Kazuho Kayama ( Kyoto Univ., JP ) kayama.kazuho.57r@st.kyoto-u.ac.jp T. G. Tsuru, T. Tanaka, H. Uchida, S. Harada, T. Okuno, Y. Amano (Kyoto Univ.) J. S. Hiraga, M. Yoshida, Y. Kamata, S. Sakuma, D. Yuhi (Kwansei-Gakuin Univ.) H. Tsunemi (Osaka Univ.), H. Matsumura (Kavli IPMU) S. Kawahito, K. Kagawa, K. Yasutomi, S. Shrestha, S. Nakanishi (Shizuoka Univ.) H. Kamehama (NIT, Okinawa College), Y. Arai, I. Kurachi (KEK) A. Takeda, K. Mori, Y. Nishioka, K. Fukuda, T. Hida, M. Yukumoto (Univ. of Miyazaki) T. Kohmura, K. Hagino, K. Oono, K. Negishi, K. Yarita (Tokyo Univ. of Science) 13th December PIXEL2018 @ Academia Sinica 臺灣 Pushing the Limits of Kyoto’s SOI Pixel Sensor for X-ray Astronomy with the Pinned Depleted Diode
Focusing On Relativistic universe and Cosmic Evolution Scintillator Requirement of Si sensor Wideband Hybrid X-ray Imager for Active Shield We have been developing X-ray Si sensor for FORCE mission. CdTe sensor Si sensor > 20 keV < 20 keV Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan ! 2 FORCE Satellite Mission ★ Wide energy range : 1 - 80 keV (Requirement) ★ Si + CdTe hybrid detector ๏ Energy resolution of < 300 eV(FWHM) @ 6 keV ๏ Time resolution of < 10 µs for anti-coincidence
Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan sensor layer → Trigger output function for good time resolution → High Density, Low Parasitic Capacitance, High Sensitivity XRPIX Advantages general XRPIX structure to charge collection efficiency. Previous devices have two known problems related “XRPIX” = series of SOI pixel sensors for X-ray detection circuit layer ( ~ 8 µm) insulator ( ~ 0.2 µm) ( ~ 200 ̶ 500 µm) ! 3 SOI Pixel Detector “XRPIX” X-ray Al Back Bias Voltage X-ray n type Si substrate (full depleted) – – – Sensor layer + + + Buried p-well 1 pixel size p + (sense-node) CMOS circuit Signal ✴ No mechanical bump bonding ✴ Standard CMOS circuit can be built ✴ Based on industrial standard technology
pixel boundary Double pixel event Total X-ray event Single pixel event sssssssqqqqqq ssssssssssssss Energy spectrum folded in one pixel at 5 keV. the pixel center ~ 4 times that at the pixel center. 1 pixel Negishi+2018 @ 5 keV ~ 362 eV center pixel Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan ! 4 Spectrum Resolution Difference at Sub-Pixel • Tail structure near pixel boundaries. • The energy resolutions at pixel boundaries are ~ 4 times larger than that at
Hayashi+2018 We define T STORE as 7.1 keV Fe-Kβ 6.4 keV Fe-Kα PH [ADU] Counts T STORE < ~ µs FORCE mission require incident position in the same pixel. T STORE ~ 1 ms T STORE ~ 100 µs T STORE ~ 10 µs T STORE ~ 1.2 µs T STORE ~ 320 ns trigger comes out exposure time after the Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan ! 5 Spectrum Shape is Related To T STORE ✴ Fake peak appears when the T STORE is short. ✴ We speculate that the charge collection efficiency is different at X-ray
We speculate that both of those problems are due to the signal charges are trapped at the interface between the sensor layer and general XRPIX structure signal charge Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan SiO 2 layer ! 6 Signal Charges are Trapped at the Interface X-ray Al Back Bias Voltage n type Si substrate (full depleted) – – – Sensor layer + + A part of signal + Buried p-well charge is lost at the 1 pixel size p + (sense-node) interface region between the insulator and the sensor layer CMOS circuit Signal
Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan PDD Harada+2018 XRPIX6E structure Harada+2018 sense node Potential [V] Buried p-well(BPW) Buried n-well(BNW) XRPIX with PDD structure Electric field simulation charge Structure Pinned Depleted Diode (PDD) Structure (Kamehama+2018) is employed to mitigate the issues in our previous devices To solve those problems we have developed XRPIX6E with PDD structure without touching the interface between the sensor layer and SiO 2 layers ! 7 Pinned Depleted Diode Structure Z C 7.0 o o r d 6.0 i n a t e 5.0 ( u m 4.0 ) 3.0 2.0 1.0 0.0 -10.0 -8.6 -7.2 -5.8 Potential (V) -4.4 -3.0 -1.6 -0.2 1.2 2.6 0.0 10.0 20.0 30.0 40.0 ) m 50.0 u ( e a t 60.0 n i d 70.0 o r o C X ✴ Highly doped buried p-well acts as shield layer to reduce noise. ✴ Signal charges are transported through stepped buried n-well to the sense node
Device Mesh X-ray Hiraga+2002 Placing a thin metal mesh with evenly spaced holes, the hole pitch is multiple to the detector pixel size, parallel to the detector surface and tilted by a small angle. →The hole shadows on the detector gradually shift positions from pixel to pixel 1pixel Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan ! 8 Mesh Experiment Tsunemi+1997 0.05
restricted by the mesh hole. expanded one pixel structure. position on the pixel from the hole shadow on the detector. 1 pixel This technique enables us to evaluate the sub-pixel resonance. Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan ! 9 Mesh Experiment Tsunemi+1997 ✴ X-ray incident position on the detector is ✴ Large number of pixels represent an ✴ We can easily determine the incident
Readout boards Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan Intensity [counts/s/eV] Energy [keV] 36 µm × 36 µm Pixel size time: 45 minutes X-ray irradiation hole diameter: 4 µm pitch: 108 µm Chamber (-15℃) Thermostatic Mesh Output spectrum from X-ray Tube taken by SDD X-ray tube XRPIX6E 4 ! 10 Experimental Setup
1 pixel Single pixel event @ 8.4 keV previous device (XRPIX3b) Energy spectrum folded in one pixel at 8.4 keV. ssssssssssss sssssssssqq Total X-ray event @ 8.4 keV Double pixel event that at the pixel center. XRPIX6E zzzzz Single pixel event Total X-ray event Double pixel event Kazuho Kayama from Kyoto University. 10 - 14 December PIXEL2018 at Academia Sinica Taiwan ~ 400 eV Negishi+2018 ~ 190 eV ~ 362 eV boundary @ 5 keV pixel pixel center ! 11 Spectrum Resolution as Sub-Pixel 120 120 120 120 120 120 120 100 100 100 100 100 100 80 80 80 80 80 80 100 60 60 60 60 60 60 40 zzzzz zzz 40 40 40 40 40 80 20 20 20 20 20 20 0 0 0 0 0 0 120 120 120 120 120 120 250 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 250 500 300 350 400 450 500 250 300 350 400 450 250 500 300 350 400 450 500 100 100 100 100 100 100 60 80 80 80 80 80 80 60 60 60 60 60 60 40 40 40 40 40 40 40 20 20 20 20 20 20 120 0 120 0 120 0 120 0 120 0 120 0 20 250 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 250 500 300 350 400 450 250 500 300 350 400 450 250 500 300 350 400 450 500 100 100 100 100 100 100 80 80 80 80 80 80 0 250 300 350 400 450 500 60 60 60 60 60 60 40 40 40 40 40 40 20 20 20 20 20 20 120 0 0 0 0 0 0 120 120 120 120 120 120 250 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 500 100 100 100 100 100 100 80 80 80 80 80 80 100 60 60 60 60 60 60 40 40 40 40 40 40 80 20 20 20 20 20 20 120 0 120 0 120 0 0 0 0 120 120 120 250 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 250 500 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 500 60 100 100 100 100 100 100 80 80 80 80 80 80 60 60 60 60 60 60 40 40 40 40 40 40 40 20 20 20 20 20 20 20 120 0 120 0 120 0 120 0 120 0 120 0 250 300 350 400 450 250 500 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 250 500 300 350 400 450 500 100 100 100 100 100 100 80 80 80 80 80 80 0 250 300 350 400 450 500 60 60 60 60 60 60 40 40 40 40 40 40 20 20 20 20 20 20 0 0 0 0 0 0 250 300 350 400 450 500 250 300 350 400 450 500 250 300 350 400 450 250 500 300 350 400 450 500 250 300 350 400 450 250 500 300 350 400 450 500 ✴ No tail structure is seen near pixel boundaries of XRPIX6E ✴ Energy resolutions near pixel boundaries are ~ 2 times larger than
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