function fname=data_file_name(prefix, title, suffix,  B_field, theta,phi,psi_el)
	str_title=sprintf("%s B field=%.5f Gauss, ellipticity=%.2f rad, theta=%.2f, phi=%.2f", title,  B_field, psi_el, theta, phi);
	fname=strcat(prefix, str_title, '.', suffix);
endfunction