Radiation damage of 1600Pixel MPPC by neutrons

ILC-CAL meeting

University of tsukuba

H.Yamazaki

Dose rate

Flux = 1.5×109 neutron/cm2/Wh (W = watt, h = hour)

…… calculated MCNP （ Monte Carlo Neutron

　 and Photon Transport Code System ） Code  

　　　　　　　　　　　　　　　　　　　 4 dose rate patterns　　　　　　　　　　　　　　　　　　　　 ↓1.5×109 neutron/cm2 /Wh×12.5/60 h×1W =3.125×108 neutron/cm2

1.5×109 neutron/cm2 /Wh×12.5/60 h×10W =3.125×109 neutron/cm2

1.5×109 neutron/cm2 /Wh×12.5/60 h×100W =3.125×1010 neutron/cm2

1.5×109 neutron/cm2 /Wh×12.5/60 h×1kW 　 =3.125×1011 neutron/cm2

Uniformity of Sample (Noise Rate,Cross-talk Probability )

The individual difference of several percent was confirmed to four samples.

Sample irradiated with 3.125×108 　n/cm2

Sample irradiated with 3.125×109 　n/cm2

Sample irradiated with 3.125×1010 n/cm2

Sample irradiated with 3.125×1011 n/cm2

Cross-talk Probability Noise Rate (Vbias)

Noise Rate (Vover )

Measurement after the irradiation

Noise Rate Cross-talk Probability

(at Vbias = -77.5V) before 108 n/cm2 109 n/cm2

NoiseRate(Hz) 346,236 569,263 3,157,690 Increased of Noise Rate 160% 910%Crosstalk probability 0.158 0.144 0.171

Noise Rate rises as dose rate goes up,Cross-talk dose not change so much by irradiation

Before the irradiation3.125×108 n/cm2

3.125×109 n/cm2

Before the irradiation3.125×109 n/cm2

3.125×109 n/cm2

Measurement after the irradiation ( 3.125×108 n/cm2)

Noise Rate Cross-talk Probability

several times measurement after irradiation

2007 11/14 Before irradiation 11/16 Just after irradiation 12/05 Before annealing at 60 ゜ C 12/06 After annealing at 60 ゜ C 12/15 The additional measurement 1 12/15 The additional measurement 2

Measurement after the irradiation ( 3.125×109 n/cm2)

Cross-talk Probabirity Noise Rate

several times measurement after irradiation

2007 11/14 Before irradiation 11/16 Just after irradiation 12/05 Before annealing at 60 ゜ C 12/06 After annealing at 60 ゜ C 12/15 The additional measurement 1 12/15 The additional measurement 2

Summary• Noise Rate rises as dose rate gose up• Cross-talk dose not change so much by irr

adiation• There are some problems for the noise rate

measurement

Plan Another analysis

…….Gain,NoiseRate(Vbias correction),After Pulse

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Noise Rate (Reference)