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A pixilated CZT drift detector

A pixilated CZT drift detector. I. Kuvvetli, C. Budtz-Jørgensen. Outline. Introduction CdZnTe drift strip detectors CZT drift pixel detectors CZT pixel detector payload on student satelite AAUSAT II Conclusion. CdZnTe drift strip detectors. The principle of the drift strip method. Cs137.

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A pixilated CZT drift detector

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  1. A pixilated CZT drift detector I. Kuvvetli, C. Budtz-Jørgensen

  2. Outline • Introduction • CdZnTe drift strip detectors • CZT drift pixel detectors • CZT pixel detector payload on student satelite AAUSAT II • Conclusion

  3. CdZnTe drift strip detectors The principle of the drift strip method Cs137 Data Model The drift strip electrodes are biased by a voltage dividerthat supplies each drift strip with a bias of Vi=Vd*(i/4), whereas the anodestrips are held at ground potential.

  4. GSFC-CZT-4 Vp= -300V, Vd= -120V, Shaping time= 1s, FWHMelc=0.8 keV

  5. CZT drift pixel detectors The pixel pitch =2 mm. The crystalsize =10x10 mm2. The center electrode radius= 0.2 mm. Inner radiusfor the first surrounding drift electrodes(G4) = 0.5 mm Thedrift electrode (G3) and (G4) width = 0.1 mm. The first drift electrodes (G4) areinterconnected externally by z-bonding technique.

  6. The measurement processes Characterization of 20 CZT drift pixel detectors IV-curve measurements (surface leakage current) 16 channels eV-ASIC Full illumination 57Co spectra Fine scan with 57Co (0.3 mm beam width) CZT drift pixel detectors

  7. CZT drift pixel detectors

  8. CZT Drift Pixel detectors

  9. CZT drift pixel detectors Surface leakage current measurements between center electrode and the closest electrode (G4)

  10. CZT drift pixel detectors Fine scan of the detector K30_04 pixel 16 and 12 Radiation source 57Co collimated (~300um beam spot diameter) Vp=-300 V, Vd=-100V (G1=0V, G2=G4=-33V, G3=-66V) ASIC shaping time =1.2 us ASIC gain=200mV/fC Step size=200 um Spectrum recording time =3000 s/step

  11. Fine scan • Spectral response depends on electron drift length • Better e or higher bias reduce the effect Pixel 16 Pixel 12 Pixel 16 Pixel 12 122 keV 136 keV 57.5 keV

  12. Fine scan • Spectral response depends on electron drift length • Better e or higher bias reduce the effect Pixel 16 Pixel 12 Pixel 16 Pixel 12 122 keV 57.5 keV 136 keV

  13. Fine scan • Spectral response depends on electron drift length • Better e or higher bias reduce the effect Pixel 16 Pixel 12 Pixel 16 Pixel 12 122 keV 57.5 keV 136 keV

  14. Fine scan Pixel 16 Pixel 12

  15. Fine scan Pixel 16 Pixel 12

  16. Fine scan Pixel 16 Pixel 12

  17. Fine scan Pixel 16 Pixel 12

  18. Fine scan Pixel 16 Pixel 12

  19. AAUSAT II • AAUSAT II is a student satellite project at the University of Aalborg, Denmark, which was initiated in the Summer of 2003. • The project is giving the students a unique chance to experience a real engineering project with real engineering problems. • A miniature Gamma ray Burst Detector (GRBD) shall be integrated and flown on AAUSAT-II. The GRBD consists of a single CdZnTe detector crystal which is equipped with a DSRI developed pixel electrode structure. The electrode structure assures good energy resolution as well as position and depth sensitivity of the CZT detector. • This mission will provide unique knowledge on the detector performance in space environment. • The mission should have a duration of at least 0.5 year where we would expect to detect ~10 intense GRB.

  20. AAUSAT II Radiation source 57Co Vp=-300 V, Vd=-100V (G1=0V, G2=G4=-33V, G3=-66V) Shaping time =1.0 us N.A. Camre, L. Drube, BA project, 2004

  21. Conclusion • 20 CZT drift pixel detectors of DSRI designed were investigated 6 detectors were acceptable. None of the 20 detectors were 100% perfect (at least 1 bad pixel). • The detector signals and the charge sharing between two pixels were studied as a function of the depth inside the detector material. • A CZT drift pixel detector system has been developed for AAUSAT II. Its performance in space will be investigated and it will possibly detect intense Gamma Ray Bursts.

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