To adjust a gamma ray spectrum's photopeak into the window, which action should be taken?

When dealing with gamma ray spectra, the photopeak represents the energy of the gamma photons detected by the system. Adjusting the photopeak into the appropriate energy window typically requires tuning the high-voltage settings of the detector.

Increasing the voltage effectively raises the energy threshold of the detecting system, allowing it to register higher energy gamma photons. This is crucial for aligning the photopeak with the specified energy range in the window. By setting the high voltage higher, the system can better encompass the photopeak, ensuring that the detected events correspond precisely to the desired energy levels, thus improving the accuracy of the spectrum analysis.

This adjustment is essential in optimizing detection efficiency and signal clarity, ensuring that the photopeak is well-placed within the established energy window, leading to better interpretation of the spectrum data.