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Featured researches published by A.Q. Kuang.


Earthquake Spectra | 2014

Christchurch Women's Hospital: Analysis of Measured Earthquake Data during the 2011–2012 Christchurch Earthquakes

Akshay Sridhar; A.Q. Kuang; Joseph Garven; Stefanie Gutschmidt; J. Geoffrey Chase; Henri P. Gavin; Robert L. Nigbor; Geoffrey W. Rodgers; Gregory A. MacRae

A network of acceleration and displacement sensors installed in the Christchurch Womens Hospital (CWH) in July 2011 captured an extensive range of earthquake signals, allowing for a unique opportunity to analyze the performance of the New Zealand South Islands only base-isolated structure. Key characteristics of a range of earthquake signals, including frequency spectra and response patterns, are identified, with particular focus on the swarm of earthquakes on 23 December 2011, including four earthquake events greater than magnitude 5.0 on the Richter scale. The findings indicate that the response of the isolators and the superstructure was essentially elastic for the events analyzed during this period. Accelerations measured above and below the isolators were similar, indicating that the behavior of the devices resembled that of rigid blocks. No significant rocking or torsional motion of the building was observed.


Review of Scientific Instruments | 2017

Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak

D. Brunner; A.Q. Kuang; B. LaBombard; W. Burke

A new servomotor drive system has been developed for the horizontal reciprocating probe on the Alcator C-Mod tokamak. Real-time measurements of plasma temperature and density-through use of a mirror Langmuir probe bias system-combined with a commercial linear servomotor and controller enable self-adaptive position control. Probe surface temperature and its rate of change are computed in real time and used to control probe insertion depth. It is found that a universal trigger threshold can be defined in terms of these two parameters; if the probe is triggered to retract when crossing the trigger threshold, it will reach the same ultimate surface temperature, independent of velocity, acceleration, or scrape-off layer heat flux scale length. In addition to controlling the probe motion, the controller is used to monitor and control all aspects of the integrated probe drive system.


Physics of Plasmas | 2016

Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak

I. Faust; Daniel Frederic Brunner; B. LaBombard; R.R. Parker; James Terry; D.G. Whyte; S. G. Baek; E. Edlund; Amanda E. Hubbard; J.W. Hughes; A.Q. Kuang; Matthew Reinke; Shunichi Shiraiwa; G.M. Wallace; J. Walk

For the first time, the power deposition of lower hybrid RF waves into the edge plasma of a diverted tokamak has been systematically quantified. Edge deposition represents a parasitic loss of power that can greatly impact the use and efficiency of Lower Hybrid Current Drive (LHCD) at reactor-relevant densities. Through the use of a unique set of fast time resolution edge diagnostics, including innovative fast-thermocouples, an extensive set of Langmuir probes, and a Lyα ionization camera, the toroidal, poloidal, and radial structure of the power deposition has been simultaneously determined. Power modulation was used to directly isolate the RF effects due to the prompt ( t<τE) response of the scrape-off-layer (SOL) plasma to Lower Hybrid Radiofrequency (LHRF) power. LHRF power was found to absorb more strongly in the edge at higher densities. It is found that a majority of this edge-deposited power is promptly conducted to the divertor. This correlates with the loss of current drive efficiency at high den...


Journal of Performance of Constructed Facilities | 2016

Christchurch Women’s Hospital: Performance Analysis of the Base-Isolation System during the Series of Canterbury Earthquakes 2011–2012

A.Q. Kuang; Akshay Sridhar; Joseph Garven; Stefanie Gutschmidt; Geoffrey W. Rodgers; J. Geoffrey Chase; Henri P. Gavin; Robert L. Nigbor; Gregory A. MacRae

AbstractLive monitoring data and simple dynamic reduced-order models of the Christchurch Women’s Hospital (CWH) help explain the performance of the base-isolation (BI) system of the hospital during the series of Canterbury earthquakes in 2011–2012. A Park-Wen-Ang hysteresis model is employed to simulate the performance of the BI system and results are compared to measured data recorded above the isolation layer and on the sixth story. Simplified single, two, and three degree-of-freedom models (SDOF, 2DOF, and 3DOF) show that the CWH structure did not behave as an isolated but as a fixed-base structure. Comparisons of accelerations and deflections between simulated and monitored data show a good match for isolation stiffness values of approximately two times of the value documented in the design specification and test protocol. Furthermore, an analysis of purely measured data revealed very little to no relative motion across the isolators for large events of moment magnitude scale (Mw) 5.8 and 6.0 that occ...


