Spin echo is a very common method in NMR experiments, but there are still some details that confuse me during solid-state NMR experiments, and I hope to get some help. My questions are:

Additionally, I observed a phenomenon during my experiment. When I performed a 1H echo experiment on ammonium dihydrogen phosphate (ADP) at a spinning rate of 50kHz, I found that a good signal could be observed with a single scan, but after every four scans, the signal became much weaker. Could you tell me what might be causing this issue? My phase cycling is shown in the figure.