1. Pedestal Tracking in action a.k.a. Active Stabilization of L1Cal Trigger Tower Zero Energy Response Philippe Laurens Michigan State University 09-Nov-2007

2. Reminder: Active Stabilization of Trigger Tower Zero Energy Response L1Cal TCC now automatically tracks and adjusts the Zero Energy Response for the Transverse Energy of each Trigger Tower, at the output from the ADF cards, i.e. the input to the TAB Cards, to remain at the design response of 8 counts = 0 GeV. –For each Trigger Tower, the Zero Energy Response Drift is measured from the average of 1008 samples (28 turns) of Live Crossing Energy. –If the measured drift is below a programmed threshold (0.5 counts) TCC immediately applies 50% of the correction needed to correct the measured drift. –If the measured drift is above the threshold, TCC does not make any correction and waits until the next sample to decide if this is a spike or a step change. At the next snapshot, and if this was a spike, do nothing and return to the 50% correction mode for future correction cycles. If this is a step, do the full correction instantly and return to the 50% method for future corrections. –These decisions are taken on a tower by tower basis.

3. Is it working? Comparison between a pre-shutdown store (without stabilization) and post- summer-07-shutdown (with active stabilization): –Store 5435 -17-May-2007- PeakLum~130E30 –Store 5682 -04-Nov-2007- PeakLum~80E30

4. Pre-Shutdown Reference: Store 5435 -- 17-May-2007

5. Post-Shutdown Example: Store 5682 -- 04-Nov-2007

6. Global view: Comparing Averages over all Trigger Towers 04-Nov-200717-May-2007 No Automatic CorrectionActive Correction Zero Energy Response SpreadZero Energy Response Stabilized Manual AdjustmentContinuous Adjustment

7. A well behaved EM Tower  Very small corrections (~1 count of Pedestal Control DAC) Adjusted Pedestal Control DAC 04-Nov-2007 17-May-2007 Manual Correction Active Correction Zero Enerrgy Response Drift

8. A “Drifty” EM Tower  Medium corrections (~10) Adjusted Pedestal Control DAC 04-Nov-2007 17-May-2007 Manual Correction Active Correction Zero Enerrgy Response Drift

9. A well behaved HD Tower  Very small corrections (~1) Adjusted Pedestal Control DAC 

10. A “Drifty” HD Tower  Medium corrections (~10)

11. HD Tower with high synchronous noise  Large corrections (~50)

12. HD Tower with high synchronous noise  Large corrections (~100)

13. Looking back at oversampled data for HD_TT(- 8, 9) (cf. Oct-06 studies )  ADF captures 4 sampling points per tick 1:159  Each point in the graph is the average (or StdDev) of 1000 samples

14. Reminder: location of 132ns Synchronous Noise in L1Cal TT Signal

15. Largest noise is in top and bottom of the North Calorimeter End Cap