We numerically investigate the high-order harmonic generation with two-colour optical field,taking into considera-tion the propagation effects.Some harmonics can be dramatically enhanced at a certain delay between the...We numerically investigate the high-order harmonic generation with two-colour optical field,taking into considera-tion the propagation effects.Some harmonics can be dramatically enhanced at a certain delay between the fundamental pulse and its second harmonics.Choice of the enhanced harmonics can be realised by changing the time delay between the two laser pulses.展开更多
The influence of vacuum polarization effects on the interactions of multiple ultra-intense lasers with plasmas is discussed. The nonlinear paraxial monochromatic model of the interactions has been improved by consider...The influence of vacuum polarization effects on the interactions of multiple ultra-intense lasers with plasmas is discussed. The nonlinear paraxial monochromatic model of the interactions has been improved by considering the Heisenberg–Euler Lagrangian density of two laser processes. Comparing the corrections of vacuum polarization effects in the collision of laser beams with one generated by a single intense laser, we find that the former has a higher order of magnitude correction. The laser collision also produces variations in the propagation direction and polarization direction of the lasers propagating in the plasma. In addition, the strong-field quantum electrodynamic(QED) effects can be enhanced by increasing the laser intensity or frequency difference, or by adjusting the incident angles of the two laser beams.展开更多
In this work, characteristics of X/γ-ray radiations by intense laser interactions with high-Z solids are investigated by means of a newlydeveloped particle-in-cell (PIC) simulation code. The PIC code takes advantage ...In this work, characteristics of X/γ-ray radiations by intense laser interactions with high-Z solids are investigated by means of a newlydeveloped particle-in-cell (PIC) simulation code. The PIC code takes advantage of the recently developed ionization and collision dynamicsmodels, which make it possible to model different types of materials based on their intrinsic atomic properties. Within the simulations, bothbremsstrahlung and nonlinear Compton scatterings have been included. Different target materials and laser intensities are considered forstudying the parameter-dependent features of X/γ-ray radiations. The relative strength and angular distributions of X/γ ray productions frombremsstrahlung and nonlinear Compton scatterings are compared to each other. The threshold under which the nonlinear Compton scatteringsbecome dominant over bremsstrahlung is also outlined.展开更多
We present a first on-chip positron accelerator based on dielectric laser acceleration.This innovative approach significantly reduces the physical dimensions of the positron acceleration apparatus,enhancing its feasib...We present a first on-chip positron accelerator based on dielectric laser acceleration.This innovative approach significantly reduces the physical dimensions of the positron acceleration apparatus,enhancing its feasibility for diverse applications.By utilizing a stacked acceleration structure and far-infrared laser technology,we are able to achieve a seven-stage acceleration structure that surpasses the distance and energy gain of using the previous dielectric laser acceleration methods.Additionally,we are able to compress the positron beam to an ultrafast sub-femtosecond scale during the acceleration process,compared with the traditional methods,the positron beam is compressed to a greater extent.We also demonstrate the robustness of the stacked acceleration structure through the successful acceleration of the positron beam.展开更多
We theoretically study the field-free molecular orientation induced by a three-color laser field. The three-color laser field with a large asymmetric degree can effectively enhance the molecular orientation. In partic...We theoretically study the field-free molecular orientation induced by a three-color laser field. The three-color laser field with a large asymmetric degree can effectively enhance the molecular orientation. In particular, when the intensity ratio of the three-color laser field is tuned to a proper value of I_3: I_2: I_1= 0.09 : 0.5 : 1, the molecular orientation can be improved by ～ 20% compared with that of the two-color laser field at intensity ratio I_2: I_1= 1 : 1 for the same total laser intensity of 2×10^(13)W/cm^2. Moreover, we investigate the effect of the carrier-envelope phase(CEP) on the molecular orientation and use the asymmetric degree of the laser field to explain the result. We also show the influences of the laser intensity, rotational temperature, and pulse duration on the molecular orientation. These results are meaningful for the theoretical and experimental studies on the molecular orientation.展开更多
