SBS Collaboration Meeting
June 3-5, 2013
Initial Evaluation of MQT Electronics
R. Chris Cuevas
1. Hardware
Overview
2. Test Results
Brief comparison to 1881 QDC Open issues(Questions)
3. Summary
Charge-To-Time-Converter (MQT)
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• The 32 channel MQT circuit board was designed for the Belle Detector• The boards included the use of the LeCroy MQT300A integrated circuit
-- The MQT boards were used to readout the Central Tracking Chamber (CDC) -- The CDC used a single ended preamplifier designed by Radeka
28 Pin Plastic Leadless Chip Carrier (PLCC)Single channel IC
32 Channel MQT Board400mm
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16 Inputs
16 Inputs
MQT Section
Bus Power
Analog Section
9U
16 Channel single ended input card(Makes testing easier)
32 Channel MQT Board Block Diagram
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From PMTNOT PreampFor Hall A application
Could be usedFor LED testpulse
NotUsed
To 1877
Charge-To-Time-Converter (MQT)
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• Relatively simple circuit sections and the boards are in excellent condition• We built a simple 16 channel coaxial input board to facilitate the testing for each
channel. • Inputs are at the rear of the board on standard DIN connectors• Output (ECL) signals are on the front panel and connect to 1877 TDC• The MQT chip is not so simple and there are a number of control bits to set the desired charge input range.
-- In contact with Dr. Richard Sumner (One of the original LeCroy members)
• Analog input section is a voltage gain of ~50 and the analog signal passes through a shaper and delay before being applied to the MQT chip
• Copy of the analog pulse is sent to a two threshold discriminator-- This signal is delayed and creates a GATE signal of ~600ns-- Analog (Charge) pulse is delayed so charge edge is 80ns after GATE edge-- Note that the Max GATE from the MQT data sheet is exceeded by 50ns-- The discriminator output is OR’ed with the MQT output so initial edge ofChannel output can be used in the TDC for timing.
MQT Board Testing
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MQT Board Testing
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Horizontal == 100nx/div
Zoom in of pulse arriving after GATEInternal self-Gating signal
MQT Board Testing
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Horizontal == 100nx/div
(Large Pulse)
Test Notes
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• CR – RC shaping time is not optimized for pulse I was using from the generator.
• Presumably the shaper section was optimized for the CDC peaking time in conjunction with the gain from the Radeka preamp. I did not make many adjustment to the pulse shape, but the shaper will differentiate if overdriven.
• Need to understand how to control the range pins of the MQT300A chips. The default is medium, but this may not be the best setting.
• The MQT board requires seven (7) different power supply voltages! -8V @ 1.3A +15V @ 1.2A -12V @ < 1A -5.2V (Vee) @ 5.39A +5V (Vcc) @ < 1A Vthresh-High 0-10V [ 0 – 1V discrimination range ] Vthresh-Low 0-10V [ 0 – 1V discrimination range ]
Test Notes
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• We refurbished an older 9U by 400mm ‘crate’ from the CLAS6 drift chamber-- The size of the crate was perfect-- The card guides and crate provided adequate cooling-- The 7 power supplies for the MQT boards was less than optimal and the-8V supply was only biased to -5.2V which was inadequate. -- The two threshold supplies were NOT biased from the Vicor supply-- In the end it was decided to power a single board and study the circuits closer
on the bench.
Additional Testing Needed
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• Configure the range control for the MQT chips so that all three ranges are ON.
• Understand the output pulse train from the MQT given a calibrated input charge pulse.-- Verify conversion time for MQT charge-- Verify maximum rate performance
• On board GATE time seems excessive and exceeds the specification of the MQT300A chip. Can be adjusted but will require component changes.
• Once pulse train output is understood and stable with a calibrated charge input, setup test with MQT board and FastBus 1877 to begin decode.-- First edge of MQT output pulse train is the discriminator edge and will be used
for timing measurement. 1877 is 500ps LSB-- Remaining pulse train edges will need to be decoded and converted to derive
charge value
Brief Comparison to 1881 FastBus ADC
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# of Channels 64
Input Type Coaxial single ended
Dynamic range 13 bit
Sensitivity 50 fC/count
Conversion Time 12us (all 64 channels)
Full scale 8192 counts (410pC)
64 event buffer YES (FastBus module)
# of Channels 32
Input Type Coaxial single ended
Dynamic range 12 bit
Sensitivity*3 ranges
10 fC/ns to 640fC/ns
Conversion Time 6us
Full scale 2620pC
Event buffer NO (Custom bus)
MQT Board1881 Board
More Comparisons
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MQT BoardDetector (PMT) 1877 TDC (96 channels or 3 MQT)
NO splitterNO delay cable (1877 operated in common STOP)Custom (High current) power supply and crateDiscriminated signal AND Charge pulse information
Detector (PMT)
Splitter
1877 TDC
1881 ADC Delay
Discriminator
GATE
STOP
Summary• Initial testing was preliminary
• Good understanding of all MQT circuit board sections• Significant questions and testing remain? Understand MQT chip pulse output stream for each range? Use calibrated charge to verify MQT conversion to 1877? What will PMT pulse shape parameters be for nominal amplitude signal? Will CR-RC shaper on MQT need significant adjustment • Power supply for MQT boards is not standard and will need fairly large current
for a full crate of MQT boards (Still less than FastBus crate)
• Acknowledgements Bill Gunning for test and crate configurationMark Taylor for quick design of 16 channel coax input test board
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