Plasma Physics and Controlled Fusion最新文献

{"title":"Reversed-direction 2-point modelling applied to divertor conditions in DIII-D *","authors":"J H Nichols, P C Stangeby, A G McLean, J M Canik, A L Moser, M W Shafer, H Q Wang","doi":"10.1088/1361-6587/ad2b90","DOIUrl":"https://doi.org/10.1088/1361-6587/ad2b90","url":null,"abstract":"A predictive form of the extended 2-point model known as the ‘reverse 2-point model’, Rev2PM, is applied to a range of detachment levels in the open lower divertor of DIII-D, showing that the experimentally measured electron temperature (<italic toggle=\"yes\">T_e\u0000</italic>) and pressure (<italic toggle=\"yes\">p_e\u0000</italic>) at the divertor entrance can be calculated within 50% from target measurements, if and only if <italic toggle=\"yes\">a posteriori</italic> corrections for convective heat flux are included in the model. Unlike the standard 2-point model, the Rev2PM calculates upstream scrape-off layer (SOL) quantities (such as separatrix <italic toggle=\"yes\">T_e\u0000</italic> and <italic toggle=\"yes\">p_e\u0000</italic>) from target conditions (such as <italic toggle=\"yes\">T_e\u0000</italic> and parallel heat flux), with volumetric power and momentum losses depending solely on target <italic toggle=\"yes\">T_e\u0000</italic>. The Rev2PM is tested against a database of DIII-D inter-ELM divertor Thomson scattering measurements, built from a series of 6 MW, 1.3 MA, LSN H-mode discharges with varied main ion density, drift direction, and nitrogen puffing rate. Measured target <italic toggle=\"yes\">T_e\u0000</italic> ranged from 0.4–25 eV over this database, and upstream <italic toggle=\"yes\">T_e\u0000</italic> ranged from 5–60 eV. Poor agreement is found between upstream measurements and Rev2PM calculations that assume purely conductive parallel heat transport. However, introducing <italic toggle=\"yes\">a posteriori</italic> corrections to account for convective heat transport brings the Rev2PM calculations within 50% of the measured upstream values across the dataset. These corrections imply that up to 99% of the parallel heat flux is carried by convection in detached conditions in the DIII-D open lower divertor, though further work is required to assess any potential dependencies on device size or divertor closure.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"44 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140315205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulations of tokamak edge plasma turbulent fluctuations based on a minimal 3D model","authors":"M V Umansky, B I Cohen, I Joseph","doi":"10.1088/1361-6587/ad2b91","DOIUrl":"https://doi.org/10.1088/1361-6587/ad2b91","url":null,"abstract":"A new simulation model for tokamak boundary plasma, SOLT3D, is implemented in the BOUT++ framework (Dudson <italic toggle=\"yes\">et al</italic> 2009 <italic toggle=\"yes\">Comput. Phys. Commun.</italic>\u0000<bold>180</bold> 1467). The simulation model includes a set of dynamic equations describing collisional boundary plasma and neutral gas in the tokamak scrape-off layer and divertor region. The model is verified against standard linear plasma instabilities and available nonlinear results. For L-mode like conditions, SOLT3D reproduces characteristics of boundary plasma turbulent fluctuations that are similar to published experimental data, in terms of the amplitude and spatial dependence of the fluctuations. It also reproduces realistic plasma fluxes on material surfaces and expected Bohm-like effective radial transport. Plasma fluctuations inferred from the simulations imply inevitably a significant level of intrinsic ‘noise’ for axisymmetric tokamak plasma transport modeling, introducing errors on the order of unity. In particular, the toroidally averaged atomic rates below 5–10 eV are strongly modified by turbulent plasma fluctuations, which should significantly affect the standard axisymmetric modeling of the tokamak edge plasma and divertor.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"54 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140315356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Testing validity of 1D models for impurity fraction scaling for divertor detachment with EDGE2D-EIRENE","authors":"A V Chankin, G Corrigan, A Huber, JET Contributors4","doi":"10.1088/1361-6587/ad2a83","DOIUrl":"https://doi.org/10.1088/1361-6587/ad2a83","url":null,"abstract":"Predictions of the Huber–Chankin (HC) scaling for the upstream impurity fraction were verified in a series of EDGE2D-EIRENE (‘code’) runs for highly radiating plasmas with nitrogen injection. The main quantity extracted from the code was poloidally averaged, from X-point to X-point, separatrix impurity fraction <italic toggle=\"yes\">c_Z\u0000</italic> in the main scrape-off layer (SOL). Variation of the main working gas (H, D and T) revealed a qualitative agreement between the model and code results owing to the very large isotope difference in the predicted <italic toggle=\"yes\">c_Z\u0000</italic> values caused primarily by the inverse isotope mass dependence of the H-mode power threshold assumed in the HC model and implemented in the code. At the same time, the variation of the toroidal field and safety factor in deuterium cases yielded no correlation between the model predictions and code results. The code showed much higher local impurity fractions (<italic toggle=\"yes\">f_Z\u0000</italic>) in the divertor compared to the main SOL, as well as large case-to-case variations in the divertor to the main SOL ratio of impurity fractions. The analysis of code results has wide-ranging consequences not only for the HC model, but also for other similar 1D models which use simple geometry ignoring strong neutral recycling in the divertor/ Different topology makes plasma parameters in the divertor and main SOL very different, resulting in different impurity charge state composition. Missing mechanisms in 1D codes (e.g. friction and thermo-forces exerted on impurity ions by main working gas ions) lead to impurity density redistribution. Neglecting all above factors, 1D models assume a constant impurity fraction along field lines.