Effects of electron heating and surface rippling on Rayleigh–Taylor instability in radiation pressure acceleration

The acceleration of ultrathin targets driven by intense laser pulses induces Rayleigh–Taylor-like instability.Apart from laser and target con-figurations,we find that electron heating and surface rippling,effects inherent to the interaction process,have an important role in instability evolution and growth.By employing a simple analytical model and two-dimensional particle-in-cell simulations,we show that the onset of electron heating in the early stage of the acceleration suppresses the growth of small-scale modes,but it has little influence on the growth of large-scale modes,which thus become dominant.With the growth of surface ripples,a mechanism that can significantly influence the growth of these large-scale modes is found.The laser field modulation caused by surface rippling generates an oscillatory ponderomotive force,directly modulating transverse electron density at a faster growth rate than that of ions and eventually enhancing instability growth.Our results show that when surface deformation becomes obvious,electron surface oscillation at 2ω0(whereω0 is the laser frequency)is excited simultaneously,which can be seen as a signature of this mechanism.

An Intermediate-field Fast Radio Burst Model and the Quasi-periodic Oscillation

Quasi-periodic oscillation(QPO)signals are discovered in some fast radio bursts(FRBs)such as FRB 20191221A,as well as in the X-ray burst associated with the galactic FRB from SGR 1935+2154.We revisit the intermediatefield FRB model where the radio waves are generated as fast-magnetosonic waves through magnetic reconnection near the light cylinder.The current sheet in the magnetar wind is compressed by a low frequency pulse emitted from the inner magnetosphere to trigger magnetic reconnection.By incorporating the wave dynamics of the magnetosphere,we demonstrate how the FRB frequency,the single pulse width,and luminosity are determined by the period,magnetic field,QPO frequency and quake energetics of the magnetar.We find that this model can naturally and self-consistently interpret the X-ray/radio event from SGR 1935+2154 and the QPO in FRB20191221A.It can also explain the observed wide energy range of repeating FRBs in a narrow bandwidth.

Spin-polarized electron beam generation in the colliding-pulse injection scheme

Employing colliding-pulse injection has been shown to enable the generation of high-quality electron beams from laser-plasma accelerators.Here,by using test particle simulations,Hamiltonian analysis,and multidimensional particle-in-cell simulations,we lay the theoretical framework for spin-polarized electron beam generation in the colliding-pulse injection scheme.Furthermore,we show that this scheme enables the production of quasi-monoenergetic electron beams in excess of 80%polarization and tens of pC charge with commercial 10-TW-class laser systems.

Ground-state mass of ^(22)Al and test of state-of-the-art ab initio calculations

The ground-state mass excess of the T_(z)=−2 drip-line nucleus ^(22)Al is measured for the first time as 18103(10)keV using the newly-developed Bρ-defined isochronous mass spectrometry method at the cooler storage ring in Lanzhou.The new mass excess value allowed us to determine the excitation energies of the two low-lying 1+states in ^(22)Al with significantly reduced uncertainties of 51 keV.When compared to the analogue states in its mirror nucleus ^(22)F,the mirror energy differences of the two 1^(+)states in the ^(22)Al-^(22)F mirror pair are determined to be−625(51)keV and−330(51)keV.The excitation energies and mirror energy differences are used to test the state-of-the-art ab initio valence-space in-medium similarity renormalization group calculations with four sets of interactions derived from the chiral effective field theory.The mechanism leading to the large mirror energy differences is investigated and attributed to the occupation of theπs_(1/2) orbital.

Discovery potential of the Glashow resonance in an air shower neutrino telescope

The in-ice or in-water Cherenkov neutrino telescope,such as IceCube,has already proved its power in measuring the Glashow resonance by searching for the bump around E_(ν)=6.3PeV arising from the W-boson production.There are many proposals for the next few decades for observations of cosmic tau neutrinos with extensive air showers,also known as tau neutrino telescopes.The air shower telescope is,in principle,sensitive to the Glashow resonance via the channel W→τν_(τ)followed by the tau decay in the air(e.g.,TAMBO,which has a geometric area of approximately 500km^(2)).Using a thorough numerical analysis,we find that the discovery significance can be up to 90%with a TAMBO-like setup if PeV neutrinos primarily originate from neutron decays,considering the flux parameters measured by IceCube as the input.The presence of new physics affecting the neutrino flavor composition can also increase the significance.However,if ultrahigh-energy neutrinos are dominantly produced from meson decays,it will be statistically difficult for an advanced proposal such as TAMBO to discriminate the Glashow resonance induced byν¯e from the intrinsicντ/ν¯_(τ)background.We have identified several limitations for such advanced telescopes,in comparison with the in-ice or in-water telescope,when measuring resonances:(i)a suppressed branching ratio of 11%for the decay W→τν_(τ);(ii)the smearing effect and reduced acceptance because the daughter neutrino takes away(y)∼75%of the energy from the W decay;and(iii)a large attenuation effect for Earth-skimming neutrinos with the resonance.

Dense matter with eXTP

In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry(eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is expected to be launched in the mid 2020 s.

多击响应的三层阳极丝位置灵敏探测器及其信号重整

最新发展起来的三层延迟线阳极,即Hexanode与标准的螺旋状延迟线(HDL)阳极相比,对多击事件有较好的响应能力．它与一对微通道板组合在一起构成的位置灵敏探测器能够响应同时或短时间间隔内到达探测器的多个粒子,并给出粒子的全部动量信息．针对Hexanode在响应多个同时或短时间间隔内到达的粒子时出现的信号丢失问题,自行编写了一个信号重整程序．经过此程序的处理后,多击响应位置灵敏探测器的死时间只存在于两个粒子同时到达探测器的同一位置时(在一定时间及位置范围内)．在最近完成的使用Hexanode探测器的近阈值e+He→3e+He++中,获得了很好的结果．