Plasma Physics and Fusion Energy Research Paddy Mc Carthy, Physics Department, UCC, 1/11/2011 Research Group: Plasma Data Analysis Group: PhD Students: MSc Students: P. J. Mc Carthy (Group Leader) R. Armstrong (Visiting Researcher) Diarmuid Curran Mike Dunne (TCD graduate!) Tom O Gorman Brendan Cahill Shane O Mahony Funders: Euratom, Max Planck Institut für Plasmaphysik, Munich TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Lecture Outline: Plasma Overview Fusion Energy and Tokamaks How the Tokamak overcomes particle drift in a closed axisymmetric system Research topics in UCC Fusion in Europe and further afield TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
What is a plasma? Plasmas are conductive assemblies of charged particles, neutrals and fields that exhibit collective effects, carry electrical currents and generate magnetic fields. TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Why are we interested in! Fusion Energy plasmas?! Potential source of safe, clean, and abundant energy.! Astrophysics! Understanding plasmas helps us understand stars and stellar evolution.! Plasma Applications! Plasmas can be used to build computer chips and to clean up toxic waste. TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011 per nucleon
!" Fission is easiest at low energies; cross-section is maximum here!" Fusion is vanisingly unlikely at low energies; cross-section is miniscule TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Puzzle: T = 1keV at centre of sun. Proton-Proton Coloumb Barrier height: How can 1 kev protons overcome a 1 MeV barrier? Answer: (Gamow, 1930) Quantum Tunnelling TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Relevant Fusion Reactions in the Laboratory 1D 2 + 1 D 2 2 He3 (0.82 MeV) + n (2.5MeV) 1T 3 (1 MeV) + p (3 MeV) 1 D2 + 2 He 3 2 He4 (3.6 MeV) + p (14.7MeV) 1D 2 + 1 T 3 2He 4 (3.5 MeV) + n (14.1MeV) 3 Li6 (7.4%) + n 2 He4 + 1 T3 + 4.8 MeV 3 Li7 (92.6%) + n 2 He4 + 1 T3 + n 2.8 MeV TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011 " 3#10 20 s m $3
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Fusion Energy - Advantages It promises a large-scale energy source with basic fuels which are abundant and available everywhere; Very low global impact on the environment no CO2 greenhouse gas emissions; Day-to-day-operation of a fusion power station would not require the transport of radio-active materials;power stations would be inherently safe, with no possibility of meltdown or runaway reactions ; There is no long-lasting radioactive waste to create a burden on future generations; While development and capital investment costs are high, the marginal cost of supply is expected to be negligible compared to that of energy derived from fossil fuels. TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Fusion Energy - Disadvantages Fusion reaction is difficult to initiate High temperatures (millions of degrees) in a clean, high vacuum environment are required; Technically complex and high capital cost reactors are needed More research and development needed to bring concept to fruition The physics is well advanced, but but technological and material challenges requiring a multi-decade sustained effort must be overcome. TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
!! Donut shape Unlike mirror, no end losses because the field lines go around and close on themselves! But major problem with particle drift if magnetic field lines are circular in form. Tokamak TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011 Schematic picture of the tokamak
Particle Drift Recap General expression for the drift velocity of the guiding centres of particles of charge q in a uniform B field and sub ject to an additional force F: Gyration Grad-B and curvature drifts Parallel motion Pololarization drift ExB drift TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Insight into drift motion Trajectories of a 75 ev electron in a B! field of 1 mt and E # fields of 0 (top), 150 V/m (middle) and 1500 V/m (bottom). TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011 Left/right half-orbits are symmetric, but updown half-orbits are strongly asymmetric => particle travels more to right than to left.
