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P Martin,
J Adamek,
P Agostinetti,
M Agostini,
A Alfier,
C Angioni,
V Antoni,
L Apolloni,
F Auriemma,
O Barana, [......],
N Pomaro,
N Pomphrey,
I Predebon,
M E Puiatti,
V Rigato,
A Rizzolo,
G Rostagni,
G Rubinacci,
A Ruzzon,
others
Nuclear Fusion. 09/2011; 51.
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ABSTRACT: This paper describes the detailed design of the Quench Protection Circuits (QPC) for the superconducting Toroidal Field (TF) and Poloidal Field (PF) magnets of the Satellite Tokamak JT-60SA, which will be installed in Naka, Japan [1]. The nominal currents to be interrupted and the maximum reapplied voltages are 25.7 kA and 2.8 kV for the TF QPCs and 20 kA and 5 kV for PF QPCs. The innovative solution proposed in the QPC design is based on a Hybrid Circuit Breaker (CB) composed of a mechanical Bypass Switch for conducting the continuous current, in parallel to a static CB for current interruption. The main choices of the final design are presented and discussed, either to confirm or to update and complete the study performed at the conceptual design level.
Fusion Engineering (SOFE), 2011 IEEE/NPSS 24th Symposium on; 07/2011
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P Martin,
J Adamek,
P Agostinetti,
M Agostini,
A Alfier,
C Angioni,
V Antoni,
L Apolloni,
F Auriemma,
O Barana, [......],
N Pomaro,
N Pomphrey,
I Predebon,
M E Puiatti,
V Rigato,
A Rizzolo,
G Rostagni,
G Rubinacci,
A Ruzzon,
others
Nuclear Fusion. 01/2011; 51(9).
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P Martin,
J Adamek,
P Agostinetti,
M Agostini,
A Alfier,
C Angioni,
V Antoni,
L Apolloni,
F Auriemma,
O Barana, [......],
N Pomaro,
N Pomphrey,
I Predebon,
M E Puiatti,
V Rigato,
A Rizzolo,
G Rostagni,
G Rubinacci,
A Ruzzon,
others
Nuclear Fusion. 01/2011; 51(9).
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D Terranova,
D Bonfiglio,
A H Boozer,
A W Cooper,
M Gobbin,
S P Hirshman,
R Lorenzini,
L Marrelli,
E Martines,
B Momo, [......],
M Spolaore,
C Taliercio,
M Valisa,
N Vianello,
Z Wang,
A Zamengo,
B Zaniol,
L Zanotto,
P Zanca,
M Zuin
[show abstract]
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ABSTRACT: The full three-dimensional (3D) approach is now becoming an important issue for all magnetic confinement configurations. It is a necessary condition for the stellarator but also the tokamak and the reversed field pinch (RFP) now cannot be completely described in an axisymmetric framework. For the RFP the observation of self-sustained helical configurations with improved plasma performances require a better description in order to assess a new view on this configuration. In this new framework plasma configuration studies for RFX-mod have been considered both with tools developed for the RFP as well as considering codes originally developed for the stellarator and adapted to the RFP. These helical states are reached through a transition to a very low/reversed shear configuration leading to internal electron transport barriers. These states are interrupted by MHD reconnection events and the large Te gradients at the barriers indicate that both current and pressure driven modes are to be considered. Furthermore the typically flat Te profiles in the helical core have raised the issue of the role of electrostatic and electromagnetic turbulence in these reduced chaos regions, so that a stability analysis in the correct 3D geometry is required to address an optimization of the plasma setup. In this view the VMEC code proved to be an effective way to obtain helical equilibria to be studied in terms of stability and transport with a suite of well tested codes. In this work, the equilibrium reconstruction technique as well as the experimental evidence of 3D effects and their first interpretation in terms of stability and transport are presented using both RFP and stellarator tools.
