M.Taguchi and T.Nobuhara(Kyoto)

HPK MPPC(Multi Pixel Photon Counter) status

Jan.17.2006 @KEK T2K280m meeting

Test Procedure ・ Observe the raw signal ・ Confirm the fundamental performance

・ gain ・ noise rate ・ crosstalk ・ PDE(photo detection efficiency) ・ Linearity

・ Confirm the performance under the real experimental environment

- scintillator+WLS fiber+MPPC ・ Laser Test (using BELLE laser system)

Already presented at the previous 280m meeting

Talk at this meeting

MPPC type used in each measurement

measurement MPPC or Russian SiPM type

Crosstalk HPK 100pixelHPK 400pixel

PDE HPK 100pixel

Linearity HPK 100pixel

Beamtest HPK 100pixelRussian 600pixel

Laser test HPK 100pixel

We studied the property of HPK100pixel type in detail because we used this type of MPPC in beamtest

Crosstalk measurement

Crosstalk‥ photons emitted from one pixel during the Geiger discharge causes the Geiger discharge at neighboring pixels

0.5p.e 1.5p.e

103

102

10

・ Assuming 2p.e noise is caused by crosstalk of 1p.e noise(accidental coincidence of 1p.e noise is negligible)

e.p5.0thanmoreevents

e.p5.1thanmoreevents

Crosstalk rate =

70.3 70.5 70.7 71.0 48.5 49.0 49.3 49.6

0.16

0.10

0.25

Crosstalk rate

Crosstalk rate

Data taken by random trigger

HPK100

HPK4000.1

74 234 478 800295 448 567 760(V)

(kHz)

Maximum crosstalk rate is 0.16(HPK100) and 0.25(HPK400)

PDE=εpixel×QE×εGeiger

PDE(photon detection efficiency)

A ratio of active area to total area (30%~70%)

Quantum efficiency of active area (60~80%)

Probability of Geiger discharge (60~80%)

Depending on MPPC type

Depending on wavelength of injected light

Depending on bias V

・ PDE(photon detection efficiency) is defined as the ratio of the number of output p.e to the number of injected photons

Measured the relative PDE to that of PMT with the following set up (about four HPK100 MPPCs)

PDE measurement

MPPC(total area 1mm2)

½ inch PMT

1mmφslit

MPPC

x

Y

slit

PMT

The view from this side

・ only the light going through 1mmφslit is detected ・ Scan the MPPC and PMT with moving stage and search the position with maximum light yield ・ The ratio of MPPC p.e to PMT p.e is taken as relative PDE of MPPC to that of PMT

・ change MPPC bias V

・ light sources are blue LED and wavelength shifting fiber(Y11)

Blue LED

WLS fiber

2mm 2mm

MPPC X scan MPPC Y scan

Measure PDE at this point

PDE measurement(cont’d)

・ The max green PDE is about 1.4 times larger than that of PMT and green PDE is larger than blue PDE

PDE(MPPC)/PDE(PMT)

green

blue

HPK100#14

294 388 524 687 70.3 70.5 70.8 71.1 Bias

V(V)Noise rate(kHz)

・ The width of scan is 2mm

×1.4

PDE measurement(cont’d)~0.8mm・ There is a distance(~0.8mm)

between surface cover and active area in HPK’s MPPC ・ so PDE should decrease effectively when using a WLS fiber because light from a WLS fiber spreads at 40°

½ inch PMT

MPPC(total area 1mm2)

WLS fiber(1mmφ)

Blue LED・ Measured the effective PDE with this set up about four HPK100e MPPCs(the method of measurement is the same as before)

40°

1mm

・ compare the PDE measured in the previous measurement

PDE measurement(cont’d)

3mm 3mm

PDE(MPPC)/PDE(PMT)

MPPC X scan MPPC Y scan Effective PDE

PDE 54%

・ The width of scan becomes 3mm due to spread of light from a WLS fiber・ The decrease of PDE due to spread of

light from a WLSF is 40~50% about four HPK100 MPPCs

388 524 　 687 86470.5 70.8 71.1 71.3Bias

V(V)Noise rate(kHz)

Effective PDE can be increased by improvement of packaging

HPK100#14

Linearity measurement(HPK100)

Blue LED

PMT(1/2 inch PMT)

MPPC (HPK100)

uniform light

・ inject uniform light from blue LED to PMT and MPPC

・ monitor the light injected to MPPC by PMT

・ examine the linearity of MPPC output against PMT output

・ linearity depends on the crosstalk rate and the number of pixels, so we measured the linearity at the point that crosstalk rate is 0.03 and 0.2 Set

up

Linearity measurement(cont’d)

10%

20%

10%

20%

Crosstalk rate 0.03

Crosstalk rate 0.2

Theoretical curve calculated with the crosstalk rate and the number of pixels

Difference from the linear extrapolation

Difference from the linear extrapolation

50p.e

injected p.e

injected p.e

injected p.e

35p.e

Fired pixel number

Fired pixel number

・ data points agree well with the theoretical curve

・ HPK100(100pixel) showed 20% nonlinearity when 35~50p.e are injected (depending on crosstalk rate)

