**5.1 Major application**

Majority of gyrotrons developed worldwide are being used for the electron cyclotron resonance heating (ECRH) of plasma in the controlled thermoneuclear fusion reactor [7]. The plasma is kept confined in the plasma vessel with the help of very high value of superconducting magnetic field (magnetic confinement). The magnetically confined plasma is then exposed to very high power millimeter wave beam generated with the help of a gyrotron. This elevates the temperature of the plasma to 100000<sup>0</sup> C. At this temperature, fusion reaction takes place. Millimeter-wave beam generated by a gyrotron is also used for the electron cyclotron current drive (ECCD), electron cyclotron resonance ion source (ECRIS) and also for the diagnostics cooling tower system (CTS). For the ITER (international thermoneuclear experimental reactor) project, it's proposed to use 20 numbers of 170 GHz long-pulse gyrotrons to generate combined heating power of 24 MW. For this purpose, till now, the highest order mode number attempted is TE34,19 for the generation of 2 MW of continuous

**Figure 14.** *2 MW Gyrotron for ECRH application.*

**Figure 15.** *140 GHz Gyrotron based ECRH system (Stellarator W7-AS).*

power at 170 GHz. The photograph of a 2 MW gyrotron for ECRH application is shown in **Figure 14**. The photograph of a ECRH System (Stellarator W7-AS) with 140 GHz gyrotron is shown in **Figure 15**.

*Gyrotron: The Most Suitable Millimeter-Wave Source for Heating of Plasma in Tokamak DOI: http://dx.doi.org/10.5772/intechopen.98857*