Toroidal curvature* Toroidal magnetic field coils! The toroidal magnetic field follows form! And therefore varies with major radius R as Top down view of the tokamak TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011 Next 5 slides based on Warwick University Physics of Fusion Power course
Toroidal curvature! The toroidal magnetic field has a gradient! Which leads to a combined curvature and!b drift in the vertical direction: From TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011 we get Note that the sign of the drift depends on the sign of the charge q ˆ R " ˆ Z ˆ 0 B 0 # B R 0 0
Toroidal curvature! The drift!!! Leads to charge separation Build up of an electric field (calculate through the balance with polarization) And then to an ExB velocity Poloidal cut of the tokamak. TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Toroidal curvature has its price! The ExB velocity! Is directed outward and will move the plasma on the wall in a short timescale (µs) Poloidal cut of the tokamak. TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Remedy : a plasma current! A toroidal current in the plasma will generate a poloidal field (field lines short way round)! Combined toroidal and poloidal fields make helical field lines so that all particle orbits sample top/inside/bottom/outside regions.! Vertical!B drift still present, but helical field lines short out any tendency towards charge separation by accelerating electrons along the field line to maintain charge neutrality.! Charge separation no longer occurs and particles are well confined. The field lines wind around helically. TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Blick in das Plasmagefäß von ASDEX Upgrade
Cross-section of ASDEX Upgrade tokamak showing toroidal and poloidal field coils TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
PDAG List of Collaborative Projects & Research Topics ASDEX Upgrade Project CLISTE Interpretive Equilibrium Code Function Parameterization MHD activity analysis to improve q profile identification Thomson Scattering analysis: ECE comparison Wendelstein 7-X Project Fast recovery of W7-X equilibria Transport and spectroscopy experiments using a DP machine ITER diagnostic design studies: Group involvement in Integrated Tokamak Modelling Taskforce TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
100 kpa Fluid Pressure v. minor radius Z! R jxb -!p Fluid pressure gradient (outward force/v) balances inward pinch force/v: jxb =!p Axisymmetry of tokamak simplifies jxb =!p: TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011 Grad-Shafranov equation: scalar, weakly nonlinear PDE
Interpretive Equilibria: Finding an equilibium to match data! Regularize source profiles: choose a functional form with a reasonable number of free parameters! Flexible form very desirable. Good choice: Cubic Splines! Initialize to a default current distribution (centred in vessel)! (i) Solve Poisson-like linear PDE for trial Jtor (R,Z) by a least squares best fit to input experimental data which must be expressible as a linear function of the free parameters! (ii) Construct updated flux function and find new plasma boundary (we are solving a free boundary problem)! (iii) Construct updated Jtor (R,Z) using updated flux surface topology and free parameter values.! Iterate steps (i)-(iii) until a convergence criterion is met Interpretive Tokamak Equilibrium at IPP Garching: CLISTE TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Physics & Astronomy Society, UCC TCD Graduate 31/1/2006 Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Equilibrium Magnetics only 12-knot spline model (28 fit parameters) flux loops B probes MSE Ped.Pres. J B neo " n e dl I SOL E18 ROE 13kA #17151, 3.850s TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Magnetics & Q=1 & DCN+LID & ROE & MSE & YAR fit flux loops B probes MSE Ped.Pres. J B neo " n e dl I SOL E18 ROE 0.5 ka #17151, 3.850s TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
The Wendelstein 7-X Stellarator (under construction in Greifswald) TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Physics & Astronomy Society, UCC 31/1/2006
Physics & Astronomy Society, UCC 31/1/2006
Physics & Astronomy Society, UCC 31/1/2006
Physics & Astronomy Society, UCC 31/1/2006
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
n e =1.1e17 m -3 T e =0.6eV P He =9.6e-3mb
n e =1.5e17 m -3 T e =0.4eV P He =1.2e-2mb
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
Four decades of progress in achieving confinement times* leading to scientific breakeven * " E = (3/2) p dv # Heating Power Physics & Astronomy Society, UCC 31/1/2006
The Future of Fusion Energy Research: ITER" ITER, the International Tokamak Experimental Reactor is being constructed at Cadarache, near Aix en Provence, on a 10 year timeframe for c. #7.5bn and will operate for c. 25 y at projected running costs of #7.5bn. " SSP TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011
R. Aymar, Nobel Symposium Stockholm, 2005
Summary Fusion offers one of the greatest hopes for a long-term solution to the problem of a viable, environmentally friendly source for the world s future energy needs. Fusion research is carried out within the framework of plasma physics, a key current area of both fundamental and applied research. At UCC, we participate (both on and off-campus) in experiments at major fusion labs in Germany and the U.K. as well as in ITER design activities. TCD Graduate Plasma Physics Module PY5012 Guest Lecture 1 st Nov 2011