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Photomultiplier Tube Physics and Operation

Carlos Hernandez FahamBrown University

NEPPSR 2009

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 2

Afterpulsing!

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 3

“Photomultiplier tube? What is that?”

- Well-known dark matter theorist touring our lab

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 4

Photomultiplier TubePhotoelectric, Electron Multiplier

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 5

Biasing

-Vbias1 -Vbias2 -Vbias4 -Vbias6 -Vbias8 -Vbias10

-Vbias3 -Vbias5 -Vbias7 -Vbias9

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 6

Biasing

Signal

-Vbias

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 7

Biasing - Using a resistor chain base

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 8

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 9

How do you use a PMT

A

B

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 10

= 5

A

B

Single Photoelectron

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 11

Gain Calibration

LED

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 12

Gain Calibration

!

P(n;µ) =µne"µ

n!

!

P(2) = 0.1" P(1)

!

µ2e"µ

2= µe"µ

# µ = 0.2

!

P(0) = e"0.2

= 0.82

!!"" " !"" #"" $"" %"" &""

!""

!"!

!"#

!"$

!"%

!=

6.4 µ = 140.8 mVnsGain = 3.5e+07 ± 4.1e+05Res = 0.289

'()*+,-./01

234/50

678+2*9:;(*5:3/+<3(+=>?+@'"#!&+*5+!&""+.

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 13

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 14

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 15

G ~ VK

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 16

! "!! #!! $!! %!! &!!! &"!! &#!! &$!! &%!! "!!!

&!&

&!"

&!'

&!#

(&)*+,-.

/01234

/0!56)(&)72-89:)(+-;381<

)

)

=>3>

?>144@>2)A@3B

)))!)C)5$DE5)F-G--

)))!)C)D#ED)F-G--

)))H@9,3)I@-JK)C)#E6)+,-LF-G--)))M-40J13@02)C)&$E6N

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 17

Advantages:

High gain (single-photoelectron signals)Low-noise

Large detection areaFast response

Low radioactivity has been achieved

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 18

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 19

Dark Current

Thermionic emissionField emission

Afterpulsing (ion feedback)RadioactivityCosmic rays

!!"# ! !"# !"$ !"% !"& !"' !"( !")

!

#!!

$!!

*+,-./012

,3

!!"# ! !"# !"$ !"% !"& !"' !"( !")

!

#!!

$!!

*+,-./012

,3

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 20

K E

Ion feedback (“afterpulsing”)

photon

photon ion

0 0.5 1 1.5 2 2.5

0

20

40

60

80

100

120

140

Time (us)

mV

0 0.5 1 1.5 2 2.5

0

20

40

60

80

100

120

140

Time (us)

mV

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 21

0 0.5 1 1.5 2 2.5

0

20

40

60

80

100

120

140

Time (us)

mV

0 0.5 1 1.5 2 2.5

0

20

40

60

80

100

120

140

Time (us)

mV

0 0.5 1 1.5 2 2.5

0

20

40

60

80

100

120

140

Time (us)

mV

0 0.5 1 1.5 2 2.5

0

20

40

60

80

100

120

140

Time (us)

mV

0 0.5 1 1.5 2 2.5

0

20

40

60

80

100

120

140

Time (us)

mV

0 0.5 1 1.5 2 2.5

0

20

40

60

80

100

120

140

Time (us)

mV

sphe

0 0.5 1 1.5 2 2.5

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Time (us)

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 22

!!"# ! !"# !"$ !"% !"& ' '"# '"$ '"% '"&

!

!"(

'

'"(

#

#"(

)

*+,-./012

,3

45*-67081+9:.;<708=*+<91>.?4!#'@./'#!!32

.

.

A=*=

B=011+=9.C+*1

D;

4;'

4;#

4;)

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 23

0.025 0.026 0.027 0.028 0.029 0.03 0.031 0.0320

0.5

1

1.5Afterpulsing Delay vs. Bias Voltage, BA0217, Main Pulse ~100 pC (Anode)

1/!

(bias) [V]

Aft

erpu

lsin

gD

elay

![µ

s]

Charge/Mass Ratio:

AP1 = 1.1 ± 0.6

AP2 = 4.00

AP3 = 15.2 ± 0.1

AP1

AP2

AP3

AP1

AP2

AP3

Tip from Hamamatsu: For the R8778, He+ is at ~ 0.5 µs

Mass-to-charge ratio:

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 24

!!"# ! !"# !"$ !"% !"& ' '"# '"$ '"% '"&

!

!"(

'

'"(

#

#"(

)

*+,-./012

,3

45*-67081+9:.;<708=*+<91>.?4!#'@./'#!!32

.

.

A=*=

B=011+=9.C+*1

D;

He+

H+N+, O+ ...& He+ reflections

< 15% from coincidence study.Ignore it for practical purposes

0 10 2010

0

101

# phe AP1

Counts

/ b

in

AP1

Data

Gaussian Fit

Mean = 8.3 ± 0.4 phe

Sigma = 1.9 phe

0 10 20 3010

0

101

102

103

104

# phe AP2

Counts

/ b

in

AP2

Data

Gaussian Fit

Mean = 5.6 ± 0.1 phe

Sigma = 2.9 phe

Mean # phe ejected from photocathode per afterpulse, BA0217 (1200 V)

0 5 10 1510

0

101

102

# phe AP3

Counts

/ b

in

AP3

Data

Gaussian Fit

Mean = 4.2 ± 0.2 phe

Sigma = 2.4 phe

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 25

5 10 20 35 50 75 1002

4

6

8

10

15

Main Pulse (# phe)

Aft

erp

uls

e (

# p

he

)

Afterpulsing charge vs. Main pulse charge, BA0217, Bias = 1200 V

AP1

AP2

AP3

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 26

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 27

0 0.5 1 1.5 2 2.5

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Afterpulsing ratio for BA0400 (average of 3001 pulses)(Bias = 1500 V)

Time (us)

Afterpulsing Ratio (APR) = 1.0%

Main pulse 84 pC (10.4 phe)Afterpulses1 pC (0.1 phe)

Cumulative APR

This is a healthy PMT

0 0.5 1 1.5 2 2.5

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Afterpulsing ratio for BA0211 (average of 3001 pulses)(Bias = 1500 V)

Time (us)

H+

He

++, H

2+

He

+

N+,O

+

H2O

N2+,O

2+

Ar+

N+,O

+ R

eflection

Ne

+

C D E F

O2+

BA

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 28

This is your PMT on drugs...

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 29

Other PMT Imperfections

LinearityQECE

ResolutionAngular response

Magnetic Field Effects

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 30

Concluding Remarks

Effective photo-detection devices

Widely used

Many advantages: high gain, low noise, fast response, etc.

Some disadvantages that we have to be aware of(dark current, AP, non-linearity, low QE, etc.)

Carlos Hernandez Faham, Brown UniversityNEPPSR 2009 31

Treat them well