photomultipliers: uniformity measurements l. pereira 1, a. morozov 1, m. m. fraga 1, l. m. s....

Photomultipliers:Uniformity measurements

L. Pereira1, A. Morozov1, M. M. Fraga1, L. M. S. Margato1, P. Assis2, R. Conceição2, F. A. F. Fraga1

1 LIP - Coimbra

2 LIP - Lisboa

IDPASC School on Digital Counting Photosensors for Extreme Low Light Levels, Lisbon 16 - 21 May 2010

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Photomultiplier tubes

Outline

The discovery of the cosmic radiation

Air fluorescence in the context of the cosmic radiation detection

Uniformity of the Auger FD PMTs

Position sensitive micropattern gaseous neutron detector with optical readout

Simulations with ANTS: Anger-camera Neutron detector Toolkit for Simulation


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Photomultiplier Tubes (PMT)

Good

High gain: up to 107

Low dark count

Fast response time: RT&FT<1ns

Large sensitive areas

Bad

Bulky

Unstable

Sensitive to magnetic fields

High voltage


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Radiant Sensitivity and Quantum Efficiency


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Between 1911 and 1912 Viktor Hess climbed into a balloon up to altitudes higher as 5000 m, and proved that there was a penetrating radiation that crossed the atmosphere and increased with altitude.

He gave this phenomenon the name "Cosmic Radiation",which later evolved to "Cosmic Rays".

The discovery of cosmic rays

For some time it was believed that Earth was the only source of natural radiation.

Hess received the Nobel prize in 1936 for the discovery of the cosmic rays.


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~ 12 Km~ 210 K

Years later in 1938, Pierre Auger discovered that cosmic rays interact with the atmosphere creating a particle shower.

He estimated that the primary particles (i.e. the particles that create the shower) should be very energetic (1015 eV).


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The particle shower is accompanied with the emission of light due to the interaction with the air molecules.

Almost all light is emitted between 300 and 400 nm, and is produced during the de-excitation of the nitrogen molecules.

The scintillation light yield is proportional to the energy of the cosmic ray.

Which means that…

If we are able to measure the amount of light during an air shower we can determined the energy of the cosmic: Fluorescence Telescopes.


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The first attempts to observe the extensive air showers

through the observation of the scintillation date from the

60’s, in the University of Cornell (USA). The research group

included the Post-Graduated student Alan Bunner, who’s

PhD thesis became a reference.

Bunner, A. N., Cosmic Ray Detection by Atmospheric Fluorescence,

Ph. D. Thesis, Cornell University (1967).


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Fluorescence detector camera: 440 PMT

Pierre Auger Observatory

Photonis XP3062

Hexagonal bi-alkali 8 stage


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PMT Uniformity

Variation of the anodic signal

along the photocathode’s surface


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Area dependence of the anode sensitivity: Experimental system

LEDs: 340 ± 15 nm, 370 nm ± 10 nm and 395 nm ± 15 nm …

XY table, ~ 25 μm resolution

Bursts of several 200 ns width pulses per position

Multistage collimator, 1 mm holes, 1 mm FWHM beam profile

PCPULSER

LED

COLLIMATOR

PMT

MOTOR DRIVEN XY TABLE

X

Y

DIGITAL OSCILLOSCOPE

PMT SIGNAL

X

Y

TRIGGER

The read out linearity was checked for the whole dynamic range using neutral density filters


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Photonis XP5602

Round Ø effective = 56 mm bi-alkali 8 stage

However for an Gama Camera grade PMT…


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The Anger Camera

In 1957 Hal Anger invented the scintillation camera known also as the gamma camera or Anger camera

Technetium (99mTc) sestamibi upper body scan for thyroid evaluation.


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An Anger type optical readout, micropattern gaseous neutron detector

Cross section: 5330 barns

PC + Position reconstruction algorithm → [X, Y]

200 300 400 500 600 700 800 900

10-2

10-1

100

101

WAVELENGTH (nm)

QU

AN

TU

M E

FF

ICIE

NC

Y (

%)

200 300 400 500 600 700 800 9000

0.5

1

1.5

2x 10

-4

INT

EN

SIT

Y

CF4 SpectrumCF4 Weighted Spectrum

Q.E.


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Avalanche light

3 bar CF4

V Anode - Cathode = 1.85 kV

I ~ 80 nA

ZoomedNo zoom

The irradiated area spanned ~16 anodes

Microstrip: IMT, Masken und Teileungen AG SN: 850771396Pitch = 1 mmAnode width = 10 μmCathode width = 600 μm


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Cathode radiant sensitivity and quantum efficiency of theHamamatsu R5070A as a function of the wavelength of the incident light

Hamamatsu R5070A

Multialkalli photocathode

Q.E. : ~10% at 300 nm maximum of ~20% at 420 nm ~2% at 800 nm

General caracteristics

Prismatic borosilicate windowSquare pyramids 1 x 1 mm2 base,45º half angle

200 300 400 500 600 700 800 900

1

1020

QU

AN

TU

M E

FF

ICIE

NC

Y (

%)

200 300 400 500 600 700 800 9000

0.5

1

1.5

2

INT

EN

SIT

Y (

a. u

.)

