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.

    1. It provides pattern matching in three time slots for 180 Hz operation, instead of two time slots that were originally done for 120 Hz.
    2.  Event code 165 has been added to the default set of events and visible in AS01 EVR RF01 Trigger Diags panel.

  1. Setting up 180 Hz timing:
    1. Navigate to astahome->Event/ASTA->LLRF->Experts->RF01 Triggers...
    2. This brings up the 'AS01 EVR RF01 Trigger Diags' panel as shown in figure above.
    3. Enable the IRQ button in the row corresponding to 165. You will see the 'Rate' PV corresponding to this row display '180.0'

  2. Before switching from 120 Hz to 180 Hz operation, first disable Gun LLRF Feedbacks:



  3. Setup the UED Gun LLRF feedback rate to 180 Hz:
    1. Bring up the PAU screen by clicking on 'PAU AS01 Gun' towards the bottom left of above VME panel.
      1. Ensure 'Activate PAU' button is 'ON'.
      2. Ensure Beam code for all the four data slots DS0,DS1,DS2 an DS3 are '0'. This corresponds to LCLS beamcode.
      3. 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.
      4. 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'.
      5. For each time slot corresponding to a data slot, there are two sets of patterns.
        1. The first row of patterns are modifier bits that provide inclusion. The second row provide exclusion.
        2. Set the exclusion masks for 'Mod. 2' for DS0,DS1 and DS2 to '0x15'. This excludes TS1,TS3,TS5 timeslots.
      6. For DS4, set it to '0xffffff'. This will exclude the fourth dataslot.
      7. All other modifier bits for all data slots should be set to 0.
      8. Change the Pipeline Index to '1' (from '2').
      9. 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.
      10. The 'Callback call rate (Hz):' field should show 180.00 after these changes. This means feedback is operating at 180 Hz.



  4. Navigate to astahome->RF/Global->Gun->Mux for PDES
    1. This brings up the 'GUN:AS01:1:PDES' panel.
    2. Ensure 'Fast Feedback' is 'OFF'

  5. Navigate to astahome->RF/Global->Gun->Mux for ADES
    1. This brings up the 'GUN:AS01:1:ADES' panel.
    2. Ensure 'Fast Feedback' is 'OFF'.
      Note: We will use the 'Offset' fields to compensate for some more of the data slot specific timeslot jitter.
      This is under investigation and for future.
      For now ensure all the four Offset PVs are 0.0


  6. Setup the PAC trigger rate to 180Hz.
    1. TTB13 'GUN PAC Control' is the trigger for the Gun PAC. 
      Disable the button corresponding to column '13' in whichever row it is enabled (Event Code '40' or '41' or '42') 
      Enable the button corresponding in row corresponding to Event Code '165' column '13'.
      Ensure that only the button corresponding to to the '165' is enabled and all others are disabled under column 13.
    2. The SSSB trigger from the PAC output. Thus, if the PAC triggers at 180 Hz, so will the SSSB.

  7. The Modulator is triggered by TTB3 'MOD TRIG Control'.
    1. Disable the button corresponding to column '3' in whichever row it is enabled (Event Code '40' or '41' or '42') 
      Enable the button corresponding in row corresponding to Event Code '165' column '3'.
      Ensure that only the button corresponding to to the '165' is enabled and all others are disabled under column 3.

  8. Setup the PAD trigger rate to 180 Hz.
    1. TTB11 'GUN PAD Control' is the trigger for the Gun PAD. 
      Disable the button corresponding to column '11' in whichever row it is enabled (Event Code '40' or '41' or '42') 
      Enable the button corresponding in row corresponding to Event Code '165' column '11'.
      Ensure that only the button corresponding to to the '165' is enabled and all others are disabled under column 11.



  9. Now enable the LLRF Gun feedback loops:

If the PAU has been configured correctly three of the four dataslots (DS0, DS1, DS2)  should be updating. This shows that the feedback is working at 180 Hz.

Navigate to astahome->RF/Global->Gun->PatternAware:


 

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