Transcript dc12-commissioning

DC12 Commissioning Status
GOALS: establish operating conditions, determine initial calibration
parameters and measure operating characteristics for the CLAS drift chambers.
HARDWARE PREREQUISITES - a list of hardware which must be built, installed and
operational before drift chamber commissioning can begin.
• Chamber Assembly - all chambers built, strung, tested (tension, continuity, hv, gas leaks), on-board
electronics tested and installed, bagged, survey points installed, on-chamber cabling done, gas
flowing, hv and lv applied, “hv conditioned” and problems fixed
• External Hardware Installed
– Gas system operational - flow tested with dummy volume
– HV supplies and distribution boxes tested and installed
– LV supplies tested and installed
– DCRB’s tested and installed
– Cabling DCRB crate to DAQ
– Cabling Level 1 trigger to DCRB input
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DC12 Commissioning Plans
Mac Mestayer
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DC12 Software Commissioning
SOFTWARE PREREQUISITES - a list of software programs and procedures
which must be written and installed before drift chamber commissioning can
begin.
• Data Acquisition - data acquisition software must be written and down-loaded into the
DCRB crates
– A minimal readout code based upon CODA must be implemented for the
DCRB’s
– The trigger supervisor must be implemented in order to send timing signals
to the DCRB’s and read out and clear signals to the crates.
– Readout software must be down-loaded into the DCRB’s to convert the
TDC outputs into the event format of (IDWIRE,TIME); in particular the
wire-to-electronics map must be defined (NOTE: an alternate scheme of
IDCHAN,TIME may be used.)
– A single event display must be available to show which wires are firing.
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DC12 Calibration: Algorithms
Algorithms - algorithms must be written to determine calibration constants along with
I/O routines to fill the banks and initialization routines to read the banks. Routines are
also needed to calculate drift distances from raw TDC readings, and to monitor drift
chamber performance.
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Calibration analysis programs which analyze the data to determine the drift velocity constants
from analysis of tracking data
Calibration initialization routines which read the calibration banks for the proper run period and
which expand the data to fill the working arrays needed by the tracking programs.
Hit routines: time to distance routines must be written which return the calculated drift time and
drift distance given specific information about the track in question, the track length, local angle
and hit position along the wire.
Event analysis programs: track finder/fitter routines including routines to determine the event
start time.
Control programs to ramp on/off and monitor trips and current of the high voltage supplies, to
monitor the low voltage readback, to monitor pressure, temperature, oxygen levels and
constituency of the gas mixture, and to control pulsing of the laser or time-delay electronic
pulsing system.
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DC12: Calibration Data Files
Data Files - calibration and monitoring banks must be defined.
• Geometry - specify wire positions in sector and global toroidal coordinate systems. There
must be special banks to contain modifications to chamber position or orientation based upon
additional information (new surveys, alignment runs with magnet off, etc.). There must also
be methods to correct for gravitational wire sag at event time.
• Time Delays - contains cable delays, signal velocity along wire, and time difference between
DCRB and FTOF time stamps.
• Drift Velocity - parameters to determine DOCA as a function of time for wires in each of the 6
super-layers, for the given B field setting, and for the current calibration period.
• Status Tables – keep time history of HV, lv, wire status
• Translation Tables - associate each wire with its electronics; STB, HVTB, cable number, DCRB,
• Monitoring Banks - for monitoring fast electronics (STB, ADB, DCRB boards as well as their
crates), HV and LV voltages and currents, general tracking parameters (such as number of hits
per crate, per event, etc.), and tracking performance: efficiency, resolution and noise
• Environmental Conditions - contains gas properties (pressure, temperature, mix ratio), B
field setting, HV configuration, DCRB discriminator threshold, etc.
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DC12 Commissioning Plans
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DC12 Commissioning Procedures
PROCEDURES: - determine that all equipment is working properly, turn on gas and
voltage, measure noise level and set thresholds, pulse electronics to verify operations
and measure delays, determine high voltage operating point, calibrate the drift velocity
function and measure the operating characteristics of the chambers.
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Verify functionality of HV, LV, gas system and de-humidifier system.
Turn on STB's; minimize noise level by searching for discrete sources
Flow gas; purge chamber, verify proper mix ratio, low $O_2$ and $H_2O$ content.
Turn on HV; look at signals and rates on DCRB scaler output
Verify that DCRB's are being read out.
Set up DAQ system and single event display.
Set discriminator thresholds to limit noise hits to less than $1-2\%$ accidental occupancy and to
prevent oscillations.
Pulse trigger and DCRB's, determine cable delays, search for cross-wiring or dead channels.
Cross-pulse TOF and DCRB's for synchronization.
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DC12: Establish Operating Parameters
Measure the operating characteristics of the chamber.
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Efficiency - determine layer efficiencies by excluding layers from fit, determine wire
efficiencies versus DOCA.
Noise Level - determine random noise by number of hits not associated with tracks, study
cross-talk and coherent noise by histogramming Ti versus Tj for all hit pairs on a track.
Resolution - study residual distributions versus track angle, DOCA, layer or chamber
region by the layer-excluded method and the no-layer-excluded method.
Do a HV scan, measuring the layer efficiency versus voltage.
Choose the high voltage operating point, balancing increasing efficiency versus current
draw (and chamber lifetime).
Choose the DCRB discriminator threshold
Write and implement a ``standard operations procedure“ document for shift personnel.
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