Near-infrared to visible upconversion luminescence was observed in a multicomponent silicate (BK7) glass containing Ce~ 3+ ions under focused infrared femtosecond laser irradiation. The emission spectra show that the ...Near-infrared to visible upconversion luminescence was observed in a multicomponent silicate (BK7) glass containing Ce~ 3+ ions under focused infrared femtosecond laser irradiation. The emission spectra show that the upconversion luminescence comes from the 4f-5d transition of the Ce~ 3+ ions. The relationship between the intensity of the Ce~ 3+ emission and the pump power reveals that a three-photon absorption predominates in the conversion process from the near-infrared into the blue luminescence. The analysis of the upconversion mechanism suggests that the upconversion luminescence may come from a three-photon simultaneous absorption that leads to a population of the 5d level in which the characteristic luminescence occurs.展开更多
Laser wakefield accelerators(LWFAs)are compact accelerators which can produce femtosecond high-energy electron beams on a much smaller scale than the conventional radiofrequency accelerators.It is attributed to their ...Laser wakefield accelerators(LWFAs)are compact accelerators which can produce femtosecond high-energy electron beams on a much smaller scale than the conventional radiofrequency accelerators.It is attributed to their high acceleration gradient which is about 3 orders of magnitude larger than the traditional ones.The past decade has witnessed the major breakthroughs and progress in developing the laser wakfield accelerators.To achieve the LWFAs suitable for applications,more and more attention has been paid to optimize the LWFAs for high-quality electron beams.A single-staged LWFA does not favor generating controllable electron beams beyond 1 Ge V since electron injection and acceleration are coupled and cannot be independently controlled.Staged LWFAs provide a promising route to overcome this disadvantage by decoupling injection from acceleration and thus the electron-beam quality as well as the stability can be greatly improved.This paper provides an overview of the physical conceptions of the LWFA,as well as the major breakthroughs and progress in developing LWFAs from single-stage to two-stage LWFAs.展开更多
A novel high-birefringence photonic crystal fiber (HB-PCF) with two zero-dispersion wavelengths (ZDWs) is designed, and an extraordinarily high modal birefringence of 1.56×10-2 is obtained at pump wavelength λp=...A novel high-birefringence photonic crystal fiber (HB-PCF) with two zero-dispersion wavelengths (ZDWs) is designed, and an extraordinarily high modal birefringence of 1.56×10-2 is obtained at pump wavelength λp=1850nm. With the designed HB-PCF, the effect of the pump parameters on the modulation instability (MI) in the anomalous dispersion region close to the second ZDWs of the HB-PCF is comprehensively studied in this work. A broadband and tunable optical amplification is achieved by controlling the pump power and the pump wavelength based on the combined operation of Raman effect and cross phase modulation. By optimizing the pump parameters, the amplification bandwidth along the fiber slow axis reaches 152 nm for the pump power Pp=280W and the pump wavelength λp=1675nm, while the gain bandwidth along the fiber fast axis is 165 nm for the pump power Pp=600W and the pump wavelength λp=1818nm.展开更多
Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG),a scaling law of HHG is established.The scaling law states that when the atomic binding energy E b,the wavelength λ and t...Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG),a scaling law of HHG is established.The scaling law states that when the atomic binding energy E b,the wavelength λ and the intensity I of the laser field change simultaneously to kE b,λ/k,and k 3 I,respectively.The characteristics of the HHG spectrum remain unchanged,while the harmonic yield is enhanced k 3 times.That HHG obeys the same scaling law with above-threshold ionization is a solid proof of the fact that the two physical processes have similar physical mechanisms.The variation of integrated harmonic yields is also discussed.展开更多
