High-power laser pulses interacting with targets can generate intense electromagnetic pulses(EMPs),which can disrupt physical experimental diagnostics and even damage diagnostic equipment,posing a threat to the reliab...High-power laser pulses interacting with targets can generate intense electromagnetic pulses(EMPs),which can disrupt physical experimental diagnostics and even damage diagnostic equipment,posing a threat to the reliable operation of experiments.In this study,EMPs resulting from multi-petawatt laser irradiating nitrogen gas jets were systematically analyzed and investigated.The experimental results revealed that the EMP amplitude is positively correlated with the quantity and energy of the electrons captured and accelerated by the plasma channel.These factors are reflected by parameters such as laser energy and nitrogen gas jet pressure.Additionally,we propose several potential sources of EMPs produced by laser-irradiated gas jets and separately analyzed their spatiotemporal distributions.The findings provide insight into the mechanisms of EMP generation and introduce a new approach to achieve controllable EMPs by regulating the laser energy and gas jet pressure.展开更多
Experimental validation of laser intensity is particularly important for the study of fundamental physics at extremely high intensities.However,reliable diagnosis of the focal spot and peak intensity faces huge challe...Experimental validation of laser intensity is particularly important for the study of fundamental physics at extremely high intensities.However,reliable diagnosis of the focal spot and peak intensity faces huge challenges.In this work,we demonstrate for the firs time that the coherent radiation farfiel patterns from laser–foil interactions can serve as an in situ,real-time,and easy-to-implement diagnostic for an ultraintense laser focus.The laser-driven electron sheets,curved by the spatially varying laser fiel and leaving the targets at nearly the speed of light,produce doughnut-shaped patterns depending on the shapes of the focal spot and the absolute laser intensities.Assisted by particle-in-cell simulations,we can achieve measurements of the intensity and the focal spot,and provide immediate feedback to optimize the focal spots for extremely high intensity.展开更多
Ultra-intense electromagnetic fields exceeding 10^(23)W∕cm^(2)are enabling breakthroughs in compact laser-driven particle accelerators and revealing new quantum electrodynamics(QED)phenomena.However,conventional lase...Ultra-intense electromagnetic fields exceeding 10^(23)W∕cm^(2)are enabling breakthroughs in compact laser-driven particle accelerators and revealing new quantum electrodynamics(QED)phenomena.However,conventional laser-focusing methods face considerable engineering challenges and require substantial costs.Focusing schemes utilizing plasma optics can produce sub-micrometer focus spots beyond the diffraction limit and substantially enhance the peak intensity;however,owing to significant energy dissipation,they may fail to simultaneously increase the laser fluence.To address these challenges,we propose a focusing scheme employing a near-critical-density hollow plasma fiber(HPF)that utilizes graded refractive index dynamics to boost both laser peak intensity and fluence at the same time.Three-dimensional particle-in-cell simulations demonstrate the HPF’s capability to focus a 4.5-μm-diameter Gaussian beam to a sub-diffraction-limited 0.6-μm-diameter spot.The peak intensity and laser fluence can be enhanced by factors of 22 and 10,respectively,marking a substantial improvement over existing plasma-based focusing schemes.Furthermore,the proposed scheme exhibits wide-range parameter adaptation and high robustness,making it suitable for direct implementation in PW-class ultra-intense laser experiments.展开更多
Correction to:Nuclear Science and Techniques(2025)36:100 https://doi.org/10.1007/s41365-025-01692-6 In this article,Fig.9 appeared incorrectly and have now been corrected in the original publication.For completeness a...Correction to:Nuclear Science and Techniques(2025)36:100 https://doi.org/10.1007/s41365-025-01692-6 In this article,Fig.9 appeared incorrectly and have now been corrected in the original publication.For completeness and transparency,both correct and incorrect versions are displayed below.展开更多
Short-lived medical isotopes and their generators are typically produced in nuclear reactors and cyclotrons that require extensive facilities.However,considering the environmental concerns and economic costs of these ...Short-lived medical isotopes and their generators are typically produced in nuclear reactors and cyclotrons that require extensive facilities.However,considering the environmental concerns and economic costs of these traditional approaches,modern laser technology,which provides extremely strong electric fields within tabletop-sized areas,can serve as a potential supplementary method.Focusing specifically on the(γ,p)generation of the vital medical isotopes^(47)Sc and^(67)Cu,we used both experimental results and PIC-GEANT4 simulations to demonstrate that laser-induced photonuclear reaction is a promising method for isotope production.We developed a model capable of calculating isotope yields under various laser conditions and acceleration mechanisms.The findings revealed that a 200 TW laser can sufficiently produce diagnostic amounts of^(47)Sc and^(67)Cu,while simultaneously providing high specific activity,which is significant in medical applications for improving treatment efficacy,enhancing image resolution,and reducing side effects.展开更多
Background: Brain disorders have become more and more common today, due to both the aging population and the ever-expanding sports community. However, a new therapeutic technology called photobiomodulation (PBM) is gi...Background: Brain disorders have become more and more common today, due to both the aging population and the ever-expanding sports community. However, a new therapeutic technology called photobiomodulation (PBM) is giving hope to thousands of individuals in need. Traumatic brain injury (TBI), dementia, post traumatic stress (PTSD) and attention deficit (ADD) disorders are in many cases quickly and safely improved by PBM. PBM employs red or near-infrared (NIR) light (600 - 1100 nm) to stimulate healing, protect tissue from dying, increase mitochondrial function, improve blood flow, and tissue oxygenation. PBM can also act to reduce edema, increase antioxidants, decrease inflammation, protect against apoptosis, and modulate the microglial activation state. All these effects can occur when light is delivered to the head, and can be beneficial in both acute and chronic brain conditions. Methods: In this case series, we used a high power, FDA-approved superpulsed laser system applied to the head to treat four chronic stroke patients. Patients received as few as three 6 - 9 minute treatments over a one-week period. The follow up time varied, but in one case was two years. Results: Patients showed significant improvement in their speech and verbal skills. Improvements were also noticed in walking ability, limb movement, less numbness, and better vision. Conclusion: The use of PBM in stroke rehabilitation deserves to be tested in controlled clinical trials, because this common condition has no approved pharmaceutical treatment at present.展开更多