Plasma Physics and Controlled Fusion 11/2010; 52(12):124023. · 2.42 Impact Factor
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M Puiatti,
Alberto Alfier,
F Auriemma,
S Cappello,
L Carraro,
R Cavazzana,
Dal S Bello,
A Fassina,
D Escande,
P Franz, [......],
P Scarin,
G Serianni,
E Spada,
A Soppelsa,
S Spagnolo,
Monica Spolaore,
C Taliercio,
Nicola Vianello,
A Zamengo,
P Zanca
Plasma Physics and Controlled Fusion 12/2009; 51:124031. · 2.42 Impact Factor
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M E Puiatti,
A Alfier,
F Auriemma,
S Cappello,
L Carraro,
R Cavazzana,
S Dal Bello,
A Fassina,
D F Escande,
P Franz, [......],
P Scarin,
G Serianni,
E Spada,
A Soppelsa,
S Spagnolo,
M Spolaore,
C Taliercio,
N Vianello,
A Zamengo,
P Zanca
[show abstract]
[hide abstract]
ABSTRACT: The reversed field pinch configuration is characterized by the presence of magnetic structures both in the core and at the edge: in the core, at high plasma current the spontaneous development of a helical structure is accompanied by the appearance of internal electron transport barriers; at the edge strong pressure gradients, identifying an edge transport barrier, are observed too, related to the position of the field reversal surface.The aim of this paper is the experimental characterization of both the internal and edge transport barriers in relation to the magnetic topology, discussing possible analogies and differences with other confinement schemes.
Plasma Physics and Controlled Fusion 11/2009; 51(12):124031. · 2.42 Impact Factor
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ABSTRACT: This paper highlights the role of power electronics and digital control in the performance improvements of RFX (Reverse Field eXperiment), a toroidal device for plasma physics studies related to nuclear fusion research. Designed and built in the `80s, it started operation in early `90s, with the mission to explore the physics of Reverse Field Pinch (RFP) configuration at high plasma current, up to 2 MA. Significant enhancements both to the machine assembly and power supply systems were introduced at the beginning of 2000s, when it was clear that active feedback control of plasma MagnetoHydroDynamics (MHD) was crucial for the improvement of plasma performance. The new design was the result of a synergic process of understanding the relevant physics and of a skilful exploitation of the new enhanced performance and flexibility given by a strong use of state of art power electronics and digital controls. Aim of the paper is also to underline the peculiarity of the power electronics applications in fusion experiments, based on an advanced use of industrial components, improved and upgraded to satisfy the unconventional requirements coming from the physics experiments. For this purpose, the paper describes the specific features of the RFX new circuit topologies and the peculiar requirements related to the integrated operation which characterizes them with respect to more conventional applications of similar power. Finally, we emphasize the role of the higher flexibility in controlling the coil currents on the progress of RFX performance in terms of MHD instability control and exploration of new regimes, which strongly improved plasma confinement in the last years.
Power Electronics and Applications, 2009. EPE '09. 13th European Conference on; 10/2009
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R Lorenzini,
Matteo Agostini,
Alberto Alfier,
V Antoni,
L Apolloni,
F Auriemma,
O Barana,
M Baruzzo,
P Bettini,
D Bonfiglio, [......],
D Terranova,
V Toigo,
M Valisa,
P Veltri,
Nicola Vianello,
P Zaccaria,
B Zaniol,
L Zanotto,
E Zilli,
M Zuin
Physics of Plasmas 05/2009; 16(5):056109-056106. · 2.15 Impact Factor
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ABSTRACT: This paper describes the feasibility studies of a hybrid DC circuit breaker (CB) for quench protection of superconducting magnets rated for current up to some tens of kiloamperes (kA) and voltage of several kilovolts (kV). The proposed scheme is based on a mechanical switch paralleled to a fully controlled static CB; integrated gate commutated thyristors (IGCTs) were selected. In normal operation, the mechanical switch handles the continuous flow of DC current minimizing the on-state losses. When protection against quench is requested, the current is diverted into the static breaker that quickly interrupts the current, withstanding the reapplied voltage of several kV. The reliable turn-ON of several IGCTs in parallel with low voltage applied between anode and cathode is an issue to be assessed to confirm the feasibility of this design solution. The paper highlights that the components commonly used as snubber or protection circuit can guarantee the turn-ON of all the devices in parallel and that the IGCTs can be turned-ON with few volts applied; this latter aspect was proved by means of specific tests. Finally, a comparison between a static only and a hybrid CB is performed, highlighting the benefits introduced by the hybrid solution.
