3. Construction and analysis of a database of MAST fishbone events
3.4 Fishbone Selection Process
The first step in selecting fishbone events to be included in the database is finding an accepted definition for the observed magnetic signatures of fishbones on MAST. On MAST, these events typically have a fundamental harmonic ([𝑛𝑛,𝑚𝑚] = (1,1)) sweeping through an experimentally observed frequency range around 35 kHz (±5 kHz) downwards to 20 kHz (±5 kHz), followed by a short period of relative quiet in the magnetics signal (the cycle can repeat if conditions are
appropriate [54]). This definition for fishbones was chosen as it requires few assumptions, has been used in existing research [32], and identifies many events.
Selected fishbone events need to be isolated from other events (such as edge-localised modes, toroidal Alfvén eigenmodes, sawtooth events, etc.) to attempt to limit observed changes in confinement represented by changes in 〈Γ〉 to only fishbone events. We chose not to include the presence (or absence) and the relative strength of higher harmonics of [𝑛𝑛,𝑚𝑚] = (1,1) as a selection factor. The experimental measure of confinement for this study, the neutron fission chamber signal, was not a selection factor to avoid biasing results.
Applying these selection criteria identified 198 fishbone candidates from the 48 discharges listed in Table 3-3. This wide selection of fishbone events allows for an investigation of a much wider range of plasma conditions and parameters than in previous studies during fishbone events on MAST.
15 To clarify: ‘Reactivity’ is average of the cross section over a velocity distribution, and ‘fusion rate’ is the
number of fusion reactions occurring in a unit of volume per time, which is inferred experimentally using the neutrons released from D-D and D-T fusion reactions.
16 A feat possible through the careful control of current profiles and plasma heating. 17 Available on CCFE Intranet
18 Such as non-operational diagnostics, mistimed processes, equipment failure, or aborted discharges. 19 Discharges classified as successful in experimental logs were included in the survey, aborted or failed
discharges were removed prior to analysis.
21
Examples of two types of fishbone activity are shown in Figure 3-3 and Figure 3-4, and a full list of these fishbone discharges is provided in Appendix A.
Table 3-3: MAST discharges selected for fishbone analysis
Discharge Date Programme Reference Discharge
26586 12/07/2011 M8-MHD-002 M8-IPS-001/002 RMPs in SND 26517
26789 9/09/2011 M8-SOL-006 RFEA experiments 26788
26855 28/09/2011 M8-IPS-004 Fast Ion Diffusion Experiment 26854
26857 28/09/2011 M8-IPS-004 Fast Ion Diffusion Experiment 26856
26859 28/09/2011 M8-IPS-004 Fast Ion Diffusion Experiment 26857
26863 28/09/2011 M8-IPS-004 Fast Ion Diffusion Experiment 26857
26864 28/09/2011 M8-IPS-004 Fast Ion Diffusion Experiment 26857
26884 29/09/2011 Fast Ion Diffusion Experiment 26864
26885 29/09/2011 Fast Ion Diffusion Experiment 26884
26886 29/09/2011 Fast Ion Diffusion Experiment 26885
26887 29/09/2011 Fast Ion Diffusion Experiment 26886
26888 29/09/2011 Fast Ion Diffusion Experiment 26887
26889 29/09/2011 Fast Ion Diffusion Experiment 26888
26970 4/10/2011 M8-T&C-004 M8-T&C-005 Low k turbulence 26968
27182 20/10/2011 Effect of relation processes on non-linear evolution of beam-driven modes 26976