Laser-accelerated ion beams(LIBs) have been increasingly applied in the field of material irradiation in recent years due to the unique properties of ultra-short beam duration, extremely high beam current, etc. Here w...Laser-accelerated ion beams(LIBs) have been increasingly applied in the field of material irradiation in recent years due to the unique properties of ultra-short beam duration, extremely high beam current, etc. Here we explore an application of using laser-accelerated ion beams to prepare graphene. The pulsed LIBs produced a great instantaneous beam current and thermal effect on the SiC samples with a shooting frequency of 1 Hz. In the experiment, we controlled the deposition dose by adjusting the number of shootings and the irradiating current by adjusting the distance between the sample and the ion source. During annealing at 1100℃, we found that the 190 shots ion beams allowed more carbon atoms to self-assemble into graphene than the 10 shots case. By comparing with the controlled experiment based on ion beams from a traditional ion accelerator, we found that the laser-accelerated ion beams could cause greater damage in a very short time. Significant thermal effect was induced when the irradiation distance was reduced to less than 1 cm, which could make partial SiC self-annealing to prepare graphene dots directly. The special effects of LIBs indicate their vital role to change the structure of the irradiation sample.展开更多
In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally studied.The results of particle-in-cell simulation...In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally studied.The results of particle-in-cell simulations indicate that ions accelerated in the sheath field around the surfaces of the nanowires are eventually confined in a plasma,contributing most to the high energy densities.The protons emitted from the front surfaces of the NWA targets provide rich information about the interactions that occur.We give the electron and ion energy densities for broad target parameter ranges.The ion energy densities from NWA targets were found to be an order of magnitude higher than those from planar targets,and the volume of the HEDP was several-fold greater.At optimal target parameters,8%of the laser energy can be converted to confined protons,and this results in ion energy densities at the GJ/cm^(3) level.In the experiments,the measured energy of the emitted protons reached 4 MeV,and the changes in energy with the NWA’s parameters were found to fit the simulation results well.Experimental measurements of neutrons from 2H(d,n)3He fusion with a yield of(24±18)×10^(6)/J from deuterated polyethylene NWA targets also confirmed these results.展开更多
The newly built Compact Laser Plasma Accelerator-Therapy facility at Peking University will deliver 60 J/1 Hz laser pulses with 30 fs duration.Driven by this petawatt laser facility,proton beams with energy up to 200 ...The newly built Compact Laser Plasma Accelerator-Therapy facility at Peking University will deliver 60 J/1 Hz laser pulses with 30 fs duration.Driven by this petawatt laser facility,proton beams with energy up to 200 MeV are expected to be generated for tumor therapy.During high-repetition operation,both prompt radiation and residual radiation may cause safety problems.Therefore,human radiological safety assessment before commissioning is essential.In this paper,we simulate both prompt and residual radiation using the Geant4 and FLUKA Monte Carlo codes with reasonable proton and as-produced electron beam parameters.We find that the prompt radiation can be shielded well by the concrete wall of the experimental hall,but the risk from residual radiation is nonnegligible and necessitates adequate radiation cooling.On the basis of the simulation results,we discuss the constraints imposed by radiation safety considerations on the annual working time,and we propose radiation cooling strategies for different shooting modes.展开更多
Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(...Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(2))femtosecond(fs)lasers with metal flat,plastic flat,and plastic nanowire-array(NWA)targets.Detailed analyses are conducted on the EMPs in terms of their spatial distribution,time and frequency domains,radiation energy,and protection.The results indicate that EMPs from metal targets exhibit larger amplitudes at varying angles than those generated by other types of targets and are enhanced significantly for NWA targets.Using a plastic target holder and increasing the laser focal spot can significantly decrease the radiation energy of the EMPs.Moreover,the composite shielding materials indicate an effective shielding effect against EMPs.The simulation results show that the NWA targets exert a collimating effect on thermal electrons,which directly affects the distribution of EMPs.This study provides guidance for regulating EMPs by controlling the laser focal spot,target parameters,and target rod material and is beneficial for electromagnetic-shielding design.展开更多
The illicit trafficking of special nuclear materials(SNMs)poses a grave threat to global security and necessitates the development of effective nuclear material identification methods.This study investigated a method ...The illicit trafficking of special nuclear materials(SNMs)poses a grave threat to global security and necessitates the development of effective nuclear material identification methods.This study investigated a method to isotopically identify the SNMs,including^(233,235,238)U,^(239-242)Pu,and^(232)Th,based on the detection of delayedγ-rays from photofission fragments.The delayedγ-ray spectra resulting from the photofission of SNMs irradiated by a 14 MeVγbeam with a total of 10~9 were simulated using Geant4.Three high-yield fission fragments,namely^(138)Cs,^(89)Rb,and^(94)Y,were selected as candidate fragments for SNM identification.The yield ratios of these three fragments were calculated,and the results from the different SNMs were compared.The yield ratio of^(138)Cs/^(89)Rb was used to identify most SNMs,including^(233,235,238)U,^(242)Pu,and^(232)Th,with a confidence level above 95%.To identify^(239-241)Pu with the same confidence,a higher total number of 10^(11)γbeams is required.However,although the^(94)Y/^(89)Rb ratio is suitable for elementally identifying SNMs,isotopic identification is difficult.In addition,the count rate of the delayedγabove 3 MeV can be used to rapidly detect the presence of nuclear materials.展开更多
