Transcript Sannino-RICH2007.ppt

LHCb Rich Detectors Control
and High Voltage Systems
Mario Sannino
On behalf of
LHCb RICH Group
Rich 2007 Trieste 19.10.2007
Rich 2007 Trieste 19.10.2007
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LHCb Rich Detectors Control and
High Voltage Systems
• An overview of the Monitoring/Control
System of the RICH Detectors in LHCb
experiment will be presented
• In particular this talk will concentrate
on the Monitoring/Control methods
fundamental for an efficient RICH
Detector operation
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LHCb RICH detectors
Mirror Support Panel
Flat mirrors Spherical mirrors
Spherical Mirror
8m
Support Structure
4m
Beam pipe
Photon detector
housing and shielding
RICH1:
2-60 GeV/c
Flat Mirror
RICH2:
17-100 GeV/c
Rich 2007 Trieste 19.10.2007
Central Tube
Photon detector housing
and magnetic shielding
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Fundamental for an efficient RICH operation are:
• Low Voltage and High Voltage control and
monitoring
• environment monitoring (temperature, pressure,
humidity)
• radiator gas quality monitoring
• mechanical stability (mirror alignment) monitoring
• detector safety
This is achieved by means of the DCS (Detector Control
System), in charge of detector operation, i.e. Monitoring,
Control and low level Safety.
DCS will also automatically recover simple problems and
restore normal operating conditions.
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LHCb
Partial Simplified view
ECS = Experiment Control System
DCS = Detector Control System
DSS = Detector Safety System
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ECS/DCS Hardware Implementation
Board level electronics
• Electronics in barracks (out of Radiation Area)
• Front-ends, Readout Units,
• Timing and Fast Control components,
• VHV Control
– Credit Card PC’s Ethernet interfaced
acting as an embedded controller
generating needed I2C, JTAG and a
parallel bus by means of a proper
“glue” logic (Glue Card)
Ethernet
• 66  85  12 mm3
• Pentium Compatible CPU
• Linux/DIM
S
I2C
JTAG
Bus
S
I2C
JTAG
Bus
S
I2C
JTAG
Bus
Credit Card PC
Glue-Card
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ECS/DCS Hardware Implementation
Front-End Electronics
• In Radiation Areas
needed I2C and JTAG
generated by the busses
• SPECS
• Serial Protocol (inspired from Atlas)
• 10Mb/s
S
I2C
JTAG
S
I2C
JTAG
S
I2C
JTAG
• Slave is radiation tolerant
• CAN protocol (0.5Mb/s)
in charge of controlling ELMB’s
(used for Environmental and Voltage monitoring)
M
SPECS
CAN
I
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Implementation of LHCb RICH Detectors Monitoring
Rich 2 ECS supervisor PC
Supervisory Level
PVSS II
(Control Room)
Control Level
(Counting Room)
Rich2
Voltage and Environment
Monitoring
Rich2
Power Supplies Control
Rich2 VHV
Power Supplies Control
Quality Monitoring
Device/Sensor Level
PLC
ELMBs
Radiation Area
Sensors
T, P,H
Voltages
LV, HV, L1
Environmental Monitoring
Voltage Monitoring
Power Supplies
Other
(DSS, …)
HPD Planes
VHV
Temp.
Safety Interlocks
Power Supplies
• Gas Quality
• Alignment
Quality Monitoring
• Environmental monitoring is implemented by means of resistive transducers
(
(PT100 &1000 for T, Diaphgram Sensors for Pressure, HMX2000-HT sensors for Humidity)
• ELMBs are CAN controlled monitoring boards with 64 analog input channel 16 bit res.
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Environmental Parameters Monitoring
HPD box
temperature
Environmental Parameters PVSS II
typical Monitoring Panels
HPD box
humidity
RICH2
CF4 radiator
temperature
<- 5 days ->
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Gas Radiator quality Monitoring (I)
The Gas Purity is critical to a reliable working of the RICH Detectors.
Speed of sound in gases depends on molecular weight: and so it can
be exploited to quickly spot gas pollution.
vsound 
 = cp/cv is the ratio of specific heats
R is the constant of gases
T is the absolute temperature
M the molecular weight
RT
M
Effect of air contamination
Gas
N
O
air
C4F10
CF4
Molecular weight
28
32
29
238
88
Speed of sound
(m/s)
at 30 C
354
332
349
~130
C4F10
CF4
n
1.0014
1.0005
Theta max
(mrad)
52.88
31.62
1% N2 qmax
52.68 (0.2)
31.55 (0.07)
3% N2
52.26 (0.62)
31.42 (0.2)
Typical
error
(mrad)
1.5
0.6
~150
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Gas quality Monitoring (II)
Speed of sound is monitored by measuring the time
that a sound pulse takes to propagate back and forth
along a gas column after having been reflected by the
opposite wall.
2 such Systems on each Rich
One on gas inlet
A second on gas outlet
The heart of the system is an electrostatic transducer
acting both as source and detector.
The time measurement is performed by a National
Instrument Acquisition Board with an internal counter
running at 20 MHz so, with a resolution of 50 ns
This is enough to detect a 1% CO2 pollution in C4F10
(see graph)
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Laser alignment monitoring system (I)
Mirror position must be known with good
precision and any change of it must be
tracked as accurately as possible.
CCDs
HPD Plane
A 0.1 mrad resolution is required as seed
for final software alignment.
