1 SDD offline status Francesco Prino INFN sezione di Torino ALICE offline week – October 20th 2008

2 Summary News since July 2008  Reconstruct and simulate data collected with ADC sampling frequency at 20 MHz (instead of 40 MHz) Could be the default configuration for pp  JITTER word treatment Important for alignment issues  New raw data format with reduced size Implemented in the HLT Under study the possibility of implementing it on the FPGAs of the acquisition cards SDD calibration:  Results from the cosmic data taking (June-October)  Developments expected in the next months

3 News since July 2008

4 ADC sampling frequency Run with ADC sampling at 20 MHz (instead of 40 MHz) since Aug. 13th 2008  Only 128 time samples needed to cover the 6.4  s of drift time  Time bin size = 50 ns (instead of 25 ns)  Reduce the dead time from 2 ms to 1 ms  GOAL: run at 1 kHz Loss of resolution small, ongoing MC studies to quantify it precisely  Default configuration for pp runs ADC sampling frequency stored in AliITSCalibrationSDD  Used both in simulation and reconstruction also the possibility of simulating data at 20 MHz has been implemented  Temporary solution: the preprocessor sets the sampling frequency to 20 MHz by default  To be done: devise a strategy to pass the sampling frequency from the JTAG/DAQ to the preprocessor In AliRoot since v4-14-Rev

5 Jitter First result from alignment test showed a significant difference in time coordinate among different DDLs  The TimeZero (= the measured drift time for a particle with zero drift distance) is significantly different for different DDLs  Affects the measured drift time in a DDL dependent way After some investigations, it has been found that a possible reason is the jitter between the time when a DDL receives the L0 trigger and the time when the trigger is sent to the front-end  Jitter is found to be is significantly different for different DDLs A jitter word is written in the raw data by each DDL  Implemented the decode of the jitter word and the correction to the measured drift time  on the trunk since October 17th 2008  On-going reconstruction in Torino of the whole statistics of cosmic runs with the trunk to check is the effect on TimeZero

6 Raw Data Format Empty event size from the CarlosRX acquisition card:  Headers+Footers (6 words x 32 bit x Nmodules): 6 kB/event  End Of Row Summary (21 bit x 512 anodes x Nmodules):350 kB/event  Fifo words:160 kB/event  Total:516 kB/event Two solutions to reduce data size have been investigated:  HLT SOLUTION: decode the data from the CarlosRX in the HLT PCs and write them in a different format Tested and validated in september  HARDWARE SOLUTION: decode the data in the FPGAs of the CarlosRX and write them in a different format Under investigation

7 New (compressed) data format Base requirements:  Reduce the data size by a factor 20 or more  Interface with the SDD Cluster Finder in the same way as the previous format In order to minimize the changes in the reconstruction software Proposed solution:  1 data word (32 bit) for each firing cell (anode/time bin)  1 control word (32 bit) at the end of the data of each module (needed by the Cluster Finder)  1 jitter word (32 bit) at the end of each DDL to store the JITTER Empty event size:  DATA:4 Bytes * number of cells firing (≈4000)  CONTROL:4 Bytes * 288 (24 DDL * 12 Carlos per DDL)  JITTER:4 Bytes * 24 (DDLs)  Total:≈ 17 kB/event

8 Implementation (I) New class AliITSCompressRawDataSDD  Used by the HLT to decode data and encode in the new format New class AliITSRawStreamSDDCompressed  Read and decode data in the new format Tested and validated at P2, event rate ≈ Hz  Example Plots from test runs: event 25 from run with HLT mode B (both data formats available in the raw data)

9 Implementation (II) New class AliITSCompressRawDataSDD  Used by the HLT to decode data and encode in the new format  Tested and validated at P2, reached event rate Hz New class AliITSRawStreamSDDCompressed  Read and decode data in the new format  Tested and validated on both real and simulated data New Class AliITSHLTforSDD and new object in OCDB  Store the HLT mode  Object stored in the OCDB and filled by the Preprocessor at the end of each PHYSICS run Modified AliITSDDLRawData, AliITSClusterFinderV2SDD, AliITSQADataMakerRec  Write/read the simulated/real data in the new format if AliITSHLTforSDD->IsModeC()==kTRUE All modifications ported to v4-15-Release

10 SDD calibration

11 Pedestal+Pulser Runs Jun-Oct 08 ADC sampling set at 20 MHz

12 Second order calibration Example: collected charge Distribution of charge of clusters from cosmic tracks  Fitted with a convolution of Landau+Gaussian Possible to extract with good precision the conversion factor from ADC units to keV  Using the knowledge of the most probable value for energy deposition of a MIP in 300  m of silicon (=82 keV)

