Detector Control and Safety System for the Electromagnetic Calorimeter of CMS

Slide 1Four Seas Conference, 5-10 September 2004, Istanbul, Turkey
Detector Control and Safety System for the Electromagnetic Calorimeter of CMS
Predrag Milenovic
Specifications of the ECAL DCS
Detailed specifications of the ECAL Safety System
ECAL SS prototype - Test-beam results
CMS ECAL DCS, Belgrade Group
Four Seas Conference, 5-10 September 2004, Istanbul, Turkey
Large Hadron Collider
Compact Muon Solenoid
ECAL design criteria
Physics goal - The discovery of the Higgs at the LHC
The favourable channel for low mass Higgs search: H→ γγ
Design criteria:
Barrel: Stochastic term (a): 2.7%, Constant term (b): 0.5%,
Noise term (c): 150 – 220 MeV
Hermetic, granular
1013 neutrons/cm2 and 1 kGy at h = 0
to 2×1014 neutrons/cm2 and 50 kGy at h = 2.6.
Fast response for 40 MHz bunch crossing rate.
Choices, Constraints, Challenges
Low light yield
Temp. sensitivity – -2.4%/ OC
Temperature dependence of crystal light yield and APD response.
Need to stabilise crystal volume temperature to 0.1oC
Temperature Stability Issue
0.45 A/channel
1 A/board
Radiation hard regulator has a drop out voltage of 1.5V
Total heat power dissipated in the whole calorimeter ~300 kW
Crystal light yield decreases by 2.2%/oC & APD gain decreases by 2.3%/OC.
Removing all excess heat is critical for the stable operation of the detector.
Systems of crucial importance for the ECAL:
Cooling system & Detector Slow Control System
Detector Control System (DCS)
ECAL DCS
Design Objectives:
(18.0oC ± 0.1oC)
Safety system for automatic FE electronics disconnection
(due to cooling problems, overheating of electronics, water leakage, over-voltage/over-current in FE)
Development of the control software (sensors, HV, LV, cooling, safety…)
Foreseen Difficulties:
large radiation dose present in ECAL
DCS Subsystems (independent on the DAQ):
Precision Temperature Monitoring (PTM)
ECAL Safety System (ESS)
ECAL Safety System
Full system autonomy in all aspects;
Independent, continuous temp. monitoring of the ECAL VFE + FE environment in both ECAL SM + EE; Precision : 0.2 oC
Archiving of temp. data and system information for analysis of the detector status and ESS performance;
Reliable hardwired interlocks with ECAL HV and LV Power Supply systems;
External Alarm Interfaces with ECAL Cooling system, Water leakage detection system, as well as interfaces with general CMS DSS and LHC TCR;
Prompt reaction on any external alarm or critical change of temperature inside the ECAL by issuing, in a proper time sequence, Warnings and Alarms to:
1. HV System Crates (hardwired interlocks),
2. LV System Crates (hardwired interlocks),
3. System Operator (soft PVSS Warning and Alarm messages);
Radiation tolerance in accordance with CMS radiation dose specifications;
Maximum possible level of robustness, reliability, safety and maintainability;
Schematic layout
Data acquisition, data processing and interlock generating - ESS PLC Layer,
System monitoring and system control - ESS Soft Layer
Several external interfaces to:
ECAL Low Voltage, ECAL High Voltage and ECAL Cooling systems,
Input from Water leakage detection system
CMS Detector Safety System (DSS),
LHC Technical Control Room (TCR).
ESS Sensor Location
NTC thermistors (EPCOS)
point ( “twin” sensors ).
8 / EB SM
8 / EE quadrant
Sensors to be calibrated to relative precision of 0.1 oC
with calibration setup developed by Belgrade group
PSI irradiation: Sensors irradiated to 4-5 times EE dose – EPCOS
sensors behaved perfectly
FE Electronic components
NTC 680 Ohms
Resistant Bridge Front-End ASIC: IBM 0.25mm 100 + 30% spares ordered (with LHC cryo group)
Bi-directional three-level programmable Internal Current Source (1mA, 10mA and 100mA),
Differential Amplifier, gain = 50 (adjustable), input range: -50mV – 50mV, output range: 0 - 5V,
Analog switches, 8 measurement modes of the chip, controlled by the Ck0, Ck1 and Ck2 bits,
Removes ASIC voltage offsets, thermocouple effects, power supply & ambient temperature dependencies
RBFE ASIC
FE Electronic components
Custom-made MUX + ‘RBFE’ test board, irradiated at PSI:
No problem, irradiated at ~ 106 x CMS balcony flux, and about 300 x CMS balcony dose
Tests in Belgrade:
with 2x better resolution.
