stxm5_displays.pro

From a STXM 5 data file, we get a 3-dimensional data array, which holds an image for each detector which was recorded in the scan. This data array can be calibrated to khz (see Sec. 13.6). But sometimes (in particular for scans done with the segmented silicon detector) we want to display linear combinations of these images. stxm5_displays.pro returns the coefficients for a number of predefined linear combinations which might be of interest in STXM 5. The calling sequence is

    IDL> stxm5_displays, disp_names, $
                         linear_combinations, $
                         n_data=n_data, $
                         long_names=long_names, $
                         list_only=list_only, $
                         i_counter=i_counter, $
                         i_clock=i_clock, $
                         i_first_sidet_channel=i_first_sidet_channel, $
                         n_sidet_channels=n_sidet_channels, $
                         no_output=no_output, $
                         help=help

To see a list of the names of all predefined combinations with their short and long names, call

    IDL> stxm5_displays, /list_only
      disp_name            long_name
      --------------------------------------------------
      Counter              Proportional Counter
      Clock                Clock Signal
      Segment 1            Silicon Detector Segment 1 (inner lower)
      Segment 2            Silicon Detector Segment 2 (inner middle)
      Segment 3            Silicon Detector Segment 3 (inner upper)
      Segment 4            Silicon Detector Segment 4 (lower left)
      Segment 5            Silicon Detector Segment 5 (upper left)
      Segment 6            Silicon Detector Segment 6 (upper right)
      Segment 7            Silicon Detector Segment 7 (lower right)
      Segment 8            Silicon Detector Segment 8 (outer dark field ring)
      Sum Inner Ring       Sum Inner Ring (Segments 1 through 3)
      Sum Quadrant Ring    Sum Quadrant Ring (Segments 4 through 7)
      BF matched           Bright Field matched (Segments 1 through 7)
      BF total             Bright Field total (Segments 1 through 8)
      DPC horizontal       Differential Phase Contrast horizontal (Segments 4+5-6-7)
      DPC vertical         Differential Phase Contrast vertical (Segments 5+6-4-7)
      DPC diagonal up      Differential Phase Contrast diagonal up (Segments 4-6)
      DPC diagonal down    Differential Phase Contrast diagonal down (Segments 5-7)
      DPC 1-3              Differential Phase Contrast Segments 1-3

To really return the coefficients, call the procedure as told above, where the parameters and keywords have the following meaning:

disp_names

is a string array which will be returned holding the short names for all predefined linear combinations (currently 19)

linear_combinations

is a 2-d float array which will be returned holding the coefficients for the linear combinations. See below for an example.

n_data

is a required keyword parameter telling how many detector channels the image data array has (size of the third dimension of the data array).

long_names

can optionally be returned, holding long, more descriptive names for the linear combinations.

list_only

Set this flag to only display your choices, see above.

i_counter, i_clock, i_first_sidet_channel, n_sidet_channels

can be specified as the indices of the corresponding detector channels in the data array, and the number of silicon detector segments. Set to $-1$ if that channel doesn't exist.

Knowing these is absolutely crucial to determine the correct linear combinations. If they are not specified, the procedure will make some guesses from the number of recorded channels. To be on the safe side though, you should specify them.

no_output

Set this keyword to suppress warnings.

The returned array linear_combinations has 2 dimensions. Each "line" in the array corresponds to one of the predefined combinations and has as many elements as the number of channels which was specified. Each element of one "line" holds the coefficient for that channel, which is usually $+1$, $0$ or $-1$.

For instance, if we have a data array with 9 recorded channels, where the first 8 are silicon detector segments 1 through 8, and the 9th channel is the clock, the "line" holding the linear combination "DPC horizontal" (calculated as Segments $4+5-6-7$) would be [0, 0, 0, 1, 1, -1, -1, 0, 0].

For scans where the proportional counter, the clock, or the silicon detector was not recorded, the coefficients for the corresponding linear combinations will all be zero.