The effect of the laser spot size on the neutron yield of table-top nuclear fusion from explosions of a femtosecond intense laser pulse heated deuterium clusters is investigated by using a simplified model, in which t...The effect of the laser spot size on the neutron yield of table-top nuclear fusion from explosions of a femtosecond intense laser pulse heated deuterium clusters is investigated by using a simplified model, in which the cluster size distribution and the energy attenuation of the laser as it propagates through the cluster jet are taken into account. It has been found that there exists a proper laser spot size for the maximum fusion neutron yield for a given laser pulse and a specific deuterium gas cluster jet. The proper spot size, which is dependent on the laser parameters and the cluster jet parameters, has been calculated and compared with the available experimental data. A reasonable agreement between the calculated results and the published experimental results is found.展开更多
This paper reports that Coulomb explosions taken place in the experiment of heteronuclear deuterated methane clusters ((CD 4 ) n ) in a gas jet subjected to intense femtosecond laser pulses (170 mJ, 70 fs) have led to...This paper reports that Coulomb explosions taken place in the experiment of heteronuclear deuterated methane clusters ((CD 4 ) n ) in a gas jet subjected to intense femtosecond laser pulses (170 mJ, 70 fs) have led to table-top laser driven DD nuclear fusion. The clusters produced in supersonic expansion had an average size of about 5 nm in radius and the laser intensity used was 3 × 10 17 W/cm 2 .The measured maximum and average energies of deuterons produced in the laser-cluster interaction were 60 and 13.5 keV, respectively. From DD collisions of energetic deuterons, a yield of 2.5(±0.4)×10 4 fusion neutrons of 2.45 MeV per shot was realized, giving rise to a neutron production efficiency of about 1.5 × 10 5 per joule of incident laser pulse energy. Theoretical calculations were performed and a fairly good agreement of the calculated neutron yield with that obtained from the present experiment was found.展开更多
This paper reports self-organized nanostructures observed on the surface of ZnO crystal after irradiation by a focused beam of a femtosecond Ti:sapphire laser with a repetition rate of 250 kHz.For a linearly polarized...This paper reports self-organized nanostructures observed on the surface of ZnO crystal after irradiation by a focused beam of a femtosecond Ti:sapphire laser with a repetition rate of 250 kHz.For a linearly polarized femtosecond laser,the periodic nanograting structure on the ablation crater surface was promoted.The period of self-organization structures is about 180 nm.The grating orientation is adjusted by the laser polarization direction.A long range Bragglike grating is formed by moving the sample at a speed of 10 μm/s.For a circularly polarized laser beam,uniform spherical nanoparticles were formed as a result of Coulomb explosion during the interaction of near-infrared laser with ZnO crystal.展开更多
An all-fiber mode-locked fiber laser was achieved with a saturable absorber based on a tapered fiber deposited with layered molybdenum selenide(MoSe_2). The laser was operated at a central wavelength of 1558.35 nm wit...An all-fiber mode-locked fiber laser was achieved with a saturable absorber based on a tapered fiber deposited with layered molybdenum selenide(MoSe_2). The laser was operated at a central wavelength of 1558.35 nm with an output spectral width of 2.9 nm, and a pulse repetition rate of 16.33 MHz. To the best of our knowledge, this is the first report on mode-locked fiber lasers using MoSe_2 saturable absorbers based on tapered fibers.展开更多
We propose to achieve far-field super-resolution imaging by using offset two-color one-photon(2C1P)excitation of reversible photoactivatable fluorescence proteins.Due to the distinctive photoswitching performance of t...We propose to achieve far-field super-resolution imaging by using offset two-color one-photon(2C1P)excitation of reversible photoactivatable fluorescence proteins.Due to the distinctive photoswitching performance of the proteins,such as dronpa,the fluorescence emission will only come from the overlapped region of activation beam and excitation beam.The analysis solution of rate equation shows that the resolution of offset 2C1P microscope is"engineered"by laser power of excitation and activation beams and the power ratio between them.Superior lateral and transverse resolution is theoretically demonstrated compared with conventional fluorescence scanning microscopy.展开更多
