Author: Myneni, G.R.
Paper Title Page
WEPPC091 A Path to Higher Q0 with Large Grain Niobium Cavities 2426
  • P. Dhakal, G. Ciovati, G.R. Myneni
    JLAB, Newport News, Virginia, USA
  The improvement of the quality factor Q0 of superconducting radio-frequency (SRF) cavities at medium accelerating gradients (~ 20 MV/m) is important in order to reduce the cryogenic losses in continuous wave accelerators for a variety of applications. In recent years, SRF cavities fabricated from ingot niobium have become a viable alternative to standard high-purity fine-grain Nb for the fabrication of high-performing SRF cavities with the possibility of significant cost reduction. Initial studies*,**, demonstrated the improvement of Q0 at medium field in cavities heat treated at 800-1000 °C without subsequent chemical etching. To further explore this treatment procedure, a new induction furnace with an all-niobium hot-zone was commissioned. A single-cell 1.5 GHz cavity fabricated from ingot material from CBMM, Brazil, with RRR~200, was heat treated with the new furnace in the temperature range 600-1400 °C for several hours. Residual resistance values below 5 nano Ω have been consistently achieved on this cavity as well as Q0 values above 4.5×1010 at 2 K and 100 mT peak surface magnetic field. Q0-values of the order of 1011 have been measured at 1.5 K.
* G. Ciovati, et al., Phys. Rev. ST Accel. Beams 13, 022002 (2010).
** G. Ciovati, et al., Proc. of the 15th Int. Conf. on RF Superconductivity, Chicago, July 25-29, 2011, paper TUPO051