J. Trieschmann, A. W. Larsen, T. Mussenbrock, S. Korsholm
For the measurement of the dynamics of fusion-born alpha particles $E_alpha leq 3.5$ MeV in ITER using collective Thomson scattering (CTS), safe transmission of a gyrotron beam at mm-wavelength (1 MW, 60 GHz) passing the electron cyclotron resonance (ECR) in the in-vessel tokamak `port plug' vacuum is a prerequisite. Depending on neutral gas pressure and composition, ECR-assisted gas breakdown may occur at the location of the resonance, which must be mitigated for diagnostic performance and safety reasons. The concept of a split electrically biased waveguide (SBWG) has been previously demonstrated in [C.P. Moeller, U.S. Patent 4,687,616 (1987)]. The waveguide is longitudinally split and a kV bias voltage applied between the two halves. Electrons are rapidly removed from the central region of high radio frequency electric field strength, mitigating breakdown. As a full scale experimental investigation of gas and electromagnetic field conditions inside the ITER equatorial port plugs is currently unattainable, a corresponding Monte Carlo simulation study is presented. Validity of the Monte Carlo electron model is demonstrated with a prediction of ECR breakdown and the mitigation pressure limits for the above quoted reference case with $^1$H$_2$ (and pollutant high $Z$ elements). For the proposed ITER CTS design with a 88.9 mm inner diameter SBWG, ECR breakdown is predicted to occur down to a pure $^1$H$_2$ pressure of 0.3 Pa, while mitigation is shown to be effective at least up to 10 Pa using a bias voltage of 1 kV. The analysis is complemented by results for relevant electric/magnetic field arrangements and limitations of the SBWG mitigation concept are addressed.
为了在ITER中使用集体汤姆逊散射(CTS)测量聚变产生的α粒子$E_alpha leq 3.5$ MeV的动力学，在容器内托卡马克“端口塞”真空中安全传输波长为mm (1 MW, 60 GHz)的回旋加速器束通过电子回旋共振(ECR)是先决条件。根据中性气体压力和成分的不同，ecr辅助气体击穿可能发生在谐振位置，出于诊断性能和安全原因，必须减轻这种击穿。分离式电偏波导(SBWG)的概念先前已在[C.P.]中得到证明Moeller, U.S. Patent 4,687,616(1987)]。波导纵向分开，在两半之间施加kV偏置电压。电子迅速从高频电场强度高的中心区域移除，减轻击穿。由于目前无法对ITER赤道端口塞内的气体和电磁场条件进行全面的实验研究，因此提出了相应的蒙特卡罗模拟研究。蒙特卡罗电子模型的有效性得到了验证，并对上述参考情况下$^1$ H $_2$(和污染物高$Z$元素)的ECR击穿和缓解压力极限进行了预测。对于具有88.9 mm内径SBWG的ITER CTS设计，预计ECR击穿将发生在0.3 Pa的纯$^1$ H $_2$压力下，而使用1 kV的偏置电压至少可有效缓解至10 Pa。相关电场/磁场布置的结果补充了这一分析，并解决了SBWG缓解概念的局限性。
{"title":"Kinetic simulation of electron cyclotron resonance assisted gas breakdown in split-biased waveguides for ITER collective Thomson scattering diagnostic","authors":"J. Trieschmann, A. W. Larsen, T. Mussenbrock, S. Korsholm","doi":"10.1063/5.0055461","DOIUrl":"https://doi.org/10.1063/5.0055461","url":null,"abstract":"For the measurement of the dynamics of fusion-born alpha particles $E_alpha leq 3.5$ MeV in ITER using collective Thomson scattering (CTS), safe transmission of a gyrotron beam at mm-wavelength (1 MW, 60 GHz) passing the electron cyclotron resonance (ECR) in the in-vessel tokamak `port plug' vacuum is a prerequisite. Depending on neutral gas pressure and composition, ECR-assisted gas breakdown may occur at the location of the resonance, which must be mitigated for diagnostic performance and safety reasons. The concept of a split electrically biased waveguide (SBWG) has been previously demonstrated in [C.P. Moeller, U.S. Patent 4,687,616 (1987)]. The waveguide is longitudinally split and a kV bias voltage applied between the two halves. Electrons are rapidly removed from the central region of high radio frequency electric field strength, mitigating breakdown. As a full scale experimental investigation of gas and electromagnetic field conditions inside the ITER equatorial port plugs is currently unattainable, a corresponding Monte Carlo simulation study is presented. Validity of the Monte Carlo electron model is demonstrated with a prediction of