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Intensive irradiation study on
Monitored Drift Tubes chambers
C. Mazzotta, E.Meoni, G.Morello, A.Policicchio, D.Salvatore, M.Schioppa
Dipartimento di Fisica, Università degli studi della Calabria and INFN Gruppo
Collegato di Cosenza
P.Branchini, S.Di Luise, E.Graziani, A.Passeri, F.Petrucci
Dipartimento di Fisica, Università Roma Tre and INFN Sezione di Roma Tre
2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Summary
2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
The ATLAS Muon Spectrometer
Particle background
Test goals & strategy
The test facilities @ ENEA Casaccia
Experimental setups
Results of gamma irradiation
Results of neutron irradiation
Results of high rate studies
Conclusions
Fabrizio Petrucci
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
MDT chambers in the ATLAS Muon Spectrometer
The research program of the ATLAS
(A Toroidal Large Acceptance Spectrometer)
experiment at the Large Hadron Collider
(LHC) requires the detection of photons,
electrons, hadron jets, missing energy and
muons with good momentum resolution
over a large acceptance.
Muon momenta are measured with large toroidal magnets and tracking is
done in air.
Large toroidal magnets (two end-cap and one barrel).
Bending power ∫Bdl~3 T m.
Fabrizio Petrucci
3 tracking stations (Inner, Middle and Outer) in 8 Large sectors and 8 Small sectors
Muon tracking detectors are mainly Monitored Drift Tubes (MDT):
good space resolution (~100 μm per point)
robust and reliable operation for many years.
In the barrel space points are also measured in r-z and r-φ planes, with a precision
of ~1 cm with 3 planes of RPC that also provide a fast trigger.
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Particle background
Low energy secondary particles from hadrons interactions with detector and machine
elements, uncorrelated to primary p-p collisions (charged particles, neutrons and photons
in the MeV range)
Total flux ~ 5 kHz/cm2 (safety factor 5 applied)
MDT sensitivity
to neutrons ~ 5 ∙10-4
to photons ~ 8·10-3
MDTs integrated charge in 10 LHC years = 0.6 C/cm.
Neutron flux in 10 years of ATLAS operation = 3.45 ∙1011 n/cm2 (Inner Barrel region)
SLHC project : 10 times higher fluxes than LHC for 10 years (~6C/cm).
Fabrizio Petrucci
Fluxes (kHz/cm2)
L=1034 cm-2 s-1 Neutrons Photons
3.45 1.20
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Test goals
Chambers have to operate in the harsh LHC background for about 10 years.
Foreseen an upgrade for S-LHC (10 times higher luminosity).
Tests performed @ ENEA Casaccia Research Center (Rome, Italy)
1. July 2005: 2 MDT bundles under photon irradiation at Calliope facility (4.8 C/cm
~ 80 ATLAS years)
2. September 2005: one of the Calliope bundles under neutron irradiation at Tapiro
reactor (1.32*1012 n/cm2 ~ 40 ATLAS years)
GOALS:
Study MDT behaviour after intensive irradiation with photons and neutrons:
Test final electronics robustness
Test material durability
Investigate gain drop
Study drift properties
Fabrizio Petrucci
Study tracking performances
Investigate MDT performance at high background rates:
Cosmic data acquired @ reactor thermal power between 50-100 mW,
corresponding to 3.3 – 10 kHz/cm2 (~ ATLAS-like neutron flux)
Study drift properties
Study tracking performances
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
The test facilities @ ENEA Casaccia Research Center
Calliope Gamma Facility:
• 6.7·104 Bq 60Co source (2 photons of 1.17
and 1.32 MeV)
• Dose in air 15.3 Gy/h 7.2·108
photons/s/cm2 at the test chamber location.
TAPIRO copper reflected fast neutron
source:
• A cylindrical core (U 98.5%,Mo 1.5%) with
fully enriched 93.5% 235U
• Neutron flux at the reactor core 2.2x1012
Fabrizio Petrucci
n/cm2/s at the maximum thermal power (5kW).
• Neutron energy range between 10-4 and 10
MeV with a broad peak around 1MeV
• Experimental setup hosted in the thermal
column.
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Experimental setup
Test detector:
Two test detectors of 6x4 identical drift tubes, 47cm long, built and tested following the
standard ATLAS wiring and quality control procedures.
Gas:
Ar-CO2 (93:7) from a premixed bottle supplied through the ATLAS standard on-chamber
distribution system. About 10 complete volume exchanges per day.
Front-End electronics:
Standard ATLAS “mezzanine board” that serves 24 tubes and contains:
- ASD (Amplifier-Shaper-Discriminator) chip
- AMT TDC for drift times measurements with a resolution of 25/32 ns
-Wilkinson ADC for leading edge charge measurements (25 ns gate)
Cosmic ray trigger:
coincidence of 3 scintillator
counters wrapped with 2 mm
Pb plates.
Fabrizio Petrucci
For the neutron test:
- Only one bundle used (bundle 2
removed and scintillator counters
avvicinati)
- Scintillator counters shielding
improved with borum powder and
cadmium foils.