Beamtest @KEK in Nov.2005

64ch MAPMT(as reference)

beam

Scintillator 1.3x2.5x50 cm3

(used in K2K scibar detector)1mmΦ fiber

HPK100e or Russian SiPM

4 layers

• 0.5 ～ 1.4GeV/c• proton & pion• ～ 100 event/spill• beam size 1x1cm2

setupMotivation・ Can the light yield for T2K near detector be obtained?(more than 5p.e for

MIP)

Alignment of fiber

・ The X Y position of active area of HPK’s MPPC is different by each sample,so alignment of fiber is necessary by each sample

X

Y

screw for fixing fiber

MPPC

fiber

・ Scan the fiber with moving stage and fix the fiber with screws at the point where MPPC signal becomes maximum

About 20% loss of light yield is possible due to misalignment of fiber

Beamtest@KEK(cont’d)

・ The measured PDE including optical contact for HPK100 and Russian SiPM are about 0.7 and 1.0 of PMT, so obtained light yield is consistent with the expectation considering the misalignment of a fiber

MPPC type MPPC p.e for MIP PMT p.e for MIP Ratio of MPPC p.e with PMT(%)

HPK100#13 9.9 18.3 54

HPK100#14 10.2 18.2 56

HPK100#16 13.3 18.2 73

Russian600#13 22.9 18.2 126

Russian600#14 17.1 18.2 94

We could obtain the light yield for T2K near detector

Laser test(HPK100)

Motivation

・ study the response of each pixel of MPPC

Feed back this information to HPK

microscop

e

Laser source

λ=825nmwidth 50ps

Moving stage1μm pitch (x , y)

Laser spot size 　≒ 10μm

Picture of microscope

MPPC

100μm

・ Efficiency distribution within 1pixel・ Uniformity of gain and efficiency in each pixel

We studied

Efficiency distribution within 1pixel

100μm100μm

100μ

m

1pixel

laser

0p.e.

1p.e.

0.5p.e.

Efficiency =Ratio of events more than 0.5p.e to total events

efficiency

・ Scan the laser in the 10mm pitch within 1 pixel(total 100scan)

Efficiency flat region of 60μm×60μm

Response of each pixel

・ Inject laser to the center of each pixel and study the response of each pixel

Relative gain

Relative efficiency

xy

xy

Total 100pixel

0.92

1.06 1.04

0.96

RMS/mean=3.6%

RMS/mean=2.5%

Response of each pixel is uniform!

x

y

Show 20% nonlinearity when 35~50p.e are injected → need more than 200pixel

The loss of light yield due to spread of light from a WLS fiber is 40~50% → can be improved by packaging

Summary

The green PDE is larger than that of PMT Light yield for MIP is 10~13p.e (at the point

that noise rate and gain satisfy T2K requirement)

Response of each pixel is uniform

About HPK100pixel MPPC

supplement

Future plan Test the new samples which recently we

got (HPK say these have higher PDE than

others) Study the response of each pixel more in

detail with the laser system for MPPC @KEK

MPPC(Multi pixel photon coutner)

100~1000 APD pixel in 1mm2

Each pixel operates as Geiger mode

(independent of input light)

The output is a sum of all the APD signals

Compact Low-cost Insensitive to the magnetic

field Low bias voltage :30~75V High gain:105~107

MPPC characters:

Signal and p.e peak

Increasing the injected light

0p.e

2p.e

1p.e

30p.e

HPK100a V=48V

・ We can count the peak up to 4p.e

・ the interval between each peak completes by 4%

Summary of gain measuremnt

Bias V

Bias V

Bias V

HPK100a

HPK400b

RUS#20

RUS#14RUS#23

RUS#22

HPK100d

HPK100e

HPK100f

HPK1600a

・ Gain=3×105~2×107

・ T=20°

・ The (dG/dV)depends on the capacitance of pixel

47 49

35 43

70 74.5

Summary of gain measurement

Bias V47.5 49.5

Bias V

6×106

HPK100e

HPK400b

・ dG/dV depends on capacitance of pixel

・ Typical gain 7×105 ～ 6×106 　 @T=20°

70 71

2×106

gaingain Russian

35 36Bias V

5×105

gain

Summary of noise rate measurement

bias voltage (V)

HPK100d

HPK100e

HPK100f

HPK1600a

bias voltage (V)

nois

e ra

te

(Hz)

RUS#20

RUS#14 RUS#23RUS#22

nois

e

rate

(Hz)

106 106

70 74 35 43

0.5p.e threshold by pulse height

1.5p.e threshold by pulse height

0.5p.e threshold by charge (in progress) @T=20°

Summary of noise rate measurement

70

104

106

Noise rate (Hz)

・ Maximum noise rate~ a few MHz・ Noise rate increases by an order of magnitude with increasing bias V by 1V

71

HPK100e

35

37

Bias V

Russian Noise rate (Hz)

Bias V48

50

106

104

HPK400b

Bias V

Noise rate (Hz)

106

104

0.5p.e threshold1.5p.e threshold

1.2GeV 1.0GeV 0.9GeV

0.8GeV 0.7GeV 0.6GeV

0.5GeV

1.2GeV 1.0GeV 0.9GeV

0.8GeV 0.7GeV 0.6GeV

0.5GeV

MPPC MAPMT

πp

P/π separation is possible

P/π separation