An Analysis of Ripple and Error Fields Induced by a Blanket in the CFETR

The Chinese Fusion Engineering Tokamak Reactor （CFETR） is an important intermediate device between ITER and DEMO. The Water Cooled Ceramic Breeder （WCCB） blanket whose structural material is mainly made of Reduced Activation Ferritic/Martensitic （RAFM） steel, is one of the candidate conceptual blanket design. An analysis of ripple and error field induced by RAFM steel in WCCB is evaluated with the method of static magnetic analysis in the ANSYS code. Significant additional magnetic field is produced by blanket and it leads to an increased ripple field. Maximum ripple along the separatrix line reaches 0.53% which is higher than 0.5% of the acceptable design value. Simultaneously, one blanket module is taken out for heating purpose and the resulting error field is calculated to be seriously against the requirement.

Error field penetration in J-TEXT tokamak based on two-fluid drift-MHD model

An externally generated resonant magnetic perturbation can induce complex non-ideal MHD responses in their resonant surfaces.We have studied the plasma responses using Fitzpatrick's improved two-fluid model and program LAYER.We calculated the error field penetration threshold for J-TEXT.In addition,we find that the island width increases slightly as the error field amplitude increases when the error field amplitude is below the critical penetration value.However,the island width suddenly jumps to a large value because the shielding effect of the plasma against the error field disappears after the penetration.By scanning the natural mode frequency,we find that the shielding effect of the plasma decreases as the natural mode frequency decreases.Finally,we obtain the m/n=2/1 penetration threshold scaling on density and temperature.

On the Transition Regime of Nonlinear Error Field Penetration in Toroidal Plasmas

The error field penetration is numerically studied in the frame of the visco-resistive magnetohydrodynamics（MHD） model.A transition scaling is obtained to link the Rutherford and Waelbroeck regimes in the nonlinear phase of error field penetration process.Furthermore,a transition density scaling of[br/BT]critne1/2 obtained in accord with recent experimental observations in the J-TEXT tokamak.

A Conceptual Design Study for the Error Field Correction Coil Power Supply in JT-60SA

This paper describes a conceptual design study for the circuit configuration of the Error Field Correction Coil （EFCC） power supply （PS） to maximize the expected performance with reasonable cost in JT-60SA. The EFCC consists of eighteen sector coils installed inside the vacuum vessel, six in the toroidal direction and three in the poloidal direction, each one rated for 30 kA-turn. As a result, star point connection is proposed for each group of six EFCC coils installed cyclically in the toroidal direction for decoupling with poloidal field coils. In addition~ a six phase inverter which is capable of controlling each phase current was chosen as PS topology to ensure higher flexibility of operation with reasonable cost.

Crustal deformation on the Chinese mainland during 1998—2004 based on GPS data

This study focuses on resolving moderate amounts of crustal motion at the continental scale based on a large volume of global positioning system（GPS） data during 1998e2014. A state-of-the-art GPS processing strategy was used to resolve position time series and velocities from carrier beat phases for all available data. Position time series were closely analyzed to estimate linear constant, coseismic displacements, postseismic motions, and other parameters. We present coseismic offsets inferred from the GPS data for the 2010 Yushu and 2014 Yutian earthquakes, and also illustrate transient postseismic motions following the 2001 Kokoxili, 2008 Wenchuan, and 2011 Tohoku-Oki earthquakes. Since not all GPS position time series dominated by postseismic motions can be modeled and corrected reasonably, we present contemporary horizontal velocities from 2009 to 2014 for campaign stations and from 1998 to 2014 for continuous stations, irrespective of postseismic deformations. Our study concludes that we need to accumulate observations over a greater duration and apply accurate postseismic modeling to correct for transient displacement in order to resolve reasonable interseismic velocity.

