arXiv subjects

T. Goodman

Publications and source records attributed to T. Goodman.

4 recordsLinked to original sources

arXiv2013

Power requirements for electron cyclotron current drive and ion cyclotron resonance heating for sawtooth control in ITER

13MW of electron cyclotron current drive (ECCD) power deposited inside the q = 1 surface is likely to reduce the sawtooth period in ITER baseline scenario below the level empirically predicted to trigger neo-classical tearing modes (NTMs). However, since the ECCD control scheme is solely predicated upon changing the local magnetic shear, it is prudent to plan to use a complementary scheme which directly decreases the potential energy of the kink mode in order to reduce the sawtooth period. In the event that the natural sawtooth period is longer than expected, due to enhanced alpha particle stabilisation for instance, this ancillary sawtooth control can be provided from > 10MW of ion cyclotron resonance heating (ICRH) power with a resonance just inside the q = 1 surface. Both ECCD and ICRH control schemes would benefit greatly from active feedback of the deposition with respect to the rational surface. If the q = 1 surface can be maintained closer to the magnetic axis, the efficacy of ECCD and ICRH schemes significantly increases, the negative effect on the fusion gain is reduced, and off-axis negative-ion neutral beam injection (NNBI) can also be considered for sawtooth control. Consequently, schemes to reduce the q = 1 radius are highly desirable, such as early heating to delay the current penetration and, of course, active sawtooth destabilisation to mediate small frequent sawteeth and retain a small q = 1 radius.

physics.plasm-ph↗

arXiv2008

Test of Particle-Assisted Tunneling for Strongly Interacting Fermions in an Optical Superlattice

Fermions in an optical lattice near a wide Feshbach resonance are expected to be described by an effective Hamiltonian of the general Hubbard model with particle-assisted tunneling rates resulting from the strong atomic interaction [Phys. Rev. Lett. 95, 243202 (2005)]. Here, we propose a scheme to unambiguously test the predictions of this effective Hamiltonian through manipulation of ultracold atoms in an inhomogeneous optical superlattice. The structure of the low-energy Hilbert space as well as the particle assisted tunneling rates can be inferred from measurements of the time-of-flight images.

cond-mat.other↗

arXiv2006

States of fermionic atoms in an optical superlattice across a Feshbach resonance

We investigate states of fermionic atoms across a broad Feshbach resonance in an optical superlattice which allows interaction only among a small number of lattice sites. The states are in general described by superpositions of atomic resonating valence bonds and dressed molecules. As one scans the magnetic field, level crossing is found between states with different symmetry properties, which may correspond to a quantum phase transition in the many-body case.

cond-mat.other↗

arXiv2004

Roughness of a Tilted Anharmonic String at Depinning

We consider the discretized model of a driven string with an anharmonic elastic energy, in a two dimensional random potential, as introduced by Rosso and Krauth. Using finite size scaling, we numerically compute the roughness of the string in a uniform applied force at the critical depinning threshold. By considering a string with a net average tilt, we demonstrate that the anharmonic elastic energy crosses the model over to the quenched KPZ universality class, in agreement with recent theoretical predictions.

cond-mat.stat-mech↗