I’m not sure what it’s seeing either. When using the laser function, I have pointed that red dot everywhere on that copper cooler. Even down inside the center of the cooler where it bolts to the tube doesn’t show any higher. I would think that possibly this may be the hottest part due to the closeness to the actual anode and the lack of airflow right there. I get the same results, maybe a tad higher, not using that laser dot function. This does seem to change with distance toward or away from the tube slightly. I’m only gonna get so close to that 3600vdc plate voltage with anything though. I’m guessing the temp gun just isn’t accurate enough for this job.