Status of the MinBias System

1
Status of the MinBias System
Ulla Blumenschein

• Introduction
• MinBias System
• MinBias Application
• QC of the readout chain
• MinBias hardware status
• MinBias software status
• Summary and Outlook

2
Tile Calorimeter
EBA
LBA
LBC

• Barrel part (h lt 1.7) of the ATLAS Hadron
  Calorimeter
• Sampling calorimeter iron/scintillating plates
  (tiles), perpendicular to beam axis
• Tiles grouped to readout units (cells) 73
  cells per Df 0.1 arranged in projective towers
  with Dh 0.1
• 3 layers A/BC/D
• each tile read-out by two PMTs
  

EBC
PMT
FE electronics
tiles
cell
3
The TileCal Readout
Cesium
In-situ Physics
Tile
Minimum Bias
Fibre
TileCal cell
Laser
Mixer
HV
PMT
PMT Block
HV Opto
HV Micro
Canbus
Divider
Charge Injection
3-in-1
L H
Mother Board
Digitizer
Analog
Integrator ADC-I
Canbus
Adder
Digital
Drawer
Optical Interface
TTC
ROD
µ Trigger
Had Trigger
Energy
4
Tile MinBias
Mean energy deposition O(MeV)

• 23 inelastic p-p interactions per BC (900 M
  int./sec) at nominal lumi
• Typically low-energy forward jets (few hard
  interactions -gt physics)
• Large fluctuation of energy deposition in a
  given cell
• Average MinBias signal spans a broad range of
  frequencies and amplitude depending on
  lumi/h/layer

• Slow integration of PMT current (10ms 110 LHC
  orbits 400000 BC 8 M inelastic interactions)
• readout rate 0.5 Hz
• Monitor each cell/PMT channel) online
• Store data offline for reference (COOL database)
• rLuminosity measurement

least exposed to MinBias
most exposed to MinBias
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TileCAL Luminosity measurement

• Physics requirements average inst. luminosity
  per lumi block O(1 min)
• ATLAS goal accuracy of 2
• Absolute Lumi measurement Roman Pods (elastic
  cross section) for low luminosities
  (1028/cm2/sec)
• Relative luminosity measurement, calibrated at
  low luminosity with Roman Pods in special runs.
  Online (luminosity monitoring) and offline
  (analysis) application
• - LUCID delayed, not sure if ready at startup
  
• - alternative methods W/Z, LAr Forward
  Calorimeter, MinBias counter, TileCAL ...

• TileCAL relative lumi measurement high
  accuracy DL/L lt 1 at nominal lumi 1034 with
  single readout
• More difficult calibration with Roman Pots at
  1028 for absolute luminosity measurement combine
  several cells, average over lumi block, increase
  bandwidth by reading only selected cells
• Important negligible electronics noise
  

Lumi Calibration
Luminosity X 1034
A13
D0
Stat accuracy () of a single measurement as a
function of luminosity
Acc ()
BC5
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MinBias System
monitoring
DCS (PVSS)
data base
Lumi monitoring
COOL
TileCAL monitoring
ROB
ROB
ROB
ROB
extracted data
SBC
SBC
SBC
SBC
TDAQ
Complete data 20 kbyte/sec
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The integrator readout path
ATLAS cavern
USA 15
INTG_OUT
PMT
INTG_GND
16 message buffers per CAN line 250
kbps
1 ADC per module 16 ADCs per CAN line) 12
bit digitizer (0-5V)
PMT
PMT
ROB
SBC
Pedestal Control
CAN Port
45(36) PMT channels per module in Barrel (EB)
Micro
Analog Bus
DAC
CAN Port
ADC
CAN Port
CAN Port
CANBus
CAN Port
ADC gains dynamic range -gt 2 mA
8
MinBias Hardware Status

• Final 15 V ADC Canbus PS installed
• Canbus connected to the final ROB in the
  TileRack. Connections to the drawers might be
  modified because of HV readout problems.
• Final ROB and SBCs commissioned. So far still
  using mobidaq but able to switch to final
  ROBs/TTCvi any time as soon as digitized readout
  moves to RODs.
• FE components (Integrator, ADC) commissioned for
  16 barrel modules (Sector 13). (One pending
  repair request). Components on the remaining
  modules certified with mobile readout (mobidick).
• Calibration/Monitoring Trigger board (SHAFT
  board) under construction (IFAE) -gt has to be
  tested in summer

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QC software for Integrator/ADC/ROB
DVS gui
Pedestal distributions

