**6.3 High magnetic field in Tokamaks**

Developments in fusion energy department have been made after the introduction of high-temperature superconductor (HTS) based technologies that imply high magnetic field induction (>18 T) for compact experiments in fusion power plants. Operation in high magnetic fields, large current densities, higher value of cryogenic temperature, and ability to withhold extreme tensile stress make HTS a suitable candidate as compared to LTS (Low-Temperature Superconductors). A large operating magnetic field range opens new opportunities to fabricate novel magnetic designs and improved magnetic confinement can be achieved for higher magnetic fields (> 16 T) with the help of HTS [99]. A maximum achievable induced field that depends upon current density present in HTSs has been a primary factor in fabrication of magnetic devices for fusion reactors as explained in basic tokamak design, in-depth studies, system codes, and tokamak magnet designs [100]. HTS offers a significant increase (~7.5 to 10–12 T) in on-axis BT in tokamak reactor which allows a significant increase in an applicable field in coil from 16 T to >20 T) as compared to LTS. Other advantages of HTS technology in fusion energy department include:


### **6.4 Future tool kit for advanced application**

As previously mentioned, HTS technology is enriched with many novel applications with medical diagnostics and energy transport/harvesting being top of the list (**Figure 8**). A major challenge faced by HTS technology is the need for extremely low temperature which is generally achieved with the help of liquid nitrogen or helium which is much costly. On the other hand, the use of H2S for cooling purposes requires high values of pressure. Fabrication of superconductors having critical temperature (Tc) values in room temperature (RT) range with easily employable materials is a challenging task. The unavailability of any predictive route and no unique agreement on pairing mechanism of HTS technology limit the scope of this search. Apart from this drawback, low manufacturing cost is another challenge that can be overcome with use of materials existing abundantly on this planet. Stability, easy fabrication procedures, and flexibility are also required. Novel and advanced approaches need to be developed to meet all these challenges for a sustainable future [103, 104].

Although seems difficult, current scientific knowledge proposes a high probability of realizing fabrication of RT superconductors in near future. Successful manufacturing of such devices will open a vast field of applications especially in the field of energy production and transport at low cost (at ambient pressure). The development of novel technologies and advanced devices could be realized and different Gedanken experiments would be applicable with the help of RT superconductors. Imagine a conducting cable having almost zero energy losses where electrical current can flow forever with no power loss. Advanced high power generating grids could be installed using RT superconductivity technology to fabricate improved transformers, fault current limiters, and novel synchronous condensers. Moreover, a wire with never depleting current could also be used as an RT SMES (superconducting magnetic energy storage) device. RT SMES device, as opposed to other typical storage devices, would offer everlasting storage of energy with negligible losses [105].

Another similar application of RT superconductors is the development of advanced bearings to be used in flywheel energy storage. Other applications include production of high-field superconducting magnets for scientific and technical use while cost-effective and improved MRI scanners would be available for medical applications. Compact and simplified fabrication (no cooling required) of rotating motors, generators, and other electromechanical devices would also be possible with RTS technology. This would open new opportunities for the production of electric motor cars and electric storage devices in the future. In transport department, a significant enhancement in levitating trains technology is also expected where superconducting magnetic levitation phenomenon could be employed. Improvement in low-power technologies like SQUIDS, detectors, filters, and sensors is also expected with the use of RT superconductors which would bring revolutionary changes in medical and information technology. Lastly, realization of compact

**71**

*High Temperature Superconductors*

*DOI: http://dx.doi.org/10.5772/intechopen.96419*

novel technology [59, 60, 106, 107].

**7. Outlook and future prospects**

while Tc isn't affected by chemical doping.

Authors have declared no 'conflict of interest'.

**Conflict of interest**

and efficient quantum and Josephson computers will also become possible with this

