Forward propagation of ultrasonic frequencies does not converge

[Lujiang-ECUST]

HI,thank you very much for freely publishing your code! I want to apply Pyfwi to the ultrasonic frequency band, when I set the time sampling rate(dt), spatial sampling rate (dh), and frequency fdom inside the inpa as the following parameters,

inpa = {
'ns':1,  # Number of sources
'sdo': 4,  # Order of FD
'fdom': 5e6,  # Central frequency of source
'dh':114e-6,  # Spatial sampling rate
'dt': 1e-8,  # Temporal sampling rate
'acq_type': 1,  # Type of acquisition (0: crosswell, 1: surface, 2: both)
't': 3.4e-6,  # Length of operation
'npml': 40,  # Number of PML
'pmlR': 1e-5,  # Coefficient for PML (No need to change)
'pml_dir': 2,  # type of boundary layer
'device': 1, # The device to run the program. Usually 0: CPU 1: GPU
# 'seimogram_shape': '3d',
'rec_dis':1,
# 'tv':{'lambda_weight':0.2, 'ax':0.2, 'az':0.2, }
# prior_model'
'fn':5E6*20
}

the maximum speed of the velocity model I used is 6300m/s, and the minimum speed is 5800m/s. After my theoretical calculations, I am sure that this set of parameter satisfies the CFL condition as well as the stability condition for staggered finite difference convergence, but it never works correctly.
I would be grateful if you could provide me with the correct set of inpa parameters for this model and frequency.