OXFORD PLASMA THEORY GROUP

PLASMA SEMINARS AND GROUP MEETINGS

The style of the seminars will be informal/chaotic/interactive, following the established tradition. The format of the presentations can be a tutorial on a topic of interest, a report on just completed/ongoing/just starting/potentially interesting research projects, a literature review, a lecture by a passing visitor or anything else worthwhile that anyone cares to suggest. The speakers will be interrupted freely and asked to defend themselves. For background reading, only the most relevant or the most recent references are posted; please follow the paper trail from there. The schedule is subject to change on short notice, but what you see posted here is always up to date; the seminars are also announced via the department's seminar server (group meetings are not). Please email Alex Schekochihin if you would like to receive email updates on these seminars. "Plasma group meetings" will discuss current affairs (ongoing projects, new litearture etc.) as well as feature some presentations that are even more informal than seminars. They are open to all members of the Oxford Plasma Theory Group. While some expected contributions are pre-announced, everything is TBC and people wishing their work to be discussed can volunteer contributions without prior notice. Unlike for the seminars, there will not be full-spam-list email reminders of the group meetings. The seminars and group meetings are organised by Michael Barnes, Felix Parra and Alex Schekochihin, please contact them with any queries or if you wish to present something.

Past seminar database:
Autumn 2007; Winter-Spring 2008; Summer 2008; Autumn 2008; HT 2009; TT 2009; Summer 2009; MT 2009; HT 2009; TT 2010; Summer 2010; MT 2010; HT 2011; TT 2011; Summer 2011; MT 2011; HT 2012; TT 2012; Summer 2012; MT 2012; HT 2013; TT & Summer 2013; MT 2013; HT 2014; TT & Summer 2014; MT 2014; HT 2015; TT & Summer 2015; MT 2015; HT 2016; TT & Summer 2016; Autumn/MT 2016; HT 2017; TT & Summer 2017; Autumn/MT 2017;

  Hilary Term of 2018

The seminars/group meetings will be on Thursday at 11:30 in 501 DWB, except where indicated otherwise below.
Note also the ALP Seminars (here is a list of all Physics seminars)

If you know exactly what you are going to do, what is the point of doing it? Pablo Picasso

Every line in your calculations ends with "=0". You are not making much progress!
Kate Hammett
We don't do the calculation because we don't know the answer, we do it because we have a conscience. Bryan Taylor
Let's change the resolution on the Unknown. Gabe Plunk
Let me put it differently: suppose we had a reactor... Per Helander
Working together takes more than one person. Bill Dorland
We can't do ultraviolence to that square bracket. Ian Abel
Field lines are forever. Bryan Taylor
This is not really an ill-posed problem, this is not a problem at all. Paul Dellar
I am just doing mathematics at the moment, but it is mathematics that has some point. Bryan Taylor
The equivalent of God in MAST is MHD, which is global and all powerful. Anthony Field
I've got a fishbone coming up. Tim Horbury
We have crossed all the i's and dotted all the t's. Job's a good'un. Ian Abel
Let us not jump in front of the bandwagon! Anonymous
It's not the triviality, it's the emptiness of it that bothers me. Bryan Taylor
This is a very inefficient way of achieving nothing. François Rincon
We Hankel all the way in and then Hankel all the way out. Joseph Parker
For the sake of fairness, let me mention that some people have objections to this, none of which are particularly valid. Chris Chen
It is better to be roughly right than precisely wrong. Maynard Keynes 

Yes, Steve, you have always known what we have only just figured out. Alfred Mallet
This is more or less right. Perhaps less. Alfred Mallet
You go ahead with your argument. I'll think. Steve Cowley
Too simple? At the end of my talk, you will beg for simplicity! Andrey Beresnyak
The point is not the point! Anonymous
This is why I am presenting this here and nowhere else: nothing is solved! Ian Abel
This calculation is not intellectual masturbation: there's no orgasm. Anonymous
There are many big Buts here... I like big Buts. Anonymous
Previous studies of this problem have been either unsatisfactory or limited in scope.---What  is the difference between these?---This means either wrong or irrelevant.
Anatoly Spitkovsky, Michael Medvedev and Steve Cowley (in conversation)
I don't give a damn about astrophysics, explain to me what is going on. Anatoly Spitkovsky
Have you subtracted the baby with the bathwater? Steve Balbus
 