Flat
Mirror
Spherical
Mirror
An optical system has been implemented
in order to monitor changes in selected
mirror segments.
Working principle:
Laser with optical fibre coupling system
delivers light to 16 fibres in Rich2 and 8
fibres in Rich1.
Each fibre has a focusing unit at its end
and is focused onto a mirror segment (4
spherical and 4 flat per side).
Beam Splitter
Common
Mounting Plate
Mirror
Focuser
A beam splitter provides a reference
beam for each fibre focused on a CCD
camera on roof of detector. A second
beam reaches the mirror and then is
reflected back to the CCD camera.
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Laser alignment monitoring system (II)
Can track difference between two beam spots,
even if spots move:
Accuracy of monitoring better than 0.01 mrads.
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VHV Power Supplies Control System (I)
In LHCb Rich a custom VHV system for the HPD field
supply was needed due to the fact that no
commercial power supply satisfied our requirements:
• 20KV output
• Ethernet network interface compatible with CERN
standard
• Reliable and modern (maintenance!)
Architecture of the system
The system is composed by 3 items:
1. Commercial HV unit:
One unit for each column.
2. Motherboard with local intelligence
One unit for each Detector
3. Control Board with optical isolation (avoid Gnd loops)
One unit for each column
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VHV Power Supplies Control System (II)
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VHV Power Supplies Control System (III)
• Commercial HV unit: ISEG CPn 200 504 10-K
– 0-20 KV output
– Imax = 0.5 mA
– Remote control: analog input 0-10V
– Possibility to set Imax with a control voltage
– Monitoring of Vout and Iout
– Reasonably priced
– Custom version possible (2 output cable to cope with the HV
splitter)
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VHV Power Supplies Control System (IV)
The Motherboard
• Standard VME size card ( 6U type)
• Local Intelligence: Credit Card PC (CCPC)
– Ethernet interface built-in
– CERN fully supported
– Easily interfaced with external devices by means of
the so called Glue Card. Connections with Control
Boards implemented by
means of 4 I2C buses
(from the Gluecard)
• Interlock Management
and distribution
entirely controlled by a
small FPGA
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VHV Power
Supplies Control
System (V)
Control Board
ISEG VHV Power Supply
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Installation of VHV Rich Power Supplies in LHCb Pit
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VHV Power Supplies Stability
(19540 ± 18) V
A stability of the ouput voltage under
load of the order of 1 ‰
is achieved as can be seen from the
aside plots where
a voltage of 19540 V with 20 V RMS max
is reported for a sample channel
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Conclusions
In LHCb a complex system in order to control and monitor the Rich
Detectors was designed and implemented
• All the needed parameters are monitored
 Environmental
 Pressure
 Temperature
 Humidity
 Quality
 Mirror Alignment
 Gas Quality
• A new VHV Power Supply System completely automatized and
remotely controlled was developed and is now working with
good performances
• In case of simple problems the system is able to recover them
restoring normal operations conditions
• In case of hard safety problems the system is able to interlock
the detector putting it in a safe state.
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Spare Slides
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LHCb RICH detectors
RICH2:
17-100 GeV/c
RICH1:
2-60 GeV/c
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Monitoring
• HPD enclosure:
– Air temperature (2 pt100).
– Humidity.
– Up to 16 temperatures (hot spots) per column
(pt1000).
– High Voltage (6 voltages per column).
– Cooling pressure.
– Light level.
– Voltages and currents (from the power supplies).
• Temperature in RICH2 radiator:
– 20 pt100 in gas volume.
– Relative pressure (no gas yet).
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Environmental Parameters Monitoring (II)
RICH2
CF4 radiator
temperature
Environmental Parameters PVSS II Monitoring Panel
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Safety
• PVSS
– Per column:
• Any high column temperature will switch off the particular column.
• Power supplies will trip at over current.
• HV disable if over-current, over/under-voltage, monitoring
problem.
– Per HPD enclosure:
• High ambient temperature will switch off whole side.
• Loss of cooling will switch off whole side.
• DSS
– Any alarm switches off whole RICH detector.
• Ambient temperature sensors.
• Chain of thermo-switches (1 per column).
• Rack related alarms.
• Light level
– Disables High voltage.
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An embedded PC is still not
a board-controller
• For controlling, configuring and monitoring FPGAs and ASICS need
rather I2C, JTAG Traditional PC interfaces: PCI, ISA, parallel port,
USB  not very suitable for chip-control
• and a high-speed, “simple”, long distance parallel bus
• Need some small adapter or “glue-”logic
• The LHCb glue-card has an I2C / FPGA controller + a fast local bus
generated from a PLX 9030 all controlled by an FPGA.
(For details see: F. Fontanelli, B. Jost, G.Mini`, N. Neufeld, R. AbdelRahman, K. Rolli, M. Sannino 10th ICALEPS Conference Geneva
2005 PO2.062)
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Laser alignment monitoring system (Ib)
 Analysis software needs to recover centre position of reference
and reflected beam with optimum accuracy and robustness.
 Beam not perfectly Gaussian so fitting method is not
appropriate for a variety of differently shaped beams
 Adopt a different approach using techniques borrowed from
image processing.
 Adopt a multi stage approach:
1. Smoothing filter
2. Edge enhancement
3. Sobel mask edge detection
4. Hough transform accumulator to determine centre of beam
5. Anomaly cut for spurious centre elimination
6. Centre spot location mask
7. Weighted average for centre determination.
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Voltages Monitoring
Rich Voltages Monitoring Panel
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