Alignment functions

This chapter introduces functions needed for alignment. Those functions use the selected counter data (plotselect) of the last scan (SCANS[-1]) for calculation.

In case of multi counters, it is possible to specify the counter to use for the alignment as parameters. i.e: cen(counter=my_counter) goto_com(counter=my_counter)

In case of multi motors (anscan), all this function can use a specific axis either for the calculation or the movement (goto_ functions). goto_cen(axis=robz) peak(axis=robz) If the axis is not specify, cen,com,peak function will return value for all axis and the goto_ function will move all motors.

Counters selection

The counter selection can be done graphically with Flint or with the plotselect user function: plotselect(<counter_list>)

Example

DEMO [2]: plotselect(sim_ct_2)

Currently plotted counter(s):
- sim_ct_2

Without argument, the command will display a help message and the list of currently selected counters.

Example

DEMO [5]: plotselect()

plotselect usage:
    plotselect(<counters>*)
example:
    plotselect(counter1, counter2)


Currently plotted counter(s):
- sim_ct_1
- sim_ct_calib_gauss
- elapsed_time

For Developpers

plotselect() user function is imported from bliss.common.standard and is built on top of bliss.common.scans.plotselect() which can be advantageously used in non interactive sequences.

The list of selected counters is stored via a HashSetting using <session_name>:plot_select as key.

cen()

This function return the fwhm center motor position and the fwhm ( Full Width at Half Maximum) of the last scan.

fwhm_center,fwhm = cen()

com()

This function return the motor position of the center of mass.

center_of_mass_pos = com()

peak()

This function return the motor position at the counter maximum.

max_pos = peak()

Go to function

• all the previous functions have a corresponding goto_XXX() function to go directly to the calculated position:
  • goto_cen()
  • goto_com()
  • goto_peak()
• Before the movement, the goto_XXX functions will print the previous position and the future position of the motor with a WARNING message.
• In case of motion abortion, the motor returns to its previous position.
• At the end of the function the motor position will be displayed in Flint unless the variable SCAN_DISPLAY.motor_position is equal to False. i.e: goto_cen will move the motor to the center of fwhm.

examples:

DEMO [11]: plotselect(simct1)

DEMO [12]: goto_cen()
WARNING  bliss.scans: Motor mm1 will move from 10.000000 to 4.337243

DEMO [13]: goto_peak()
WARNING  bliss.scans: Motor mm1 will move from 4.337243 to 10.000000

DEMO [14]: goto_com()
WARNING  bliss.scans: Motor mm1 will move from 10.000000 to 4.805529

where()

To display current position of the motor used in the last scan use:

    where()