Calor 2002, 25-29 march 2002Auguste Besson1 Argon purity measurement of the D0 calorimeter Auguste Besson (ISN - Grenoble) for the D0 collaboration 10

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.


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


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

)


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


• 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


ATCATCGeneral General

setupsetup


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)


Signal cables

High Voltage

sources

LN2 exchange


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


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


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


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.


• 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


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)


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

)


Alpha : C.C. and calibration, exampleAlpha : C.C. and calibration, example

Measured / nominal

C.C.C.C.C.C.C.C.


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


(Andrieux et al. NIM A 427, 568 -1999)(Andrieux et al. NIM A 427, 568 -1999)


averageaverageaverageaverage


• 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.


Beta: paramBeta: parameters vs pol.eters vs pol.

BdApol A et B given by the calibration.A et B given by the calibration.


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

)


Beta: example of C.C. measurementBeta: example of C.C. measurement

C.C.C.C.C.C.C.C.


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.


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.


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)


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.”


Documents

Calor 2002, 25-29 march 2002Auguste Besson1 Argon purity measurement of the D0 calorimeter Auguste Besson (ISN - Grenoble) for the D0 collaboration 10