Calor 2002, 25-29 march 2002 Auguste Besson 1
Argon purity measurement of Argon purity measurement of the D0 calorimeter the D0 calorimeter
Argon purity measurement of Argon purity measurement of the D0 calorimeter the D0 calorimeter
Auguste Besson Auguste Besson (ISN - Grenoble)(ISN - Grenoble)
for the D0 collaborationfor the D0 collaboration
1010thth International Conference on Calorimetry in High Energy PhysicsInternational Conference on Calorimetry in High Energy Physics Calor 2002. Calor 2002.1010thth International Conference on Calorimetry in High Energy PhysicsInternational Conference on Calorimetry in High Energy Physics Calor 2002. Calor 2002.
Calor 2002, 25-29 march 2002 Auguste Besson 2
Argon purity measurement of the Argon purity measurement of the calorimeter calorimeter
Argon purity measurement of the Argon purity measurement of the calorimeter calorimeter
• Argon Test Cell (A.T.C.)
– measures the equivalent O2 pollution with 2 radioactive sources & .
– general setup, cryostat, electronics
• Calibration Source Source
• Measurements and results
• Conclusion
A. Besson, Y. Carcagno, G. Mondin, G. Sajotwith help from Solveig ALBRAND, Germain BOSSON,
Philippe MARTIN
Calor 2002, Auguste Besson Auguste Besson 3
The D0 calorimeterThe D0 calorimeter• 1 Barrel + 2 End Caps1 Barrel + 2 End Caps• Liquid ArgonLiquid Argon• U (EM) / Cu-Stainless steel (Had.)U (EM) / Cu-Stainless steel (Had.)• 5000 towers : 5000 towers :
x x = 0.1 x 0.1 = 0.1 x 0.1• 4 EM read out layers4 EM read out layers• 4/5 Had read out layers4/5 Had read out layers (EM) / E ~ 16% / (EM) / E ~ 16% / EE (Had) / E ~ 50% / (Had) / E ~ 50% / EE
Central Cal.Central Cal.Central Cal.Central Cal. South End CapSouth End CapSouth End CapSouth End CapNorth End CapNorth End CapNorth End CapNorth End Cap
Calor 2002, 25-29 march 2002 Auguste Besson 4
Why do we have to monitor the Argon Why do we have to monitor the Argon purity ?purity ?
• Shower :liquid argon ionization.
• Liquid Argon purity :Any electronegative molecule (O2 ) absorbs electrons and decreases the signal.
E=10kV/cm, gap=2mm (ATLAS LARG-NO-53)
• Need purity better than ~ 0.5 ppm
• Monitor precisely the pollution.
Pollution (ppm)Pollution (ppm)Pollution (ppm)Pollution (ppm) (
coll
ecte
d s
ign
al)
/ (id
eal s
ign
al)
(col
lect
ed s
ign
al)
/ (id
eal s
ign
al)
(co
llec
ted
sig
nal
) / (
idea
l sig
nal
)(c
olle
cted
sig
nal
) / (
idea
l sig
nal
)
Calor 2002, 25-29 march 2002 Auguste Besson 5
Principles: 2 radioactive sources Principles: 2 radioactive sources and and
• ALPHA
5.5 MeV, T = 430 ans
• BETA
3.5 MeV, T = 1 an, 40kBq
Am241
Ru106
• Sources electrodeposited on a stainless steel electrode.• Sources immerged in liquid Argon (@ ~ 85 K).• Ionisation, drift of the charges in an adjustable electric field E through a gap between electrodes : d = 2.15 mm.• The collected charge depends on the pollution p and on the field E.
Gap : d = 2.15 mm
Gap : d = 2.15 mm
Calor 2002, 25-29 march 2002 Auguste Besson 6
• System used in Run I (1992-96)• LAr stocked in a dewar for 5
years in a dewar (~ 20 000 gallons)
• Upgrade for Run II– New Beta source– New electronics (preAmplis, Pulsers, etc.)– Data acquisition soft in LabWindows/CVI– Added a O2 pollution system for calibration– complete check of the cryostat (leak detection, checks of valves, etc.)