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"71 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140315204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"QScatter: numerical framework for fast prediction of particle distributions in electron-laser scattering","authors":"Óscar Amaro, Marija Vranic","doi":"10.1088/1361-6587/ad2975","DOIUrl":"https://doi.org/10.1088/1361-6587/ad2975","url":null,"abstract":"The new generation of multi-PetaWatt laser facilities will allow tests of strong field quantum electrodynamics (QED), as well as provide an opportunity for novel photon and lepton sources. The first experiments are planned to study the (nearly) head-on scattering of intense, focused laser pulses with either relativistic electron beams or high-energy photon sources. In this work, we present a numerical framework that can provide fast predictions of the asymptotic particle and photon distributions after the scattering. The method detailed in this manuscript can include multiple features such as spatial and temporal misalignment between the laser and the scattering beam, broadband electron beams, and beam divergence. The expected mean energy, energy spread, divergence or other observables are calculated by combining an analytical description and numerical integration. This method can provide results within minutes on a personal computer, which would otherwise require full-scale 3D QED-PIC simulations using thousands of cores. The model, which has been compiled into an open-source code <monospace>QScatter</monospace>, may be used to support the analysis of large-size data sets from high-repetition rate experiments, leveraging its speed for optimization or reconstruction of experimental parameters.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"19 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140010939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metal evaporation dynamics in electron cyclotron resonance ion sources: plasma role in the atom diffusion, ionisation, and transport","authors":"A Pidatella, D Mascali, A Galatà, B Mishra, E Naselli, L Celona, R Lang, F Maimone, G S Mauro, D Santonocito, G Torrisi","doi":"10.1088/1361-6587/ad2428","DOIUrl":"https://doi.org/10.1088/1361-6587/ad2428","url":null,"abstract":"We present a numerical study of metals dynamics evaporated through resistively heated ovens in electron cyclotron resonance (ECR) plasma traps, used as metal ion beam injectors for accelerators and multi-disciplinary research in plasma physics. We use complementary numerical methods to perform calculations in the framework of the PANDORA trap. The diffusion and deposition of metal vapours at the plasma chamber’s surface are explored under molecular flow regime, with stationary and time-dependent particle fluid calculations via COMSOL Multiphysics®. The ionisation of vapours is then studied in the strongly energised ECR plasma. We have developed a Monte Carlo (MC) code to simulate the in-plasma metal ions’ dynamics, coupled to particle-in-cell simulations of the plasma physics in the trap. The presence of strongly inhomogeneous plasmas leads to charge-exchange and electron-impact ionisations of metals, in turn affecting the deposition rate/pattern of the metal on the walls of the trap. Results show how vapours dynamics depends both on evaporated metals and the plasma target. The ¹³⁴Cs, ¹⁷⁶Lu, and ⁴⁸Ca isotopes were investigated, the first two being radioisotopes interesting for the PANDORA project, and the third as one of the most required rare isotope by the nuclear physics community. We present an application of the study: MC computing the <italic toggle=\"yes\">γ</italic> activity due to the deposited radioactive neutral nuclei during the measurement time, we quantitatively estimated the overall <italic toggle=\"yes\">γ</italic>-detection system’s efficiency using GEANT4, including the poisoning <italic toggle=\"yes\">γ</italic>-signal from the walls of the trap, relevant for the <italic toggle=\"yes\">γ</italic>-tagging of short-lived nuclei’s decay rate in the PANDORA experiment. This work can give valuable support both to the evaporation technique and plasma source optimisation, for improving the metal ion beam production, avoiding huge deposit/waste of metals known to affect the long-term source stability, as well as for radio-safety aspects and reducing material waste in case of rare isotopes.