We derive the gravitational-wave(GW)strain upper limits from resolvable supermassive black-hole binaries using the data from the Five-hundred-meter Aperture Spherical radio Telescope,in the context of the Chinese Puls...We derive the gravitational-wave(GW)strain upper limits from resolvable supermassive black-hole binaries using the data from the Five-hundred-meter Aperture Spherical radio Telescope,in the context of the Chinese Pulsar Timing Array project.We focus on circular orbits in theμHz GW frequency band between 10^(−7)and 3×10^(−6)Hz.This frequency band is higher than the traditional pulsar timing array band and is less explored.We used the data of the millisecond pulsar PSR J1713+5307 observed between 2019 August and 2021 April.A dense observation campaign was carried out in 2020 September to allow for theμHz band coverage.Our sky-averaged continuous source upper limit at the 95%confidence level at 1μHz is 1.26×10^(−12),while the same limit in the direction of the pulsar is 4.77×10^(−13).展开更多
Fast Radio Bursts(FRBs) are enigmatic millisecond-duration radio transients of extra-galactic origin, whose underlying mechanisms and progenitors remain poorly understood. FRBs are broadly classified into two categori...Fast Radio Bursts(FRBs) are enigmatic millisecond-duration radio transients of extra-galactic origin, whose underlying mechanisms and progenitors remain poorly understood. FRBs are broadly classified into two categories: repeating FRBs, which emit multiple bursts over time, and one-off FRBs, which are detected as single events. A central question in FRB research is whether these two classes share a common origin. In this study, we present observations of FRB 20240114A, a repeating FRB that entered a hyperactive phase in 2024 January. We conducted a 318 hr monitoring campaign using the Kunming 40-Meter Radio Telescope(KM40M) in the S-band(2.187–2.311 GHz), during which we detected eight radio bursts. We analyzed their properties, including dispersion measure, bandwidth, pulse width, flux, fluence, and energy. Additionally, we searched for counterparts in overlapping data from the Five-hundred-meter Aperture Spherical Telescope(FAST) in the L-band(1.0–1.5 GHz). While no bursts were temporally aligned between the two telescopes, we identified one FAST burst that arrived approximately 6 ms after one of the KM40M bursts. The absence of FAST counterparts for the KM40M bursts suggests that individual bursts from FRB 20240114A are likely narrow-band, with fractional bandwidths less than 10%. By comparing the cumulative event rates from KM40M and FAST observations, we found that the two measurements are compatible, indicating a possible flattening of the event rate at higher energies. This feature aligns with observations of one-off FRBs, supporting the hypothesis that repeating and oneoff FRBs may share a common origin.展开更多
Objective: Photobiomodulation (also known as Low Level Laser. LLLT or Cold Laser;Photo Medicine (PM)) has been a vital adjunct therapy in our clinical practice over 5 years, observations of improvement in cognition an...Objective: Photobiomodulation (also known as Low Level Laser. LLLT or Cold Laser;Photo Medicine (PM)) has been a vital adjunct therapy in our clinical practice over 5 years, observations of improvement in cognition and personality were noted in several patients. As a result, selected patients with Alzheimer’s Disease, vascular dementia, post-traumatic brain injury and other neuro-degenerative diseases were treated at clinical practices in Buffalo, New York;Sarasota, Florida;Lafayette, Indiana;Phoenix, Az., and Baton Rouge, La. Over 60 patients were treated with an average of 4 times over an 8-day period all reported/exhibited improvement in their condition, except that two men who were in their seventies were in robust health but had no short-term memory and no improvement was observed. However, Theralase has developed a more efficacious system which will be more efficacious, due to increased power for ATP activation. Method: Over 150 patients with the above conditions were treated in various areas (depending on diagnosis) including the prefrontal cortex, temporal lobe, Hippocampus, and Circle of Willis for duration of two and one-half minutes every 48 hours for 5 - 6 treatments. We utilized the Theralase multi-probe (905 nm/660 nm) at 60 miliwatts. It utilizes 5 - 905 nm near infra-red diodes and 4 infra-red 660 laser diodes with a peak power of 50,000 milliwatts at peak and pulse duration of 200 nanoseconds [1]. The PTSD patients were evaluated utilizing the co-occurring disorders program screening and assessment form. Conclusion: Dementia patients exhibited varying degrees of improvement in cognitive function and personality, leading to improved quality of life and decreased caregiver burden. PTSD patients’ improvement was objectively measured by formal neuropsychological testing utilizing the form. All PTSD patients scored no emotional problems after 3 - 5 treatments and all experienced overall sense of well-being. One experienced return of ability to smell he had not had for 5 years. Similar results were reported in a Japanese study where 15 patients were followed for a year. This non-invasive and non-systemic modality of therapy could play a key role in treating progressive neurodegenerative conditions, improving quality of life, and reducing health care costs.展开更多
Extensive research has now been conducted and published for the treatment of dementia or Alzheimer’s disease, traumatic brain injury (TBI) and other brain disorders using photobiomodulation (PBM), also known as low-l...Extensive research has now been conducted and published for the treatment of dementia or Alzheimer’s disease, traumatic brain injury (TBI) and other brain disorders using photobiomodulation (PBM), also known as low-level laser therapy (LLLT). However, minimal information is available regarding the use of LLLT for the treatment of Attention Deficit Hyperactivity Disorder (ADHD). We have been using LLLT in our practice for over 15 years addressing chronic pain and injury issues. However, our work with brain injuries is more recent, and we have published three case studies, one describing a serious traumatic brain injury and two describing our success with dementia/Alzheimer’s disease and PTSD. Currently, there is very little published evidence regarding efficacious therapy for ADHD. The case studies presented here, suggest that LLLT can provide alleviation of these symptoms, with some improvement reported after just a single treatment, without any need for pharmaceutical intervention.展开更多
