of factors, including energy consumption of communication between nodes, remaining energy of the nodes,and the distance between nodes and base station(BS). In the steady phase, one-hop routing and multiple-hop routing are combined to transmit data between CHs to improve energy efficiency. The forward CH is selected as relay node according to the values of path cost. The simulation results show that the proposed algorithm performs better in balancing network energy consumption, and it can effectively improve the data transmission efficiency and prolong the network lifetime, as compared with LEACH, LEACH-C(LEACH-centralized) and NDAPSO-C(an adaptive clustering protocol based on improved particle swarm optimization) algorithms.

Design of low-energy on-chip electro-optical 1 × M wavelength-selective switches

A theoretical design is presented for a 1 × M wavelength-selective switch(WSS) that routes any one of N incoming wavelength signals to any one of M output ports. This planar on-chip device comprises of a 1 × N demultiplexer, a group of N switching "trees" actuated by electro-optical or thermo-optical means, and an M-fold set of N × 1multiplexers. Trees utilize 1 × 2 switches. The WSS insertion loss is proportional to [log_2(M+N +1)]. Along with cross talk from trees, cross talk is present at each cross-illuminated waveguide intersection within the WSS, and there are at most N-1 such crossings per path. These loss and cross talk properties will likely place a practical limit of N=M=16 upon the WSS size. By constraining the 1 × 2 switching energy to^1 f J∕bit, we find that resonant, narrowband 1 × 2 switches are required. The 1 × 2 devices proposed here are nanobeam Mach–Zehnders and asymmetric contra-directional couplers with grating assistance.

An improved Monte Carlo method of low-energy electron scattering in solids

The studies on the theories and calculation method of low-energy electron scattering(LEES) in solids have provided a basis for the development of electron microscopy andelectron beam lithography. In the energy region where the primary energy of incident elec-

A THEORY ON LOW-ENERGY ELECTRON SCATTERING IN SOLIDS AND MONTE CARLO CALCULATION

The process of low-energy electron scattering (LEES) in solids is described by using astrict theory, and a direct simulation method proposed in this paper. Pendry’s method basedon the partial-wave expansion has been improved, which can be employed to calculate theelastic scattering between an electron and atoms. The contributions of shell electrons, con-ductive electrons and plasma excitations are considered in the calculation of the inelasticscattering; electron scattering and cascade process of secondary electrons are simulated by theMonte Carlo method. The secondary electron yields, the energy spectrum curve and thebackscattering electron coefficients for Cu are evaluated at the various energies, and thetheoretical results are in agreement with Kashikawa’s experiments.

Linking evolutionary mode to palaeoclimate change reveals rapid radiations of staphylinoid beetles in low-energy conditions

Staphylinoidea(Insecta:Coleoptera)is one of the most species-rich groups in animals,but its huge diversity can hardly be explained by the popular hypothesis(co-radiation with angiosperms)that applies to phytophagous beetles.We estimated the evolutionary mode of staphylinoid beetles and investigated the relationship between the evolutionary mode and palaeoclimate change,and thus the factors underlying the current biodiversity pattern of staphylinoid beetles.Our results demonstrate that staphylinoid beetles originated at around the Triassic-Jurassic bound and the current higher level clades underwent rapid evolution(indicated by increased diversification rate and decreased body size disparity)in the Jurassic and in the Cenozoic,both with low-energy climate,and they evolved much slower during the Cretaceous with high-energy climate.Climate factors,especially low 02 and high C02,promoted the diversification rate and among-clade body size disparification in the Jurassic.In the Cenozoic,however,climate factors had negative associations with diversification rate but little with body size disparification.Our present study does not support the explosion of staphylinoid beetles as a direct outcome of the Cretaceous Terrestrial Revolution(KTR).We suppose that occupying and diversifying in refuge niches associated with litter may elucidate rapid radiations of staphylinoid beetles in low-energy conditions.

Effects of the tensor force on low-energy heavy-ion fusion reactions:a mini review

In recent several years,the tensor force,one of the most important components of the nucleon-nucleon force,has been implemented in time-dependent density functional theories and it has been found to influence many aspects of low-energy heavy-ion reactions,such as dissipation dynamics,sub-barrier fusions,and low-lying vibration states of colliding partners.Especially,the effects of tensor force on fusion reactions have been investigated from the internuclear potential to fusion crosssections systematically.In this work,we present a mini review on the recent progress on this topic.Considering the recent progress of low-energy reaction theories,we will also mention more possible effects of the tensor force on reaction dynamics.

A low-power and low-energy flexible GF(p) elliptic-curve cryptography processor

We investigate the use of two integer inversion algorithms,a modified Montgomery modulo inverse and a Fermat's Little Theorem based inversion,in a prime-field affine-coordinate elliptic-curve crypto-processor.To perform this,we present a low-power/energy GF(p) affine-coordinate elliptic-curve cryptography(ECC) processor design with a simplified architecture and complete flexibility in terms of the field and curve parameters.The design can use either of the inversion algorithms.Based on the implementations of this design for 168-,192-,and 224-bit prime fields using a standard 0.13 μm CMOS technology,we compare the efficiency of the algorithms in terms of power/energy consumption,area,and calculation time.The results show that while the Fermat's theorem approach is not appropriate for the affine-coordinate ECC processors due to its long computation time,the Montgomery modulo inverse algorithm is a good candidate for low-energy implementations.The results also show that the 168-bit ECC processor based on the Montgomery modulo inverse completes one scalar multiplication in only 0.4 s at a 1 MHz clock frequency consuming only 12.92 μJ,which is lower than the reported values for similar designs.

Biological effects of low-energy C ion implantation on sesame(Sesamum indicum L.)

Field cultivation experiments on white sesame(Sesamum indicum L.)seeds implanted with low-energy C ion showed that different dosages of C ion implantation pro-duce different biological effects.Sesame plants in 6 different dosage groups with C ion density respectively at 1×10^(11),1×10^(12),1×10^(15),5×10^(15),1×10^(16),5×10^(16)ion/cm2 were superior to the control group in plant height,leaf number,stalk diameter and leaf size.Further,sesame plants in these groups flower and seed earlier than those in the control group,and single plant yield also increased.Of all the groups,the 5×10^(15)ion/cm2 dosage group yielded the best effect,whereas the 1×10^(17)/cm^(2)dosage group showed an evident inhibitory effect of ion implantation on the germination and growth of the sesame seeds.