1. *Shuji Maeo 1,2, Takayuki Yanagida 1, Yuui Yokota 1 and Akira Yoshikawa 1,3 1 Division of Physical Process Design, Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University 2 Japan Association for the Advancement of Medical Equipment 3 New Industry Creation Hatchery Center(NICHe), Tohoku University

2. High energy radiation measurements Scintillation counter is useful. Radiation Scintillator Light detector To processor… Typical detector is Photo Multiplier Tube(PMT). Problems Energy resolution is not enough. It can not use in magnetic fields. Going to semiconductor LightElectrical signal ・ In Conventional photo diode(PD), signal intensity is low, noise level is high(low S/N ratio). ・ In Avalanche PD(APD), S/N ratio is not so high.

3. Improvement of S/N ratio in Scintillation counter Using an Silicon drift detector (SDD) as light detector Estimations using the SDD Problems and Next plan High energy resolution ↓ Applying PD array etc. ↓ High contrast imaging In this report

4. PMTSi-pin PDAPDSDD StructureElectron from Photocathode is amplified by dynode. Semiconductor witn pn junction. Similar to pin PD. Electron is amplified by avalanche effect for high reverse bias. Small anode at center of the detector can collect charge efficiently by electric field. Count rate>10 7 cps>10 4 cps>10 6 cps Energy resolution× △△ ○ Characteristic- High voltage operation. - Susceptible by ambient electric field and magnetic field. - Cheapness. - Easy operation. - Large signal - High voltage operation. - Large leakage current. - Expensive. - High energy resolution.

5. Electron can be collected efficiently for electric field formed by ring like cathode. Anode capacitance is low for small anode size.. Field Effect Transistor(FET) can be constructed at SDD directly. Thermal noise can be reduced for cooling by the peltier cooler. High energy resolution and high count rate are available. Structure of the SDD P. Lechner et al., Nucl. Instrum. Methods, vol. A-377, 346 (1996).

6. Simulation results of peak shape depended on each resolution.

7. FWHM ： 1.7 keV (2.9%) Np-Lα 13.9 keV Np-Lβ 17.7 keV Np-Lγ 20.8 keV γ 26.4 keV γ 59.5 keV conventional Si-pin PD Spectrum of 241 Am measured by conventional Si-pin PD the SDD Spectrum of 241 Am measured by the SDD Np-Lα 13.9 keV Np-Lβ 17.7 keV Np-Lγ 20.8 keV γ 26.4 keV γ 59.5 keV FWHM ： 0.8 keV (1.3%) Hamamatsu (S1722-02)KETEK

8. Calibration curve Np-Lα 13.9 keV Np-Lβ 17.7 keV Np-Lγ 20.8 keV γ 26.4 keV γ 59.5 keV It can be estimated that linearity between pulse height and energy.

9. Red LED voltage / mV 100200300400500600700 Out put signal distribution of LED light (red) applied each bias Relation between pulse height and LED bias It can be estimated that linearity between pulse height and luminosity.

10. High energy resolution High energy radiation spectrometry Imaging  Qualitative analysis  Accurately  Quantitative analysis  Sensitive  Image  High Contrast  Meas. time  become Short

11. Scintillator Effective area of SDD (7 mm 2 ) Peltier cooler Coupling by optical grease Pre AMP (OursTex Co. Ltd.) Shaping AMP (CleaPulse; 4417) Multi channel analyzer (Amptek; MCA8000A) Scheme of output signal SDD (KETEK GmbH)

12. 661.7 keV Back scatter peak 661.7 keV FWHM : 66.5 keV(10%) FWHM : 79.5 keV(12%) conventional Si-pin PD  -ray response of the CsI(Tl) with the conventional Si-pin PD SDD  -ray response of the CsI(Tl) with the SDD

13.  -ray response of the CsI(Tl) with the SDD.  -ray response of the GSO(Gd2SiO5:Ce) with the SDD. CsI:TlGSO(Gd 2 SiO 5 :Ce) wavelength(nm) 約 530 約 430 luminosity(ph/MeV) 約 60,000 約 10,000 Quantum efficiency of each semiconductor detector. RI source:137Cs Shaping time:0.5  sec. Meas.time:1000 sec. RI source:137Cs Shaping time:0.5  sec. Meas.time:1000 sec.

14. ConditionNormal (packaged)Open (without grease) Open (with grease) Leakage current / nA0.1101 From these results, the humidity and air dusts had a big impact for large leakage current. photodiode package Normal Si-PD Package opened Grease coated

15. From these results, the capacitance was not effected in surface condition of the detector.

16. Analog signal processing Digital signal processing High count rate Low noise level Pre AMP AD converter Pulse height Scheme of output signal Shaping AMP Multi channel analyzer Pulse height event No. Pre AMP Pulse height event No.

17. The SDD system was applied to scintillation light detector. High energy resolution (compared with conventional PD) and good linearity were demonstrated. Scintillation light response was achieved. However noise level should be decrease. Reduction of the large noise level. Carefully handling after open package Digital Signal Processor (DSP) will be applied for signal collection. Energy resolution → under 5 %(@661.7 keV) → imaging device