Around the world, a neglected hope exists to reduce energy costs using superconductivity in power transmissions. In the nearby future of transportation, Mag-1 eV trains use superconductivity for eliminating friction to poise train cars above the rail. Who knows? Maybe one-day smartphones with long-lasting battery timing up to months or more would be manufactured based on superconductivity electronics. High-Tc era exposed remarkable production with a new superconductor family (Tc ≥ 23 K) discovered every few years in its first 25 years. Prediction of future discoveries is difficult as each class is chemically distinct from the others but some indicators are quite obvious. Future HTSCs are incredible having considerable (≥50%) nonmetal content based on known materials with high-Tc. 'Metalnonmetal' group associates very high Tc's having nonmetal contents of 40–60% with simple ionic bond considerations. Since 2008, none of any element in previous high-Tc families had featured except Fe. Spin–Spin fluctuations are necessary for the superconducting mechanism of cuprates and iron arsenide materials with highest-Tc, where transition metals are required in heavy-fermion (intermetallic) superconductor PuCoGa (Tc = 18 K) with f-block magnetism [29, 108]. In near future, such materials doped with nonmetals would lead towards tremendous discoveries. Other electronic instabilities may arise on basis of non-magnetic mechanisms, as suppression of charge disproportionation for the bismuthate superconductors. In metal-nonmetal families, chemical doping is prescribed to put an end to spin/charge-ordered ground state inducing superconductivity. This may happen due to incidental band overlap (as in YBa2Cu3O7) but sometimes by nonaliovalent substitutions of non-stoichiometry. However, disorders in metal-nonmetal's networks lead to subduing superconductivity. To obtain high-Tc's, chemical tuning of additional parts of the network (charge reservoir) manifested via difference between maximum Tc for BaBi1-xPbxO3 (13 K, essential Bi sites doping) and for Ba1-xKxBiO3 (30 K, secondary Ba sites doping). Another high-Tc materials class is portrayed by bonding among metals and nonmetals which is attributed to high content values of nonmetals (100% in case of pure organic SCs). Elements forming strong covalent bonds and networks, B and C are restricted to this group but similar nonmetals (O, N, S, P, Si) can act as dopants as well. Highest obtained Tc (41 K) so far, owing to predictions from optimal BCS (weak-coupling) and superconductivity acts like BCS in this group. For A3C60 and MgB2 (and also YPd2B2C) with proper stoichiometry, the optimal electronic structure for superconductivity is attained

*Transition Metal Compounds - Synthesis, Properties, and Application*

**6.4 Future tool kit for advanced application**

[101, 102].

future [103, 104].

with negligible losses [105].

4.Operational Robustness: Compact high-field devices suffer no typical intrinsic limits (density, pressure) as they operate in normalized plasma domains. Currently, operative devices demonstrate such operating domains including safety factor (q), normalized beta (βN), and confinement enhancement factor (H).

As previously mentioned, HTS technology is enriched with many novel applications with medical diagnostics and energy transport/harvesting being top of the list (**Figure 8**). A major challenge faced by HTS technology is the need for extremely low temperature which is generally achieved with the help of liquid nitrogen or helium which is much costly. On the other hand, the use of H2S for cooling purposes requires high values of pressure. Fabrication of superconductors having critical temperature (Tc) values in room temperature (RT) range with easily employable materials is a challenging task. The unavailability of any predictive route and no unique agreement on pairing mechanism of HTS technology limit the scope of this search. Apart from this drawback, low manufacturing cost is another challenge that can be overcome with use of materials existing abundantly on this planet. Stability, easy fabrication procedures, and flexibility are also required. Novel and advanced approaches need to be developed to meet all these challenges for a sustainable

Although seems difficult, current scientific knowledge proposes a high probability of realizing fabrication of RT superconductors in near future. Successful manufacturing of such devices will open a vast field of applications especially in the field of energy production and transport at low cost (at ambient pressure). The development of novel technologies and advanced devices could be realized and different Gedanken experiments would be applicable with the help of RT superconductors. Imagine a conducting cable having almost zero energy losses where electrical current can flow forever with no power loss. Advanced high power generating grids could be installed using RT superconductivity technology to fabricate improved transformers, fault current limiters, and novel synchronous condensers. Moreover, a wire with never depleting current could also be used as an RT SMES (superconducting magnetic energy storage) device. RT SMES device, as opposed to other typical storage devices, would offer everlasting storage of energy

Another similar application of RT superconductors is the development of advanced bearings to be used in flywheel energy storage. Other applications include production of high-field superconducting magnets for scientific and technical use while cost-effective and improved MRI scanners would be available for medical applications. Compact and simplified fabrication (no cooling required) of rotating motors, generators, and other electromechanical devices would also be possible with RTS technology. This would open new opportunities for the production of electric motor cars and electric storage devices in the future. In transport department, a significant enhancement in levitating trains technology is also expected where superconducting magnetic levitation phenomenon could be employed. Improvement in low-power technologies like SQUIDS, detectors, filters, and sensors is also expected with the use of RT superconductors which would bring revolutionary changes in medical and information technology. Lastly, realization of compact

5.Steady-State Physics: A blend of high-field, compact size, improved current profile, and high value of safety factor will generate a device having steady-state operation and high gain with good control over external current

**70**

and efficient quantum and Josephson computers will also become possible with this novel technology [59, 60, 106, 107].
