Modeling of NBI Heating and Current Drive with Different Types of NBI Device Configurations in KSTAR

L. Terzolo,권재민,J. Y. Kim 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.5

For flexible control of the plasma pressure and the current profiles, which is essential to achieve a high-performance plasma and its long-pulse operation, the Korea Superconducting Tokamak Advanced Research (KSTAR) is going to implement several heating and current systems, including a neutral beam injection (NBI) device. In an effort to find a more optimum configuration of the KSTAR NBI system, a simulation study of NBI heating and current drive by using the NUBEAM code for three different types of NBI configurations is given. The radial profiles of the NBI power deposition and the plasma current drive are shown to be sensitive to the NBI configurations considered, particularly in relatively low density plasmas. For a more flexible control of the off-axis current profile, a new configuration, different from the first NBI device currently installed at KSTAR, would be desirable for the second NBI system, which will be fabricated and installed in the near future.

Modeling of Neutral Beam Injection Heating and Current Drive during the Ramp-up Phase in KSTAR

L. Terzolo 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.11

For flexible control of the plasma pressure and the current profiles, which are essential for ahigh performance plasma with long pulse operation, KSTAR is going to implement several heatingand current systems, which include Neutral Beam Injection (NBI), Ion Cyclotron Resonant Heting(ICRH)/Fast Wave Current Drive (FWCD), Lower Hybrid Current Drive (LHCD), and EclectronCyclotron Heating (ECH)/Electron Cyclotron Current Drive (ECCD). Here, the NBI system istypically used for the central heating and current drive. For the time being, only one NBI device(composed of 3 sources) is available in KSTAR. The first two sources were successfully commissionedin 2010 and 2013. The last source will be installed in 2014. In this work, we present a simulationstudy of the heating and current drive of the first NBI system (3 sources) during the ramp-upphase. We consider two different NBI configurations (low and high beam energy). The simulation isperformed with NUBEAM, a well-recognized Monte-Carlo code. Several different types of KSTARtarget equilibria (scan from lower to higher plasma density) are used for the calculation of thecurrent drive, the heating and the different NB losses (shinethrough, charge exchange and badorbit). The study shows the dependency of those quantities on the plasma density, the position ofthe NB source and the beam energy. It also shows that because of the shinethrough loss is too high,each NB source cannot be used when the plasma density is under a certain threshold. This studycan be used to determine the starting time of the different NB sources during the KSTAR ramp-upphase.

Physics-based integrated modeling of the energy confinement time scaling laws for the H- and L-modes in the KSTAR-type tokamak model

Kim, J.Y.,Han, H.S.,Terzolo, L. International Atomic Energy Agency 2017 Nuclear fusion Vol.57 No.7

<P>In an effort to clarify the physics origin of the energy confinement time scaling law in H-mode plasmas, a new analysis method is first proposed where the stored energy is separated into two parts—one coming from the marginal stability with the pedestal boundary condition and the other related to the turbulent dynamics. The method is then applied for the analysis of the global scaling law, as initial examples, focusing on the four parameters of plasma current, input power, magnetic field and density in the KSTAR-type tokamak model. It is shown that the method can provide more quantitative and explicit information on how various physics elements, such as the linear stability, nonlinear turbulent dynamics and pedestal boundary, contribute to the global scaling factor. While this method is not directly applicable, the L-mode is also considered for comparison, trying to clarify how a difference in the scaling law can occur between the H- and L-modes.</P>

Is Follow-up of Adrenal Incidentalomas Always Mandatory?

Giuseppe Reimondo,Alessandra Muller,Elisa Ingargiola,Soraya Puglisi,Massimo Terzolo 대한내분비학회 2020 Endocrinology and metabolism Vol.35 No.1

Adrenal masses are mainly detected unexpectedly by an imaging study performed for reasons unrelated to any suspect of adrenaldiseases. Such masses are commonly defined as “adrenal incidentalomas” and represent a public health challenge because they areincreasingly recognized in current medical practice. Management of adrenal incidentalomas is currently matter of debate. Althoughthere is consensus on the need of a multidisciplinary expert team evaluation and surgical approach in patients with significant hormonal excess and/or radiological findings suspicious of malignancy demonstrated at the diagnosis or during follow-up, the inconsistency between official guidelines and the consequent diffuse uncertainty on management of small adrenal incidentalomas still represents a considerable problem in terms of clinical choices in real practice. The aim of the present work is to review the proposed strategies on how to manage patients with adrenal incidentalomas that are not candidates to immediate surgery. The recent European Society of Endocrinology/European Network for the Study of Adrenal Tumors guidelines have supported the view to avoid surveillance in patients with clear benign adrenal lesions <4 cm and/or without any hormonal secretion; however, newer prospective studies are needed to confirm safety of this strategy, in particular in younger patients.

