Y.Fukuda at LowNu2003

InP crystal
Solid state detector using indium for
pp/7Be solar neutrino measurement
Supported by Grant-in Aid for Scientific Research (B)
KAKENHI 13440066
Y.Fukuda
Miyagi University of Education
Y.Koshio, S.Moriyama, M.Shiozawa and Y.Takeuchi
ICRR, University of Tokyo
T.Inutsuka and T.Izawa
Solid state division, Hamamatsu Photonics K.K
20th of May, 2003

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Y.Fukuda at LowNu2003

10-32∆m in eV

2

Status of Solar Neutrino Oscillation

0.1%
0.32%
10-4

KamLANDFirst result

1%

3.2%

Global fit(SK+Cl+Ga+SNO)

10%
10-510νe→νµ/τ (95%C.L.)-1

12tan (Θ)

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Y.Fukuda at LowNu2003

Projects to detect low energy solar neutrinos νe elastic scattering experiment¾ XMASS (Liquid Xe scintillator)¾ CLEAN (Liquid Neon scintillator)¾ HERON (Liquid Hellium at 50mK + scintillation)¾ TPC (Hellium + CH4 gas chamber)¾ Genius (Ge detector in LN2)
¾ ……

 νe charged current experiment¾ LENS (In/Ye loaded liquid scintillator)¾ SIREN (160Gd loaded liquid scintillator)¾ MOON (100Mo)¾ …..

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Y.Fukuda at LowNu2003

Neutrino capture using indium and their advantages
R.S.Raghavan Phs.Rev.Lett37(1976)259

Real-time measurement
ν energy measurable(Ee=Eν-114.2keV)3 fold coincidence to extract
neutrino signal
115In
β−decay from(τ1/2=6×1014yr)
Correlated chance coincidenceBremsstrahlungCorrelated chance coincidence
impuritiesνe + 115In → 115Sn* + e−
115Sn*(4.70µs) → 115Sn +γ1(115keV) + γ2(497keV)
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Y.Fukuda at LowNu2003

History of InP SSD development¾Y.Suzuki et el., Indium Phosphide solid state detector NIMA275(1988)142

CCE is 60% for α particle and 76% for 60keV γ-rayDetector size is small (limited by an epitaxial growth)
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Y.Fukuda at LowNu2003

Current status of InP SSD development¾ H.El-Abbassi et al., NIMA 466(2001)46
VGF semi-insulating Fe-doped InP bulk detector
CCE~72% for 5.46MeV alpha particle¾ F.Dubecky et al., NIMA487(2002)27
VGF SI InP with Schottky electrodes
volume 0.25mm3 CCE~82% with 14% (FWHM) of resolution for60keV gamma¾ A.Owens et al., NIMA 487(2002)435
SI Fe-doped InP detector for X-ray measurement
size 3mmx3mmx180mm P+ contact
2.5keV (FWHM) for 5.9keV and 12keV for 88keV of resolution at-60 degree
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Y.Fukuda at LowNu2003

Semi-Insulating (SI) InP detector¾ well established material¾ <A> ~ 80.2 (almost same as Ge/GaAs)¾ band gap 1.34eV (can be used in RT)¾ high resistance （０．５〜０．９４）ｘ１０８Ω・ｃｍ¾ fast mobility ２０００〜２２００ｃｍ２／Ｖ・ｓ
Possible work as bulk type detector
cf. 10cm x 10cm x 500µm in thickness 24ｇ
In 2ton would capture 0.5ppνe／day →~100,000 units
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Y.Fukuda at LowNu2003

InP crystal made by Vertical Gradient Freeze (VGF)
H.El-Abbassi et al., NIMA 466(2001)47

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Y.Fukuda at LowNu2003

Background measurement of SI InP substrait
counts/10keV/sec

diameter 5cm thickness 500µm mass 1.5g
-210InP 156730sec-3

BG 1611723sec

10U-series 5X10-11g/g
Th-series 3X10-11g/g-410-510-610-7100500

1000

1500

2000

2500

3000

Ge detector Energy (keV)
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9Y.Fukuda at LowNu2003