ECR breakdown and the mitigation pressure limits for the above quoted reference case with $^1$H$_2$ (and pollutant high $Z$ elements). For the proposed ITER CTS design with a 88.9 mm inner diameter SBWG, ECR breakdown is predicted to occur down to a pure $^1$H$_2$ pressure of 0.3 Pa, while mitigation is shown to be effective at least up to 10 Pa using a bias voltage of 1 kV. The analysis is complemented by results for relevant electric/magnetic field arrangements and limitations of the SBWG mitigation concept are addressed.","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"16 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83872807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-03-04DOI: 10.21203/RS.3.RS-279306/V1
Yichen Fu, H. Qin
Plasmas have been recently studied as topological materials. We attempt at a comprehensive picture of the topological phases, topological phase transitions, and the bulk-edge correspondence of magnetized cold plasmas. We find that there are 10 topological phases in the parameter space of density $n$, magnetic field $B$, and parallel wavenumber $k_{parallel}$. They are separated by the surfaces of Langmuir wave-L wave resonance, Langmuir wave-cyclotron wave resonance, and zero magnetic field. For fixed $B$ and $k_{parallel}$, only the phase transition at the Langmuir wave-cyclotron wave resonance corresponds to edge modes. A sufficient and necessary condition for the existence of this new type of edge modes is given and verified by numerical solutions. The edge modes fall into four categories characterized by different behaviors of the Fermi arcs or Fermi-arcs-like curves. We demonstrate that edge modes exist not only on a plasma-vacuum interface but also on more general plasma-plasma interfaces. This finding broadens the possible applications of these exotic excitations in space and laboratory plasmas.
{"title":"Topological phases, topological phase transition, and bulk-edge correspondence of magnetized cold plasmas","authors":"Yichen Fu, H. Qin","doi":"10.21203/RS.3.RS-279306/V1","DOIUrl":"https://doi.org/10.21203/RS.3.RS-279306/V1","url":null,"abstract":"Plasmas have been recently studied as topological materials. We attempt at a comprehensive picture of the topological phases, topological phase transitions, and the bulk-edge correspondence of magnetized cold plasmas. We find that there are 10 topological phases in the parameter space of density $n$, magnetic field $B$, and parallel wavenumber $k_{parallel}$. They are separated by the surfaces of Langmuir wave-L wave resonance, Langmuir wave-cyclotron wave resonance, and zero magnetic field. For fixed $B$ and $k_{parallel}$, only the phase transition at the Langmuir wave-cyclotron wave resonance corresponds to edge modes. A sufficient and necessary condition for the existence of this new type of edge modes is given and verified by numerical solutions. The edge modes fall into four categories characterized by different behaviors of the Fermi arcs or Fermi-arcs-like curves. We demonstrate that edge modes exist not only on a plasma-vacuum interface but also on more general plasma-plasma interfaces. This finding broadens the possible applications of these exotic excitations in space and laboratory plasmas.","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"17 13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90471623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-19DOI: 10.1002/ESSOAR.10506282.1
D. Graham, Y. Khotyaintsev, M. André, A. Vaivads, A. Chasapis, W. Matthaeus, A. Retinò, F. Valentini, D. Gershman
Plasmas in Earth's outer magnetosphere, magnetosheath, and solar wind are essentially collisionless. This means particle distributions are not typically in thermodynamic equilibrium and deviate sig...