Observing and timing a group of millisecond pulsars with high rotational stability enables the direct detection of gravitational waves(GWs).The GW signals can be identified from the spatial correlations encoded in the...Observing and timing a group of millisecond pulsars with high rotational stability enables the direct detection of gravitational waves(GWs).The GW signals can be identified from the spatial correlations encoded in the times-of-arrival of widely spaced pulsar-pairs.The Chinese Pulsar Timing Array(CPTA)is a collaboration aiming at the direct GW detection with observations carried out using Chinese radio telescopes.This short article serves as a“table of contents”for a forthcoming series of papers related to the CPTA Data Release 1(CPTA DR1)which uses observations from the Five-hundred-meter Aperture Spherical radio Telescope.Here,after summarizing the time span and accuracy of CPTA DR1,we report the key results of our statistical inference finding a correlated signal with amplitude logA_(c)=-14.4_(-2.8)^(+1.0)for spectral index in the range ofα∈[-1.8,1.5]assuming a GW background(GWB)induced quadrupolar correlation.The search for the Hellings–Downs(HD)correlation curve is also presented,where some evidence for the HD correlation has been found that a 4.6σstatistical significance is achieved using the discrete frequency method around the frequency of 14 n Hz.We expect that the future International Pulsar Timing Array data analysis and the next CPTA data release will be more sensitive to the n Hz GWB,which could verify the current results.展开更多
Extensive research is ongoing in the use of Photobiomodulation (PBM, often referred to as low-level or cold laser therapy) to treat Alzheimer’s disease as well as other debilitating diseases. The following case studi...Extensive research is ongoing in the use of Photobiomodulation (PBM, often referred to as low-level or cold laser therapy) to treat Alzheimer’s disease as well as other debilitating diseases. The following case studies further confirm that PBM could be a breakthrough approach to limit the progression of insidious diseases. We present four cases, two with mild to moderate dementia and two with more advanced symptoms. Several publications have shown beneficial results, however, several weeks of daily treatments were necessary. The cases described here suggest that moderate and advanced dementia cases can be significantly improved with three or four eight-minute treatments over a 5 - 7-day period when using super-pulsing technology on Monday-Wednesday-Friday schedule (Figure 1). Gives a brief visual explanation of super-pulsing versus continuous wave technology.展开更多
Laser-driven proton-induced x-ray emission(laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spur...Laser-driven proton-induced x-ray emission(laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spurted within nanoseconds and accompanied by strong electromagnetic pulses(EMP), so traditional multi-channel detectors are no longer applicable.In this work, we designed a reflective elliptical crystal spectrometer for the diagnosis of laser-PIXE. The device can detect the energy range of 1 keV–11 ke V with a high resolution. A calibration experiment was completed on the electrostatic accelerator of Peking University using samples of Al, Ti, Cu, and ceramic artifacts. The detection efficiency of the elliptical crystal spectrometer was obtained in the order of 10-9.展开更多
This paper provides an overview of the current status of ultrafast and ultra-intense lasers with peak powers exceeding100 TW and examines the research activities in high-energy-density physics within China.Currently,1...This paper provides an overview of the current status of ultrafast and ultra-intense lasers with peak powers exceeding100 TW and examines the research activities in high-energy-density physics within China.Currently,10 high-intensity lasers with powers over 100 TW are operational,and about 10 additional lasers are being constructed at various institutes and universities.These facilities operate either independently or are combined with one another,thereby offering substantial support for both Chinese and international research and development efforts in high-energy-density physics.展开更多
Carbon nanotube foams(CNFs)have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons.Here we report the recent advances in the fabrication techniqu...Carbon nanotube foams(CNFs)have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons.Here we report the recent advances in the fabrication technique of such targets.With the further developed floating catalyst chemical vapor deposition(FCCVD)method,large-area(>25 cm^(2))and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets.The density and thickness of the CNF can be controlled in the range of 1−13 mg/cm^(3)and 10−200µm,respectively,by varying the synthesis parameters.The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.展开更多
基金supported by the National Grand Instrument Project(No.2019YFF01014404)the Natural Science Foundation of China(Nos.12122501,61631001,11921006,U2241281,and 11975037)the Foundation of Science and Technology on Plasma Physics Laboratory(No.6142A04220108)。
文摘High-power laser pulses interacting with targets can generate intense electromagnetic pulses(EMPs),which can disrupt physical experimental diagnostics and even damage diagnostic equipment,posing a threat to the reliable operation of experiments.In this study,EMPs resulting from multi-petawatt laser irradiating nitrogen gas jets were systematically analyzed and investigated.The experimental results revealed that the EMP amplitude is positively correlated with the quantity and energy of the electrons captured and accelerated by the plasma channel.These factors are reflected by parameters such as laser energy and nitrogen gas jet pressure.Additionally,we propose several potential sources of EMPs produced by laser-irradiated gas jets and separately analyzed their spatiotemporal distributions.The findings provide insight into the mechanisms of EMP generation and introduce a new approach to achieve controllable EMPs by regulating the laser energy and gas jet pressure.
