PEP-II LLRF Gap Voltage Control Panel


Overview

This panel contains the various constants necessary to control the station gap voltage. This is an interesting task since the actuator changes depending on if the direct RF feedback loop is closed or open.  With the direct loop open, the actuator is the HVPS output voltage. With the direct loop closed, the reference IQ voltages (either from the gap module or from the RF Processing (RFP) module if it is configured to operate without a gap module) controls the gap voltage.

The gap voltage panel can be accessed from the Feedback panel or some of the other buried panels.

TUNE or ON State with Direct Loop OFF

In TUNE, ON_CW, or ON_FM state with the direct loop OFF, the gap voltage is controlled by the HVPS output voltage.  The following equation converts the gap voltage error into HVPS output voltage change.  There is a restriction on how much the HVPS setpoint can change on each iteration:

Delta HVPS voltage = Err * Gain Factor * Conversion

ON_CW State - Direct Loop ON - GVF Module Missing

In ON_CW state with the direct loop ON, the gap voltage is controlled by the baseband IQ reference voltages.  The station can be configured to operate without a Gap module by changing a pair of jumpers in the RFP module. The following constants support this condition.

ON_CW State - Direct Loop ON - GVF Module Available

In ON_CW state with the direct loop ON, the gap voltage is controlled by the baseband IQ reference voltages.  The following parameters are used to setup the normal hardware configuration which includes a Gap module to produce the baseband IQ reference voltages.  The following constants support this condition.