{"title":"Non-Maxwellianity of electron distributions near Earth's magnetopause","authors":"D. Graham, Y. Khotyaintsev, M. André, A. Vaivads, A. Chasapis, W. Matthaeus, A. Retinò, F. Valentini, D. Gershman","doi":"10.1002/ESSOAR.10506282.1","DOIUrl":"https://doi.org/10.1002/ESSOAR.10506282.1","url":null,"abstract":"Plasmas in Earth's outer magnetosphere, magnetosheath, and solar wind are essentially collisionless. This means particle distributions are not typically in thermodynamic equilibrium and deviate sig...","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85766849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper we present theory of novel micro-bunching instability. We named it Plasma-Cascade Instability
本文提出了一种新型微聚束不稳定性理论。我们将其命名为等离子级联不稳定性
{"title":"Theory of Plasma-Cascade Instability","authors":"V. Litvinenko, Gang Wang","doi":"10.2172/1760645","DOIUrl":"https://doi.org/10.2172/1760645","url":null,"abstract":"In this paper we present theory of novel micro-bunching instability. We named it Plasma-Cascade Instability","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77668934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The theory of the ion cyclotron (IC) electrostatic parametric instabilities of the inhomogeneous plasma which are driven by the inhomogeneous electric field of the fast wave (FW) in front of FW antenna is developed. It is found that the spatial inhomogeneity of the parametric IC turbulence and of the drift turbulence is at the origin of the flows which transport a large part of FW power, deposited to the bulk of plasma adjacent to the inner side of the last closed magnetic surface, to the scrape-off layer and later to the divertor mostly along field lines.
{"title":"Ion cyclotron parametric turbulence and anomalous convective transport of the inhomogeneous plasma in front of the fast wave antenna","authors":"V. Mikhailenko, V. Mikhailenko, H. Lee","doi":"10.1063/5.0040946","DOIUrl":"https://doi.org/10.1063/5.0040946","url":null,"abstract":"The theory of the ion cyclotron (IC) electrostatic parametric instabilities of the inhomogeneous plasma which are driven by the inhomogeneous electric field of the fast wave (FW) in front of FW antenna is developed. It is found that the spatial inhomogeneity of the parametric IC turbulence and of the drift turbulence is at the origin of the flows which transport a large part of FW power, deposited to the bulk of plasma adjacent to the inner side of the last closed magnetic surface, to the scrape-off layer and later to the divertor mostly along field lines.","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76008563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Stanek, R. Clay, M. Dharma-wardana, M. Wood, K. Beckwith, M. Murillo
Macroscopic simulations of dense plasmas rely on detailed microscopic information that can be computationally expensive and is difficult to verify experimentally. In this work, we delineate the accuracy boundary between microscale simulation methods by comparing Kohn-Sham density functional theory molecular dynamics (KS-MD) and radial pair potential molecular dynamics (RPP- MD) for a range of elements, temperature, and density. By extracting the optimal RPP from KS-MD data using force-matching, we constrain its functional form and dismiss classes of potentials that assume a constant power law for small interparticle distances. Our results show excellent agreement between RPP-MD and KS-MD for multiple metrics of accuracy at temperatures of only a few electron volts. The use of RPPs offers orders of magnitude decrease in computational cost and indicates that three-body potentials are not required beyond temperatures of a few eV. Due to its efficiency, the validated RPP-MD provides an avenue for reducing errors due to finite-size effects that can be on the order of $sim20%$.
{"title":"Efficacy of the radial pair potential approximation for molecular dynamics simulations of dense plasmas","authors":"L. Stanek, R. Clay, M. Dharma-wardana, M. Wood, K. Beckwith, M. Murillo","doi":"10.1063/5.0040062","DOIUrl":"https://doi.org/10.1063/5.0040062","url":null,"abstract":"Macroscopic simulations of dense plasmas rely on detailed microscopic information that can be computationally expensive and is difficult to verify experimentally. In this work, we delineate the accuracy boundary between microscale simulation methods by comparing Kohn-Sham density functional theory molecular dynamics (KS-MD) and radial pair potential molecular dynamics (RPP- MD) for a range of elements, temperature, and density. By extracting the optimal RPP from KS-MD data using force-matching, we constrain its functional form and dismiss classes of potentials that assume a constant power law for small interparticle distances. Our results show excellent agreement between RPP-MD and KS-MD for multiple metrics of accuracy at temperatures of only a few electron volts. The use of RPPs offers orders of magnitude decrease in computational cost and indicates that three-body potentials are not required beyond temperatures of a few eV. Due to its efficiency, the validated RPP-MD provides an avenue for reducing errors due to finite-size effects that can be on the order of $sim20%$.","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90993345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Appelbe, A. Velikovich, M. Sherlock, C. Walsh, A. Crilly, S. O' Neill, J. Chittenden
High energy gain in inertial fusion schemes requires the propagation of a thermonuclear burn wave from hot to cold fuel. We consider the problem of burn propagation when a magnetic field is orthogonal to the burn wave. Using an extended-MHD model with a magnetized $alpha$ energy transport equation we find that the magnetic field can reduce the rate of burn propagation by suppressing electron thermal conduction and $alpha$ particle flux. Magnetic field transport during burn propagation is subject to competing effects: field can be advected from cold to hot regions by ablation of cold fuel, while the Nernst and $alpha$ particle flux effects transport field from hot to cold fuel. These effects, combined with the temperature increase due to burn, can cause the electron Hall parameter to grow rapidly at the burn front. This results in the formation of a self-insulating layer between hot and cold fuel that reduces electron thermal conductivity and $alpha$ transport, increases the temperature gradient and reduces the rate of burn propagation.