Investigating deuteron–deuteron(DD)fusion reactions in a plasma environment similar to the early stages of the Big Bang is an important topic in nuclear astrophysics.In this study,we experimentally investigated such ...Investigating deuteron–deuteron(DD)fusion reactions in a plasma environment similar to the early stages of the Big Bang is an important topic in nuclear astrophysics.In this study,we experimentally investigated such reactions,using eight laser beams with the third harmonic impacting on a deuterated polyethylene target at the ShenGuang-II Upgrade laser facility.This work focused on the application of range-filter(RF)spectrometers,assembled from a 70 lm aluminum filter and two CR-39 nuclear track detectors,to measure the yields of primary DD-protons.Based on the track diameter calibration results of 3 MeV protons used to diagnose the tracks on the RF spectrometers,an approximate primary DD-proton yield of(8.5±1.7)×10^6 was obtained,consistent with the yields from similar laser facilities worldwide.This indicates that the RF spectrometer is an effective way to measure primary DD-protons.However,due to the low yields of D^3He-protons and its small track diameter,CR-39 detectors were unable to distinguish it from the background spots.Using other accurate detectors may help to measure these rare events.展开更多
A general solution of the electrostatic potential that determines the maximum light-ion energy is derived for the test-particle acceleration model by taking into account the influence of the substrate-ion density grad...A general solution of the electrostatic potential that determines the maximum light-ion energy is derived for the test-particle acceleration model by taking into account the influence of the substrate-ion density gradient.It is shown that the substrate-ion density structure is also dependent on laser pulse duration.In the picosecond or sub-picosecond regime,the decreasing density gradient of the substrate-ions leads to an evident reduction in the acceleration efficiency of the light-ions.However,this kind of influence is negligible in the ultrashort regime.展开更多
基金Project supported by Chinese Academy of Sciences,the National Natural Science Foundation (Grant Nos. 10734080,10523003,60921004,10904157,and 60978012)973 Project (Grant No. 2006CB806000)Shanghai Commission of Science and Technology(Grant Nos. 06DZ22015 and 07PJ14091)
文摘We numerically investigate the high-order harmonic generation with two-colour optical field,taking into considera-tion the propagation effects.Some harmonics can be dramatically enhanced at a certain delay between the fundamental pulse and its second harmonics.Choice of the enhanced harmonics can be realised by changing the time delay between the two laser pulses.
基金supported by the National Natural Science Foundation of China (Grant No. 11805117)the Shanghai Leading Academic Discipline Project (Grant No. S30105)。
文摘The influence of vacuum polarization effects on the interactions of multiple ultra-intense lasers with plasmas is discussed. The nonlinear paraxial monochromatic model of the interactions has been improved by considering the Heisenberg–Euler Lagrangian density of two laser processes. Comparing the corrections of vacuum polarization effects in the collision of laser beams with one generated by a single intense laser, we find that the former has a higher order of magnitude correction. The laser collision also produces variations in the propagation direction and polarization direction of the lasers propagating in the plasma. In addition, the strong-field quantum electrodynamic(QED) effects can be enhanced by increasing the laser intensity or frequency difference, or by adjusting the incident angles of the two laser beams.
基金This work was supported by Science Challenge Project(No.TZ2016005)National Natural Science Foundation of China(No.11605269,11674341 and 11675245)National Basic Research Program of China(Grant No.2013CBA01504).
文摘In this work, characteristics of X/γ-ray radiations by intense laser interactions with high-Z solids are investigated by means of a newlydeveloped particle-in-cell (PIC) simulation code. The PIC code takes advantage of the recently developed ionization and collision dynamicsmodels, which make it possible to model different types of materials based on their intrinsic atomic properties. Within the simulations, bothbremsstrahlung and nonlinear Compton scatterings have been included. Different target materials and laser intensities are considered forstudying the parameter-dependent features of X/γ-ray radiations. The relative strength and angular distributions of X/γ ray productions frombremsstrahlung and nonlinear Compton scatterings are compared to each other. The threshold under which the nonlinear Compton scatteringsbecome dominant over bremsstrahlung is also outlined.
