RBX Hit Time Leveling/Synchronization

Problem Description

• Signal Timing across HCAL channels varies due to time-of-flight of the particle to the tower in question, the optical path length of the scintillator light collected and directed to photodetectors, and inherent variances within electrical components.
• Want to synchronize these times so signals with the same provenance appear to arrive simultaneously across the whole detector.

Method

• We have per-channel delay settings to fiddle with, and per-RBX TTCrx phase settings that shift all 72 channels of an RBX at once.
• However, up till now the TTCrx phase settings have been used primarily to synchronize the transmission/reception phases of the signal over optical fiber, and thereby reduce/eliminate 'latency jumps' of the transmitted signal.
• The most recent 'Jose' scheme of HCAL latency control implemented in the HTRs is said to free up RBX TTCrx phase settings so that per RBX time can be leveled more easily.
• It is claimed nevertheless that the RBX phase scans performed as part of the previous latency control scheme are still valid and also already flatten the timing of the RBXes with respect to each other.
• So to verify: plot the RBX average times from splash data last fall against the current set of RBX TTCrx phase tune values and see if they are correlated. Miscorrelations should coincide with hardware interventions where some electrical component contributing to timing variations has been replaced or repaired.

Preliminary results

• TTCrx phase settings are online, splash timing for HB and HE provided by J. Damgov, and can also be found at JDSplashTimingPhi.

HB: Correlation looks promising

• TTCrx phase latest tune and HB splash timing vs iPhi:
  

• TTCrx phase latest tune - HB splash timing vs. iPhi, centered:
  

• TTCrx phase latest tune vs. HB splash timing:
  

HE: Much weaker correlation observed, differences are on the order of the values themselves

• TTCrx phase latest tune and HE splash timing vs iPhi:
  

• TTCrx phase latest tune - HE splash timing vs. iPhi, centered:
  

• Correlation of TTCrx Phase Setting vs splash timing for HE:
  

• Correlation of TTCrx Phase Setting vs splash timing for HE, RBXes with CCMs replaced since splash removed:
  

• Correlation of TTCrx Phase Setting vs splash timing for HE, only RBXes with CCMs replaced since splash are plotted:
  

-- PhilDudero - 15 Jun 2009