This is not rigour, unless you mean rigor mortis. Ian Abel
I wouldn't say these are theoretical arguments... Let's just call them arguments. François Rincon
You can never be too happy with the state of your closure. Amitava Bhattacharjee
For this plot, 1 is 6.--- Weeell, not even. Steve Cowley and Steve Balbus
Это качественное объяснение недостаточно качественное. Eugene Churazov
If you mean it seriously, this is actually a very good question. Minhyong Kim
[these quotes are mostly from Oxford plasma seminars and Vienna meetings]

Wk Date
Time
& place
Speaker & Topic
Background reading
Comings and goings
(incl. visitors in town)

Thu
Jan 4
No seminar
0
Thu
Jan 11
11:30
501
DWB
Plasma Seminar (organised by ALEX)
Adnane Osmane (Aalto, Finland) --- Electron phase-space holes in planetary radiation belts
ApJ 846, 83 (2017)
PRL 111, 235002 (2013)

Fri
Jan 12
9:30
Culham
Pease Rm
CCFE Science Meeting (organised by SARAH NEWTON)
Alex Schekochihin (Oxford) --- Two etudes on unexpected behaviour of drift-wave turbulence near stability threshold
I will discuss some recent results — numerical and experimental — on the nature of drift-wave turbulence in MAST, obtained in the doctoral theses of Ferdinand van Wyk [1,4], Michael J. Fox [2] and Greg Colyer [3]. At ion scales, in the presence of flow shear, we find numerically [1,4] a type of transition to turbulence that is new (as far as we know) in the tokamaks, but reminiscent of some fluid dynamical phenomena (e.g., pipe flows or accretion discs in astrophysics): close to threshold, the nonlinear saturated state and the associated anomalous heat transport are dominated by long-lived coherent structures, which drift across the domain, have finite amplitudes, but are not volume filling; as the system is taken away from the threshold into the more unstable regime, the number of these structures increases until they overlap and a more conventional chaotic state emerges. Such a transition has its roots in the subcritical nature of the turbulence in the presence of flow shear. It can be diagnosed in terms of the breaking of the statistical up-down symmetry of turbulence: this manifests itself in the form of tilted two-point correlation functions and skewed distributions of the fluctuating density field, found both in simulations and in BES-measured density fields in MAST [2]. The governing (order) parameter in the system is the distance from the threshold, rather than individual values of equilibrium gradients; the symmetries — and drift-wave/zonal-flow turbulence of conventional type — are restored away from the threshold. The experiment appears to lie just at the edge of this latter transition rather than at the exact stability threshold. At electron scales in MAST, the conventional streamer-dominated state of ETG turbulence turns out to be a long-time transient, during which an initially unimportant zonal component continues to grow slowly, eventually leading to a new saturated state dominated by zonal modes, rather similar to ITG turbulence [3]. In this regime, the heat flux turns out to be proportional to the collision rate, in approximate agreement with the experimentally observed collisionality scaling of the energy confinement in MAST. Our explanation of this effect is based on a model of ETG turbulence dominated by zonal–nonzonal interactions and on an analytically derived scaling of the zonal-mode damping rate with the electron–ion collisionality. These developments open some intriguing possibilities both for enterprising theoreticians tired of the V&V routine and for ingenious experimentalists interested in making use of tokamaks to probe transitions to turbulence in nonlinear plasma systems.
[1] JPP 82, 905820609 (2016)
[2] PPCF 59, 034002 (2017)
[3] PPCF 59, 055002 (2017)
[4] PPCF 59, 114003 (2017)
I
Thu
Jan 18.
11:30
TBA
Plasma Group Meeting (organised by MICHAEL)
Free discussion of current affairs: contributions welcome


II
Thu
Jan 25.
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
TBA


III
Thu
Feb 1.
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
TBA


IV
Thu
Feb 8.
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
Michele Romanelli (UKAEA) --- TBA/TBC


V
Thu
Feb 15.
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
TBA

Peter Catto
(MIT)
VI
Thu
Feb 22.
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
TBA