Need only (power, signal) 5V
Programmable Microcontroller test board, irradiated at PSI:
No problem, irradiated at ~ 106 x CMS balcony flux, and about 300 x CMS balcony dose
Purpose :
communication (RS485), does ADC
blocking
Memory checksum sent: Control against SEU
FE Layer – ESS Unit
Redundant readout - 4 SM or one Endcap
12 in total units needed for (EE+EB+EB+EE)
Radiation tolerant can sustain radiation levels orders of magnitudes higher than those expected on the CMS balconies
Redundant architecture - maximum reliability - minimum possible loss of temp. information from the inside of ECAL
Reliability analysis (for 4 designs)
This layout with 8 RBFEs/4SM has smallest prob. to loose large number of modules in case of component failure
Functional layout of ESS Unit in control of four ECAL Super Modules
ECAL Test Beam
Slow Control (DCS) and Monitoring:
LV, HV and Laser monitoring
Cooling and temperature stability
Online/Offline software
H4-Beamline, CERN
ECAL Test-beam results with final electronics
Energy (GeV)
Target calorimetry resolution achieved with new electronics design!
Resolution(mm)
ECAL Test-beam results with final electronics
In situ: Fast intercalibration based on f symmetry in energy flow 2% in few hours
Energy/momentum of isolated electron from W→ en 0.5% in 2 months
Absolute energy scale from Z → e+e-
Test Beam LY
Labo LY corr
Test Beam LY – Labo LY corr
Relative channel calibration can be obtained from Lab with a precision of 4 %
We cannot calibrate every crystal with an electron beam.
Obtain a first calibration point from component data: crystal light yield, APD & PA gain.
ESS test-beam setup with SM0
SM0
ESS test-beam results with SM0
ECAL SS (FE + Interface) PCB
Calibration curve for one ESS sensor
Noise dependence on RBFE position
(ΔL ~ 40m)
Noise distributions
~0.04°C
~0.025°C
ESS test-beam results with SM0
ESS test-beam results – Example
Oscillations of temperature of the air inside and outside of the SM0 are correlated!
System performance satisfactory !!!
-> ESS interlock ! -> LV off !
Back-up slides
Schematic layout
Data acquisition, data processing and interlock generating - ESS PLC Layer,
System monitoring and system control - ESS Soft Layer
Several external interfaces to:
ECAL Low Voltage, ECAL High Voltage and ECAL Cooling systems,
Input from Water leakage detection system
CMS Detector Safety System (DSS),
LHC Technical Control Room (TCR).
RS485
RS485
ESS FE Layer
TSS FE is modular system made of ESS Units as independent modules, all identical
Each TSS unit has its own, independent and redundant power supply;
Each TSS unit provides redundant readout for four SM or one Endcap.
There are 12 in total (1+5+5+1) units needed for (EE+EHB+EHB+EE)
There will be at least 3-5 spare TSS units (about 16-24 spare entries in total);
TSS units can be interconnected in order to be controlled in parallel by the same
PLC Control Signals --> possibility for parallel readout of several EB Super Modules
and reduces the cabling between the Counting Room and the ESS Racks on the
balconies;
Redundant architecture of the ESS readout unit : provide maximum reliability,
so that, in the case of malfunction of any internal electronic components, the unit still
works properly with minimum possible loss of temperature information from the inside
of ECAL
All the electronic components of ESS FE Units have been shown (recent tests at PSI)
that they can sustain radiation levels orders of magnitudes higher than those expected
on the balconies...
FE Layer – ESS Rack
Panel Layout of ECAL SS Unit
Conclusions and Outlook

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Detector Control and Safety System for the Electromagnetic Calorimeter of CMS