13 SDD Calibration objects (I) DDLMapSDD  One AliITSDDLModuleMapSDD object with the DDL map  Contains: conversion from DDL/Carlos (hardware) numbers to aliroot module number  Updated: by hand at the beginning of each data taking period (last update June 2008), no need to update after 1st reco pass HLTforSDD (new in v4-15-Release)  One AliITSHLTforSDD object with the HLT mode which defines the data format  Contains: flag for HLT mode  Updated: by the SDD preprocessor (query the HLT status) at each PHYSICS run, no need to update after 1st reco pass MapsTimeSDD:  One array of 520 AliITSMapSDD objects  Contains: matrices with systematic deviations on the drift time coordinate of the reconstructed points  Updated: never (static objects)

14 SDD Calibration objects (II) CalibSDD  One array of 260 AliITSCalibrationSDD objects with the calibration parameters used in both simulation and reconstruction Note: parameters used only in simulation moved to AliITSSimuParam  Contains: baselines, noise and gain for each anode + flag for bad module, bad chip, bad anode + flag for zero suppression and ADC sampling frequency  Updated: by the preprocessor after each PEDESTAL+PULSER runs, not expected to be updated after 1st reco pass  Developments: extract automatically the ADC sampling frequency from the JTAG and query it from the preprocessor RespSDD  One AliITSresponseSDD object with calibration parameters (common to all the 260 SDD detectors) used only in reconstrucion  Contains: TimeZero, conversion factor ADC  keV  Updated: from offline analysis of RecPoints

15 SDD Calibration objects (III) DriftSpeedSDD  One array of 520 AliITSDriftSpeedArraySDD objects (one for each drift side of the 260 SDD detectors)  Contains: drift speed (parametrized) vs. anode number  Updated: by the preprocessor after each INJECTOR run.  Development: in the next data taking drift speed estimated also during PHYSICS runs using the dedicated injector triggers DCS data points (only for reference)  Contains: 260 HV values  1 per module 260 MV values  1 per module 520 temperature values  1 per hybrid + Status values  Updated: every 2 minutes only if the value exits from confidence band around last stored value Calculate drift field backup estimation of drift speed

16 Calibration: summary and to-do Run Types and DAs  New DA will be developed to analyze injector triggers collected during physics runs  No major modifications on the existing DAs for PEDESTAL, PULSER and INJECTOR runs  DA operation successful, (rare) failures due to DCS DP retrieval Run Types and Preprocessor  No modification expected in the run types to be handled by the preprocessor (PULSER, INJECTOR, PHYSICS)  For the PULSER run, devise a way to retrieve the ADC sampling frequency from the JTAG  For the PHYSICS runs the retrieval of the drift speed from the new DA will be added OCDB objects  Correction maps (MapsTimeSDD): presently under investigation the possibility of size reduction (presently 14 MB)

17 Backup

18 Status of the QA Code for RecPoint QA ready and tested and committed to aliroot trunk (M. Siciliano, P. Cerello) Histograms for the online expert  1081 from raw data + 6 from RecPoints Histograms for the offline shifter:  2 from raw data (Z-phi occupancy x 2 layers)  4 from Rec Points (Z-phi + charge x 2 layers) Work in progress on the checker

19 Raw Data Format SDD acquisition chain:  260 Modules, each reading 512 anodes x 256(128) time bin cells  260 Carlos cards (1 for each module, inside the ITS) Apply Zero Suppression, data format  24 CarlosRX cards (DDLs) each treating the data of 12 Carlos Each CarlosRX has 4 FIFOs each treating the data of 3 Carlos Control words written by CARLOS in the raw data:  21 bit of End of Row summary for each anode 260(modules)* 512 (anodes)*21 bit = 2795 kbit/event = 350 kBytes/event  3 Headers (32 bit words) for each Carlos  3 Footers (32 bit words) for each Carlos 246(modules) * 6 * 32 = 47 kbit/event = 6 kBytes/event Other words are added by the CarlosRX to manage the (frequent) changes of FIFO transmitting the data

20 Carlos+CarlosRX data format Headers (red: FIFO words, blu: Carlos Headers, black: data words): 64) | | 80) f3e01810 e0044b94 | K.. | 96) | | 112) a | | 128) c b | | Data (red: FIFO words, black: data words): 592) b98221c8 f98221c |...0.!...! | 608) b98021c8 f98221c b98021c8 |.!...! !.. | 624) f98021c b98221c8 f98221c8 |.! !...!.. | 640) a21c8010 ce | | 656) c8010 c21c | | Footers (red: FIFO words, blu: Carlos Footers, green: CarlosRX footers, black: data words): 27552) c fffffff 3fffffff |...0 D......?...? | 27568) 3fffffff fffffff 3fffffff |...? ?...? | 27584) 3fffffff 3f1f1f1f 3f1f1f1f 3f1f1f1f |...?...?...?...? | 27600) a 3fffffff 3fffffff | ?...? | 27616) 3fffffff 3f1f1f1f 3f1f1f1f 3f1f1f1f |...?...?...?...? |

21 New (compressed) data format Data word: Control bit Carlos identifier (0-11) Detector side (0-1) Anode number (0-255) Time bin number (0-255) ADC counts (10 bits)