Ordered by ILL to the large scale prototype

Ø 25 mm


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X-Axis (mm)

Y-A

xis

(mm

)

25 30 35 40 45 5025

30

35

40

45

50

55

20 30 40 50 600

20

40

60

80

100X=38 mm

Y-Axis (mm)

Rel

ativ

e O

utpu

t (%

)

20 30 40 50 600

20

40

60

80

100Y=40 mm

X-Axis (mm)

Rel

ativ

e O

utpu

t (%

)

3040

50

3040

50

0

50

100

X-Axis (mm)Y-Axis (mm)

Rel

ativ

e O

utpu

t (%

)

20

40

60

80

100

SN6203, 1Kv, 395nm, 0degrees

~30 %

SN 6203, λ = 395 nm


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PMT-to-PMT variation for the same model

0 10 20 300

10

20

30

X (mm)

Y (

mm

)

SN: 6289, = 395 nm, step = 1 mm

0 10 20 300

10

20

30

X (mm)

Y (

mm

)

SN: 6279, = 395 nm, step = 1 mm

0 10 20 300

10

20

30

X (mm)

Y (

mm

)

SN: 6299, = 395 nm, step = 1 mm

10

20

30

40

50

60

70

80

90

100

0 10 20 300

10

20

30

X (mm)

Y (

mm

)

SN: 6291, = 395 nm, step = 1 mm

10

20

30

40

50

60

70

80

90

100


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25 30 35 40 45 50 550

10

20

30

40

50

60

70

80

90

100

X (mm)

Rel

ativ

e ou

tput

(%

)

SN6203, 1kV, 395nm, HighRes 0.1 mm

27 31 35 39 43 47 51 5535

37

39

X (mm)

SN6203, 1kV, 395nm, Step = 0.1 mm

Y (

mm

)

75

80

85

90

95

Relative anode sensitivity of an 18 × 4 mm2 area scanned with a 0.1 mm step.

Sensitivity varies according the prismatic structure pitch. These variations may be larger than 10 %.

Fine detail analysis

~ 10 %


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Effect of the earth magnetic field in the sensitivity pattern

X-Axis (mm)

Y-A

xis

(mm

)

25 30 35 40 45 5025

30

35

40

45

50

55

20 30 40 50 600

20

40

60

80

100X=38 mm

Y-Axis (mm)

Rel

ativ

e O

utpu

t (%

)

20 30 40 50 600

20

40

60

80

100Y=40 mm

X-Axis (mm)

Rel

ativ

e O

utpu

t (%

)

3040

50

3040

50

0

50

100


Rel

ativ

e O

utpu

t (%

)

10

20

30

40

50

60

70

80

90

100


X-Axis (mm)

Y-A

xis

(mm

)

30 40 5025

30

35

40

45

50

55

20 30 40 50 600

20

40

60

80

100X=39 mm

Y-Axis (mm)

Re

lativ

e O

utp

ut (

%)

10 20 30 40 50 600

20

40

60

80

100Y=40 mm

X-Axis (mm)

Re

lativ

e O

utp

ut (

%)

20

40

20

40

600

50

100


Re

lativ

e O

utp

ut (

%)

20

40

60

80

100


Position 1, 0º Position 2, 180º


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3040

5040

600

50

100

Hamamatsu R5070A, SN6203, 1 kV, 395 nm, 0º, w/ Mag. Shielding


Re

lativ

e O

utp

ut (

%)

X-Axis (mm)

Y-A

xis

(mm

)

25 30 35 40 45

35

40

45

50

55

30 35 40 45 50 55 600

20

40

60

80

100X=35 mm

Y-Axis (mm)

Re

lativ

e O

utp

ut (

%)

20 25 30 35 40 45 500

20

40

60

80

100Y=44 mm

X-Axis (mm)

Re

lativ

e O

utp

ut (

%)

10

20

30

40

50

60

70

80

90

100

X-Axis (mm)

Y-A

xis

(mm

)

25 30 35 40 45 50

35

40

45

50

55

60

30 40 50 600

20

40

60

80

100X=36 mm

Y-Axis (mm)

Rel

ativ

e O

utpu

t (%

)

20 25 30 35 40 45 50 550

20

40

60

80

100Y=45 mm

X-Axis (mm)

Rel

ativ

e O

utpu

t (%

)

20

4040

600

50

100


Rel

ativ

e O

utpu

t (%

)

20

40

60

80

100

SN6203, 1Kv, 395nm, 180degrees, Magnetic Shielding

With magnetic shielding (mu-metal)

Pos 1 , 0º Pos 2 , 180º


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Wavelength dependence

λ = 395 nm λ = 630 nm

0 5 10 15 20 25 300

20

40

60

80

100

X (mm)