基金supported by the Guangdong High Level Innovation Research Institute(Grant No.2021B0909050006)the National Grand Instrument Project(Grant No.2019YFF01014402)+1 种基金the National Natural Science Foundation of China(Grant No.12205008)support from the National Science Fund for Distinguished Young Scholars(Grant No.12225501)。
文摘Experimental validation of laser intensity is particularly important for the study of fundamental physics at extremely high intensities.However,reliable diagnosis of the focal spot and peak intensity faces huge challenges.In this work,we demonstrate for the firs time that the coherent radiation farfiel patterns from laser–foil interactions can serve as an in situ,real-time,and easy-to-implement diagnostic for an ultraintense laser focus.The laser-driven electron sheets,curved by the spatially varying laser fiel and leaving the targets at nearly the speed of light,produce doughnut-shaped patterns depending on the shapes of the focal spot and the absolute laser intensities.Assisted by particle-in-cell simulations,we can achieve measurements of the intensity and the focal spot,and provide immediate feedback to optimize the focal spots for extremely high intensity.
基金supported by the National Grand Instrument Project(Grant No.2019YFF01014402)the National Key Research and Development Program of China(Grant No.2024YFF0726304)+2 种基金the Guangdong High Level Innovation Research Institute(Grant No.2021B0909050006)the National Natural Science Foundation of China(Grant No.12205008)W.Ma acknowledges support from the National Science Fund for Distinguished Young Scholars(Grant No.12225501)。
文摘Ultra-intense electromagnetic fields exceeding 10^(23)W∕cm^(2)are enabling breakthroughs in compact laser-driven particle accelerators and revealing new quantum electrodynamics(QED)phenomena.However,conventional laser-focusing methods face considerable engineering challenges and require substantial costs.Focusing schemes utilizing plasma optics can produce sub-micrometer focus spots beyond the diffraction limit and substantially enhance the peak intensity;however,owing to significant energy dissipation,they may fail to simultaneously increase the laser fluence.To address these challenges,we propose a focusing scheme employing a near-critical-density hollow plasma fiber(HPF)that utilizes graded refractive index dynamics to boost both laser peak intensity and fluence at the same time.Three-dimensional particle-in-cell simulations demonstrate the HPF’s capability to focus a 4.5-μm-diameter Gaussian beam to a sub-diffraction-limited 0.6-μm-diameter spot.The peak intensity and laser fluence can be enhanced by factors of 22 and 10,respectively,marking a substantial improvement over existing plasma-based focusing schemes.Furthermore,the proposed scheme exhibits wide-range parameter adaptation and high robustness,making it suitable for direct implementation in PW-class ultra-intense laser experiments.
文摘Correction to:Nuclear Science and Techniques(2025)36:100 https://doi.org/10.1007/s41365-025-01692-6 In this article,Fig.9 appeared incorrectly and have now been corrected in the original publication.For completeness and transparency,both correct and incorrect versions are displayed below.
文摘Short-lived medical isotopes and their generators are typically produced in nuclear reactors and cyclotrons that require extensive facilities.However,considering the environmental concerns and economic costs of these traditional approaches,modern laser technology,which provides extremely strong electric fields within tabletop-sized areas,can serve as a potential supplementary method.Focusing specifically on the(γ,p)generation of the vital medical isotopes^(47)Sc and^(67)Cu,we used both experimental results and PIC-GEANT4 simulations to demonstrate that laser-induced photonuclear reaction is a promising method for isotope production.We developed a model capable of calculating isotope yields under various laser conditions and acceleration mechanisms.The findings revealed that a 200 TW laser can sufficiently produce diagnostic amounts of^(47)Sc and^(67)Cu,while simultaneously providing high specific activity,which is significant in medical applications for improving treatment efficacy,enhancing image resolution,and reducing side effects.
文摘Background: Brain disorders have become more and more common today, due to both the aging population and the ever-expanding sports community. However, a new therapeutic technology called photobiomodulation (PBM) is giving hope to thousands of individuals in need. Traumatic brain injury (TBI), dementia, post traumatic stress (PTSD) and attention deficit (ADD) disorders are in many cases quickly and safely improved by PBM. PBM employs red or near-infrared (NIR) light (600 - 1100 nm) to stimulate healing, protect tissue from dying, increase mitochondrial function, improve blood flow, and tissue oxygenation. PBM can also act to reduce edema, increase antioxidants, decrease inflammation, protect against apoptosis, and modulate the microglial activation state. All these effects can occur when light is delivered to the head, and can be beneficial in both acute and chronic brain conditions. Methods: In this case series, we used a high power, FDA-approved superpulsed laser system applied to the head to treat four chronic stroke patients. Patients received as few as three 6 - 9 minute treatments over a one-week period. The follow up time varied, but in one case was two years. Results: Patients showed significant improvement in their speech and verbal skills. Improvements were also noticed in walking ability, limb movement, less numbness, and better vision. Conclusion: The use of PBM in stroke rehabilitation deserves to be tested in controlled clinical trials, because this common condition has no approved pharmaceutical treatment at present.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11875077,11975037,and 11921006)the National Grand Instrument Project of China(Grant Nos.2019YFF01014400 and 2019YFF01014404).
