21.11.03 anatoli konoplyannikov

121.11.03 Anatoli Konoplyannikov

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



HCAL 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.

The HCAL high voltage (HV) system consists of:

* about 1500 CW bases, those soldered on the PMT’s 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.

HCAL CW base circuit diagram.

High voltage system



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 10^4, 10^5, 10^6.

PMT ZL2595 Gain variation (R=500M connected to GND)

0,95

0,96

0,97

0,98

0,99

1

1,01

0 2 4 6 8 10 12

anode current (mkA)

Gai

n d

evia

tio

n

G10^4

G10^5

G10^6

CW base main characteristics



HCAL

Photo of HCAL CW base with Hamamatsu PMT.

High voltage system



HCAL

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.

216 – channels DAC board block diagram

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 160*250 mm2.

High voltage system



HCAL LED monitoring design

Sketch of the optical part of the LED monitoring system

The LED monitoring system is mainly aimed at:

• a middle term monitoring of the PMT gain stability,

• an ADC sample time calibration and adjustment

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.




LED driver block diagram

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 40*70 mm*mm

mechanical design is optimised for HCAL




Photo of the light mixer with LED driver and PIN diode amplifier printed circuit boards



HCAL

LED monitoring design

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

LED signal50 Gev pions

Comparison the signal shape for 50 GeV pions and LED signal



HCAL

Synopsis of LED Trigger Board (LEDTB)

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.



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.



HCAL

Photo of the 8 – channels integrator and readout boards

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 sec/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.



HCAL

Photo of the rack with the hydraulic and control electronic crates

Garage for radioactive source storage



HCAL 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

PMT with CW base



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



HCAL LFB rack with crates

6U VME size crate for Cs source monitoring, and control electronics

Two boards of HV and LED DAC control voltage + one board of Integrators Readout connected to ECS

33 * 40 wire flat cable

Crate with hydraulic apparatus

LED triggering Board connected to TTC and ECS

850 coax cables of 3 mm diameter

Sketch of the electronic boards and crates integration on the HCAL detector

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.



HCAL System Board description Number of boards per half of HCAL

HV 216- channels DAC of the HV and LED control voltage 4Power Supply: + 80 V (1 A) 1 + 6 V (0.2 A) 1 - 6 V (0.2 A) 1

LED monitoring 9U VME 64 – channels LED triggering 1Power Supply: - 40 V (0.1 A) 1 +6 V (0.2 A) 1 - 6 V (7 A) 1

Cs calibration and monitoring 520 – channels Integrators Readout Board 2

16-channels Capsule location sensor (SIN) monitoring board 4Hydraulic control board 1Garage control board 1Power Supply: ~ 220 V (3 A) 1 + 9 V (2 A) 1 + 12 V (5 A) 1 - 12 V (3 A) 1 + 6 V (2 A) 1

The list of the half HCAL electronic boards integrated outside of the detector



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

Documents

cw base current gain

hcal high voltage hv

cw base voltage ripple

cw bases

dc anode current gain

led monitoring system

integration of hv

hcal cw base circuit