基金supported by the National Natural Science Foundation of China(Grant No.11975214).
文摘We present a first on-chip positron accelerator based on dielectric laser acceleration.This innovative approach significantly reduces the physical dimensions of the positron acceleration apparatus,enhancing its feasibility for diverse applications.By utilizing a stacked acceleration structure and far-infrared laser technology,we are able to achieve a seven-stage acceleration structure that surpasses the distance and energy gain of using the previous dielectric laser acceleration methods.Additionally,we are able to compress the positron beam to an ultrafast sub-femtosecond scale during the acceleration process,compared with the traditional methods,the positron beam is compressed to a greater extent.We also demonstrate the robustness of the stacked acceleration structure through the successful acceleration of the positron beam.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61221064,61078037,11134010,61205208,and 61521093)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB16)the International S&T Cooperation Program of China(Grant No.2016YFE0119300)
文摘We theoretically study the field-free molecular orientation induced by a three-color laser field. The three-color laser field with a large asymmetric degree can effectively enhance the molecular orientation. In particular, when the intensity ratio of the three-color laser field is tuned to a proper value of I_3: I_2: I_1= 0.09 : 0.5 : 1, the molecular orientation can be improved by ～ 20% compared with that of the two-color laser field at intensity ratio I_2: I_1= 1 : 1 for the same total laser intensity of 2×10^(13)W/cm^2. Moreover, we investigate the effect of the carrier-envelope phase(CEP) on the molecular orientation and use the asymmetric degree of the laser field to explain the result. We also show the influences of the laser intensity, rotational temperature, and pulse duration on the molecular orientation. These results are meaningful for the theoretical and experimental studies on the molecular orientation.
基金Supported by the National Natural Science Foundation of China under Grant No 10774153, the National Basic Research Program of China, and the Shanghai Rising-Star Program.
基金Project supported bythe National Natural Science Foundation of China (50125258 and 60377040)
文摘Near-infrared to visible upconversion luminescence was observed in a multicomponent silicate (BK7) glass containing Ce~ 3+ ions under focused infrared femtosecond laser irradiation. The emission spectra show that the upconversion luminescence comes from the 4f-5d transition of the Ce~ 3+ ions. The relationship between the intensity of the Ce~ 3+ emission and the pump power reveals that a three-photon absorption predominates in the conversion process from the near-infrared into the blue luminescence. The analysis of the upconversion mechanism suggests that the upconversion luminescence may come from a three-photon simultaneous absorption that leads to a population of the 5d level in which the characteristic luminescence occurs.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11127901,11425418,and 61221064)the National Basic Research Program of China(Grant No.2011CB808100)the Science and Technology Talent Project of Shanghai City,China(Grant Nos.12XD1405200 and 12ZR1451700)
文摘Laser wakefield accelerators(LWFAs)are compact accelerators which can produce femtosecond high-energy electron beams on a much smaller scale than the conventional radiofrequency accelerators.It is attributed to their high acceleration gradient which is about 3 orders of magnitude larger than the traditional ones.The past decade has witnessed the major breakthroughs and progress in developing the laser wakfield accelerators.To achieve the LWFAs suitable for applications,more and more attention has been paid to optimize the LWFAs for high-quality electron beams.A single-staged LWFA does not favor generating controllable electron beams beyond 1 Ge V since electron injection and acceleration are coupled and cannot be independently controlled.Staged LWFAs provide a promising route to overcome this disadvantage by decoupling injection from acceleration and thus the electron-beam quality as well as the stability can be greatly improved.This paper provides an overview of the physical conceptions of the LWFA,as well as the major breakthroughs and progress in developing LWFAs from single-stage to two-stage LWFAs.