Peter Catto
(MIT)
VII
Thu
Mar 1
11:30
501
DWB
Plasma Group Meeting (organised by ALEX)
Alex Schekochihin & Yohei Kawazura --- Progress towards theory of ion vs. electron heating in plasma turbulence (TBC)
draft paper
from speaker
on request
Peter Catto
(MIT)
Fri
Mar 2
14:00
Culham
CCFE Student Seminar
Alex Schekochihin (Oxford) --- TBA

VIII
Thu
Mar 8
11:30
501
DWB
Plasma Seminar (organised by ALEX)
Angelo Limone (Siemens Industry Software Computational Dynamics Ltd Digital Factory, London) --- Simulating the plasma state for industrial applications
Plasma physicists traditionally focus their attention on astrophysics and nuclear fusion. However, a composite zoo of plasma applications does exist and---surprisingly---has even a certain economic impact. Thin semiconductor layers, for instance, used in our ubiquitous smartphones and displays are produced also via techniques that use the plasma state as catalyst. In circuit breakers of whichever voltage size the plasma state is something that has to be quenched, and quickly. Some other few applications of industrial plasmas will be described, in particular I will be discussing the tough challenges that the average engineer might have to tackle when trying to model plasma flows via numerical simulations and the problems that a Computational Fluid Dynamics software provider has to face in order to deliver a solver that can help the design engineer with realism and on an "industrially reasonable" timescale.

Angelo Limone
(Siemens)
9
Thu
Mar 15
11:30
501
DWB
Plasma Seminar (organised by MICHAEL)
Will Potter (Oxford Astro) --- Magnetisation and reconnection rates in jets



Thu
Mar 22
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
TBA



Tue
Mar 27
10:00
Culham
Special JET Seminar (organised by JON HILLESHEIM)
Troy Carter (UCLA) ---  Studies of ICRF physics using the Large Plasma Device
The Basic Plasma Science Facility (BaPSF) at UCLA is a US national user facility for studies of fundamental processes in magnetized plasmas. The centerpiece of the facility is the Large Plasma Device (LAPD), a 20m long, magnetized linear plasma device. This LAPD has been utilized to study a number of fundamental processes, including: dispersion and damping of kinetic and inertial Alfven waves, flux ropes and magnetic reconnection, three-wave interactions and parametric instabilities of Alfven waves, turbulence and transport and interactions of energetic ions and electrons with plasma waves. A brief overview of research using the facility will be given, followed by a more detailed discussion of research relevant to ICRF heating and current drive in fusion devices. Recent experiments in LAPD have studied high power (~200kW) fast wave excitation (f ∼ 2 − 10fci). Highlights of this work include documenting: the structure and scaling of RF sheaths, the formation of convective cells and associated density modification, and parasitic coupling to the slow mode in the low density plasma in front of the antenna [Martin, et al., PRL 119, 205002 (2017)].

Troy Carter
(UCLA)
Thu
Mar 29
11:30
Dobson
Room
Plasma Seminar (organised by ALEX)
Archie Bott (Oxford ALP) --- 1001 plasma instabilities at high beta (TBC)
preprint
from author
on request

Thu
Apr 5
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
TBA

Troy Carter
(UCLA)

Thu
Apr 12
11:30
501
DWB
Plasma Group Meeting (organised by ALEX)
TBA


0
Thu
Apr 19.
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
TBA


I
Thu
Apr 26
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
TBA


II
Thu
May 3
11:30
501
DWB
Plasma Group Meeting (organised by ALEX)
Toby Adkins --- Dupree's phase-space turbulence revisited (TBC)
MMathPhys
report from
author on request

III
Thu
May 10
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
TBA


IV
Thu
May 17
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
TBA


V
Thu
May 24
11:30
501
DWB
Plasma Group Meeting (organised by ALEX)
TBA


VI
Thu
May 31
11:30
501
DWB
Plasma Group Meeting (organised by FELIX)
TBA


VII
Thu
June 7.
11:30
501
DWB
Plasma Group Meeting (organised by MICHAEL)
TBA


VIII
Thu
June 14
11:30
501
DWB
Plasma Group Meeting (organised by ALEX)
TBA


9
Thu
June 21
11:30
501
DWB




Thu
June 28
11:30
501
DWB




Thu/Fri
July 5-6
Rudolf Peierls Symposium for Theoretical Physics
Eliot Quataert
(UC Berkeley)