A magnetic diagnostic suite for the Pegasus-III experiment

Reusch, Joshua A.; Aslin, Mary W.; Bongard, Michael W.; Diem, Stephanie J.; Goetz, John A.; Nornberg, Mark D.; Rajendra, Anupama S.; Redd, Sophie; Sanchez, Cuauhtemoc Rodriguez; Sassella, Rachel K.; Sontag, Aaron C.; Weberski, Justin D.; Winz, Gregory R.

doi:10.1063/5.0219341

A magnetic diagnostic suite for the Pegasus-III experiment

Journal Article · Wed Sep 11 00:00:00 EDT 2024 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/5.0219341· OSTI ID:2453890

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University of Wisconsin-Madison, WI (United States); University of Wisconsin-Madison
University of Wisconsin-Madison, WI (United States)

Pegasus-III is an ultralow aspect ratio spherical tokamak providing a dedicated US experiment for comparative solenoid-free startup studies. A new magnetic diagnostic suite for equilibrium and low frequency (<200 kHz) magnetohydrodynamic mode analysis has been installed. These new diagnostics address the significant challenges of measuring magnetic field in a high noise environment with the majority constrained to fit in an 8 mm diagnostic gap on the high field side. Electrostatic switching noise generated by the 16 independent current feedback-controlled power supplies produces dV_cm/dt ~ 1 kV/μs and volt level common mode noise on the magnetics. Immunity to this switching noise is accomplished through differential signal runs and signal processing, along with end-to-end electromagnetic interference shielding. The magnetic measurements are simultaneously digitized at 1 MHz and conditioned by precision 8 pole Butterworth filters with a corner frequency of 200 kHz to prevent aliasing down to the 16-bit level over the full passband. Ex-vessel calibrations of the B_p coils were completed with a typical uncertainty of <0.5%. Stray toroidal field pickup from coil misalignment or positioning errors is corrected using a physics-based model. Comparisons of the corrected measurements to modeling agree to within 1.3% on average. This is within the 1.5% measurement uncertainty that a sensitivity analysis determined is needed for accurate fast boundary and equilibrium reconstruction.

Research Organization:: University of Wisconsin-Madison, WI (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: SC0019008

OSTI ID:: 2453890

Journal Information:: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 9 Vol. 95; ISSN 0034-6748

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

References (10)

Public Data Set: A Magnetic Diagnostic Suite for the Pegasus-III Experiment Reusch, Joshua; Aslin, Mary; Bongard, Michael University of Wisconsin-Madison https://doi.org/10.18138/2349303	dataset	January 2024
EMI on diagnostics and control circuits due to switching power supplies Gaio, E.; Piovan, R.; Toigo, V. Fusion Engineering and Design, Vol. 75-79 https://doi.org/10.1016/j.fusengdes.2005.06.109	journal	November 2005
The Poloidal Divertor Experiment(PDX) and the Princeton Beta Experiment(PBX) Bol, K.; Okabayashi, M.; Fonck, R. Nuclear Fusion, Vol. 25, Issue 9 https://doi.org/10.1088/0029-5515/25/9/026	journal	September 1985
Equilibrium properties at very low aspect ratio in the Pegasus toroidal experiment Sontag, A. C.; Diem, S. J.; Fonck, R. J. Nuclear Fusion, Vol. 48, Issue 9 https://doi.org/10.1088/0029-5515/48/9/095006	journal	August 2008
Electron Bernstein wave heating and diagnostic Laqua, Heinrich Peter Plasma Physics and Controlled Fusion, Vol. 49, Issue 4 https://doi.org/10.1088/0741-3335/49/4/R01	journal	March 2007
Advancing local helicity injection for non-solenoidal tokamak startup Bongard, M. W.; Bodner, G. M.; Burke, M. G. Nuclear Fusion, Vol. 59, Issue 7 https://doi.org/10.1088/1741-4326/ab17e3	journal	May 2019
Magnetic Turbulence and Current Drive During Local Helicity Injection Richner, N. J.; Bodner, G. M.; Bongard, M. W. Physical Review Letters, Vol. 128, Issue 10 https://doi.org/10.1103/PhysRevLett.128.105001	journal	March 2022
Digital Control and Power Systems for the Pegasus-III Experiment Bongard, Michael W.; Borchardt, Michael T.; Diem, Stephanie J. IEEE Transactions on Plasma Science, Vol. 50, Issue 11 https://doi.org/10.1109/TPS.2022.3165694	journal	November 2022
A Coaxial Helicity Injection System for Nonsolenoidal Startup Studies on the PEGASUS-III Experiment Reusch, Joshua A.; Raman, Roger; Bongard, Michael W. IEEE Transactions on Plasma Science, Vol. 50, Issue 11 https://doi.org/10.1109/TPS.2022.3171510	journal	November 2022
The New PEGASUS-III Experiment Sontag, Aaron C.; Bongard, Michael W.; Borchardt, Michael T. IEEE Transactions on Plasma Science, Vol. 50, Issue 11 https://doi.org/10.1109/TPS.2022.3184626	journal	November 2022

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