{"title":"Magnetic field transport in propagating thermonuclear burn","authors":"B. Appelbe, A. Velikovich, M. Sherlock, C. Walsh, A. Crilly, S. O' Neill, J. Chittenden","doi":"10.1063/5.0040161","DOIUrl":"https://doi.org/10.1063/5.0040161","url":null,"abstract":"High energy gain in inertial fusion schemes requires the propagation of a thermonuclear burn wave from hot to cold fuel. We consider the problem of burn propagation when a magnetic field is orthogonal to the burn wave. Using an extended-MHD model with a magnetized $alpha$ energy transport equation we find that the magnetic field can reduce the rate of burn propagation by suppressing electron thermal conduction and $alpha$ particle flux. Magnetic field transport during burn propagation is subject to competing effects: field can be advected from cold to hot regions by ablation of cold fuel, while the Nernst and $alpha$ particle flux effects transport field from hot to cold fuel. These effects, combined with the temperature increase due to burn, can cause the electron Hall parameter to grow rapidly at the burn front. This results in the formation of a self-insulating layer between hot and cold fuel that reduces electron thermal conductivity and $alpha$ transport, increases the temperature gradient and reduces the rate of burn propagation.","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76405657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Z. Nie, Yipeng Wu, Chaojie Zhang, W. Mori, C. Joshi, W. Lu, C. Pai, J. Hua, Jyhpyng Wang
This paper discusses numerical and experimental results on frequency downshifting and upshifting of a 10 $mu$m infrared laser to cover the entire wavelength (frequency) range from $lambda$=1-150 $mu$m ($nu$=300-2 THz) using two different plasma techniques. The first plasma technique utilizes frequency downshifting of the drive laser pulse in a nonlinear plasma wake. Based on this technique, we have proposed and demonstrated that in a tailored plasma structure multi-millijoule energy, single-cycle, long-wavelength IR (3-20 $mu$m) pulses can be generated by using an 810 nm Ti:sapphire drive laser. Here we extend this idea to the THz frequency regime. We show that sub-joule, terawatts, single-cycle terahertz (2-12 THz, or 150-25 $mu$m) pulses can be generated by replacing the drive laser with a picosecond 10 $mu$m CO$_2$ laser and a different shaped plasma structure. The second plasma technique employs frequency upshifting by colliding a CO$_2$ laser with a rather sharp relativistic ionization front created by ionization of a gas in less than half cycle (17 fs) of the CO$_2$ laser. Even though the electrons in the ionization front carry no energy, the frequency of the CO$_2$ laser can be upshifted due to the relativistic Doppler effect as the CO$_2$ laser pulse enters the front. The wavelength can be tuned from 1-10 $mu$m by simply changing the electron density of the front. While the upshifted light with $5
本文讨论了10 $mu$ m红外激光器在$lambda$ =1-150 $mu$ m ($nu$ =300-2太赫兹)的整个波长(频率)范围内，采用两种不同的等离子体技术实现频率降移和升移的数值和实验结果。第一种等离子体技术是利用非线性等离子体尾迹中驱动激光脉冲的降频。基于该技术，我们提出并证明了在定制等离子体结构中，使用810 nm Ti:蓝宝石驱动激光器可以产生多毫焦耳能量，单周期，长波红外(3-20 $mu$ m)脉冲。这里我们将这个想法扩展到太赫兹频率范围。我们展示了亚焦耳，太瓦，单周期太赫兹(2-12太赫兹，或150-25 $mu$ m)脉冲可以通过用皮秒10 $mu$ m CO $_2$激光器和不同形状的等离子体结构代替驱动激光器产生。第二种等离子体技术通过CO $_2$激光与CO $_2$激光在不到半周期(17 fs)的时间内电离气体产生的相当尖锐的相对论性电离锋相碰撞，利用频率上移。尽管电离前沿的电子不携带能量，但当CO $_2$激光脉冲进入电离前沿时，由于相对论多普勒效应，CO $_2$激光的频率可以上移。波长可以从1-10 $mu$ m通过简单地改变前面的电子密度。当含有$5
