Page 2 - ntegrated diagnostic and data analysis system of the C-2W advanced beam-driven field-reversed configuration plasma experiment

REVIEW OF SCIENTIFIC INSTRUMENTS 89, 10K114 (2018)
Integrated diagnostic and data analysis system of the C-2W advanced
beam-driven field-reversed configuration plasma experiment
M. C. Thompson,a) T. M. Schindler, R. Mendoza, H. Gota, S. Putvinski, M. W. Binderbauer, and TAE Teamb)
TAE Technologies, Inc., Foothill Ranch, California 92610, USA
(Presented 16 April 2018; received 26 April 2018; accepted 3 August 2018; published online 19 October 2018)
The new C-2W experiment (also called Norman) at TAE Technologies, Inc. studies the evolution of field-reversed configuration (FRC) plasmas sustained by neutral beam injection. Data on the FRC plasma performance are provided by a comprehensive suite of diagnostics that includes over 700 magnetic sensors, four interferometer systems, multi-chord far-infrared polarimetry, two Thomson scattering systems, ten types of spectroscopic measurements, multiple fast imaging cameras with selectable atomic line filters, bolometry, reflectometry, neutral particle analyzers, and fusion product detectors. Most of these diagnostic systems are newly built using experience and data from the pre- ceding C-2U experiment to guide the design process. A variety of commercial and custom acquisition electronics collect over 4000 raw signals from the C-2W diagnostics. These data are processed into physics results using a large-scale database of diagnostics metadata and analysis software, both built using open-source software tools. Published by AIP Publishing. https://doi.org/10.1063/1.5037693
I. INTRODUCTION
Field-reversed configurations (FRCs) are compact toroidal magnetic confinement systems with little or no
1,2
preceding C-2U6 and C-27 experiments. Much of the expan- sion and improvements, see Table I, were driven by an increased interest in the open-field-line plasma and divertor or end tank region which has a large impact on the core FRC and overall system performance. Accordingly, the C-2W diag- nostics suite is divided in three zones of focus: FRC Core and SOL, Plasma Jet, and Divertor (see Fig. 1). Plasma parame- ters vary substantially in these three zones and this variation is reflected in the choice of diagnostic instruments employed in each. Note that C-2W has both an inner and an outer diver- tor on each side of the device, and either one can be used as the main termination point of the plasma jet as shown in the two frames of Fig. 1. Switching to the inner divertor after formation and translation of the FRCs will provide shorter con- nection lengths, which should improve biasing performance. Sections II A–II C detail the three plasma zones and the key diagnostics used in each on C-2W.
A. FRC core and scrape-off-layer diagnostics
The shape of the FRC plasma is defined by the sepa-
ratrix between the closed magnetic field lines of the toroid
and the open field lines of the SOL. The separatrix radius
rs ∼ 35 cm is approximately equal to the excluded-flux radius
the radius of the chamber wall, B0 ∼ 680 G is the initial uniform
magnetic field present in the chamber before the entry of the
FRC, and Be ∼ 820 G is the total external field measured out-
side the FRC. This simple theory of r∆φ calculation required
toroidal field.
plasma’s own diamagnetic currents, which are strong enough to reverse the exterior magnetic field, and only requires solenoidal coils located outside of a simply connected vac- uum vessel. The core plasma is enclosed by a scrape-off-layer (SOL) that coalesces into axial jets beyond each end of the FRC, which forms a natural linear divertor. The C-2W3 exper- iment is the successor to the C-2U4 program, which was an upgrade and continuation of the C-25 device. C-2W is designed to study the merging, and subsequent sustainment and heating, of two FRCs that are formed separately and collided in a central confinement vessel (CV). Key new features implemented for the C-2W experimental program include increased total neu- tral beam (NB) input power up to ∼21 MW (hydrogen atoms, tunable energy of 15–40 keV) with tilted injection angle, addi- tional inner divertors with field expanders and high pumping capacity to minimize electron cooling, enhanced edge-biasing capability for stability control, upgraded particle inventory control systems, an improved suite of diagnostic instruments, and a new data analysis architecture.
The FRC topology is generated by the
1,2
conserves flux, rs ≈r∆φ =rw
r∆φ.
Assuming the FRC is centered in the CV and it perfectly
1 − B0/Be, where r􏰁 ∼ 80 cm is
√
II. DIAGNOSTIC SUITE OF C-2W
The diagnostic suite of C-2W consists of a large set of new and inherited instruments that represent a continuation of the diagnostics program that has rapidly grown through the
Note: Paper published as part of the Proceedings of the 22nd Topical Confer- ence on High-Temperature Plasma Diagnostics, San Diego, California, April 2018.
a)mthompson@tae.com. URL: www.tae.com.
8,9
tion of circumferential B-dot probes integrated with a flux loop
significant correction on both C-2 and C-2U.
inside a single mineral insulated cable has eliminated many
The introduc-
b)TAE Team members are listed in Nucl. Fusion 57, 116021 (2017). 0034-6748/2018/89(10)/10K114/5/$30.00
89, 10K114-1 Published by AIP Publishing.
errors in the r∆φ measurement on C-2W.
over 700 individual magnetic probe coils on C-2W including
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In total, there are