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We demonstrate that aligned carbon-nanotube arrays are efficient transporters of laser-generated mega-ampere electron currents over distances as large as a millimeter. A direct polarimetric measurement of the temporal and the spatial evolution of the megagauss magnetic fields (as high as 120 MG) at the target rear at an intensity of (10(18)-10(19)) W/cm2 was corroborated by the rear-side hot electron spectra. Simulations show that such high magnetic flux densities can only be generated by a very well collimated fast electron bunch.
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http://dx.doi.org/10.1103/PhysRevLett.108.235005 | DOI Listing |
Rev Sci Instrum
August 2024
Culham Centre for Fusion Energy, UKAEA, Culham, United Kingdom.
Validated and accurate edge profiles (temperature, density, etc.) are vitally important to the Mega Ampere Spherical Tokamak Upgrade (MAST-U) divertor and confinement effort. Density profile reflectometry has the potential to significantly add to the measurement capabilities currently available on MAST-U (e.
View Article and Find Full Text PDFPhys Rev E
October 2023
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Benign termination of mega-ampere (MA) level runaway current has been convincingly demonstrated in recent JET and DIII-D experiments, establishing it as a leading candidate for runaway mitigation on ITER. This comes in the form of a runaway flush by parallel streaming loss along stochastic magnetic field lines formed by global magnetohydrodynamic instabilities, which are found to correlate with a low-Z injection that purges the high-Z impurities from a post-thermal-quench plasma. Here, we show the competing physics that govern the postflush reconstitution of the runaway current in an ITER-like reactor where significantly higher current is expected.
View Article and Find Full Text PDFRev Sci Instrum
October 2023
United Kingdom Atomic Energy Authority, Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom.
A detailed description of the Langmuir probe system on Mega Ampere Spherical Tokamak Upgrade is presented. The system features 850 tile-embedded probes and 40 bespoke electronic modules that each have the capability to drive and acquire data from up to 16 probes in a time-multiplexed manner. The system provides spatiotemporal-resolved measurements (1 cm and ∼1 ms, respectively) in the divertor region of ion saturation current, electron temperature, and floating potential.
View Article and Find Full Text PDFPhys Rev Lett
December 2021
Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology, Center for Advanced Material Diagnostic Technology, and College of Engineering Physics, Shenzhen Technology University, Shenzhen 518118, People's Republic of China.
Transport of high-current relativistic electron beams in dense plasmas is of interest in many areas of research. However, so far the mechanism of such beam-plasma interaction is still not well understood due to the appearance of small time- and space-scale effects. Here we identify a new regime of electron beam transport in solid-density plasma, where kinetic effects that develop on small time and space scales play a dominant role.
View Article and Find Full Text PDFRev Sci Instrum
January 2019
Central Laser Facility, Rutherford Appleton Laboratory, Oxfordshire QX11 0QX, United Kingdom.
Optical Kerr gating technique has been employed to investigate the life history of relativistic electrons in solids by temporally gating their Cherenkov emission. Mega-ampere currents of relativistic electrons are created during ultra-intense (2 × 10 W/cm) laser-solid interactions. In order to measure the lifetime of these relativistic electrons in solids, we temporally gate their Cherenkov emission using an optical Kerr gate (OKG).
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