Thomson scattering diagnostic for the measurement of ion species fraction

Abstract

Simultaneous Thomson scattering measurements of collective electron-plasma and ion-acoustic fluctuations have been utilized to determine ion species fraction from laser produced CH plasmas. The CH2 foil is heated with 10 laser beams, 500 J per beam, at the Omega Laser facility. Thomson scattering measurements are made 4 mm from the foil surface using a 30 J 2ω probe laser with a 1 ns pulse length. Using a series of target shots the plasma evolution is measured from 2.5 ns to 9 ns after the rise of the heater beams. Measuring the electron density and temperature from the electron-plasma fluctuations constrains the fit of the two-ion species theoretical form factor for the ion feature such that the ion temperature, plasma flow velocity and ion species fraction are determined. The ion species fraction is determined to an accuracy of ±0.06 in species fraction.

Refractive Index Seen by a Probe Beam Interacting with a Laser-Plasma System

“…In principle, hydrogen -being lighter and having a higher charge to mass ratio -is expected to lead the plasma channel expansion, leaving a higher concentration of carbon in the interaction region. This effect has been observed previously using simultaneous electron and ion feature Thomson scattering in an expanding CH plasma [26,27]. However, assessing this quantitatively requires multi-ion-fluid simulations and is considered outside the scope of this study.…”

Resolving the bulk ion region of millimeter-wave collective Thomson scattering spectra at ASDEX Upgrade

“…Signatures of the ion cyclotron motion and ion Bernstein waves are of particular interest for their sensitivity to ion density ratios. This has been used for measurements of the isotopic composition [30][31][32][33][34] , and it could potentially be exploited for measurements of the fuel ion ratio in burning DT-plasmas 35,36 . However, accessing the detailed information contained in the bulk ion region of CTS spectra requires a frequency resolution beyond what is generally achieved with the cavity filters commonly used for fast-ion measurements.…”

Concept to diagnose mix with imaging x-ray Thomson scattering

“…Carbon foam is desired instead of a low-density plastic foam that may include hydrogen because recent Thomson scattering experiments have observed ion species variation in CH 2 foils. 17 Laser beams will irradiate the Be, driving a strong shock, which decays into a blast wave after the laser pulse ends. The blast wave crosses the perturbed interface and hydrodynamic instabilities, including the RM and RT instabilities, develop.…”