Setting up ASTA UED LLRF for 180 Hz operation
ASTA UED derives its timing from LCLS EVG timing system.
LCLS EVG now has a new event code '165' for 180 Hz operation on beamcode 0 for LCLS.
Currently the masks for the event code 165 have been setup to exclude time slots 1,3 and 5 with the exclusion mask of 0x15 in Modifier 2.
Thus time slots 2,4 and 6 alone are active.
Each time slot corresponds to 60 Hz. Thus the three active time slots support 3*60Hz = 180 Hz operation.
Please do not change the Event modifier bits. Leave them as they are now:
The VME Master IOC-AS01-RF01 has been modified to look for the above patterns.
- It provides pattern matching in three time slots for 180 Hz operation, instead of two time slots that were originally done for 120 Hz.
- Event code 165 has been added to the default set of events and visible in AS01 EVR RF01 Trigger Diags panel.
- Setting up 180 Hz timing:
- Navigate to astahome->Event/ASTA->LLRF->Experts->RF01 Triggers...
- This brings up the 'AS01 EVR RF01 Trigger Diags' panel as shown in figure above.
- Enable the IRQ button in the first row corresponding to 165. You will see the 'Rate' PV corresponding to this row display '180.0'
- Setup the feedback rate to 180 Hz:
- Then bring up the PAU screen by clicking on 'PAU AS01 Gun' towards the bottom left of above VME panel.
- Ensure 'Activate PAU' button is 'ON'.
- Ensure Beam code for all the four data slots DS0,DS1,DS2 an DS3 are '0'. This corresponds to LCLS beamcode.
- Set the Time slot for DS0 to '2', for DS1 to '4' and for S2 to '6'. These correspond to the three included timeslots TS2, TS4, TS6.
- The last data slot is not included in the feedback loop - so it does not matter what it is set to. Leave it at '1'.
- For each time slot corresponding to a data slot, there are two sets of patterns.
- The first row of patterns are modifier bits that provide inclusion. The second row provide exclusion.
- Set the exclusion masks for 'Mod. 2' for DS0,DS1 and DS2 to '0x15'. This excludes TS1,TS3,TS5 timeslots.
- For DS4, set it to '0xffffff'. This will exclude the fourth dataslot.
- All other modifier bits for all data slots should be set to 0.
- Change the Pipeline Index to '1' (from '2').
- Reduce the 'Delay (usec)' to '850' (from '970'). We will have to play with this value till we optimize feedback performance.
This is just a starter value. - The 'Callback call rate (Hz):' field should show 180.00 after these changes. This means feedback is operating at 180 Hz.
- Then bring up the PAU screen by clicking on 'PAU AS01 Gun' towards the bottom left of above VME panel.
- Then bring up the PAU screen by clicking on 'PAU AS01 Gun' towards the bottom left of above VME panel.
- Ensure 'Activate PAU' button is 'ON'.
- Ensure Beam code for all the four data slots DS0,DS1,DS2 an DS3 are '0'. This corresponds to LCLS beamcode.
- Set the Time slot for DS0 to '2', for DS1 to '4' and for S2 to '6'. These correspond to the three included timeslots TS2, TS4, TS6.
- The last data slot is not included in the feedback loop - so it does not matter what it is set to. Leave it at '1'.
- For each time slot corresponding to a data slot, there are two sets of patterns.
- The first row of patterns are modifier bits that provide inclusion. The second row provide exclusion.
- Set the exclusion masks for 'Mod. 2' for DS0,DS1 and DS2 to '0x15'. This excludes TS1,TS3,TS5 timeslots.
- For DS4, set it to '0xffffff'. This will exclude the fourth dataslot.
- All other modifier bits for all data slots should be set to 0.
- Change the Pipeline Index to '1' (from '2').
- Reduce the 'Delay (usec)' to '850' (from '970'). We will have to play with this value till we optimize feedback performance.
This is just a starter value. - The 'Callback call rate (Hz):' field should show 180.00 after these changes. This means feedback is operating at 180 Hz.
- Ensure 'Activate PAU' button is 'ON'.
- Ensure Beam code for all the four data slots DS0,DS1,DS2 an DS3 are '0'. This corresponds to LCLS beamcode.
- Set the Time slot for DS0 to '2', for DS1 to '4' and for S2 to '6'. These correspond to the three included timeslots TS2, TS4, TS6.
- The last data slot is not included in the feedback loop - so it does not matter what it is set to. Leave it at '1'.
- For each time slot corresponding to a data slot, there are two sets of patterns.
- The first row of patterns are modifier bits that provide inclusion. The second row provide exclusion.
- Set the exclusion masks for 'Mod. 2' for DS0,DS1 and DS2 to '0x15'. This excludes TS1,TS3,TS5 timeslots.
- For DS4, set it to '0xffffff'. This will exclude the fourth dataslot.
- All other modifier bits for all data slots should be set to 0.
- Change the Pipeline Index to '1' (from '2').
- Reduce the 'Delay (usec)' to '850' (from '970'). We will have to play with this value till we optimize feedback performance.
This is just a starter value. - The 'Callback call rate (Hz):' field should show 180.00 after these changes. This means feedback is operating at 180 Hz.
6. Navigate to astahome->RF/Global->Gun->Mux for PDES
This brings up the 'GUN:AS01:1:PDES' panel.
Ensure 'Fast Feedback' is 'OFF'.
7. Navigate to astahome->RF/Global->Gun->Mux for ADES
This brings up the 'GUN:AS01:1:ADES' panel.
Ensure 'Fast Feedback' is 'OFF'.
Note: We will use the 'Offset' fields to compensate for some more of the jitter. This is under investigation and for future.
For now ensure all the four Offset PVs are 0.0