Transcript VLPC system and Cosmic Ray test results M. Ellis Daresbury Tracker Meeting 30th August 2005

VLPC system and
Cosmic Ray test results
M. Ellis
Daresbury Tracker Meeting
30th August 2005
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Analog Front-End (AFE) Version 2
 New
design of the readout electronics for
VLPCs.
 Step along the path to AFEII-t, which will
add the ability to record TDC information
for each hit.
 Prototype AFEII boards have been used
for the first time at D0 for work on the
MICE tracker.
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MICE tracker readout with VLPCs
Waveguides
Tracker
LVDS cables to
VLSB module
AFEII boards
VLPC cryostat
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VLPC operating conditions
Temperature needs to be kept at 9.00 ± 0.02 K.
Cryostat/cryo-cooler combination controlled to
hold cold-end at 6.8 K with heater on a feedback loop.
 VLPC cassettes have 8 heaters, controlled
through the AFE board, that bring the
temperature up to 9.0 K and maintain it.
 Select appropriate bias voltage to optimise gain
vs noise rate. Optimisation depends on expected
data-taking rate.
 Bias voltage is applied through the AFE board.
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LVDS / VLSB
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Low Voltage Differential Signaling (LVDS) is
used to transfer the ADC data from an AFE
board to a VME memory module.
 The cable is connected to the AFE board
through the AFE back-plane.
 VME LVDS Serdes Buffer (VLSB) boards are
VME devices containing memory and an LVDS
interface.
 When the AFE board passes through a dataacquisition cycle, the ADC values are sent to the
corresponding VLSB board and can then be
accessed over a VME/PCI interface (BIT3).
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LVDS cables
LVDS and VLSB
1553
Trigger/Timing
VME/PCI
VLSB modules
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Initialisation
 AFE
boards need to be initialised before
data-taking can begin.
 This is achieved through the Mil-1553
interface. One 1553 can control all 4
boards on a MICE 2-cassette cryostat.
 Initialisation includes:
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FPGA power on, programming and testing
Trigger Pipeline (TRIP) chip programming
VLPC bias voltage and temperature control
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Timing and Triggering
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FPGAs require a 53 MHz clock.
AFE board has a number of operating modes:
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Initialise
Acquire
Digitise
Readout
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The clock and mode control used to be provided
by a SaSEQ board, now provided by an Avnet
board.
 Avnet is able to control all 4 boards on a MICE
cryostat at once and requires no software
intervention to perform a
trigger/acquire/digitise/readout cycle.
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Avnet Board
RS232 cable
Connection to AFE Backplane
External trigger
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Readout Sequence
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External trigger is generated (e.g. cosmic ray trigger
scintillators).
Trigger is ANDed with a pattern that matches the
tevatron bunch structure (needed for now, will be
replaced in later use for MICE).
If trigger is accepted, signal is passed to Avnet board.
Avnet board causes the AFE boards to acquire, digitise
and readout the data to the VLSB modules and then sets
the AFE boards ready for the next trigger.
Data is retrieved from the VLSB modules over the
VME/PCI interface to a Linux PC.
Timing is critical as the trigger signal to the Avnet board
needs to arrive 7 “bunch crossings” after the light from
the tracker arrives at the VLPCs.
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Progress at FNAL

After a number of problems, have managed to
operate the MICE cryostat with 4 AFEII boards.
 Linux software written for MICE can now perform
almost all of the initialisation sequence and was
used for all data-taking.
 Took data with an LED pulser attached to each
VLPC cryostat in turn and then connected the
tracker and collected a few thousand cosmic ray
triggers!
 Tracker system has been sent to Japan and is
being setup there now...
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G4MICE
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Several new features have been implemented in
preparation for the use of G4MICE in data-taking
and analysis of the KEK data:
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User applications
A few SciFi classes are now persistent
Interface to CERNLIB to make PAW histograms, etc
Code to decode raw data format
Code to handle calibration data
Code to handle “decoding” information (so far only for
original three stations)
First version of visualisation
Existing reconstruction already works with real data
classes.
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Pedestal Widths
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Calibrations – Cassettes 105 & 111
10 PE
Cassette 105
10 PE
Cassette 111
One channel from each cassette.
Note 105 has a gain of ~20k and 111 has a gain of ~40k
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High Gain Cassette – More Light
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Calibration Results
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First look at Cosmic data
Still require work on “cabling” information (i.e. which
board/channel/MCM is connected to which
Station/Plane/Fibre)
 Cabling information only for original three stations at the
moment.
 Calibration applied to raw hits and normal pattern
recognition applied up to the level of space points.
 Still need CMM data on station positions before attempt
at tracking can be made.
 Need to construct a “dead channel” list to remove first 4
channels readout over LVDS. These channels are
corrupted due to the very low data-taking rate. This is
only an issue < 0.5 Hz!
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Light Yield (no tracking cuts)
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Doublet Clusters
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Hit Distribution
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Next Steps
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Add code to cope with new station/waveguide
decoding.
Make best guess of waveguide connections to
new station (otherwise try all plausible options...)
Obtain and use CMM information for station
alignment.
Improve calibration information.
Check higher-level reconstruction (points and
tracks).
Finish executables and scripts for KEK test.
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