m. fraga, prague, may 17th. 2006 the role of temperature on air fluorescence measurements m. fraga...

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M. Fraga, Prague, May 17th. 2 006 The role of temperature on air The role of temperature on air fluorescence measurements fluorescence measurements M. Fraga 1 , A. Onofre 1,2 , N. F. Castro 1 , F. Fraga 1 , L. Pereira 1 , F. Veloso 1 , P. Vieira 1 , R. Ferreira Marques 1 , M. Pimenta 3 , A. Policarpo 1 J. A. C. Gonçalves 4 , C. C. Bueno 4 1 LIP- Coimbra, Dep. Física, Univ. Coimbra, 3004-516 Coimbra, Portugal 2 UCP, R. Dr. Mendes Pinheiro, 24, 3080 Figueira da Foz, Portugal 3 LIP-IST, Av. Elias Garcia 14, 1100-149 Lisboa, Portugal 4 IPEN and PUC, S. Paulo, Brasil

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M. Fraga, Prague, May 17th. 2006

The role of temperature on air fluorescence The role of temperature on air fluorescence measurementsmeasurements

M. Fraga1, A. Onofre1,2, N. F. Castro1, F. Fraga1, L. Pereira1, F. Veloso1, P. Vieira1, R. Ferreira Marques1, M. Pimenta3, A. Policarpo1

J. A. C. Gonçalves4, C. C. Bueno4

1 LIP- Coimbra, Dep. Física, Univ. Coimbra, 3004-516 Coimbra, Portugal2UCP, R. Dr. Mendes Pinheiro, 24, 3080 Figueira da Foz, Portugal

3 LIP-IST, Av. Elias Garcia 14, 1100-149 Lisboa, Portugal4IPEN and PUC, S. Paulo, Brasil

M. Fraga, Prague, May 17th. 2006

Layout:Layout:

• Theory;

• Experimental set-up;

• Previous measurements taken with alpha particles as excitation source (Nc versus T for = const.);

• Simulation of the chamber and correction factors evaluation;

• Corrected data versus T and comparison with recent measurements;

• Further tests – the need of a precise knowledge of the behaviour all the components of the experimental set up;

• Conclusions and plans for the future

M. Fraga, Prague, May 17th. 2006

In steady state conditions, the light yield for the v’v’’ band is given by:

with

The rate constant is given by:

F () represents the fraction of the excitation processes which produce

photons that arrive at the PMT window.

NN22 scintillation scintillation

2nd positive system (300-400 nm)2nd positive system (300-400 nm)

v'0*2´´v´v''v'v ]'v,N[AY

)scm(Tk8

vk 1321

Br

v '1 2v ' 2 xv '

1

k k N k X

v 'v ''ph v 'v '' vN ( ,T) ( ,T) A ( ,T) ( ) F

1 v 'k A

M. Fraga, Prague, May 17th. 2006

Experimental set-up and data (raw) on Dec. Experimental set-up and data (raw) on Dec. 2004 – Jan. 20052004 – Jan. 2005

PM2 PM1

Interferencefilter

Fused silicawindows

Fused silicawindows

Freezer

PM1, PM2 - XP2020Q

Cooling unit

to vacuum pump

gas input

PM3

-30 -20 -10 0 10 20 300,84

0,86

0,88

0,90

0,92

0,94

0,96

0,98

1,00

1,02

1,04

1,06

434 hPa 520 hPa 600 hPa 688 hPa 818 hPa

L rel

temperature (ºC)

Excitation source: particles (5.4 MeV)

M. Fraga, Prague, May 17th. 2006

Am-241 source Am-241 source outside the chamber, outside the chamber,

exposed to airexposed to air

– For a constant , as the temperature is lowered, the energy loss outside the chamber increases:

• the mean energy, <>, with which the a particle enters the chamber is

lower for lower temperatures;

• the length of the track is also shorter for lower temperatures ;

f

R ' i iv 'v '' v ' v '' v ' exc0 S 2

dE 1 dScos T( )( ,T) A

d 4 r dx'

x'

N

thin mylar window

y = 6 mm

M. Fraga, Prague, May 17th. 2006

Filter TransmissionFilter Transmission** : T( : T(ii))

Filter: Melles Griot, c = 340 nm; = 10 nm

2i

CWL CWL,0sin

1n

For small angles of incidence, i

*S. Klepser, AirLight 03, Dec. 2003, Bad Liebenzell, Germany.