IEEE Transactions on Appiled Superconductivity 05/2009; · 1.04 Impact Factor
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ME PUIATTI,
A ALFIER,
F AURIEMMA,
S CAPPELLO,
L CARRARO,
R CAVAZZANA,
S DAL BELLO,
A FASSINA,
DF ESCANDE,
P FRANZ, [......],
P SCARIN,
G SERIANNI,
E SPADA,
A SOPPELSA,
S SPAGNOLO,
M SPOLAORE,
C TALIERCIO,
N VIANELLO,
A ZAMENGO,
P ZANCA
Plasma Physics and Controlled Fusion 01/2009; 51(12). · 2.42 Impact Factor
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ME PUIATTI,
A ALFIER,
F AURIEMMA,
S CAPPELLO,
L CARRARO,
R CAVAZZANA,
S DAL BELLO,
A FASSINA,
DF ESCANDE,
P FRANZ, [......],
P SCARIN,
G SERIANNI,
E SPADA,
A SOPPELSA,
S SPAGNOLO,
M SPOLAORE,
C TALIERCIO,
N VIANELLO,
A ZAMENGO,
P ZANCA
Plasma Physics and Controlled Fusion 01/2009; 51(12). · 2.42 Impact Factor
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ME PUIATTI,
A ALFIER,
F AURIEMMA,
S CAPPELLO,
L CARRARO,
R CAVAZZANA,
S DAL BELLO,
A FASSINA,
DF ESCANDE,
P FRANZ, [......],
P SCARIN,
G SERIANNI,
E SPADA,
A SOPPELSA,
S SPAGNOLO,
M SPOLAORE,
C TALIERCIO,
N VIANELLO,
A ZAMENGO,
P ZANCA
Plasma Physics and Controlled Fusion 01/2009; 51(12). · 2.42 Impact Factor
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P MARTIN,
L APOLLONI,
ME PUIATTI,
J ADAMEK,
M AGOSTINI,
A ALFIER,
SV ANNIBALDI,
V ANTONI,
F AURIEMMA,
O BARANA, [......],
RB WHITE,
D YADIKIN,
P ZACCARIA,
A ZAMENGO,
P ZANCA,
B ZANIOL,
L ZANOTTO,
E ZILLI,
H ZOHM,
M ZUIN
NUCLEAR FUSION. 01/2009; 49(10).
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M Valisa,
T Bolzonella,
P Buratti,
L Carraro,
R Cavazzana,
S Dal Bello,
P Martin,
R Pasqualotto,
J S Sarff,
M Spolaore, [......],
G Spizzo,
C Taliercio,
D Terranova,
V Toigo,
N Vianello,
D Yadikin,
P Zaccaria,
B Zaniol,
E Zilli,
M Zuin
[show abstract]
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ABSTRACT: Optimization of machine operation, including plasma position control, density control and especially feedback control on multiple magnetohydrodynamic modes, has led RFX-mod to operate reliably at 1.5 MA, the highest current ever achieved on a reversed field pinch (RFP). At high current and low density the magnetic topology spontaneously self-organizes in an Ohmical helical symmetry, with the new magnetic axis helically twisting around the geometrical axis of the torus. The separatrix of the island disappears leaving a wide and symmetric thermal structure with large gradients in the electron temperature profile. The new topology still displays an intermittent nature but its overall presence has reached 85% of the current flat-top period. The large gradients in the electron temperature profile appear to be marginal for the destabilization of ion temperature gradient modes on the assumption that ions and electrons have the same gradients. There are indications that higher currents could provide the conditions under which to prove the existence of a true helical equilibrium as the standard RFP configuration.
Plasma Physics and Controlled Fusion 11/2008; 50(12):124031. · 2.42 Impact Factor
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L Marrelli,
P Zanca,
M Valisa,
G Marchiori,
A Alfier,
F Bonomo,
M Gobbin,
P Piovesan,
D Terranova,
M Agostini, [......],
C Taccon,
C Taliercio,
V Toigo,
N Vianello,
P Zaccaria,
B Zaniol,
L Zanotto,
E Zilli,
G Zollino,
M Zuin
[show abstract]
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ABSTRACT: RFX-mod is a reversed field pinch (RFP) experiment equipped with a system that actively controls the magnetic boundary. In this paper we describe the results of a new control algorithm, the clean mode control (CMC), in which the aliasing of the sideband harmonics generated by the discrete saddle coils is corrected in real time. CMC operation leads to a smoother (i.e. more axisymmetric) boundary. Tearing modes rotate (up to 100 Hz) and partially unlock. Plasma–wall interaction diminishes due to a decrease of the non-axisymmetric shift of the plasma column. With the ameliorated boundary control, plasma current has been successfully increased to 1.5 MA, the highest for an RFP. In such regimes, the magnetic dynamics is dominated by the innermost resonant mode, the internal magnetic field gets close to a pure helix and confinement improves.
