HLT - IRTG Heidelberg

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1 Δεκ 2013 (πριν από 3 χρόνια και 8 μήνες)

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> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

1
/18



ALICE HLT


in the TPC Commissioning


IRTG Seminar

Heidelberg


January 2008

Jochen Thäder

Kirchhoff Institute of Physics

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

2
/18

ALICE
-

Overview

heavy
-
ion mode


5.5 ATeV pb
-
pb


10 MHz interaction
rate

Aim :

Creation of the Quark
-
Gluon Plasma



a state of matter predicted to exist during the
first few microseconds after the big bang

TPC

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

3
/18

ALICE


High
-
Level Trigger (HLT)


Large off
-
the
-
shelf PC cluster farm


Several hundred nodes.


Tasks:


Incoming data reduction


~ 22 GB/s (HI mode)


1.25 GB/s (to permanent storage)


Trigger decisions


Event rejection



Online data reconstruction

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

4
/18

ALICE Time Projection Chamber (TPC)


Drift chamber


Inside the L3 solenoid
(
homogeneous B
-
field)


Main tracking device


Largest data producer


36 sectors (
on 2 sides
)


216 readout partions (
patch
)


~ 26 rows per patch


~ 90 pads per row


= 557,568 pads

OROC

IROC

row

pad

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

5
/18

Reconstruction Steps

Raw Data

(
Ordering , Zero Suppression
)

Cluster Finding

(in readout partition)

Tracking

(
Conformal
-
Mapping / Track Follower
)


-

Data amount

+ Computing amount

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

6
/18

HLT
-

TPC Online Monitoring (AliHLTGUI)


Reconstructed event visualisation in real time


Supports HLT developers to finalize online
reconstruction algorithms


Supports detectors specialists to understand detector



Connects to every
data source in HLT
online analysis chain


Displays:


Raw data


Cluster data


Track data

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

7
/18

General Features AliHLTGUI


Selection of single sectors, range of sectors, pair of
sectors, all


Event loop / single events


Show track parameters


Cuts on track parameters (nHits, p
t
, charge,...)


Used / unused cluster (in respect to tracking process)


3D display / histograms


Option of saving histograms


Easy extendible for special needs

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

8
/18

Features AliHLTGUI (1)


Pad Display


Signal histograms for raw ADC data
with neighbouring pad


Padrow Display


Padrow histogram for raw ADC data


Front Display


Endcap view TPC histogram

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

9
/18

Features AliHLTGUI (2)


3D Display


Geometry, raw ADC data, cluster, tracks


Selection of single sectors, range of
sectors, pair of sectors, all sectors



Charge Display


Charge distribution of found Clusters

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

10
/18

Features AliHLTGUI (3)


Residuals Display


Residual distribution of
all tracks


Residuals of single
tracks


Track parameter of
single tracks

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

11
/18

AliHLTGUI
-

Class Layout

3 Layers


Graphical User Interface (GUI) Layer



Qt based


Interface Layer


Handles Qt <
--
> ROOT, data input from HLT chain


Worker Layer


ROOT based


AliHLTTPCDisplay Worker

AliHLTTPCDisplay Worker

Worker Layer

Interface Layer

GUI Layer

ROOT

Containter

AliHLTTPCDisplayMain

Control panel

action

action

action

ROOT action

response

response

response

ROOT response

Data

AliHLTGUI

AliHLTTPCDisplayXXX

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

12
/18

HLT Cluster for the TPC Commissiong


7 Opteron PCs in CR2

connected to TPC via DDLs


1 Opteron PC in TPC Cleanroom



running test setup for



TPC


DAQ


HLT interfaces



All equipped with :


HLT Data framework


AliRoot offline framework


modified TPC analysis
components


HLT TPC Online Display

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

13
/18

TPC Commissioning
-

Setup

TPC sector

TR

TDS

Front
-
End Processors

second sector

HLT
-

cluster

FEP

CF

RP

H
-
RORC

BDW

RP

H
-
RORC

BDW

FEP

H
-
RORC

BDW

H
-
RORC

BDW

FEP

H
-
RORC

BDW

CF

RP

H
-
RORC

BDW

CF

CF

RP

CF

RP

CF

RP

DAQ

HLT

Online

Display

reconstrcution

data flow

display

data flow

Components

RP :RORCPublisher

CF: ClusterFinder

TR: Tracker

TDS: TCPDumpSubscriber

BDW: BinaryDataWriter

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

14
/18

General Experiences for HLT


Several issues not related to analysis
components


Hardware


Infrastructure


Hardware / Software Interface




Typical startup problems



All solved



Not so much time for reconstruction tests

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

15
/18

Issues related to Raw Data


Raw data from TPC not
zero suppressed




Lots of noise



Clusterfinding /
Tracking impossible


Solution:


Noise Reduction


Zero
-
Suppression added


Occupancy limit for single
pads added

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

16
/18

Laser Event with Central Membrane

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

17
/18

Issues related to Tracking


TPC not designed for tracks parallel


(or small angle) to rows



Existing tracker not designed for
tracks parallel (or small angle) to
padrows

cosmic particle



New tracking approach


Based on cellular automaton of Ivan Kisel


First version finished and tested in last week of
data taking


Further tests necessary

> IRTG


Heidelberg 2007
<

Jochen Thäder


University of Heidelberg

18
/18

Further working fields


Implementation of combined TPC
-
TRD


Jet trigger for the HLT (
Not yet started
)


Improvement of the TPC tracking algorithms


TRD tracks as seeds for jets


Continued with TPC tracks


Search for


High pT jets in hadron
-
hadron collisions


Di
-
jets in pb
-
pb collisions



Prepare the HLT for first year ALICE