基金the National Natural Science Foundation of China(Grant No.11226148)the Scientific Research Foundation of Zhejiang Province,China(Grant No.LY12F05006)the Education Department Foundation of Zhejiang Province,China(Grant No.Y201121906)
文摘A novel high-birefringence photonic crystal fiber (HB-PCF) with two zero-dispersion wavelengths (ZDWs) is designed, and an extraordinarily high modal birefringence of 1.56×10-2 is obtained at pump wavelength λp=1850nm. With the designed HB-PCF, the effect of the pump parameters on the modulation instability (MI) in the anomalous dispersion region close to the second ZDWs of the HB-PCF is comprehensively studied in this work. A broadband and tunable optical amplification is achieved by controlling the pump power and the pump wavelength based on the combined operation of Raman effect and cross phase modulation. By optimizing the pump parameters, the amplification bandwidth along the fiber slow axis reaches 152 nm for the pump power Pp=280W and the pump wavelength λp=1675nm, while the gain bandwidth along the fiber fast axis is 165 nm for the pump power Pp=600W and the pump wavelength λp=1818nm.
基金supported by the National Natural Science Foundation of China (Grant Nos.10774153 and 61078080)the National Basic Research Program of China (Grant Nos.2010CB923203 and 2011CB808103)
文摘Using a nonperturbative quantum electrodynamics theory of high-order harmonic generation (HHG),a scaling law of HHG is established.The scaling law states that when the atomic binding energy E b,the wavelength λ and the intensity I of the laser field change simultaneously to kE b,λ/k,and k 3 I,respectively.The characteristics of the HHG spectrum remain unchanged,while the harmonic yield is enhanced k 3 times.That HHG obeys the same scaling law with above-threshold ionization is a solid proof of the fact that the two physical processes have similar physical mechanisms.The variation of integrated harmonic yields is also discussed.
基金Project supported by the National Basic Research Program of China (Grant No 2006CB806000)the National Natural Science Foundation of China (Grant No 10535070)
文摘The effect of the laser spot size on the neutron yield of table-top nuclear fusion from explosions of a femtosecond intense laser pulse heated deuterium clusters is investigated by using a simplified model, in which the cluster size distribution and the energy attenuation of the laser as it propagates through the cluster jet are taken into account. It has been found that there exists a proper laser spot size for the maximum fusion neutron yield for a given laser pulse and a specific deuterium gas cluster jet. The proper spot size, which is dependent on the laser parameters and the cluster jet parameters, has been calculated and compared with the available experimental data. A reasonable agreement between the calculated results and the published experimental results is found.
基金supported by the National Basic Research Program of China (Grant No 2006CB806000)the National Natural Science Foundation of China (Grant No 10535070)
文摘This paper reports that Coulomb explosions taken place in the experiment of heteronuclear deuterated methane clusters ((CD 4 ) n ) in a gas jet subjected to intense femtosecond laser pulses (170 mJ, 70 fs) have led to table-top laser driven DD nuclear fusion. The clusters produced in supersonic expansion had an average size of about 5 nm in radius and the laser intensity used was 3 × 10 17 W/cm 2 .The measured maximum and average energies of deuterons produced in the laser-cluster interaction were 60 and 13.5 keV, respectively. From DD collisions of energetic deuterons, a yield of 2.5(±0.4)×10 4 fusion neutrons of 2.45 MeV per shot was realized, giving rise to a neutron production efficiency of about 1.5 × 10 5 per joule of incident laser pulse energy. Theoretical calculations were performed and a fairly good agreement of the calculated neutron yield with that obtained from the present experiment was found.