RE

LA

TIV

E O

UT

PU

T (

%)

SN: HB6186, = 395 nm, Y = 18 mm

X (mm)

Y (

mm

)

SN: HB6186, = 395 nm

0 5 10 15 20 25 30

5

10

15

20

25

30

0

20

40

60

80

100

0 5 10 15 20 25 300

20

40

60

80

100

X (mm)

RE

LA

TIV

E O

UT

PU

T (

%)

SN: HB6186, = 630 nm, Y =15 mm

X (mm)

Y (

mm

)

SN: HB6186, = 630 nm

0 5 10 15 20 25 300

5

10

15

20

25

30

0

20

40

60

80

100


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Angle dependence of the anode sensitivity: Experimental system

Step motor: 1.8º / step

Δθ = 1.8º

AXES OF ROTATION

30 mm

0 20 40 60 80

1

10

100

ANGLE (º)

SP

OT

MA

JOR

AX

IS (

mm

)

ANGLE = 87ºSPOT DIAMETER > 19 mm


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-80 -40 0 40 800

0.2

0.4

0.6

0.8

1

1.2HORIZONTAL LEFT

ANGLE

RE

LA

TIV

E O

UT

PU

T

-80 -40 0 40 800

0.2

0.4

0.6

0.8

1

1.2CENTER

ANGLE-80 -40 0 40 80

0

0.2

0.4

0.6

0.8

1

1.2HORIZONTAL RIGHT

ANGLE

-80 -40 0 40 800

0.2

0.4

0.6

0.8

1

1.2VERTICAL UP

ANGLE

RE

LA

TIV

E O

UT

PU

T

-80 -40 0 40 800

0.2

0.4

0.6

0.8

1

1.2DIAGONAL

ANGLE-80 -40 0 40 80

0

0.2

0.4

0.6

0.8

1

1.2VERTICAL DOWN

ANGLE

λ = 395 nm

V. UP

V. DOWN

H. LEFT H. RIGHTCENTER

DIAGONAL

-+

6 mm


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-80 -40 0 40 800

0.2

0.4

0.6

0.8

1

1.2

HORIZONTAL LEFT

ANGLE

RE

LA

TIV

E O

UT

PU

T

-80 -40 0 40 800

0.2

0.4

0.6

0.8

1

1.2

CENTER

ANGLE-80 -40 0 40 80

0

0.2

0.4

0.6

0.8

1

1.2

HORIZONTAL RIGHT

ANGLE

-80 -40 0 40 800

0.2

0.4

0.6

0.8

1

1.2

VERTICAL UP

ANGLE

RE

LA

TIV

E O

UT

PU

T

-80 -40 0 40 800

0.2

0.4

0.6

0.8

1

1.2

DIAGONAL

ANGLE-80 -40 0 40 80

0

0.2

0.4

0.6

0.8

1

1.2

VERTICAL DOWN

ANGLE

λ = 630 nm

V. UP

V. DOWN

H. LEFT H. RIGHTCENTER

DIAGONAL

-+

6 mm


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Main parameters

Fix

PMTsConfiguration: 7 HexagonaldPMT center-to-center: 27 mmWindow: borosilicateWindow thickness: 5mm

Simulation parametersNº of neutrons: 1000 Photons per neutron in 4π: 360000Event location algorithm: Center of gravity (Anger)

Scintillation spectrum CF4 - 5 bar

Variable

PMT diameter: 21 mm (effective) or 25 mm (w/ experimental uniformity maps)PMT-MS : 10 mm e 15 mmAngular dependence: ACTIVATEd (w/ exp. data) / NOT ACTIVATEDUniformity: ACTIVATED (w/ exp. data) / NOT ACTIVATED

Simulations with ANTSAnger-camera Neutron detector Toolkit for Simulation

[ Andrei Morozov: [email protected] ]


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Distance between the MSCG plane and PMTs = 15 mm

X (mm) Y (mm) Res. X (mm) Res. Y (mm) 0 0 0.717 0.74219.5 0 0.655 0.78613.5 6.5 0.605 0.601

X (mm) Y (mm) Res. X (mm) Res. Y (mm) Var. Res. X (%) Var. Res. Y (%)0 0 0.635 0.623 -9 -1219.5 0 0.343 0.556 -8 -1113.5 6.5 0.282 0.290 -8 -5

X (mm) Y (mm) Res. X (mm) Res. Y (mm) Var. Res. X (%) Var. Res. Y (%)0 0 0.636 0.623 -7 -1319.5 0 0.365 0.550 0 -213.5 6.5 0.293 0.315 -6 -1

σ < 2%

Table 1 Flat uniformity and angular dependence.

Table 2 Angular dependence.

Table 3 Uniformity and angular dependence considered.


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The End

photomultipliers: uniformity measurements l. pereira 1, a. morozov 1, m. m. fraga 1, l. m. s....

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