Plasma Physics and Controlled Fusion 11/2007; 49(12B):B359. · 2.42 Impact Factor
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ABSTRACT: In this paper, the conceptual design of a hybrid DC circuit breaker for quench protection (QP) of superconducting magnets in fusion experiments is presented. In this applications currents of the order of tens of kilo-ampere have to be sustained in steady state and interrupted in case of quench with reapplied voltage of several kilo-volt. The scheme proposed for the QP is based on a mechanical switch to handle the current in steady state operation paralleled to a static circuit breaker for the current interruption. IGCTs available on the market have been selected to analyse the obtainable performance; the relationship among the current to be interrupted, the IGCT junction temperature rise, the opening time of the mechanical switch and the number of devices in parallel, as well as between the reapplied voltage and the number of devices in series are reported and discussed.
Fusion Engineering, 2007. SOFE 2007. 2007 IEEE 22nd Symposium on; 07/2007
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S. Martini,
M. Agostini,
C. Alessi,
A. Alfier,
V. Antoni,
L. Apolloni,
F. Auriemma,
P. Bettini,
T. Bolzonella,
D. Bonfiglio, [......],
V. Toigo,
M. Valisa,
N. Vianello,
P. Zaccaria,
P. Zanca,
B. Zaniol,
L. Zanotto,
E. Zilli,
G. Zollino,
M. Zuin
[show abstract]
[hide abstract]
ABSTRACT: The modified RFX is a very flexible device used for a variety of control schemes for MHD instabilities and for advanced reverse field pinch scenarios. Relative to the previous machine, RFX-mod has a thin Cu shell with vertical field penetration time τS, lowered from 450 to 50 ms and shell/plasma proximity from b/a = 1.24–1.1. Toroidal equilibrium is feedback-controlled and new power supplies provide better B control. Newly designed graphite tiles protect the vessel from localized power deposition. A mesh of 192 external saddle coils, supervised by a digital feedback system, controls radial fields due to field errors and MHD modes. The paper presents an overview of the very encouraging results obtained using both new and 'standard' advanced operational modes in the current range 0.3–1 MA. A dramatic improvement of plasma performance was obtained by using the saddle coils to cancel all the radial field components, an operation mode dubbed virtual shell (VS). The toroidal voltage was lowered by more than 25% and the pulse length was tripled, up to 7 times the τS. Steady-state RFP pulses are now limited only by the applied volt-seconds. The improved magnetic boundary also has an effect on the tearing modes underlying the sustainment of the RFP, whose core amplitude is more than halved. The VS combined with new schemes for the active rotation of the MHD dynamo modes has allowed us to obtain reliable and well-controlled long RFP pulses in the MA current range. This results in a 100% increase in the particle and energy confinement time relative to the previous experiment and opens the possibility of exploring the machine performance in the 2 MA design range.
Nuclear Fusion 07/2007; 47(8):783. · 4.09 Impact Factor
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ABSTRACT: Inflammatory processes are a rare cause of peripheral facial palsy. In most cases even massive infection does not lead to a loss of facial nerve function. In the literature, only 8 cases of facial paralysis associated with parotid cyst have been described.
We present a case of facial palsy caused by an inflamed cyst of the parotid gland. The patient was operated on with the diagnosis malignant parotid tumor. The pathological report showed a squamous epithelial cyst, massive lymphocytic infiltration.
As a rule the combination parotid gland lesion and facial palsy is a sign of malignancy, clinicians should be aware that, on rare occasions, facial nerve dysfunction may result from benign parotid gland disease.
Laryngo-Rhino-Otologie 02/2006; 85(1):43-5. · 0.97 Impact Factor
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ABSTRACT: This paper describes a comparative analysis of two different circuit solutions for the ion source power supplies of the neutral beam injector test bed for the international thermonuclear experimental reactor. The performances of the two layouts have been evaluated by means of numerical simulations, in terms of dynamic performance, ripple amplitude and cut-off times; the results are presented and discussed in the paper
Fusion Engineering 2005, Twenty-First IEEE/NPS Symposium on; 10/2005