Plasma Physics and Controlled Fusion | 2018

Intermittent electron density and temperature fluctuations and associated fluxes in the Alcator C-Mod scrape-off layer

Ralph Kube; Odd Erik Garcia; Audun Theodorsen; D. Brunner; A.Q. Kuang; B. LaBombard; James Terry

Embargo of 12 months from date of publishing on accepted manuscript version. Published version available in https://doi.org/10.1088/1361-6587/aab726> Plasma Physics and Controlled Fusion (2018) 60, (6), 065002 IOP publishing statement: http://ioppublishing.org/wp-content/uploads/2016/05/J-VAR-LF-0216-Author-Rights-New-5.pdf


Fusion Engineering and Design | 2018

Conceptual design study for heat exhaust management in the ARC fusion pilot plant

A.Q. Kuang; N. Cao; A. J. Creely; C.A. Dennett; J. Hecla; B. LaBombard; R.A. Tinguely; E. A. Tolman; H. Hoffman; M. Major; J. Ruiz Ruiz; D. Brunner; P. Grover; C. Laughman; Brandon Sorbom; D.G. Whyte

Abstract The ARC pilot plant conceptual design study has been extended beyond its initial scope [B. N. Sorbom et al., FED 100 (2015) 378] to explore options for managing ∼525 MW of fusion power generated in a compact, high field (B0 = 9.2 T) tokamak that is approximately the size of JET (R0 = 3.3 m). Taking advantage of ARC’s novel design – demountable high temperature superconductor toroidal field (TF) magnets, poloidal magnetic field coils located inside the TF, and vacuum vessel (VV) immersed in molten salt FLiBe blanket – this follow-on study has identified innovative and potentially robust power exhaust management solutions. The superconducting poloidal field coil set has been reconfigured to produce double-null plasma equilibria with a long-leg X-point target divertor geometry. This design choice is motivated by recent modeling which indicates that such configurations enhance power handling and may attain a passively-stable detachment front that stays in the divertor leg over a wide power exhaust window. A modified VV accommodates the divertor legs while retaining the original core plasma volume and TF magnet size. The molten salt FLiBe blanket adequately shields all superconductors, functions as an efficient tritium breeder, and, with augmented forced flow loops, serves as an effective single-phase, low-pressure coolant for the divertor, VV, and breeding blanket. Advanced neutron transport calculations (MCNP) indicate a tritium breeding ratio of ∼1.08. The neutron damage rate (DPA/year) of the remote divertor targets is ∼3–30 times lower than that of the first wall. The entire VV (including divertor and first wall) can tolerate high damage rates since the demountable TF magnets allow the VV to be replaced every 1–2 years as a single unit, employing a vertical maintenance scheme. A tungsten swirl tube FLiBe coolant channel design, similar in geometry to that used by ITER, is considered for the divertor heat removal and shown capable of exhausting divertor heat flux levels of up to 12 MW/m2. Several novel, neutron tolerant diagnostics are explored for sensing power exhaust and for providing feedback control of divertor conditions over long time scales. These include measurement of Cherenkov radiation emitted in FLiBe to infer DT fusion reaction rate, measurement of divertor detachment front locations in the divertor legs with microwave interferometry, and monitoring “hotspots” on the divertor chamber walls via IR imaging through the FLiBe blanket.


Review of Scientific Instruments | 2016

Feedback system for divertor impurity seeding based on real-time measurements of surface heat flux in the Alcator C-Mod tokamak

D. Brunner; W. Burke; A.Q. Kuang; B. LaBombard; B. Lipschultz; Scot A. Wolfe


Nuclear materials and energy | 2017

High-field side scrape-off layer investigation: Plasma profiles and impurity screening behavior in near-double-null configurations

B. LaBombard; A.Q. Kuang; D. Brunner; I. Faust; R. Mumgaard; Matthew Reinke; J. L. Terry; J.W. Hughes; J. Walk; M. Chilenski; Y. Lin; E. Marmar; G. Wallace; D.G. Whyte; S. M. Wolfe; S.J. Wukitch


Nuclear Fusion | 2017

Impurity screening behavior of the high-field side scrape-off layer in near-double-null configurations: prospect for mitigating plasma?material interactions on RF actuators and first-wall components

B. LaBombard; A.Q. Kuang; D. Brunner; I. Faust; R. Mumgaard; M.L. Reinke; J. L. Terry; N.T. Howard; J.W. Hughes; M. Chilenski; Y. Lin; E. Marmar; J. E. Rice; P. Rodriguez-Fernandez; G.M. Wallace; D.G. Whyte; S. M. Wolfe; S.J. Wukitch


Nuclear materials and energy | 2017

Design and operation of a high-heat flux, flush-mounted ‘rail’ Langmuir probe array on Alcator C-Mod

A.Q. Kuang; D. Brunner; B. LaBombard; R. Leccacorvi; R. Vieira

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D. Brunner

Massachusetts Institute of Technology

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B. LaBombard

Massachusetts Institute of Technology

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J. L. Terry

Massachusetts Institute of Technology

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D.G. Whyte

University of Wisconsin-Madison

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J.W. Hughes

Massachusetts Institute of Technology

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S. M. Wolfe

Massachusetts Institute of Technology

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E. Marmar

Massachusetts Institute of Technology

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I. Faust

Massachusetts Institute of Technology

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S.J. Wukitch

Massachusetts Institute of Technology

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