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"64 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140010938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reduction of fast ion drag in the presence of ‘hollow’ non-Maxwellian electron distributions","authors":"A P L Robinson","doi":"10.1088/1361-6587/ad238f","DOIUrl":"https://doi.org/10.1088/1361-6587/ad238f","url":null,"abstract":"It is argued that the electronic stopping power in a plasma should be expected to exhibit significant differences in the presence of effects that shift the electron distribution function away from a Maxwellian. This is potentially important for nuclear reactions produced by laser-driven ion beams, where non-Maxwellian effects may have to be considered. We have calculated the electronic stopping power for a number of model distributions. Importantly, comparisons with the Maxwellian are done under the condition of energy density parity. ‘Hollow’ electron distribution functions (e.g. <inline-formula>\u0000<tex-math><?CDATA $f propto v^nf_{text{max}}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi>f</mml:mi><mml:mo>∝</mml:mo><mml:msup><mml:mi>v</mml:mi><mml:mi>n</mml:mi></mml:msup><mml:msub><mml:mi>f</mml:mi><mml:mrow><mml:mtext>max</mml:mtext></mml:mrow></mml:msub></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad238fieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>) could be expected to show a reduced stopping power (when <inline-formula>\u0000<tex-math><?CDATA $v_mathrm{i}/v_mathrm{t} lt 1$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msub><mml:mi>v</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">i</mml:mi></mml:mrow></mml:msub><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:msub><mml:mi>v</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">t</mml:mi></mml:mrow></mml:msub><mml:mo>&lt;</mml:mo><mml:mn>1</mml:mn></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad238fieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>). We show that this is indeed the case and that the difference can become a factor of 70. The super-Gaussian electron distribution function, on the other hand, will always show a higher stopping power than the Maxwellian for orders greater than 2.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"5 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140011042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parametric analysis of electron beam quality in laser wakefield acceleration based on the truncated ionization injection mechanism","authors":"Srimanta Maity, Alamgir Mondal, Eugene Vishnyakov, Alexander Molodozhentsev","doi":"10.1088/1361-6587/ad238e","DOIUrl":"https://doi.org/10.1088/1361-6587/ad238e","url":null,"abstract":"Laser wakefield acceleration (LWFA) in a gas cell target separating injection and acceleration section has been investigated to produce high-quality electron beams. A detailed study has been performed on controlling the quality of accelerated electron beams using a combination of truncated ionization and density downramp injection mechanisms. For this purpose, extensive two-dimensional particle-in-cell simulations have been carried out considering a gas cell target consisting of a hydrogen and nitrogen mixture in the first part and pure hydrogen in the second part. Such a configuration can be realized experimentally using a specially designed capillary setup. Using the parameters already available in the existing experimental setups, we show the generation of an electron beam with a peak energy of 500–600 MeV, relative energy spread less than <inline-formula>\u0000<tex-math><?CDATA $5%$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mn>5</mml:mn><mml:mi mathvariant=\"normal\">%</mml:mi></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad238eieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>, normalized beam emittance around 1.5 mm-mrad, and beam charge of 2–5 pC/<italic toggle=\"yes\">µ</italic>m. Our study reveals that the quality of the accelerated electron beam can be independently controlled and manipulated through the beam loading effect by tuning the parameters, e.g. laser focusing position, nitrogen concentration, and gas target profile. These simulation results will be useful for future experimental campaigns on LWFA, particularly at ELI Beamlines.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"16 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139770639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling of high-field-side high-density regime in the Globus-M2 tokamak","authors":"K Dolgova, E Vekshina, V Rozhansky","doi":"10.1088/1361-6587/ad1b89","DOIUrl":"https://doi.org/10.1088/1361-6587/ad1b89","url":null,"abstract":"Formation of a high-field-side high-density (HFSHD) regime and the role of the high-field-side (HFS) poloidal electric field in the scrape-off layer of the spherical tokamak Globus-M2 are analyzed using SOLPS-ITER edge plasma simulations. The dependence of the HFS poloidal electric field sign and, consequently, radial drift fluxes on the discharge density is discussed. It is demonstrated that the HFS poloidal electric field is the key element in the formation of a HFSHD regime in the Globus-M2 tokamak as in ASDEX Upgrade. It is demonstrated that the physics of HFSHD formation in a small spherical tokamak is similar to that suggested by Kaveeva <italic toggle=\"yes\">et al</italic> (2009 <italic toggle=\"yes\">36th EPS Conf. on Plasma Physics</italic>) and is in line with experimental observations and modeling, performed later on ASDEX Upgrade.