  Local dissipation of RF power in superconducting radio frequency cavities
create so called hot spots, primary precursors of cavity quench driven by
either thermal or magnetic instability. These hot spots are detected by a
temperature mapping system, and a large increase in temperature on the outer
surface is detected during cavity quench events. Here, we have used combined
magnetic and temperature mapping systems using anisotropic magnetoresistance
(AMR) sensors and carbon resisters to locate the hot spots and areas with high
trapped flux on a 3.0 GHz single-cell Nb cavity during the RF tests at 2.0 K.
The quench location and hot spots were detected near the equator when the
residual magnetic field in the Dewar is kept < 1 mG. The hot spots and quench
locations moved when the magnetic field is trapped locally, as detected by
T-mapping system. No significant dynamics of trapped flux is detected by AMR
sensors, however, change in magnetic flux during cavity quench is detected by a
flux gate magnetometer, close to the quench location. The result provides the
direct evidence of hot spots and quench events due to localized trapped
vortices.