{"title":"Ultra-short pulse generation from mid-IR to THz range using plasma wakes and relativistic ionization fronts","authors":"Z. Nie, Yipeng Wu, Chaojie Zhang, W. Mori, C. Joshi, W. Lu, C. Pai, J. Hua, Jyhpyng Wang","doi":"10.1063/5.0039301","DOIUrl":"https://doi.org/10.1063/5.0039301","url":null,"abstract":"This paper discusses numerical and experimental results on frequency downshifting and upshifting of a 10 $mu$m infrared laser to cover the entire wavelength (frequency) range from $lambda$=1-150 $mu$m ($nu$=300-2 THz) using two different plasma techniques. The first plasma technique utilizes frequency downshifting of the drive laser pulse in a nonlinear plasma wake. Based on this technique, we have proposed and demonstrated that in a tailored plasma structure multi-millijoule energy, single-cycle, long-wavelength IR (3-20 $mu$m) pulses can be generated by using an 810 nm Ti:sapphire drive laser. Here we extend this idea to the THz frequency regime. We show that sub-joule, terawatts, single-cycle terahertz (2-12 THz, or 150-25 $mu$m) pulses can be generated by replacing the drive laser with a picosecond 10 $mu$m CO$_2$ laser and a different shaped plasma structure. The second plasma technique employs frequency upshifting by colliding a CO$_2$ laser with a rather sharp relativistic ionization front created by ionization of a gas in less than half cycle (17 fs) of the CO$_2$ laser. Even though the electrons in the ionization front carry no energy, the frequency of the CO$_2$ laser can be upshifted due to the relativistic Doppler effect as the CO$_2$ laser pulse enters the front. The wavelength can be tuned from 1-10 $mu$m by simply changing the electron density of the front. While the upshifted light with $5 <lambda(mu$m$)< 10$ propagates in the forward direction, that with $1 <lambda(mu$m$)< 5$ is back-reflected. These two plasma techniques seem extremely promising for covering the entire molecular fingerprint region.","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74693848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-02DOI: 10.1103/PHYSREVACCELBEAMS.24.011302
P. King, K. Miller, N. Lemos, J. Shaw, B. Frances Kraus, M. Thibodeau, B. Hegelich, J. Hinojosa, P. Michel, C. Joshi, K. Marsh, W. Mori, A. Pak, A. Thomas, F. Albert
The two-temperature relativistic electron spectrum from a low-density ($3times10^{17}$~cm$^{-3}$) self-modulated laser wakefield accelerator (SM-LWFA) is observed to transition between temperatures of $19pm0.65$ and $46pm2.45$ MeV at an electron energy of about 100 MeV. When the electrons are dispersed orthogonally to the laser polarization, their spectrum above 60 MeV shows a forking structure characteristic of direct laser acceleration (DLA). Both the two-temperature distribution and the forking structure are reproduced in a quasi-3D textsc{Osiris} simulation of the interaction of the 1-ps, moderate-amplitude ($a_{0}=2.7$) laser pulse with the low-density plasma. Particle tracking shows that while the SM-LWFA mechanism dominates below 40 MeV, the highest-energy ($>60$ MeV) electrons gain most of their energy through DLA. By separating the simulated electric fields into modes, the DLA-dominated electrons are shown to lose significant energy to the longitudinal laser field from the tight focusing geometry, resulting in a more accurate measure of net DLA energy gain than previously possible.