0º Transmission curve as given by the manufacturer

Otherwise it has to be measured:

0

300

600

900

1200

1500

1800

300 310 320 330 340 350 360

wavelength (nm)

Nc

(u.a

.)

10º

15º

20º

25º

30º

35º

40º

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25 30 35 40

angle of incidence (º)

Irel

(337

nm

)

M. Fraga, Prague, May 17th. 2006

Monte Carlo simulation using GEANT4 codeMonte Carlo simulation using GEANT4 code**

Outside the chamber:

air (273 K)air (273 K)

Inside:

N2 (336 hPa at 20ºC)

<track> = 46 mm

N2 (818 hPa at 20ºC)

<track> = 22 mm

Outside the chamber: PPair air < 0.1 torr< 0.1 torr

Inside: Dry air (434 hPa at 20ºC)

5 events 5 events

5 events

* Note: pressure effects on light yields are not included in the simulation

M. Fraga, Prague, May 17th. 2006

Results of simulation: typical Results of simulation: typical FF (( factors with air at 1013 hPa factors with air at 1013 hPa outside the chamberoutside the chamber

Uncertainties in <Nph_PM>/ :• < 2% - due to variations of atmospheric pressure • < 1% - due temperature variations

818 hPa 336 hPa

dE/dx dE/dx

<Nph_PM> <Nph_PM>

250 260 270 280 290 3001.5

1.6

1.7

1.8

1.9

2.0

<N

ph_P

M>

/

T (K)

2.92

2.96

3.00

3.04

3.08

3.12

P20ºC

= 818 hPa

Elo

ss (

MeV

)

250 260 270 280 290 3001.68

1.72

1.76

1.80

<N

ph_P

M>

/

T (K)

2.56

2.60

2.64

2.68

2.72

P20ºC

= 336 hPa

Elo

ss (

Me

V)

M. Fraga, Prague, May 17th. 2006

Introducing the corrections to the experimental data (0-0 band) ...Introducing the corrections to the experimental data (0-0 band) ...

one gets ...

250 260 270 280 290 300

0.85

0.90

0.95

1.00

1.05

<N

ph_P

M>

/ (

norm

.)

T (K)

250 hPa 336 hPa 434 hPa 520 hPa 600 hPa 688 hPa 818 hPa

-30 -20 -10 0 10 200.80

0.85

0.90

0.95

1.00

1.05

1.10

336 hPa 434 hPa 520 hPa 600 hPa 688 hPa 818 hPa

#coi

nc/s

norm

0ºC

temperature (ºC)

-30 -20 -10 0 10 200.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

336 hPa 434 hPa 520 hPa 600 hPa 688 hPa 818 hPa

Rno

rm

Temperature (ºC)

ph _ PM

#coinc / sR

N

M. Fraga, Prague, May 17th. 2006

-30 -20 -10 0 10 20 30

0.20

0.25

0.30

0.35

0.40 336 hPa 434 hPa 520 hPa 600 hPa 688 hPa 818 hPa 817 hPa

R (

a.u

.)

temperature (ºC)

Light yield versus t (ºC) .

Values are corrected for the geometrical factors and different energy losses inside the chamber.

For constant one would expect that:

and

or

v '1

A ' B' T

1R

A ' B' T

1A B T

R 15.6 15.8 16.0 16.2 16.4 16.6 16.8 17.0 17.2

0.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

336 hPa 434 hPa 520 hPa 600 hPa 688 hPa 818 hPa

1/R

(re

l.)

T0.5 (K0.5)

Inverse of light yield versus . T

M. Fraga, Prague, May 17th. 2006

300 400 500 600 700 800 900

2.5

3.0

3.5

4.0

4.5

5.0

5.5

1/R

(a

.u.)