基金Project supported by the Shanghai Leading Academic Discipline Project (Grant No T0104)the Shanghai Nano-technology Promotion Center and Science & Technology of Shanghai Municipality (Grant No 0652nm005)Innovation Fund of Shanghai University,China
文摘This paper reports self-organized nanostructures observed on the surface of ZnO crystal after irradiation by a focused beam of a femtosecond Ti:sapphire laser with a repetition rate of 250 kHz.For a linearly polarized femtosecond laser,the periodic nanograting structure on the ablation crater surface was promoted.The period of self-organization structures is about 180 nm.The grating orientation is adjusted by the laser polarization direction.A long range Bragglike grating is formed by moving the sample at a speed of 10 μm/s.For a circularly polarized laser beam,uniform spherical nanoparticles were formed as a result of Coulomb explosion during the interaction of near-infrared laser with ZnO crystal.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB0504500)the National Natural Science Foundation of China(Grant Nos.61475171,61705244,61307056,and 61875052)the Natural Science Foundation of Shanghai,China(Grant Nos.17ZR1433900 and17ZR1434200)
文摘An all-fiber mode-locked fiber laser was achieved with a saturable absorber based on a tapered fiber deposited with layered molybdenum selenide(MoSe_2). The laser was operated at a central wavelength of 1558.35 nm with an output spectral width of 2.9 nm, and a pulse repetition rate of 16.33 MHz. To the best of our knowledge, this is the first report on mode-locked fiber lasers using MoSe_2 saturable absorbers based on tapered fibers.
基金Supported by the National Natural Science Foundation of China(No 10804116).
文摘We propose to achieve far-field super-resolution imaging by using offset two-color one-photon(2C1P)excitation of reversible photoactivatable fluorescence proteins.Due to the distinctive photoswitching performance of the proteins,such as dronpa,the fluorescence emission will only come from the overlapped region of activation beam and excitation beam.The analysis solution of rate equation shows that the resolution of offset 2C1P microscope is"engineered"by laser power of excitation and activation beams and the power ratio between them.Superior lateral and transverse resolution is theoretically demonstrated compared with conventional fluorescence scanning microscopy.
基金supported in part by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB160203)the National Natural Science Foundation of China(Nos.11875311 and 11421505).
文摘Investigating deuteron–deuteron(DD)fusion reactions in a plasma environment similar to the early stages of the Big Bang is an important topic in nuclear astrophysics.In this study,we experimentally investigated such reactions,using eight laser beams with the third harmonic impacting on a deuterated polyethylene target at the ShenGuang-II Upgrade laser facility.This work focused on the application of range-filter(RF)spectrometers,assembled from a 70 lm aluminum filter and two CR-39 nuclear track detectors,to measure the yields of primary DD-protons.Based on the track diameter calibration results of 3 MeV protons used to diagnose the tracks on the RF spectrometers,an approximate primary DD-proton yield of(8.5±1.7)×10^6 was obtained,consistent with the yields from similar laser facilities worldwide.This indicates that the RF spectrometer is an effective way to measure primary DD-protons.However,due to the low yields of D^3He-protons and its small track diameter,CR-39 detectors were unable to distinguish it from the background spots.Using other accurate detectors may help to measure these rare events.
基金supported by the National Natural Science Foundation of China (Grant No. 10734080)the National Basic Research Program of China (Grant No. 2006CB806000)+1 种基金the Chinese Academy of Sciences,the Shanghai Commission of Science and Technology (Grant Nos. 06DZ22015 and 0652nm005)the Hunan Provincial Natural Science Foundation of China (GrantNo. 09JJ3012)
文摘A general solution of the electrostatic potential that determines the maximum light-ion energy is derived for the test-particle acceleration model by taking into account the influence of the substrate-ion density gradient.It is shown that the substrate-ion density structure is also dependent on laser pulse duration.In the picosecond or sub-picosecond regime,the decreasing density gradient of the substrate-ions leads to an evident reduction in the acceleration efficiency of the light-ions.However,this kind of influence is negligible in the ultrashort regime.