• ROB functionalities receive/send data, trigger,
  mask buffers ...
• ADC functionalities ADC-CANbus communication,
  ADC settings, Automated Scan (tests), Fast Dump
  (MinBias), 3in1 card settings ...
• Integrator pedestals dead/noisy channels,
  channel-by-channel coherence, stability in time
  (analysed offline)
• Light leak test fast integrator pedestals in
  order to check for lightleaks/leakage currents of
  PMTs upon turnon of the HV
• Integrator gains gain switches (6 gains),
  linearity, calibration constants

10
Gains calibration

• Uses a charge injection scan (100 events per
  point, 11 points per gain) to calibrate the 6
  gains
• Checks routinely for different, more trivial
  sources of failures (cards not switched,
  pedestals not in correct range ...)
• Precission 10e-5
• Stable in time (order of hours tested so far)
  within the precission of the measurement

Verify card selection
Slope, chi2, pedestal, noise for each gain
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Gains test QC application

• Gains test integrated in DVS and part of the QC
  procedure
• Check linearity of the gains and functionality
  of the gain switches
• Overview of the noise for each gain
• Check if 3in1 cards are selected properly
• Check the charge injection system independently
  from the digitized readout -gt diagnosis of a 3in1
  card problem

Damaged gain switch (card 40)
Damaged charge injection system
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Gains calibration ToDo list

• Precission of the measurement is large enough to
  resolve systematic effects in the CIS system and
  the ADC -gt apply corrections (and switch to
  laser system once it is available ?)
• Check compatibility of different readout methods
  (CONVERT (MinBias) lt-gt Automated Scan
  (calibration)
• Check for long-term stability (order of
  weeks/months)

Fit of the gains
Residuals (large precission)
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Noise problems

• In the integrator pedestal data taken with the
  final Finger Low Voltage Power Supplies (FLVPS)
  the pedestal noise in average 4 times larger than
  with commercial temporary power suppies used in
  the test beam.

Consequences for MinBias Readout - Tile
luminosity cannot be calibrated - up to 15 X
more time for same accuracy
Typical noise with Linear LVPS (LBA47)
Noise with Finger LVPS (LBA51)
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Noise problems

• Channel-by-channel coherence pattern suggested a
  dominant source in the 500 Hz range Bricks with
  low load run in discontinuous mode -gt voltage
  oszillations

Channel-by-channel correlation pattern in (LBA50)
Lower noise level with temporary noise
reduction in LBA48
lt-2ms-gt

• Temporary fix resistance in parallel to the
  module and capacitance
• Final fix modify bricks (several months)

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The MinBias Software
TDAQ tools
Configuration
Tile VME boards
DVS
ROB library
Run Start
MinBias library
IADC library
DVS QC
Monitor
TTC library
Transfer to DCS/COOL
Data base access
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MinBias Software Status

• C libraries with methods for VME-based
  operation of front end electronics have been
  developed/extended
• QC procedures for front end and back end
  electronics which use the new libraries
  developed/extended and applied successfully in
  commissioning
• Developed calibration tool for the 6 gains of
  the integrator electronics -gt calibration
  constants, transferred to COOL data base
• Developed C MinBias library which contains
  all MinBias TDAQ methods following Ilyas C-based
  MinBias software
• Stand-alone DAQ tools for configuration, running
  and retrieving of the data (to be included into
  TDAQ framework in summer)
• Addidional temporary methods for commissioning
  purpose (different readout methods, timing
  measurements, switch backends mobidaq/final ...)
• Performance checks of MinBias software with 4
  modules in parallel (largest number available so
  far with fixed FLVPS) Comparison with DVS
  readout (single module), stability, data rate

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Pedestal data (run 4 modules in parallel)
All PS with temporary noise killers

• Use pedestal data to validate the MinBias
  readout
• Characteristic quantity Channel-by-channel
  pedestal RMS

LBA45
LBA48
LBA46
LBA47

• Reference Well established single-module
  test-readout (Automated Scan)
• Trigger ROB, 95 Hz

LBA45
LBA46
LBA47
LBA48
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Different Readout procedures
LBA46 MinBias run (CONVERT)
Reference Single-module automated scan run
Reference Single-module automated scan run
LBA46 MinBias run (FASTDUMP)
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Outlook

• Integrate the stand-alone tools into TDAQ
  framework and check for incompatibilities in
  configuration.
• Integrate the readout into DCS
• Tool for data storage COOL data base
• Check timing in detail and try to increase
  performance further
• Test details (algorythm for cycling 16 ADCs at
  15 data buffers, long-term stability of readout,
  handling of bad channels/modules ...)

• More advanced commissioning status needed for
  further MinBias development
  
  - full CAN line (daisy chain, 16
  modules) instrumented and certified
  
  - stability at the timescale of
  days - enough time
  slots for tests (no high-priority problem
  handling)