MSP430FR6047: ADC capture waveform abnormal

Hi Teams,

I built a platform as same as the one in the Application Report “Liquid Concentration Sensing” (the same 2MHz transducers and 3D printed fixture) basing on  EVM430-FR6047. (Figure 1).

Then I connected the EVM and set the parameters on the USS according to the user's guide "SLAU810B". (Figure 2)

I set the "Transmit Frequency" F1=2000, the others parameters were kept default value. (Figure 3) 

But my ADC capture is abnormal. (Figure 4)

I had tried the way in Chapter 4.3 of SLAU810B, but the ADC Capture didn't change.

I browsed other posts in the E2E forums and didn't find the same problem as I did. It's the first time I use this application. Could you give me some advice to improve the ADC Capture.

Thanks!

Figure 1

Figure 2

Figure 3

Figure 4