文摘Laser-accelerated ion beams(LIBs) have been increasingly applied in the field of material irradiation in recent years due to the unique properties of ultra-short beam duration, extremely high beam current, etc. Here we explore an application of using laser-accelerated ion beams to prepare graphene. The pulsed LIBs produced a great instantaneous beam current and thermal effect on the SiC samples with a shooting frequency of 1 Hz. In the experiment, we controlled the deposition dose by adjusting the number of shootings and the irradiating current by adjusting the distance between the sample and the ion source. During annealing at 1100℃, we found that the 190 shots ion beams allowed more carbon atoms to self-assemble into graphene than the 10 shots case. By comparing with the controlled experiment based on ion beams from a traditional ion accelerator, we found that the laser-accelerated ion beams could cause greater damage in a very short time. Significant thermal effect was induced when the irradiation distance was reduced to less than 1 cm, which could make partial SiC self-annealing to prepare graphene dots directly. The special effects of LIBs indicate their vital role to change the structure of the irradiation sample.
基金This work was supported by the NSFC innovation group project(Grant No.11921006)the National Grand Instrument Project(Grant No.2019YFF01014402)+1 种基金the United States Department of Energy(Grant No.DE-FG03-93ER40773)the NNSA(Grant No.DENA0003841)(CENTAUR).The PIC simulations were carried out using the High-Performance Computing Platform of Peking University。
文摘In this work,the high-energy-density plasmas(HEDP)evolved from joule-class-femtosecond-laser-irradiated nanowire-array(NWA)targets were numerically and experimentally studied.The results of particle-in-cell simulations indicate that ions accelerated in the sheath field around the surfaces of the nanowires are eventually confined in a plasma,contributing most to the high energy densities.The protons emitted from the front surfaces of the NWA targets provide rich information about the interactions that occur.We give the electron and ion energy densities for broad target parameter ranges.The ion energy densities from NWA targets were found to be an order of magnitude higher than those from planar targets,and the volume of the HEDP was several-fold greater.At optimal target parameters,8%of the laser energy can be converted to confined protons,and this results in ion energy densities at the GJ/cm^(3) level.In the experiments,the measured energy of the emitted protons reached 4 MeV,and the changes in energy with the NWA’s parameters were found to fit the simulation results well.Experimental measurements of neutrons from 2H(d,n)3He fusion with a yield of(24±18)×10^(6)/J from deuterated polyethylene NWA targets also confirmed these results.
基金supported by the National Natural Science Foundation of China(Grant No.12205008)the NSFC Innovation Group Project(Grant No.11921006)+1 种基金the National Grand Instrument Project(Grant Nos.2019YFF01014402 and 2019YFF01014403)the National Science Fund for Distinguished Young Scholars(Grant No.12225501).
文摘The newly built Compact Laser Plasma Accelerator-Therapy facility at Peking University will deliver 60 J/1 Hz laser pulses with 30 fs duration.Driven by this petawatt laser facility,proton beams with energy up to 200 MeV are expected to be generated for tumor therapy.During high-repetition operation,both prompt radiation and residual radiation may cause safety problems.Therefore,human radiological safety assessment before commissioning is essential.In this paper,we simulate both prompt and residual radiation using the Geant4 and FLUKA Monte Carlo codes with reasonable proton and as-produced electron beam parameters.We find that the prompt radiation can be shielded well by the concrete wall of the experimental hall,but the risk from residual radiation is nonnegligible and necessitates adequate radiation cooling.On the basis of the simulation results,we discuss the constraints imposed by radiation safety considerations on the annual working time,and we propose radiation cooling strategies for different shooting modes.
基金This work was supported by the National Natural Science Foundation of China(Nos.12122501,11975037,61631001,and 11921006)the National Grand Instrument Project(Nos.2019YFF01014400,2019YFF01014404)the Foundation of Science and Technology on Plasma Physics Laboratory(No.6142A04220108).
文摘Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(2))femtosecond(fs)lasers with metal flat,plastic flat,and plastic nanowire-array(NWA)targets.Detailed analyses are conducted on the EMPs in terms of their spatial distribution,time and frequency domains,radiation energy,and protection.The results indicate that EMPs from metal targets exhibit larger amplitudes at varying angles than those generated by other types of targets and are enhanced significantly for NWA targets.Using a plastic target holder and increasing the laser focal spot can significantly decrease the radiation energy of the EMPs.Moreover,the composite shielding materials indicate an effective shielding effect against EMPs.The simulation results show that the NWA targets exert a collimating effect on thermal electrons,which directly affects the distribution of EMPs.This study provides guidance for regulating EMPs by controlling the laser focal spot,target parameters,and target rod material and is beneficial for electromagnetic-shielding design.