Study of the spectrum effect on the threshold of resonant magnetic perturbation penetration on J-TEXT

The spectrum effect on the penetration of resonant magnetic perturbation(RMP) is studied with upgraded in-vessel RMP coils on J-TEXT.The poloidal spectrum of the RMP field,especially the amplitudes of 2/1 and 3/1 components,can be varied by the phase difference between the upper and lower coil rows,ΔΦ=Φ_(top)-Φ_(bottom),where Φ_(top)and Φ_(bottom)are the toroidal phases of the n=1 field of each coil row.The type of RMP penetration is found to be related to ΔΦ,including the RMP penetration of either 2/1 or 3/1 RMP and the successive penetrations of 3/1 RMP followed by the 2/1 RMP.For cases with penetration of only one RMP component,the penetration thresholds measured by the corresponding resonant component are close for variousΔΦ.However,the 2/1 RMP penetration threshold is significantly reduced if the 3/1 locked island is formed in advance.The changes in the rotation profile due to 3/1 locked island formation could partially contribute to the reduction of the 2/1 thresholds.

SST-1 Refurbishment Progress: an Update

Refurbishment of steady state tokamak （SST-1） primarily focused at addressing the issues and bottle-necks involving various subsystems of SST-1 as observed during earlier commis- sioning attempts, have progressed significantly. Under the refurbishment spectrum, all joints in the superconducting magnet system have been re-fabricated as low DC leak tight joint resistances, all toroidal field （TF） magnets have been equipped with 5 K radiation shields on the inner side and successfully tested for their rated parameters in cold under nominal currents, all vessel sectors and modules have been baked and tested under representative conditions, supporting helium and ni- trogen cryogenic facilities have been made 〉 99% reliable in various envisaged operating scenarios of SST-1. The reassemblies of the critical subsystems of the SST-1 machine shell have progressed aggressively and are nearing completion. Auxiliaries such as the baking facility for the vacuum vessel and first wall components, current leads assembly distributions, synchronized timing sys- tem, reliable data acquisition and plasma control systems as well as essential diagnostics have also been readied towards the first plasma. A detailed engineering validation of the assembled SST-1 machine shell including field error measurements has been planned prior to first plasma attempts.

Analysis and mitigation of bump magnetic field tracking errors in a multiturn injection system

Purpose The Space Environment Simulation and Research Infrastructure(SESRI)is a cluster of accelerators designed to simulate the cosmic radiation environment by generating particles of various types and energies.Among these accelerators,a synchrotron in the 300 MeV proton and heavy ion accelerator complex utilizes a multiturn injection scheme with four bump magnets to accumulate proton and heavy ion beams effectively.However,the bump magnetic field experiences a rapid drop rate of up to 1000 T/s,inevitably leading to a deviation(field tracking error)from the ideal magnetic field.The injection efficiency and particle distribution are significantly affected by this field tracking error,as evaluated by the ACCSIM code.Method During the device testing stage,the sources of field tracking errors were identified by analysis of the bump power supplies and the field of the magnets.Mitigation techniques were then implemented to reduce the field tracking error from[Math Processing Error]to[Math Processing Error]throughout the entire power supply,transmission cable,and magnet chain.Results Moreover,the successful injection and accumulation of beams during the operational phase of the synchrotron confirmed the effectiveness of the proposed mitigation methods.Additionally,a magnetic field measurement system was developed to monitor the magnetic field tracking error online.Conclusion The combination of the field tracking error mitigation methods and the measurement system provides valuable guidance for optimizing the magnetic fields with rapid drop rates.

Study on the effects of chromaticity and magnetic field tracking errors at CSNS/RCS

The Rapid Cycling Synchrotron （RCS） is a key component of the China Spallation Neutron Source （CSNS）. For this type of high intensity proton synchrotron, the chromaticity, space charge effects, and magnetic field tracking errors between the quadrupoles and the dipoles can induce beta function distortion and tune shift, and induce resonances. In this paper, the combined effects of chromaticity, magnetic field tracking errors and space charge on beam dynamics at CSNS/RCS are studied systemically. 3-D simulations with different magnetic field tracking errors are performed by using the code ORBIT, and the simulation results are compared with the case without tracking errors.