• Calibration of system (2000)
• Dewar purity measurement– July 2000 and october 2000 (before filling the Calorimeter)
• Calorimeter measurements :– December 2000 and Dec. 2001
A.T.C. historyA.T.C. historyA.T.C. historyA.T.C. history
Calor 2002, 25-29 march 2002 Auguste Besson 7
ATCATCGeneral General
setupsetup
Calor 2002, 25-29 march 2002 Auguste Besson 8
ATC operating conditionATC operating condition
Temperature (K)Temperature (K)Temperature (K)Temperature (K)
Pre
ssu
re (
bar
ab
solu
te)
Pre
ssu
re (
bar
ab
solu
te)
Pre
ssu
re (
bar
ab
solu
te)
Pre
ssu
re (
bar
ab
solu
te)
Calor 2002, 25-29 march 2002 Auguste Besson 9
Signal cables
High Voltage
sources
LN2 exchange
Calor 2002, 25-29 march 2002 Auguste Besson 10
Alpha source measurements Alpha source measurements Alpha source measurements Alpha source measurements particle : highly ionizing particle Energy deposited over ~ 20 m constant currant • Ramping on the electric field E (~20 values)• Collected charge = f (E,p)• ~ 40 000 evts / value• normalized signal :
pedestalpulserpedestalsignalEQ )(
Pedestal Signal Pulser
Calor 2002, 25-29 march 2002 Auguste Besson 11
Alpha : principles of the measurementAlpha : principles of the measurementAlpha : principles of the measurementAlpha : principles of the measurement
),()()( 0 pEAbsErecombinQEQ
)1(),(),( ),(/ pEded
pEpEAbs
pEpE /),( With absorption length
• Recombination
• Collected charge
• Absorption
)1ln(1)( Erecombin )1( bEecEa
(a,b,c = constants)
with
Trapping constant := 0.142 0.014 cm2.kV-1.ppm
Calor 2002, 25-29 march 2002 Auguste Besson 12Alpha: absorptionAlpha: absorption
Theoritical expression Theoritical expression of the absorptionof the absorption
Theoritical expression Theoritical expression of the absorptionof the absorption
Calor 2002, 25-29 march 2002 Auguste Besson 13
Alpha absorption: an exampleAlpha absorption: an exampleAlpha absorption: an exampleAlpha absorption: an example
E (kV/cm)
Abs
orpt
ion
Fit of Abs(E,p) vs E.
Argon from dewar.
– Black : fit = 0.37 ppm
– Blue : fit - 0.1 ppm
– Red : fit + 0.1ppm
Calor 2002, 25-29 march 2002 Auguste Besson 14
Alpha : errors estimatesAlpha : errors estimatesAlpha : errors estimatesAlpha : errors estimates• Statistic errors :
– Statistics and fit error ~ 0.07 ppm
• Systematic errors :– High Voltage ~ 2 %
– gap between electrodes : d = 2.15 0.05 mm
– Error on parameters:
a = 474 1.4 kV/cm
b = 0.143 0.006 cm/kV
c = 0.403 0.010
– trapping constant = 0.142 0.014
• Other systematics :– electronics and non linearity of the preamp.
– temperature effects, etc.Need a calibration.Need a calibration.
Calor 2002, 25-29 march 2002 Auguste Besson 15
• Recipe– Start from a high purity
Argon sample < 0.1 ppm– Pollute with a well known
amount of O2 (for instance 0.5 ppm)– mix well, wait for 1 or 2
hours– Measure
Alpha calibrationAlpha calibrationAlpha calibrationAlpha calibration
Calor 2002, 25-29 march 2002 Auguste Besson 16
Errors on the pollution :• Volume of liquid Argon : 8-10 liters 5 %• Volume of O2 : 8.3 0.1 cm3
• Pressure of O2 : 15 0.5 P.S.I.
Calibration Calibration (2)(2)Calibration Calibration (2)(2)
Source
Measured / nominal
E (kV/cm)
Abs
orpt
ion
Error on the nominalpollution ~ 10 %
Error on the nominalpollution ~ 10 %
Calor 2002, 25-29 march 2002, A.Besson Auguste Besson
Argon Sample
Nominal Pollution
Measured Pollution
Cylinder 1 0.1 0.07 0.040.12
Cylinder 2 0.1 0.07 0.050.12
Cylinder 3 0.1 0.07 0.060.12
Cylinder 4 0.1 0.07 0.110.12
Cylinder 5 0.1 0.07 0.120.12
Polluted 0.40 0.11 0.43 0.12
Polluted 0.50 0.12 0.45 0.12
Polluted 0.52 0.12 0.49 0.12
Polluted 0.63 0.16 0.58 0.13
Polluted 0.69 0.15 0.77 0.13
Polluted 0.90 0.20 0.40 0.13
Polluted 0.97 0.14 1.01 0.14
Polluted 1.05 0.18 1.21 0.15
Polluted 1.30 0.25 1.34 0.16
Polluted 3.50 0.39 3.84 0.23
Polluted 4.00 0.44 4.04 0.30
Polluted 5.00 0.55 5.07 0.35
Alpha : calibration resultsAlpha : calibration resultsN
omin
al (
ppm
)
Measured (ppm)
Calor 2002, 25-29 march 2002 Auguste Besson 18
Alpha : errors Alpha : errors Alpha : errors Alpha : errors
measured pollution Error
0.2 ppm 0.12
0.3 ppm 0.12
0.5 ppm 0.12
1.0 ppm 0.14
2.0 ppm 0.18
3.0 ppm 0.23
5.0 ppm 0.35
Linear Fit gives the final errors.