基金supported by the National Key Research and Development Program(No.2022YFA1603300)the National Natural Science Foundation of China(Nos.U2230133,12305266,11921006,12405282)National Grand Instrument Project(No.2019YFF01014400)。
文摘The illicit trafficking of special nuclear materials(SNMs)poses a grave threat to global security and necessitates the development of effective nuclear material identification methods.This study investigated a method to isotopically identify the SNMs,including^(233,235,238)U,^(239-242)Pu,and^(232)Th,based on the detection of delayedγ-rays from photofission fragments.The delayedγ-ray spectra resulting from the photofission of SNMs irradiated by a 14 MeVγbeam with a total of 10~9 were simulated using Geant4.Three high-yield fission fragments,namely^(138)Cs,^(89)Rb,and^(94)Y,were selected as candidate fragments for SNM identification.The yield ratios of these three fragments were calculated,and the results from the different SNMs were compared.The yield ratio of^(138)Cs/^(89)Rb was used to identify most SNMs,including^(233,235,238)U,^(242)Pu,and^(232)Th,with a confidence level above 95%.To identify^(239-241)Pu with the same confidence,a higher total number of 10^(11)γbeams is required.However,although the^(94)Y/^(89)Rb ratio is suitable for elementally identifying SNMs,isotopic identification is difficult.In addition,the count rate of the delayedγabove 3 MeV can be used to rapidly detect the presence of nuclear materials.
基金supported by the FAST Key projectsupported by the National SKA Program of China (2020SKA0120100)+4 种基金the National Natural Science Foundation of China (NSFC, Grant Nos. 12041303 and 12250410246)the CAS-MPG LEGACY projectfunding from the Max-Planck Partner Groupsupport from the XPLORER PRIZE and 20 yr long-term support from Dr. Guojun Qiaosupported by Major Science and Technology Program of Xinjiang Uygur Autonomous Region No. 2022A03013-4
文摘We derive the gravitational-wave(GW)strain upper limits from resolvable supermassive black-hole binaries using the data from the Five-hundred-meter Aperture Spherical radio Telescope,in the context of the Chinese Pulsar Timing Array project.We focus on circular orbits in theμHz GW frequency band between 10^(−7)and 3×10^(−6)Hz.This frequency band is higher than the traditional pulsar timing array band and is less explored.We used the data of the millisecond pulsar PSR J1713+5307 observed between 2019 August and 2021 April.A dense observation campaign was carried out in 2020 September to allow for theμHz band coverage.Our sky-averaged continuous source upper limit at the 95%confidence level at 1μHz is 1.26×10^(−12),while the same limit in the direction of the pulsar is 4.77×10^(−13).
基金supported by the National SKA Program of China (grant No. 2020SKA0120100)the Special Project of Foreign Science and Technology Cooperation, Yunnan Provincial Science and Technology Department (grant No. 202003AD150010)+4 种基金the National Key R&D Program of China (grant No. 2022YFC2205203)the National Natural Science Foundation of China (NSFC, grant Nos. 12073076, 12173087, 12041303, and 12063003)the CAS “Western Light Youth Project,” Yunnan Fundamental Research Projects (grant Nos. 202401AT070144 and 202505AO120021)funding from the Max-Planck Partner Groupsupport from the XPLORER PRIZE
文摘Fast Radio Bursts(FRBs) are enigmatic millisecond-duration radio transients of extra-galactic origin, whose underlying mechanisms and progenitors remain poorly understood. FRBs are broadly classified into two categories: repeating FRBs, which emit multiple bursts over time, and one-off FRBs, which are detected as single events. A central question in FRB research is whether these two classes share a common origin. In this study, we present observations of FRB 20240114A, a repeating FRB that entered a hyperactive phase in 2024 January. We conducted a 318 hr monitoring campaign using the Kunming 40-Meter Radio Telescope(KM40M) in the S-band(2.187–2.311 GHz), during which we detected eight radio bursts. We analyzed their properties, including dispersion measure, bandwidth, pulse width, flux, fluence, and energy. Additionally, we searched for counterparts in overlapping data from the Five-hundred-meter Aperture Spherical Telescope(FAST) in the L-band(1.0–1.5 GHz). While no bursts were temporally aligned between the two telescopes, we identified one FAST burst that arrived approximately 6 ms after one of the KM40M bursts. The absence of FAST counterparts for the KM40M bursts suggests that individual bursts from FRB 20240114A are likely narrow-band, with fractional bandwidths less than 10%. By comparing the cumulative event rates from KM40M and FAST observations, we found that the two measurements are compatible, indicating a possible flattening of the event rate at higher energies. This feature aligns with observations of one-off FRBs, supporting the hypothesis that repeating and oneoff FRBs may share a common origin.
文摘Objective: Photobiomodulation (also known as Low Level Laser. LLLT or Cold Laser;Photo Medicine (PM)) has been a vital adjunct therapy in our clinical practice over 5 years, observations of improvement in cognition and personality were noted in several patients. As a result, selected patients with Alzheimer’s Disease, vascular dementia, post-traumatic brain injury and other neuro-degenerative diseases were treated at clinical practices in Buffalo, New York;Sarasota, Florida;Lafayette, Indiana;Phoenix, Az., and Baton Rouge, La. Over 60 patients were treated with an average of 4 times over an 8-day period all reported/exhibited improvement in their condition, except that two men who were in their seventies were in robust health but had no short-term memory and no improvement was observed. However, Theralase has developed a more efficacious system which will be more efficacious, due to increased power for ATP activation. Method: Over 150 patients with the above conditions were treated in various areas (depending on diagnosis) including the prefrontal cortex, temporal lobe, Hippocampus, and Circle of Willis for duration of two and one-half minutes every 48 hours for 5 - 6 treatments. We utilized the Theralase multi-probe (905 nm/660 nm) at 60 miliwatts. It utilizes 5 - 905 nm near infra-red diodes and 4 infra-red 660 laser diodes with a peak power of 50,000 milliwatts at peak and pulse duration of 200 nanoseconds [1]. The PTSD patients were evaluated utilizing the co-occurring disorders program screening and assessment form. Conclusion: Dementia patients exhibited varying degrees of improvement in cognitive function and personality, leading to improved quality of life and decreased caregiver burden. PTSD patients’ improvement was objectively measured by formal neuropsychological testing utilizing the form. All PTSD patients scored no emotional problems after 3 - 5 treatments and all experienced overall sense of well-being. One experienced return of ability to smell he had not had for 5 years. Similar results were reported in a Japanese study where 15 patients were followed for a year. This non-invasive and non-systemic modality of therapy could play a key role in treating progressive neurodegenerative conditions, improving quality of life, and reducing health care costs.