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"3 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139509547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The magnetic gradient scale length explains why certain plasmas require close external magnetic coils","authors":"John Kappel, Matt Landreman, Dhairya Malhotra","doi":"10.1088/1361-6587/ad1a3e","DOIUrl":"https://doi.org/10.1088/1361-6587/ad1a3e","url":null,"abstract":"The separation between the last closed flux surface of a plasma and the external coils that magnetically confine it is a limiting factor in the construction of fusion-capable plasma devices. This plasma-coil separation must be large enough so that components such as a breeding blanket and neutron shielding can fit between the plasma and the coils. Plasma-coil separation affects reactor size, engineering complexity, and particle loss due to field ripple. For some plasmas it can be difficult to produce the desired flux surface shaping with distant coils, and for other plasmas it is infeasible altogether. Here, we seek to understand the underlying physics that limits plasma-coil separation and explain why some configurations require close external coils. In this paper, we explore the hypothesis that the limiting plasma-coil separation is set by the shortest scale length of the magnetic field as expressed by the <inline-formula>\u0000<tex-math><?CDATA $nabla mathbf{B}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi mathvariant=\"normal\">∇</mml:mi><mml:mrow><mml:mi mathvariant=\"bold\">B</mml:mi></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad1a3eieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> tensor. We tested this hypothesis on a database of <inline-formula>\u0000<tex-math><?CDATA $gt$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mo>&gt;</mml:mo></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad1a3eieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>40 stellarator and tokamak configurations. Within this database, the coil-to-plasma distance compared to the minor radius varies by over an order of magnitude. The magnetic scale length is well correlated to the coil-to-plasma distance of actual coil designs generated using the <monospace>REGCOIL</monospace> method (Landreman 2017 <italic toggle=\"yes\">Nucl. Fusion</italic>\u0000<bold>57</bold> 046003). Additionally, this correlation reveals a general trend that larger plasma-coil separation is possible with a small number of field periods.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"38 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139509546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Generation of meter-scale hydrogen plasmas and efficient, pump-depletion-limited wakefield excitation using 10 GeV electron bunches","authors":"C Zhang, D Storey, P San Miguel Claveria, Z Nie, K A Marsh, M Hogan, W B Mori, E Adli, W An, R Ariniello, G J Cao, C Clarke, S Corde, T Dalichaouch, C E Doss, C Emma, H Ekerfelt, E Gerstmayr, S Gessner, C Hansel, A Knetsch, V Lee, F Li, M Litos, B O’Shea, G White, G Yocky, V Zakharova, C Joshi","doi":"10.1088/1361-6587/ad1ae4","DOIUrl":"https://doi.org/10.1088/1361-6587/ad1ae4","url":null,"abstract":"High repetition rates and efficient energy transfer to the accelerating beam are important for a future linear collider based on the beam-driven plasma wakefield acceleration scheme (PWFA-LC). This paper reports the first results from the Plasma Wakefield Acceleration Collaboration (E300) that are beginning to address both of these issues using the recently commissioned FACET-II facility at SLAC national accelerator laboratory. We have generated meter-scale hydrogen plasmas using time-structured 10 GeV electron bunches from FACET-II, which hold the promise of dramatically increasing the repetition rate of PWFA by rapidly replenishing the gas between each shot compared to the hitherto used lithium plasmas that operate at 1–10 Hz. Furthermore, we have excited wakes in such plasmas that are suitable for high gradient particle acceleration with high drive-bunch to wake energy transfer efficiency- a first step in achieving a high overall energy transfer efficiency. We have done this by using time-structured electron drive bunches that typically have one or more ultra-high current (<inline-formula>\u0000<tex-math><?CDATA $gt$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mo>&gt;</mml:mo></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad1ae4ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>30 kA) femtosecond spike(s) superimposed on a longer (∼0.4 ps) lower current (<inline-formula>\u0000<tex-math><?CDATA $lt$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mo>&lt;</mml:mo></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad1ae4ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>10 kA) bunch structure. The first spike effectively field-ionizes the gas and produces a meter-scale (30–160 cm) plasma, whereas the subsequent beam charge creates a wake. The length and amplitude of the wake depends on the longitudinal current profile of the bunch and plasma density. We find that the onset of pump depletion, when some of the drive beam electrons are nearly fully depleted of their energy, occurs for hydrogen pressure <inline-formula>\u0000<tex-math><?CDATA $unicode{x2A7E}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mtext>⩾</mml:mtext></mml:math>\u0000<inline-graphic xlink:href=\"ppcfad1ae4ieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>1.5 Torr. We also show that some electrons in the rear of the bunch can gain several GeV energies from the wake. These results are reproduced by particle-in-cell simulations using the QPAD code. At a pressure of ∼2 Torr, simulation results and experimental data show that the beam transfers about 60% of its energy to the wake.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":"251 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139509544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}