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Data taking strategy
Slow control monitoring of current, gas flow, temperature and pressure.
Gamma irradiation test:
Irradiation periods followed by cosmic runs.
Irradiation period: trigger off, HV=3800 V, P=1.1 bar to accumulate ~5 C/cm in 20
days. Total amount of photons 8.9*1014 γ/cm2.
Cosmic runs: source off, trigger on, MDTs operating at standard conditions.
Neutron irradiation test:
Irradiation periods followed by cosmic runs.
Irradiation period: trigger off, MDTs operating at standard conditions, reactor operated at
thermal power from 100 W to 400 W, corresponding to an overall integrated flux of
1.32∙1012 n/cm2 (~ 40 ATLAS years)
Cosmic runs: source off, trigger on, MDTs operating at standard conditions.
Fabrizio Petrucci
High background rates sample:
Cosmic data samples acquired @ reactor thermal power between 50-100 mW,
corresponding to 3.3 – 10 kHz/cm2 (~ ATLAS-like neutron flux)
Cosmic data samples acquired @ reactor off for comparison
Intensive irradiation study on Monitored Drift Tubes chambers
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We have monitored the drift parameters with
2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Results of gamma irradiation increasing accumulated charge.
Two examples here:
x p
f(x) p exp
4
1 p xp
5 1 exp 2
p
3
Rise time (p3) is related to spatial
resolution.
It shows to be constant as the
accumulated charge increases.
(x p 2 ) 2
f(x) p1 exp
Fabrizio Petrucci
x p3
Peak abscissa (p2) gives
information on integrated
charge and gas gain
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Results of gamma irradiation (II)
Study of tracking efficiency of a single tube:
Track fit excluding hit of the examinated tube;
Residual= rdrift measured - rdrift extrapolated
Tube efficient if : Residual<5· Space_resolution.
Drift
Reconstru circle
cted Track
Fabrizio Petrucci
residual
No significant systematic effects found as
accumulated charge increases.
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Results of neutron irradiation
Mean variation of ADC peak with respect to
reference run.
Values compatible within 1σ.
No gain loss after massive neutron irradiation.
RTs calculated for 4 different integrated flux 5σ efficiency:
runs. Comparisons to reference run within Values are stable around 97% within
±25 m. statistical errors.
Fabrizio Petrucci
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Results of high rate studies
Single tube 5s efficiency
ADC peaks vs drift time
Fabrizio Petrucci
Cosmic runs and high rate runs
Typical trend for Ar-CO2 mixture (also
are compared.
from simulation)
No performance deterioration at high
No efficiency variation.
rates
Stable around 97%.
No gain loss in high rate environment.
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Wire microscopy and chemical analysis
Non irradiated wire
After irradiation 7 wires from both test
chambers in different positions analyzed by SEM
(Scanning Electron Microscopy) and EDX
(Energy Dispersive X-ray)
3 samples (4 cm) for each tube: gas inlet side,
gas outlet side, middle
Reference samples: 3 x 4cm wires from the
micro-photo of tube sections
same spool
Irradiated wires show the same pollution Irradiatiated wire
detected on the reference ones
Fabrizio Petrucci
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
CONCLUSIONS
Intensive neutron and photon irradiation test was performed on final MDT-like test
chambers.
After overall accumulated charge of 4.8 C/cm and an integrated neutron flux of 1.32*1012
n/cm2 ):
good electronics response
no gas leak observed: stable behaviour of o-rings, end-plugs, gas distribution elements
no damage evidences from chemical analysis on wires
no gain drop observed from ADC studies
negligible variation of drift properties from RT studies
no reconstruction efficiency loss
No significative difference from standard performance has been observed in a high (3.3 –
10 kHz/cm2) background environment.
Fabrizio Petrucci
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
BACKUP SLIDES
Fabrizio Petrucci
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
two multilayers of 3 (in Middle and Outer rings) or 4
(in the Inner ring) layers of staggered drift tubes each.
thin wall (400 μm thick) 3 cm diameter aluminum
tubes.
low longitudinal diffusion gas mixture,
93%Ar−7%CO2, absolute pressure of 3 bar.
Gold-plated W-Re anode wire, 50 μm diameter is
tensioned at 350 g crimped in copper pins.
low gas gain of 2×104 (3080 V andode voltage) to
avoid ageing effects.
Fabrizio Petrucci
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Background in the ATLAS muon spectrometer
Fluxes (in kHz/cm2) with GCALOR simulation 2003 (Atlas Radiation Background Task Force)
Fabrizio Petrucci
Intensive irradiation study on Monitored Drift Tubes chambers
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2006 IEEE NSS - Oct. 30, 2006 · San Diego, Ca
Results of gamma irradiation (II)
Typical ADC spectrum. Fit on the central
region with:
(x p 2 ) 2
f(x) p1 exp
Peak abscissa (p2) gives
x p3 information on integrated
charge and gas gain
Fabrizio Petrucci
Intensive irradiation study on Monitored Drift Tubes chambers
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