Performances of the Photo-Diode Detectors for the T/BCD in the ISS-CREAM Experiment H. J. HYUN ([email protected])1, T. ANDERSON2, D. ANGELASZEK3, J. B. BAE1, S. J. BAEK4,M. COPLEY3, S. COUTU2, J. H. HAN3, H. G. HUH3, Y. S. HWANG1, D. H. KAH1, K. H. KANG1, H. J. KIM1, K. C. KIM3, K. KWASHNAK3, J. LEE4, M. H. LEE3, J. T. LINK5,6, L. LUTZ3, J. W. MITCHELL5, S. NUTTER7, O. OFOHA3, H. PARK1, I. H. PARK4, J. M. PARK1, P. PATTERSON3, E. S. SEO3, J. WU3, Y. S. YOON3 1 Kyungpook NaSonal University, Daegu 702-‐701, South Korea 2 Pennsylvania State University, University Park, PA 16802, USA 3 University of Maryland, College Park, MD 20740, USA 4 Sungkyunkwan University, Suwon 440-‐746, South Korea 5 NASA GSFC, Greenbelt, MD 20771, USA 6 CRESST(USRA), Columbia, MD 21044, USA 7 Northern Kentucky University, Highland Heights, KY41099, USA ISS-CREAM Experiment • • Cosmic rays follow a broken power law : one at ‘knee’ and one at ‘ankle’ • knee : galactic accelerators reach their energetic limits • ankle : the galactic cosmic ray intensity falls below the intensity of cosmic rays from ultra high-energy (UHE) cosmic rays (Swordy, 2001) The ISS-CREAM instrument consists of a Silicon Charge Detector (SCD) to identify incident cosmic rays, a sampling tungsten/scintillator calorimeter for energy measurement of all nuclei, a segmented Top/ Bottom Counting Detector (TCD and BCD) for e/p separation, and a Boronated Scintillator Detector (BSD) for additional e/p separation and detecting neutron signals ISS-‐CREAM Instrument E.S. Seo, ICRC2013 hCp://www.physics.utah.edu/~whanlon/spectrum.html • ISS-CREAM (Cosmic Ray Energetics And Mass on the International Space Station experiment) • planned for a launch to the ISS in Feb. 2015 12 15 measure the energy spectral features from 10 eV to > 10 eV and • composition that might be related to the supernova acceleration limit • provide keys to understanding the origin, acceleration and propagation of CREAM Interface Loca<on on JEM-‐EF (EFU2) cosmic rays Photo-Diode Detectors, TCD and BCD Opera<onal principle of the TCD and BCD • Electron/proton separation for electron and gamma-ray physics ⇐ by using the difference between electromagnetic and hadronic showers • Provide redundant trigger for ISS-CREAM calorimeter and MIP (Minimum Ionizing Particle) trigger for calibration Silicon Photo-Diode Schema<c diagram of the TCD and BCD Exploded view of the (a) TCD, and (b) BCD • The silicon photo-diode converts scintillation light to electric current, and electronhole pairs are also produced by penetrating cosmic rays TCD • The charge signals are amplified by VLSI charge amp/ hold circuits (VA-TA) Photograph of the photo-‐diodes on 6-‐inch and 650 μm thickness silicon wafer high resistivity, <100>, 650 μm thick, and ntype silicon wafers The real size of the PD is 2.3 × 2.3 cm2 with an active area of 2.0 × 2.0 cm2 The PDs are fabricated at ETRI (Electronics and Telecommunications Research Institute) in Daejeon, Korea mean 8.47 sigma 1.89 MPV 143 pedestal Bulk capacitance (le\) and leakage currents (right) of the photo-‐diodes as a func<on of the reverse bias voltages 60 ~ 75 % for the wavelength range from 400 to 450 nm BCD Thickness of plastic scintillator (mm) 5 10 Number of PDs 400 400 Area covered by PDs (mm2) 500 × 500 600 × 600 901 × 551 × 30 951 × 651 × 33 Thermal-Vacuum Test @ KARI • During the test, the detectors are normally operated except for at low temperature +55 ℃ 3 hrs 4 hrs 3 hrs -20 ℃ 3 hrs 3 hrs -40 ℃ 3 hrs 3 hrs 3 hrs • Because there is a glitch in one of control signals, the detectors show the abnormal behavior such as not turned on at low temperature and this is debugged after the test TCD and BCD in thermal-‐vacuum chamber • Rigidity check by Signal-‐to-‐noise ra<o measurement result by using cosmic muons and coincidence trigger TCD in Z-‐axis vibraSon test Signature Sine Sweep Swept Sine BCD in X-‐axis vibraSon test Sine Burst TCD in Z-‐axis random vibra<on test Random VibraSon BCD in X-‐axis random vibra<on test Quantum efficiency Summary and Plan 3 hrs 2 hrs signal Exposed to 1.18 × 1011 protons/cm2 (> 5000 rad) The leakage current is increased up to about 50 nA/ cm2 but the quality of the PD does not change in our criteria for the best sensor (<100 nA/cm2) 3 hrs +40 ℃ Vibration Test @ Keimyung Univ. • Radiation hardness test using a 45 MeV proton beam • • TCD Dimension (mm3) BCD • Silicon photo-diodes (PD) is fabricated on 6-inch, • • Assembly of photo-‐diodes and plas<c scin<llator • comparing distribution of resonant frequencies and by functionally operating before/after each test The detectors are normally operated during the test and there is no crack and no broken parts by visual inspection • The photo-diode detectors, TCD and BCD are developed for the ISSCREAM experiment and are functionally well operated • They are ready for integration and whole integrated ISS-CREAM instrument will be launched in Feb. 2015
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