#### V.H. Hall-Chen J. Damba F.I. Parra Q.T. Pratt C.A. Michael S. Peng T.L. Rhodes N.A. Crocker J.C. Hillesheim R. Hong S Ni W.A. Peebles C.E. Png J. Ruiz Ruiz

We use the beam model of Doppler backscattering (DBS), which was previously derived from beam tracing and the reciprocity theorem, to shed light on mismatch attenuation. This attenuation of the backscattered signal occurs when the wavevector of the probe beam’s electric field is not in the plane perpendicular to the magnetic field. Correcting for…

Preprint#### M. R. Hardman F. I. Parra C. Chong T. Adkins M. S. Anastopoulos-Tzanis M. Barnes D. Dickinson J. F. Parisi H. Wilson

Ion-gyroradius-scale microinstabilities typically have a frequency comparable to the ion transit frequency.…

Preprint#### V. H. Hall-Chen F. I. Parra J. C. Hillesheim

We use beam tracing — implemented with a newly-written code, Scotty — and the reciprocity theorem to derive a model for the linear backscattered power of the Doppler Backscattering (DBS) diagnostic. Our model works for both the O-mode and X-mode in tokamak geometry (and certain regimes of stellarators). We present the analytical derivation of o…

Preprint#### J F Parisi F I Parra C M Roach C Giroud W Dorland D R Hatch M Barnes J C Hillesheim N Aiba J R Ball P G Ivanov

Local linear gyrokinetic simulations show that electron temperature gradient (ETG) instabilities are the fastest growing modes for kyρi >~ 0.1 in the steep gradient region for a JET pedestal discharge (92174) where the electron temperature gradient is steeper than the ion temperature gradient. Here, ky is the wa…

Preprint Published#### P G Ivanov A A Schekochihin W Dorland A R Field F I Parra

The saturated state of turbulence driven by the ion-temperature-gradient instability is investigated using a two-dimensional long-wavelength fluid model that describes the perturbed electrostatic potential and perturbed ion temperature in a magnetic field with constant curvature (a Z-pinch) and an equilibrium temperature gradient. Numerical simulat…

Preprint Published#### C. Giroud N. Aiba F. Militello C. Challis A. Chankin B. Lomanowski D. Hatch J. Harrison D. Frigione D. Moulton S. Pamela F. Parra J. Parisi I. Putzai D. Refy S. Saarelma C. Stavrou B. Tal E. Belonohy S. Brezinsek S. Buller C. Bowman E. Delabie A. Field J. Fontdecaba A. Huber A. Meigs S. Menmuir J. Simpson JET Contributors

Preprint Published

#### V.H. Hall-Chen F.I. Parra J.C. Hillesheim

The use of Doppler Backscattering (DBS) in spherical tokamaks is challenging since the magnetic pitch angle can be large (up to 35, compared to 15 in standard tokamaks like JET). Moreover the pitch angle varies both spatially and temporally. Hence, the probe beam is generally not perpendicular to the magnetic field. This misalignment, which affec…

Preprint Published#### V.H. Chen F.I. Parra J.C. Hillesheim

The Doppler Backscattering (DBS) microwave diagnostic enables the non-perturbative characterisation of density fluctuations and flows, both at the edge and the core of the plasma. The large magnetic pitch angle (up to 35 degrees, compared to 15 degrees in standard tokamaks like JET) and the time-varying magnetic equilibrium make the use of DBS in s…

Preprint Published#### M. R. Hardman M. Barnes C. M. Roach F. I. Parra

Multiple space and time scales arise in plasma turbulence in magnetic confinement fusion devices because of the smallness of the square root of the electron-to-ion mass ratio and the consequent disparity of the ion and electron thermal gyroradii and thermal speeds. Direct simulations of this turbulence that include both ion and electron space-ti…

Preprint Published#### Alessandro Geraldini Felix Parra Fulvio Militello

Using a kinetic model for the ions and adiabatic electrons, we solve a steady state, electron-repelling magnetic presheath in which a uniform magnetic field makes a small angle α

Preprint Published