ExpPara
Experimental parameters necessary to define the scattering geometry for a 2D detector.
bm_ctr_x, bm_ctr_y specify the beam center position, defined as the pixel coordinates
of the intersection between the beam and the detector.
ratioDw is the sample-to-detector distance, defined as a dimensionless ratio between
this distance and the horizontal dimenson of the detector sensing area.
wavelength is the x-ray wavelength, in angstrom ( \(\unicode{x212B}\) ) .
flip defines how the detector image should be reoriented when read from the data file.
The numberical value is the number of 90-deg rotations. The image is first mirrored
(lef and right) if the value is negative.
rot_matrix is the rotation matrix that translate the detector pixel position into
coordinates in the lab reference frame. This matrix should be calculated in classes
inhereted from ExpPara, where the method of calculatiing this rotation matrix is defined.
sample_normal, incident_angle are parameters that define the sample orientation in grazing
incident geometry ( only effective when grazing_incidence is True ).
From these parameters, these reciprocal coordinates for each pixel are then calculated:
Q : the amplitude of the scattering vector, in \(\unicode{x212B}^{-1}\)
Phi : the azimuthal angle, \(\phi\), in degrees.
Qr, Qn : projection of the scattering vector perpendicular/paralell to the sample
normal (grazing incidence)
xQ, yQ: projection of the scattering vector in the horizontal/vertical directions.
These common correction factors are also calculated:
FPol is the polarization vector, assuming that the x-ray is linearly polarized along
the horizontal direction (synchrotron radiation).
FSA accounts for the difference in the solid angle each pixel opens to the sample.
Mask
Mask for the scattering data to eliminate pixels to be excluded from data processing. A mask in py4xs is typically defined as a collection of geometric shapes. The mask should have the same dimension as the detector image.
map : the actual bit map that indicate excluded pixels
read_file() : read the mask from a text file that defines the collection
of shapes, one per line . Valid shapes include:
rectangles: r xc yc width height tilt_angle
circles: c xc yc radius
holes (inverse of circles): h xc yc radius
polygons: p x1 y1 x2 y2 ... x1 y1
read_from_8bit_tif() : create the mask map from a 8-bit tif file. All the pixels
with the numerical value of 255 will be considered as part of the mask. This is useful
to be used together with Data2d.save_as_8bit_tif(), which creates a tif file from
the 2D data. The tif file can be then modified in an image editor like gimp, where
the mask is painted white.
reload() : re-read the text mask that defines the mask. Any addition to the
mask after the last read will be lost.
add_item() : add new shapes into the existing mask
DetectorConfig
All detector-related information
extension : detector extension/designation that appears in the data file name
exp_para : experimental parameters for the detector, as defined above
s2d_distance: sample-to-detector distance, in \(mm\)
mask : as defined above [this is saved under exp_para for now]
dark, flat : dark field and flat field data needed to apply corrections.
pre_process() : method for performing drak field and flat feld corrections. This is not implemented but
can be defined by the user.