Slits

Table of contents

• 2-Blade Slits
  • 2slit.adl
  • RELTOCENTER macro
  • Calibration and synchronization
• 4-Blade and XIA Slits

2-Blade Slits

2slit.adl

The 2-blade slit database (2slit.db) provides coordinated control of two slit blades through four virtual motors: “-“, “+”, “size”, and “center”.

The display pictured above uses EPICS analog output records for virtual motors. There is a second version of the 2-blade slit software that uses soft motor records for virtual motions, which is more convenient for spec users. See 2slit*soft* in src, Db, and op directories.

RELTOCENTER macro

The 2slit.db database can operate in two modes, controlled by the RELTOCENTER macro:

Value	Description
RELTOCENTER=0 (default)	Both motors are in the same coordinate system. When the center position is increased, both motors’ .VAL fields increase. Both motors must have the same engineering units.
RELTOCENTER=1	Motor .VAL fields increase as the slit opens. Both motors must have the same engineering units.

Calibration and synchronization

The slit software keeps all readback values current regardless of how the actual motors are moved or recalibrated, but it does not automatically reset the slit drive values when the underlying motors are moved directly. To synchronize, use the “SYNC” button on the display, which reads the actual motor drive values and sets the slit drive values accordingly.

To recalibrate slit positions, press “Set”, type in the desired current position, and press “Use”. This uses the “Set” buttons and user/dial offsets of both underlying motors.

4-Blade and XIA Slits

4slitGraphic.adl	xia_slit_full.adl

The 4-blade slit graphic display provides a visual overview of all four blades with size and center readbacks. The XIA HSC slit support communicates with XIA hardware via an SNL program (xia_slit.st) and provides coordinated size and center control.