Basic idea of InP solid state detector for solar neutrino
measurements
InP

High energy resolution, high granularity
High speed read out, No quenching

InPHigh BG reduction could be done
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Y.Fukuda at LowNu2003

Promptelectron

400

300

103102event

500

event

event

Monte Carlo signal simulation
Delayedγ in center

200
10100
100200400

600

8000keV103102Delayedγ inNaI

6008001000

InP center (116keV + 497keV γ)

Entries

1010400keV

event

event

InP center (pp prompt)

2007819

total

21010100200300

400500600700γ

800900 1000

NaI (116keV + 497keV γ)

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keV

10100

200

300

400

500

600l

700

800

900 1000keV

InP center pp ν11

Y.Fukuda at LowNu2003

InP SI proto-type detector (phase-I)

6mm500µm（ presented by Hamamatsu photonics）
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Y.Fukuda at LowNu2003

Property of proto-type detector
ＩｎＰデバイス Ｖ−Ｉ特性２５℃

15.010.0

電流 [μ A]

5.00.0３㎜□
６㎜□-5.0-10.03mm□ 27V3mm□ -27V6mm□ 27V6mm□ -27V

1.122 [μA]-0.9615 [μA]6.903 [μA]-4.339 [μA]4060-15.0-100-80-60-40-2002080

100

Dark current can be
reduced by lowering thetemperature.
I[A]=T2/3exp(-Eg/2kBT)

電圧 [V] 温度特性
ＩｎＰデバイス1000.000.018µA for 36mm2 InP@100V and -40degree

素子抵抗 [MΩ]

100.0040-2 3㎜□
44-3 3㎜□
49-3 3㎜□
40-3 6㎜□
44-2 6㎜□
49-3 6㎜□

10.001.000.100.010102030405060708090100（presented by Hamamatsu Photonics）

温度 [℃]

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Y.Fukuda at LowNu2003

Response for alpha particle
InP SI 3mmX3mm 5.48MeV α

InP SI 6mmX6mm 5.48MeV α

20th of May, 2003

signal could be seen,
however no single
peak

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Y.Fukuda at LowNu2003

Charge Collection Efficiency
1000V CCE : 62%

900V CCE : 60%

800V

CCE : 51%

700V CCE : 44%

600V CCE : 37%

500V CCE : 28%

electron/hole pair production energy for InP : 4.2eV
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Comparison with UK group
H.El-Abbassi et al., NIMA 466(2001)47

Maximum CCE is obtained by 60% for 9mm2 InP(but 13% for 36mm2 InP)
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Y.Fukuda at LowNu2003

Explanation of CCE for SI InP
α particledx0µ : mobility [m2v-1s-1]
v : carrier velocity [ms-1]
E : electric field [vm-1]
V0[volts] d : thickness of SI InP
x0 : range of α particle
E=V0/d v=µE=µV0/d

average length L=τv=µτV0/dτ : carrier lifetime [s]µτ is measured by H.El-Abassi et al. NIMA466(2001)47µτ = 5 - 8 x 10-7 [cm2V-1] (@-21 to 19 degree)Thus L=5x10-7[cm2V-1] x 1000[V]/500[µm]=0.01 [cm] >> x0 (~16µm in InP 4MeV α)
Howeve, it means not enough for the entire volume
to collect all charge
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How to get higher CCE
For full depletion of detector volume,¾ Increase bias voltage¾ Lower temperature (µτ becomes large, and also BG shouldbe reduced)

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Y.Fukuda at LowNu2003

Results and Future¾ Active area 9mm2 and 36mm2 with 500µm thickness
proto-type InP detector were tested¾ Alpha particle signal was clearly seen
¾ CCE is obtained by 60% for 9mm2 and 13% for36mm2¾ New proto-type detectors (phase-II) will comesoon
 36mm2 SI InP with a peltier cooler 36mm2 SI InP applied by schottky barrier
cf 38.5mm2X140µm detector NIMA458(2001)400¾ If CCE achieve over 80%, then large activearea with 900mm2 detector (phase-III) will betested within this year
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Proto-type InP detector (phase-II) with Peltier cooler

20th of May, 2003

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