文摘Extensive research has now been conducted and published for the treatment of dementia or Alzheimer’s disease, traumatic brain injury (TBI) and other brain disorders using photobiomodulation (PBM), also known as low-level laser therapy (LLLT). However, minimal information is available regarding the use of LLLT for the treatment of Attention Deficit Hyperactivity Disorder (ADHD). We have been using LLLT in our practice for over 15 years addressing chronic pain and injury issues. However, our work with brain injuries is more recent, and we have published three case studies, one describing a serious traumatic brain injury and two describing our success with dementia/Alzheimer’s disease and PTSD. Currently, there is very little published evidence regarding efficacious therapy for ADHD. The case studies presented here, suggest that LLLT can provide alleviation of these symptoms, with some improvement reported after just a single treatment, without any need for pharmaceutical intervention.
基金supported by the National SKA Program of China(2020SKA0120100)the National Natural Science Foundation of China(Nos.12041303 and 12250410246)+1 种基金the CAS-MPG LEGACY projectfunding from the Max-Planck Partner Group。
文摘Observing and timing a group of millisecond pulsars with high rotational stability enables the direct detection of gravitational waves(GWs).The GW signals can be identified from the spatial correlations encoded in the times-of-arrival of widely spaced pulsar-pairs.The Chinese Pulsar Timing Array(CPTA)is a collaboration aiming at the direct GW detection with observations carried out using Chinese radio telescopes.This short article serves as a“table of contents”for a forthcoming series of papers related to the CPTA Data Release 1(CPTA DR1)which uses observations from the Five-hundred-meter Aperture Spherical radio Telescope.Here,after summarizing the time span and accuracy of CPTA DR1,we report the key results of our statistical inference finding a correlated signal with amplitude logA_(c)=-14.4_(-2.8)^(+1.0)for spectral index in the range ofα∈[-1.8,1.5]assuming a GW background(GWB)induced quadrupolar correlation.The search for the Hellings–Downs(HD)correlation curve is also presented,where some evidence for the HD correlation has been found that a 4.6σstatistical significance is achieved using the discrete frequency method around the frequency of 14 n Hz.We expect that the future International Pulsar Timing Array data analysis and the next CPTA data release will be more sensitive to the n Hz GWB,which could verify the current results.
文摘Extensive research is ongoing in the use of Photobiomodulation (PBM, often referred to as low-level or cold laser therapy) to treat Alzheimer’s disease as well as other debilitating diseases. The following case studies further confirm that PBM could be a breakthrough approach to limit the progression of insidious diseases. We present four cases, two with mild to moderate dementia and two with more advanced symptoms. Several publications have shown beneficial results, however, several weeks of daily treatments were necessary. The cases described here suggest that moderate and advanced dementia cases can be significantly improved with three or four eight-minute treatments over a 5 - 7-day period when using super-pulsing technology on Monday-Wednesday-Friday schedule (Figure 1). Gives a brief visual explanation of super-pulsing versus continuous wave technology.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11975037 and 11921006)the National Grand Instrument Project of China (Grant Nos. 2019YFF01014400 and 2019YFF01014404)。
文摘Laser-driven proton-induced x-ray emission(laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spurted within nanoseconds and accompanied by strong electromagnetic pulses(EMP), so traditional multi-channel detectors are no longer applicable.In this work, we designed a reflective elliptical crystal spectrometer for the diagnosis of laser-PIXE. The device can detect the energy range of 1 keV–11 ke V with a high resolution. A calibration experiment was completed on the electrostatic accelerator of Peking University using samples of Al, Ti, Cu, and ceramic artifacts. The detection efficiency of the elliptical crystal spectrometer was obtained in the order of 10-9.
文摘This paper provides an overview of the current status of ultrafast and ultra-intense lasers with peak powers exceeding100 TW and examines the research activities in high-energy-density physics within China.Currently,10 high-intensity lasers with powers over 100 TW are operational,and about 10 additional lasers are being constructed at various institutes and universities.These facilities operate either independently or are combined with one another,thereby offering substantial support for both Chinese and international research and development efforts in high-energy-density physics.
基金National Grand Instrument Project(No.2019YFF01014402)NSFC innovation group project(No.11921006)National Natural Science Foundation of China(Nos.11775010,11535001,and 61631001).
文摘Carbon nanotube foams(CNFs)have been successfully used as near-critical-density targets in the laser-driven acceleration of high-energy ions and electrons.Here we report the recent advances in the fabrication technique of such targets.With the further developed floating catalyst chemical vapor deposition(FCCVD)method,large-area(>25 cm^(2))and highly uniform CNFs are successfully deposited on nanometer-thin metal or plastic foils as double-layer targets.The density and thickness of the CNF can be controlled in the range of 1−13 mg/cm^(3)and 10−200µm,respectively,by varying the synthesis parameters.The dependence of the target properties on the synthesis parameters and the details of the target characterization methods are presented for the first time.
