21.11.03 Anatoli Konoplyannikov

1
Design and integration of HV, LED monitoring and
calibration system for HCAL

• Overview of the subsystems design
• High voltage system.
• LED monitoring system.
• Cs137 radioactive source calibration system.
• Integration of the HV, LED monitoring and
  radioactive source calibration systems on the
  HCAL detector

21.11.03 Anatoli Konoplyannikov
2
Design and integration of HV, LED monitoring and
calibration system for HCAL
High voltage system
The Cockcroft-Walton (CW) base for
photomultipliers is used for LHCb calorimeters.
The PMT chosen for the calorimeters is Hamamatsu
photo-multiplier R7899-20. The CW solution has
the following advantages over conventional
passive divider and transistor bases
individual gain adjustment efficient
operation at high rate low power
dissipation low voltage cabling and
connectors reducing total cost.
HCAL CW base circuit diagram.
The HCAL high voltage (HV) system consists of
about 1500 CW bases, those soldered on the PMTs
leads and placed in each cell of HCAL,
eight 216 channels DAC boards for
HV control voltage distribution,
three power supply units (80
V, - 6 V). The DAC boards are placed around the
detector and the analogue HV control voltages are
distributed to each base by a flat cable.
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
High voltage system
Oscillogram of a CW base voltage ripple on
dynode DY10
The gain deviation as function of the DC anode
current for three gains 104, 105, 106.
CW base main characteristics
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
High voltage system
Photo of HCAL CW base with Hamamatsu PMT.
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
High voltage system
The architecture of the subsystem is chosen
taking into account following considerations    
     The DAC ICs should be kept in a region with
a lowest level of radiation.        The easy
access for board exchange should be foreseen.
A cable length should be minimized in order to
avoid a ground loop voltage shift.
The board includes 200 channels of DAC integrated
circuit for HV control and 16 channels for LED
light intensity control. For readout of the
control voltages, the multiplexers and ADC IC are
used. An estimated power consumption is about 1.5
W per board and a board size is about 160250
mm2.
216 channels DAC board block diagram
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
LED monitoring design

• The LED monitoring system is mainly aimed at
• a middle term monitoring of the PMT gain
  stability,
• an ADC sample time calibration and adjustment

Sketch of the optical part of the LED monitoring
system

• The LED monitoring system consists of four
  functional parts
• optical mixer and light distribution fibers,
• LED driver with LED and PIN diode with amplifier
  for a LED light stability monitoring. The PIN
  diode signal after amplification is sent to the
  LFB front-end electronics board.
• light intensity control board with DACs ,
• LED triggering pulse distribution board.

21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
LED monitoring design
The dedicated HCAL versions of the LED driver and
PIN diode amplifier were developed. The main LED
driver features are         controlled light
intensity         edge sensitive triggering
       overshot circuit allows to decrease the
trailing edge of a light flash         dimension
of the printed board is 4070 mmmm mechanical
design is optimised for HCAL
LED driver block diagram
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
LED monitoring design
LED
PIN diode
Photo of the light mixer with LED driver and PIN
diode amplifier printed circuit boards
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
LED monitoring design
LED signal
50 Gev pions
Oscillograms of the 50 Gev pions signals and LED
signals for clipped and non-clipped cases. Signal
clipped on 1.2 m coax with 22 Ohm termination
Comparison the signal shape for 50 GeV pions and
LED signal
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
LED monitoring design
For LED trigger pulse distribution a 64
channels dedicated board has to be developed. It
will be placed in to the spare slot of the 9U
LFB crate. This crate is connected to TTC and ECS
systems.
Synopsis of LED Trigger Board (LEDTB)
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL

• 137Cs radioactive source calibration system
•    System overview
• The reliable and stable calibration method has
  been developed and tested with HCAL Prototype.
  Its aim is to monitor the detector properties,
  like ageing of plastic and fibers, and give an
  absolute reference for the cell calibration. The
  radioactive 137Cs gamma-source that has 30 years
  half-life is used. Three sources encapsulated in
  the stainless steel pipe were obtained, with
  activities of 5, 8 and 10 mCi.
• The HCAL calibration system incorporates the
  following parts
• continuous 8 mm diameter stainless steel pipe
  that is fed through the middle of all
  scintillating tiles and filled with a distilled
  water
• a computer controlled hydraulic pump and valves
  that create a reversible water flow in the pipe
  and therefore move the capsule with a radioactive
  source throughout the detector
• an automated garage with a 5 cm thick lead wall,
  to safely keep the source between calibration
  runs
• integrated on-detector electronics to measure the
  PMT current when the source is moved from cell to
  cell across the HCAL.

21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
PMT anode current produced by radioactive source
is integrated by an electronic integrator with a
decay time of order of 2 msec. Readout board
collects analog signal from one module
phototubes, digitizes them and stores into a
local memory (it takes 125 msec/module). Then the
data are transferred to a computer through CAN
bus interface (it takes about 4 msec). The
readout continues till the source run through the
module. Two or five 8 - channel integrator
boards (placed into the module) and 520 channel
readout board (placed on the detector) have been
developed.
Photo of the 8 channels integrator and readout
boards
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
6U VME size crate for control and
monitoring electronics
Garage for radioactive source storage
crate with hydraulic apparatus
Photo of the rack with the hydraulic and control
electronic crates
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
PMT with CW base
   Integration of the HV, LED monitoring and
radioactive source systems on the HCAL
detector.     Placement of the electronic boards
and connection with ECS The electronic boards of
mentioned systems will be placed partially into
the HCAL modules and around the detector. There
are two options for the board integration on the
detector. Main option is the electronics
placement on the top and bottom platforms. In
this case one has easy access to all boards, but
the cable length of the analog control signals is
not minimal. Another option is to distribute the
boards on the side of detector. In this case the
cable length is minimal, but the access is less
convenient.
Photo of the internal cabling and CW base
integration into HCAL module
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
2 or 5 (16 or 40 channel HCAL module) 8 contact
coax connectors for connection with Front-End
crate
5 pin connector for PIN diodes and LED triggering
signals
2 of 10 pin connectors for CW base and LED power
supply
34 pin connector for Cs calibration system
2 of 40 pin connectors for HV control signals
HCAL module side panel with connectors
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
LFB rack with crates

• The estimated cross-sections of the cables
  integrated on the HCAL side are following
• coax cables cross-section is about 120 120
  mm2,
• flat cables cross-section is about 70 100 mm2.

LED triggering Board connected to TTC and ECS
6U VME size crate for Cs source monitoring, and
control electronics
Garage
33 40 wire flat cable
850 coax cables of 3 mm diameter
Two boards of HV and LED DAC control voltage
one board of Integrators Readout connected to ECS
Sketch of the electronic boards and crates
integration on the HCAL detector
Crate with hydraulic apparatus
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL
The list of the half HCAL electronic boards
integrated outside of the detector
21.11.03 Anatoli Konoplyannikov
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Design and integration of HV, LED monitoring and
calibration system for HCAL

• Procedure of the PMTs assembly and cabling
  needed manpower
• 1500 PMTs and CW base assembly 3 man-weeks
• 1500 PMT CW base test and Gain vs HV
  measurement 6 man-weeks
• 44 sets of coax and flat cables preparation and
  installation inside HCAL 8 man-weeks
• 1500 PMT CW base installation into modules 3
  man-weeks

21.11.03 Anatoli Konoplyannikov