P20ºC

(hPa)

2

21 N

v 1

1 kIf 0 k 1 P

k X ,

2

v1 2 N x X

1;

k k P k P

2N 2 11

and A B P where B / A k / kR

Dependence of Light Yield on Pressure, at room temperatureDependence of Light Yield on Pressure, at room temperature

Inverse of light yield versus pressure at room temperature (0-0 band at 337 nm)

B/A = (5.8±1.4)×10-3 hPa-1

(2.8 MeV) P = 30-500 hPa 8.8×10-3 hPa-1 Brunet 1973, PhD Thesis

(5.3 MeV), P > 300 hPa 5.4×10-3 hPa-1 Duchaffaut 1969, PhD Thesis

(4.3 MeV), P < 190 hPa 8.3×10-3 hPa-1 Tatischeff 1967, PhD Thesis

k20/k10

For T = constant,

M. Fraga, Prague, May 17th. 2006

Improvement in the experimental set-up: very low pressure in the Improvement in the experimental set-up: very low pressure in the region of the alpha sourceregion of the alpha source

M. Fraga, Prague, May 17th. 2006

Experimental data with the Experimental data with the sourcesource in a low pressure atmosphere in a low pressure atmosphere

-25 -20 -15 -10 -5 0 5 10 15 20

0.70

0.75

0.80

0.85

0.90

0.95

#co

inc/

s

temperature (ºC)

P20ºC

= 890 hPa down up

-30 -20 -10 0 10 20 301.10

1.15

1.20

1.25

1.30

1.35

#co

inc/

s

temperature (ºC)

P20ºC

= 675 hPa

-20 -10 0 10 20 300.88

0.90

0.92

0.94

0.96

0.98

1.00

1.02

1.04

1.06

#co

inc/

s

temperature (ºC)

336 hPa

-30 -20 -10 0 10 20 300.50

0.51

0.52

0.53

0.54

0.55

0.56

0.57

0.58

0.59

P20ºC

= 520 hPa down up1

#co

inc/

s

temperature (ºC)

M. Fraga, Prague, May 17th. 2006

200 300 400 500 600 700 800 9000.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

Elo

ss/E

i

P20ºC

(hPa)

24

27

30

33

36

39

42

45

48

51

<p

ath

> (m

m)

Fraction of the alpha particle energy, lost in the gas.

particle source in a low pressure environment.

200 300 400 500 600 700 800 9000.5

1.0

1.5

2.0

2.5

3.0

3.5

<p

h_

de

t>/

P20ºC

(hPa)

Correction factors :Correction factors :

For P20º = 243 hPa,

(#coinc/s)Patm/(#coinc/s)low P = 1.26 ± 0.03

and

<Nph_PM>Patm/<Nph_PM>low P = 1.16 ± 0.08

M. Fraga, Prague, May 17th. 2006

Dry Air - NDry Air - N22+ O+ O2 2 (80:20)(80:20)(H2O < 3 ppm, CnHm < 0.5 ppm)

O2 – (20 ±1) %

-20 -10 0 10 20 300.080

0.085

0.090

0.095

0.100

0.105

0.110

#co

inc/

s

temperature (ºC)

440 hPa

M. Fraga, Prague, May 17th. 2006

Further corrections:Further corrections:

• variation of the PMT gain with T

m = - 0.121 (±0.008) #/ºC for = 337 nm;

• Variation of quantum efficiency of the photocathode with T – in progress

• Variation of the transmission of the interference filter with T – in progress

-10 -5 0 5 10 15 20 25 30

54

55

56

57

58

59

60

pe

ak

cha

nn

el

temperature (ºC)

0

5

10

15

20

25

0 20 40 60 80 100 120 140 160

# canal

Nc

(s-1

)

M. Fraga, Prague, May 17th. 2006

Study of the transmission of the IFStudy of the transmission of the IF

Set-up :

Data from Melles Griot

375 400 425 450 475 500 525 5500.000

0.005

0.010

0.015

0.020

0.025

Y = A + B X----------------------------------------A 8.29739E-4 5.5495E-4B 3.79734E-5 1.15368E-6---------------------------------------- = 337 nm, =0.014 nm/º,

peak=0.6 nm

(n

m/º

)

(nm)

M. Fraga, Prague, May 17th. 2006

Conclusions and plans for the futureConclusions and plans for the future

• A coherent set of results were obtained under particle excitation .

• The expected dependence on T is not clear from the present set of

experimental data and further studies and tests are needed (and they are

underway).

• An important issue is to lower the temperature of the gas below -20º ; this

implies improvements on the experimental set-up (studies are underway).

• Simulation of the chamber will go on.

• Measurements using particles (Sr-90) (already underway) will be carried

out ;