Effect of coupling currents on the dynamic inductance during fast transient in superconducting magnets

Abstract-After LHC will be turned off, a new, more energetic machine will be needed in order to explore unknown regions of the high-energy physics. For this reason, the project Future Circular Collider (FCC) has started, with the goal of developing a 100 km circumference collider of 50 TeV proton beams. The Eurocircol collaboration is part of the FCC study under the European Community leadership, and it aims to develop a conceptual design of FCC within 2019. One of the main targets is to design a bending dipole able to reach 16 T operation magnetic field, in order to accomplish the size and energy constraints. Such a magnetic field can be reached using Nb3Sn conductors at their highest performance. One option under exploration is the Cosθ dipole, by INFN of Milano and Genova. One of the aspects to be taken into consideration is the amount of conductor needed, because of the relatively high cost of superconducting cables involving Nb3Sn. The amount of superconductor in the cross-section conductor area is a discriminant element for the choice of the magnet lay-out. At the same time enough copper stabilizer must be included in order to limit the Joule dissipation in case of quench. For these reasons, together with the very high stored energy, quench protection is one of the most challenging aspects of the design. In this paper, the quench protection of the cosθ design is presented. A standard quench protection study is accompanied by a less conservative study which includes AC effects on the power dissipation inside the coils and on the magnet inductance, in order to not exclude preventively more convenient designs, and to develop a more performing magnet as possible.

Section: Introductionmentioning

confidence: 99%

Quench Protection Study of the Eurocircol 16 T cosθ Dipole for the Future Circular Collider (FCC)

Marinozzi

Bellomo

Caiffi

et al. 2017

“…Nevertheless, these effects have been experimentally observed [1][2], the model developed for their simulation using QLASA has been experimentally validated [12], and they are confirmed by an innovative method of magnet inductance measurement during a fast current decay [13], therefore they have been included as nominal. Moreover, the reported numbers are probably yet conservative, because it has been showed that quench back, which is not included, strongly affects the fast decays [2].…”

Section: Hot Spot Temperaturementioning

confidence: 99%

Quench Protection Study of the Updated MQXF for the LHC Luminosity Upgrade (HiLumi LHC)

Marinozzi

Ambrosio

Ferracin

et al. 2016

Abstract-In 2023, the LHC luminosity will be increased, aiming at reaching 3000 fb-1 integrated over 10 years. In order to obtain this target, new Nb3Sn low-β quadrupoles (MQXF) have been designed for the interaction regions. These magnets present a very large aperture (150 mm, to be compared with the 70 mm of the present NbTi quadrupoles), and a very large stored energy density (120 MJ/m 3 ). For these reasons, quench protection is one of the most challenging aspects of the design of these magnets. In fact, protection studies of a previous design showed that the simulated hot spot temperature was very close to the maximum allowed limit of 350 K; this challenge motivated improvements in the current discharge modeling, taking into account the so-called dynamic effects on the apparent magnet inductance. Moreover, quench heaters design has been studied going into more details. In this paper, a protection study of the updated MQXF is presented, benefitting from the experience gained by studying the previous design. A study of the voltages between turns in the magnet is also presented during both normal operation and most important failure scenarios.

“…In absence of transitory losses and quench, the magnet differential inductance would equal the nominal value of L 0 =12.2 mH and the coil resistance would be nil during the entire discharge. Thus, the transport current would decay exponentially, following (8) with R c =0 and…”

Section: A Energy Extraction Systemmentioning

confidence: 99%

“…Quantitative studies of the effects of transitory loss on the magnet's differential inductance and coil resistance allow improved simulations of quench protection discharges [8], [13], [14]. Accurate modeling of transitory losses are mandatory in order to satisfactorily simulate magnet discharges using the CLIQ (Coupling-Loss Induced Quench) method [15]- [17].…”

mentioning

confidence: 99%

Modeling of Interfilament Coupling Currents and Their Effect on Magnet Quench Protection

Ravaioli

Auchmann

Chlachidze

et al. 2017

Self Cite

Abstract-Variations in the transport current of a superconducting magnet cause several types of transitory losses. Due to its relatively short time constant, usually of the order of a few tens of milliseconds, inter-filament coupling loss can have a significant effect on the coil protection against overheating after a quench. This loss is deposited in the strands and can facilitate a more homogeneous transition to the normal state of the coil turns. Furthermore, the presence of local inter-filament coupling currents reduces the magnet's differential inductance, which in turn provokes a faster discharge of the transport current. The Lumped-Element Dynamic Electro-Thermal (LEDET) model of a superconducting magnet has been developed to reproduce these effects. Simulations are compared to experimental electrical transients and found in good agreement. After its validation, the model can be used for predicting the performance of quench protection systems based on energy extraction, quench heaters, the newly developed CLIQ protection system, or combinations of those. The impact of inter-filament coupling loss on each protection system is discussed.