在低密度($3times10^{17}$ cm $^{-3}$)激光尾流场自调制加速器(SM-LWFA)中，观察到电子能量约为100 MeV时，两温相对论电子能谱在$19pm0.65$和$46pm2.45$ MeV之间跃迁。当电子与激光偏振方向正交分散时，其60 MeV以上的光谱呈现直接激光加速(DLA)的分叉结构特征。在准三维textsc{Osiris}模拟中再现了1-ps、中等振幅($a_{0}=2.7$)激光脉冲与低密度等离子体相互作用的双温分布和分叉结构。粒子跟踪表明，虽然SM-LWFA机制在40 MeV以下占主导地位，但最高能量($>60$ MeV)的电子通过DLA获得大部分能量。通过将模拟电场分离成模式，DLA主导的电子显示出从紧密聚焦几何形状的纵向激光场损失大量能量，从而比以前可能更准确地测量净DLA能量增益。
{"title":"Predominant contribution of direct laser acceleration to high-energy electron spectra in a low-density self-modulated laser wakefield accelerator","authors":"P. King, K. Miller, N. Lemos, J. Shaw, B. Frances Kraus, M. Thibodeau, B. Hegelich, J. Hinojosa, P. Michel, C. Joshi, K. Marsh, W. Mori, A. Pak, A. Thomas, F. Albert","doi":"10.1103/PHYSREVACCELBEAMS.24.011302","DOIUrl":"https://doi.org/10.1103/PHYSREVACCELBEAMS.24.011302","url":null,"abstract":"The two-temperature relativistic electron spectrum from a low-density ($3times10^{17}$~cm$^{-3}$) self-modulated laser wakefield accelerator (SM-LWFA) is observed to transition between temperatures of $19pm0.65$ and $46pm2.45$ MeV at an electron energy of about 100 MeV. When the electrons are dispersed orthogonally to the laser polarization, their spectrum above 60 MeV shows a forking structure characteristic of direct laser acceleration (DLA). Both the two-temperature distribution and the forking structure are reproduced in a quasi-3D textsc{Osiris} simulation of the interaction of the 1-ps, moderate-amplitude ($a_{0}=2.7$) laser pulse with the low-density plasma. Particle tracking shows that while the SM-LWFA mechanism dominates below 40 MeV, the highest-energy ($>60$ MeV) electrons gain most of their energy through DLA. By separating the simulated electric fields into modes, the DLA-dominated electrons are shown to lose significant energy to the longitudinal laser field from the tight focusing geometry, resulting in a more accurate measure of net DLA energy gain than previously possible.","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"131 ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91454911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Particle energy chirp is shown to be a useful instrument in the staging laser wake field acceleration directed to generation of high-quality dense electron beams. The chirp is a necessary tool to compensate non-uniformity of acceleration field in longitudinal direction and achieve essential reduction of energy dispersion. This is demonstrated via particle-in-cell simulations exploiting the splitting technique for plasma and beam electrons. Properly chosen beam chirps allow decrease in the energy dispersion of order of magnitude in every single stage during acceleration to the GeV energy range.
{"title":"Electron Beam Chirp Dexterity in Staging Laser Wake Field Acceleration","authors":"N. Pathak, A. Zhidkov, T. Hosokai","doi":"10.1063/5.0040897","DOIUrl":"https://doi.org/10.1063/5.0040897","url":null,"abstract":"Particle energy chirp is shown to be a useful instrument in the staging laser wake field acceleration directed to generation of high-quality dense electron beams. The chirp is a necessary tool to compensate non-uniformity of acceleration field in longitudinal direction and achieve essential reduction of energy dispersion. This is demonstrated via particle-in-cell simulations exploiting the splitting technique for plasma and beam electrons. Properly chosen beam chirps allow decrease in the energy dispersion of order of magnitude in every single stage during acceleration to the GeV energy range.","PeriodicalId":8461,"journal":{"name":"arXiv: Plasma Physics","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87589473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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