Neutron emission in neutral beam heated KSTAR plasmas and its application to neutron radiography

KSTAR team,Kwak, J.G.,Kim, H.S.,Cheon, M.S.,Oh, S.T.,Lee, Y.S.,Terzolo, L. North-Holland ; Elsevier Science Ltd 2016 Fusion engineering and design Vol.109 No.1

The main mission of Korea Superconducting Tokamak Advanced Research (KSTAR) program is exploring the physics and technologies of high performance steady state Tokamak operation that are essential for ITER and fusion reactor. Since the successful first operation in 2008, the plasma performance is enhanced and duration of H-mode is extended to around 50s which corresponds to a few times of current diffusion time and surpassing the current conventional Tokamak operation. In addition to long-pulse operation, the operational boundary of the H-mode discharge is further extended over MHD no-wall limit(β<SUB>N</SUB>~4) transiently and higher stored energy region is obtained by increased total heating power (~6MW) and plasma current (I<SUB>p</SUB> up to 1MA for ~10s). Heating system consists of various mixtures (NB, ECH, LHCD, ICRF) but the major horse heating resource is the neutral beam(NB) of 100keV with 4.5MW and most of experiments are conducted with NB. So there is a lot of production of fast neutrons coming from via D(d,n)<SUP>3</SUP>He reaction and it is found that most of neutrons are coming from deuterium beam plasma interaction. Nominal neutron yield and the area of beam port is about 10<SUP>13</SUP>-10<SUP>14</SUP>/s and 1m<SUP>2</SUP> at the closest access position of the sample respectively and neutron emission could be modulated for application to the neutron radiography by varying NB power. This work reports on the results of quantitative analysis of neutron emission measurements and results are discussed in terms of beam-plasma interaction and plasma confinement. It also includes the feasibility study of neutron radiography using KSTAR.

Characteristics of toroidal rotation and ion temperature pedestals between ELM bursts in KSTAR H-mode plasmas

Ko, S. H.,Kwon, J. M.,Ko, W. H.,Kim, S. S.,Jhang, H.,Terzolo, L. American Institute of Physics, 2016 Physics of plasmas Vol.23 No.6

Experiment and simulation of tearing mode evolution with electron cyclotron current drive in KSTAR

Kim, Kyungjin,Na, Yong-Su,Kim, Minhwa,Jeon, Y.M.,Lee, K.D.,Bak, J.G.,Choi, M.J.,Yun, G.S.,Lee, S.G.,Park, S.,Jeong, J.H.,Terzolo, L.,Na, D.H.,Yoo, M.G. Elsevier 2015 CURRENT APPLIED PHYSICS Vol.15 No.4

<P><B>Abstract</B></P> <P>The tearing mode (TM) plasma instability was observed in low confinement (L-mode) plasmas when non-axisymmetric magnetic perturbation (MP) was applied using external coils during 2011 campaign of KSTAR. Based on the collected information of the magnetic island location in a plasma, a discharge was designed for suppression of a (2,1) TM mode by adjusting electron cyclotron (EC) launcher angles to the estimated island position. Here, the (m,n) notation describes the poloidal mode number and the toroidal mode number of the TM, respectively. The discharge is analysed with experimental observations and numerical simulations. Mirnov coil (MC) arrays and electron cyclotron emission (ECE) are used for analysis of the island width and the location as well as the mode number. The EC deposition and its alignment with the island are estimated by X-ray imaging crystal spectroscopy (XICS) and ECE measurements. An integrated numerical system is employed for modelling of this discharge to analyse a temporal evolution of the mode activity by integrating plasma equilibrium, transport, heating and current drive, and the magnetic island evolution, in a self-consistent way. The effect of EC current drive is discussed by comparing with another TM discharge but without ECCD. Some possibilities for classifying this mode to neoclassical tearing mode (NTM) and stabilisation effect of ECCD are suggested based on the experimental observation and the simulation results.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Suppression of (2,1) TM/NTM by applying ECH/CD for the first time in KSTAR. </LI> <LI> Suppression of the mode examined by experimental observations and simulations. </LI> <LI> Simulation of a mode without ECCD to compare with/without the applied control. </LI> </UL> </P>