Error vs nominal pollution (ppm)
Nominal Pollution (ppm)
Err
or m
easu
rem
ent (
ppm
)
Calor 2002, 25-29 march 2002 Auguste Besson 19
Alpha : C.C. and calibration, exampleAlpha : C.C. and calibration, example
Measured / nominal
C.C.C.C.C.C.C.C.
Calor 2002, 25-29 march 2002 Auguste Besson 20
Nominal Pollution (ppm)
Trapping constant Trapping constant measurement measurement• Trapping constant Trapping constant : : Relates absorption length , field E and pollution p :
• main error for absolute main error for absolute measurements.measurements.• Its value is not very well Its value is not very well known :known :
• With our calibration :With our calibration :
pEpE /),(
= 0.141 = 0.141 0.011 cm 0.011 cm22.ppm/kV.ppm/kV = 0.141 = 0.141 0.011 cm 0.011 cm22.ppm/kV.ppm/kV
p
aram
eter
= 0.142 = 0.142 0.014 cm 0.014 cm22.ppm/kV.ppm/kV = 0.142 = 0.142 0.014 cm 0.014 cm22.ppm/kV.ppm/kV
(Andrieux et al. NIM A 427, 568 -1999)(Andrieux et al. NIM A 427, 568 -1999)
= 0.138 = 0.138 0.019 cm 0.019 cm22.ppm/kV.ppm/kV = 0.138 = 0.138 0.019 cm 0.019 cm22.ppm/kV.ppm/kV
averageaverageaverageaverage
Calor 2002, 25-29 march 2002 Auguste Besson 21
• Characteristics – Complete spectrum.– Low ionizing particle
• the tracks cross the gap– Use a trigger gap in
Coincidence to decrease the noise
• No theoritical formula : empirical fit
Beta Source Beta Source Beta Source Beta Source
)(2)(),( EbeEgEcdapedestalpulser
pedestalpESignal
With a, b, c, d, g parameters of the fit.
Calor 2002, 25-29 march 2002 Auguste Besson 22
Beta: paramBeta: parameters vs pol.eters vs pol.
BdApol A et B given by the calibration.A et B given by the calibration.
Calor 2002, 25-29 march 2002 Auguste Besson 23
Beta: errorsBeta: errors
Measured Measured pollutionpollution
ErrorError
0.1 ppm 0.09
0.2 ppm 0.10
0.3 ppm 0.10
0.5 ppm 0.12
0.8 ppm 0.15
1.0 ppm 0.17
1.2 ppm 0.19
1.5 ppm 0.22
Pollution (ppm)
Err
or m
easu
rem
ent (
ppm
)
Calor 2002, 25-29 march 2002 Auguste Besson 24
Beta: example of C.C. measurementBeta: example of C.C. measurement
C.C.C.C.C.C.C.C.
Calor 2002, 25-29 march 2002 Auguste Besson 25
Beta: example of N.E.C. measurementBeta: example of N.E.C. measurement
N.E.C.N.E.C.N.E.C.N.E.C.
Calor 2002, 25-29 march 2002 Auguste Besson 26
Beta: example of S.E.C. measurementBeta: example of S.E.C. measurement
S.E.C.S.E.C.S.E.C.S.E.C.
Calor 2002, 25-29 march 2002 Auguste Besson 27
Summary of measurementsSummary of measurementsSummary of measurementsSummary of measurements
Measurements compatible and stableMeasurements compatible and stable
SampleSample ALPHAALPHA BETABETA DateDate
DewarDewar 0.340.340.10.155
-- July 2000July 2000
DewarDewar 0.330.330.10.155
-- Oct. 2000Oct. 2000
C.C.C.C. 0.490.490.10.155
0.380.380.110.11 Dec. 2000Dec. 2000
N.E.C.N.E.C. 0.160.160.10.155
0.210.210.100.10 Dec. 2000Dec. 2000
C.C.C.C. 0.070.070.10.122
0.100.100.090.09 Dec. 2001Dec. 2001
N.E.C.N.E.C. 0.110.110.10.122
0.090.090.090.09 Dec. 2001Dec. 2001
S.E.C.S.E.C. 0.170.170.10.122
0.140.140.100.10 Dec. 2001Dec. 2001
(ppm)(ppm)(ppm)(ppm)
Calor 2002, 25-29 march 2002 Auguste Besson 28
Conclusion and outlookConclusion and outlookConclusion and outlookConclusion and outlook• Errors on measurements :
Absolute measurements and errors.
better than 0.15 ppm
• We checked the stability of purity compared to last year measurements.
Purity OK for the 3 calorimeters < 0.5 ppm
No need to apply correction for calorimeter response
Give a calibration for the alpha internal cells of the calorimeter (Purity monitoring by Mainz Univ.)
• Trapping constant measurement
“Experiments must be reproduceable, they should fail the same way each time.”
Calor 2002, 25-29 march 2002 Auguste Besson 29