Transcript High Voltage Analysis of Monitored Drift Tube Performance Divine Kumah

High Voltage Analysis of
Monitored Drift Tube
Performance
Divine Kumah
Summer 2003
CERN, Switzerland
Mentor: Dan Levin
Project Overview
Investigate High
Voltage spectra tool
for tube & electronics
performance for the
ATLAS Muon detector
Compare diagnostic
tool with TDC spectra
Analysis
Atlas Overview
(A Toroidal LHC Aparatus)
General-purpose
experiment to study
proton-proton collisions in
the LHC
144 member institutions
with 17500 scientists
Range of Study includes:
– Search for Higgs Boson
– Origins of CP violation
– Search for Supersymmetric
particles
Atlas Setup
(A Toroidal LHC Aparatus)
Inner Tracking Detector
EM Calorimeter
Hadronic Calorimeter
Muon Detector
Toroidal Electromagnets
Muon Chamber Setup
Side View of Muon System
MDT Chamber Setup
Each MDT
consists of 2
multilayers
separated by a
crossframe.
Each multilayer
has 3 or 4 layers
of cylindrical gas
filled aluminum
tubes
•Tube diameter 30mm
•Gas Mixture
•Ar (93%), CO2 (7%)
•Tungsten sense wire (anode)
Tube Operation
HV between inner wire and outer tube
creates E field
A charged particle traversing the tube
ionizes the gas molecules creating ion/epairs
Primary electrons accelerated by E field
toward anode
Avalanche produced if primary e- have
enough energy to ionize other gas atoms
Creation of avalanche improves strength of
generated signal.
Spatial resolution obtained from
measurement of drift time
MDT Integration and Tests
Gas System
Electronics
Monitoring Devices
Chamber Alignment
Dead tube/Mezz card identification
350,000 tubes from 11 instiutions in 6 different countries have to
be tested fast!
Drift Time Analysis
Drift time measurement
– Requires mounting with
Trigger Devices
– Histograms for hit tubes for
cosmic ray tests at nominal
threshold (40 mV)
– Fixed high voltage (3080V)
– Mount for 2-3 days to
obtain 10,000 hits per tube
for Cosmic Ray test
Drift Time versus Frequency plot
High Voltage Analysis
HV scans of chambers measuring
counting rates of tubes
Software random triggers
2.25 ms time window
Data taken at 100 kHz
Runs performed for 106 events
HV between 2.1kV & 3.4kV
Prominent feature studied was
characteristic plateau
Period for data acquisition < 1 hour!
HV Tube Spectra
Proportional Region
– Field Proportional to
signal
Plateau Region
– Signal Fairly constant
– Region of high
efficiency
– Strong signal
Exponential Region
– Gas Breakdown due
to electric field
– False Data, high
noise probability
Data Acquisition
Acquire Data for HV increments of 50V
Data Files produced using FILA
– 1 file per HV
– Fila Data Format – TDC, Channel, # of Hits
CalcFreq Program calculates Hit frequency
Frequency = # Hits / (length * # events * tau)
Input File : File with list of Fila output filenames, HV and
number of events
Eg: A line from the input file would be
– EIS2400.data.out
2400
1000343
Data Acquisition
Create a ROOT tree of tube statistics with
the following branches
Tube ID
Tube Length
Hits
Zero Hits
Frequency
Error
High Voltage
Data Analysis
Create (±3 sigma)
Envelope for freq\HV
data and save list of
tubes outside the
envelope
– 4-degree polynomial fit
Find dead and noisy
tubes
Data Analysis: Plateau Parameters
Plateau Parameters as follows:
– Freq/HV graphs fitted with 4-degree poly.
– Start of plateau  Minimum of 1st Derivative
of the polynomial
– Middle of Plateau  Minimum of 2nd
Derivative of the 4-degree polynomial
– Freq at Operation Voltage (3080V) ~ Freq at
3100V
– Width  Midplat - Startplat
Data Analysis: Plateau Parameters
A scatter diagram of the 2
parameters against each
other for all the tubes
Mezz Card diagnostics
from parameter/mezz
card plots
Data Analysis: Plateau Parameters
Plots for Middle of Plateau indicating interesting activity on Mezz Card 5
Time Spectra versus HV Analysis
*Efficiency from Time spectra Analysis and HV analysis compared
Conclusion
A Cosmic Ray MDT test for tube
studies has been investigated
Parameters have been extracted
corresponding to physical features of
MDT tubes from HV / Frequency plots
Procedure may compare relatively
favorably with current Drift time studies
due to the fact that data can be taken
in a relatively short time (~1 hour
compared to 2-3 days for Drift time
studies)
Acknowledgements
The University of Michigan CERN REU
Program
Jean Krisch, Homer Neal, Tom Dershem
My Mentor, Dan Levin
DOE, FORD
The UM REU crew, Shirit Cohen
QUESTIONS??