Modeling of neoclassical tearing mode stabilization by electron cyclotron heating and current drive in tokamak plasmas

Kyungjin Kim,Yong-Su Na,Hyun-Seok Kim,M. Maraschek,E. Poli,J. Stober,H. Zohm,F. Felici,O. Sauter,Y.S. Park,L. Terzolo,ASDEX Upgrade team,TCV Team 한국물리학회 2016 Current Applied Physics Vol.16 No.8

An integrated numerical system is established to model time-dependent behavior of the neoclassical tearing mode (NTM) in a tokamak which solves the modified Rutherford equation (MRE) by coupling with plasma transport, equilibrium, heating and current drive. The MRE is formulated in a simple form to be well-suited for time-dependent simulations including a predictive purpose for the feedback controller design by coupling the electron cyclotron effect self-consistently. In particular the electron cyclotron heating (ECH) effect is newly included to the MRE in addition to the electron cyclotron current drive (ECCD) effect to investigate their impact to stabilize the NTM. The integrated numerical system is applied to experiments for benchmarking in which NTMs are stabilized by ECCD and by ECH at ASDEX Upgrade and TCV, respectively. The impact of ECCD and ECH on stabilizing NTMs is identified in the simulations.

Experiment and simulation of tearing mode evolution with electron cyclotron current drive in KSTAR

김경진,나용수,김민화,Y.M. Jeon,K.D. Lee,J.G. Bak,M.J. Choi,윤건수,S.G. Lee,S. Park,J. H. Jeong,L. Terzolo,D.H. Na,M.G. Yoo,KSTAR Team 한국물리학회 2015 Current Applied Physics Vol.15 No.4

The tearing mode (TM) plasma instability was observed in low confinement (L-mode) plasmas when non-axisymmetric magnetic perturbation (MP) was applied using external coils during 2011 campaign of KSTAR. Based on the collected information of the magnetic island location in a plasma, a discharge was designed for suppression of a (2,1) TM mode by adjusting electron cyclotron (EC) launcher angles to the estimated island position. Here, the (m,n) notation describes the poloidal mode number and the toroidal mode number of the TM, respectively. The discharge is analysed with experimental observations and numerical simulations. Mirnov coil (MC) arrays and electron cyclotron emission (ECE) are used for analysis of the island width and the location as well as the mode number. The EC deposition and its alignment with the island are estimated by X-ray imaging crystal spectroscopy (XICS) and ECE measurements. An integrated numerical system is employed for modelling of this discharge to analyse a temporal evolution of the mode activity by integrating plasma equilibrium, transport, heating and current drive, and the magnetic island evolution, in a self-consistent way. The effect of EC current drive is discussed by comparing with another TM discharge but without ECCD. Some possibilities for classifying this mode to neoclassical tearing mode (NTM) and stabilisation effect of ECCD are suggested based on the experimental observation and the simulation results.

Toroidal rotation profile structure in KSTAR L-mode plasmas with mixed heating by NBI and ECH

Shi, Y.J.,Ko, S.H.,Kwon, J.M.,Ko, W.H.,Diamond, P.H.,Yi, S.,Ida, K.,Lee, K.D.,Jeong, J.H.,Seo, S.H.,Hahn, S.H.,Yoon, S.W.,Bae, Y.S.,Terzolo, L.,Yun, G.S.,Bitter, M.,Hill, K. IOP 2016 Nuclear fusion Vol.56 No.1

<P>The structure of the toroidal rotation profile with mixed heating by neutral beam injection (NBI) and electron cyclotron resonance heating (ECH) has been investigated in KSTAR L-mode plasmas. ECH with varying resonance layer positions was used for heating a mix control. The experimental results show that ECH causes a counter-current rotation increment both for off-axis and on-axis ECH heating. For L-mode plasmas, off-axis ECH produces larger counter-current rotation than on-axis ECH. Analysis of ion heat and momentum transport for the ECH L-mode plasmas shows that the electron temperature gradient is the main reason for the degradation of ion heat confinement and also the main driving force for the non-diffusive momentum flux. As a possible mechanism for the counter-current intrinsic torque with ECH, the transition of the turbulence mode from ion temperature gradient (ITG) to the trapped electron mode (TEM) with the resulting sign change of turbulence driven residual stress is suggested. A linear gyro-kinetic analysis shows the ITG  →  TEM transition occurs in a localized region during ECH injection, and the trend of TEM excitation is consistent with the observed macroscopic trend of the toroidal rotation.</P>