27525 15/11/2011 M8-T&C-004 Low k turbulence in H-mode 26500
27526 15/11/2011 M8-T&C-004 Low k turbulence in H-mode 26500
27527 15/11/2011 M8-T&C-004 Low k turbulence in H-mode 26500
27528 15/11/2011 M8-T&C-004 Low k turbulence in H-mode 26500
27672 1/12/2011 M8-T&C-010 27671
27917 15/12/2011 M8-FPP-006 Fast Ion redistribution 26789
27918 15/12/2011 M8-FPP-006 Fast Ion redistribution 26789
27919 15/12/2011 M8-FPP-006 Fast Ion redistribution 26789
27920 15/12/2011 M8-FPP-006 Fast Ion redistribution 26789
27922 15/12/2011 M8-FPP-006 Fast Ion redistribution 27921
27924 15/12/2011 M8-FPP-006 Fast Ion redistribution 27922
27928 15/12/2011 M8-FPP-006 Fast Ion redistribution 27924
28186 20/01/2012 M8-T&C-012 L-H threshold 28182
28268 25/01/2012 M8-FPP-006: quantify fast ion redistribution due to chirping modes 28267
28982 10/06/2013 CP3S charger testing 28787
29113 20/06/2013 M9-SOL-005 M9-IPS-001 M9-MHD-006 Spark gap injector, scenario development and the effect of beta on edge stability 28787
29114 20/06/2013 M9-SOL-005 M9-IPS-001 M9-MHD-006 Spark gap injector, scenario development and the effect of beta on edge stability 29113
29115 20/06/2013 M9-SOL-005 M9-IPS-001 M9-MHD-006 Spark gap injector, scenario development and the effect of beta on edge stability 29114
29125 20/06/2013 M9-SOL-005 M9-IPS-001 M9-MHD-006 Spark gap injector, scenario development and the effect of beta on edge stability 29114
29126 20/06/2013 M9-SOL-005 M9-IPS-001 M9-MHD-006 Spark gap injector, scenario development and the effect of beta on edge stability 29114
29128 20/06/2013 M9-SOL-005 M9-IPS-001 M9-MHD-006 Spark gap injector, scenario development and the effect of beta on edge stability 29126
29130 20/06/2013 M9-SOL-005 M9-IPS-001 M9-MHD-006 Spark gap injector, scenario development and the effect of beta on edge stability 28982
29131 20/06/2013 M9-SOL-005 M9-IPS-001 M9-MHD-006 Spark gap injector, scenario development and the effect of beta on edge stability 28982
29132 20/06/2013 M9-SOL-005 M9-IPS-001 M9-MHD-006 Spark gap injector, scenario development and the effect of beta on edge stability 28982
29181 24/06/2013 M9-IPS-001 Scenario development 28982
29182 24/06/2013 M9-IPS-001 Scenario development 28982
29196 25/06/2013 M9-IPS-002 Fast Ion Redistribution 29176
29201 25/06/2013 M9-IPS-002 Fast Ion Redistribution 29200
29207 25/06/2013 M9-IPS-002 Fast Ion Redistribution 29182
29208 25/06/2013 M9-IPS-002 Fast Ion Redistribution 29207
29209 25/06/2013 M9-IPS-002 Fast Ion Redistribution 29208
29210 25/06/2013 M9-IPS-002 Fast Ion Redistribution 29209
29219 25/06/2013 M9-IPS-002 Fast Ion Redistribution 29215
29222 25/06/2013 M9-IPS-002 Fast Ion Redistribution 29221
29245 26/06/2013 M9-FPP-002 M9-IPS-002 Supression of Alfven Eigenmodes/ Fast ion redistribution 29194
29246 26/06/2013 M9-FPP-002 M9-IPS-002 Supression of Alfven Eigenmodes/ Fast ion redistribution 29031
29247 26/06/2013 M9-FPP-002 M9-IPS-002 Supression of Alfven Eigenmodes/ Fast ion redistribution 29246
29248 26/06/2013 M9-FPP-002 M9-IPS-002 Supression of Alfven Eigenmodes/ Fast ion redistribution 29246
29249 26/06/2013 M9-FPP-002 M9-IPS-002 Supression of Alfven Eigenmodes/ Fast ion redistribution 29248
29250 26/06/2013 M9-FPP-002 M9-IPS-002 Supression of Alfven Eigenmodes/ Fast ion redistribution 29249