The Nuclear Compton Telescope (NCT) is a balloon-borne soft gamma-ray (0.2-10 MeV) telescope designed to study astrophysical sources of nuclear line emission and gamma-ray polarization. The heart of NCT is an array of 12 cross-strip germanium detectors (GeDs), providing high spectral resolution (~0.3-0.9% FWHM at 662 keV for most channels) and capability of tracking each photon interaction with full 3D position resolution to 2 mm3. The determined energy and position of interactions in NCT allow Compton imaging, which effectively reduces background and provides polarimetric sensitivity, at moderate angular resolution (~5° FWHM ARM) through event reconstruction. The entire set of detectors and their cryostat are enclosed inside a well of anticoincidence BGO shield, giving an overall field of view (FOV) of ~3.2 sr. The instrument is mounted in a pointed, autonomous balloon platform (gondola).

Before 2010, NCT had flown successfully on two conventional balloon flights in Fort Sumner, New Mexico. The first was a 6-hour prototype flight with two-GeDs at float altitude (~40 km) on June 1, 2005. It succeeded in measuring the soft gamma-ray atmospheric background and the galactic anti-center region. The second flight with 10-GeDs (Fig. 1 right) was launched on May 17, 2009. The total duration was ~38.5 hours with nine of the ten detectors operational for a total of 22 hours at about 35 km to 40 km altitude. The primary science goal was to observe the Crab Nebula and Pulsar. The science instrument performed well during the flight, except for anomalies from the azimuthal pointing system on the first day and from power system on the second. Minor damage of the instrument upon landing made a subsequent flight possible in a short time. The third flight with the same ten-detector instrument was attempted in spring 2010 from Alice Springs, Australia, as NCT’s first southern-hemisphere flight to conduct observations of the Galactic Center Region. However, there was a launch accident that caused major payload damage and prohibited a balloon flight.

NCT is a joint effort of several institutions in Taiwan and in the US. This thesis mainly focuses on the NCT 2009 balloon-flight mission, the ground calibrations, and the detection of the Crab Nebula, in which the author played a major role.

[1] Agostinelli, S. et al., "GEANT4 - a simulation toolkit”, Nuclear Instruments and Methods in Physics Research Section A 506, 250-303 (2003).
[2] Allison, J., Amako, K., Apostolakis, J., Araujo, H., Dubois, P. A., Asai, M., Barrand, G., Capra, R., Chauvie, S., Chytracek, R., Cirrone, G. A. P., Cooperman, G., Cosmo, G., Cuttone, G., Daquino, G. G., Donszelmann, M., Dressel, M., Folger, G., Foppiano, F., Generowicz, J., et al., “Geant4 developments and applications,” IEEE Transactions on Nuclear Science 53, 270-278 (Feb 2006).
[3] Amman, M. and Luke, P. N., “Three-dimensional position sensing and field shaping in orthogonal-strip germanium gamma-ray detectors,” Nuclear Instruments and Methods in Physics Research A 452, 155–166 (September 2000).
[4] Amman, M., Luke, P. N., and Boggs, S. E., “Amorphous-semiconductor-contact germanium-based detectors for gamma-ray imaging and spectroscopy,” Nuclear Instruments and Methods in Physics Research A 579, 886–890 (September 2007).
[5] Amrose, S., Boggs, S. E., Coburn, W., Holland, G., Lin, R. P., and Smith, D. M., “Numerical simulations of 3D positioning in cross-strip Ge detector,” in Proc. Nucl. Sci. Symp. Conf. Rec. 1, 230–233. (2001).
[6] Amrose, S., Boggs, S. E., Coburn, W., Lin, R. P., and Smith, D. M., “Calibration of 3D position in a Ge cross-strip detector,” Nucl. Instrum. Meth. Phys. Res. A 505, 170–173 (2003).
[7] Arons, J., “Pair creation above pulsar polar caps – geometrical structure and energetics of slot gaps,” ApJ 266, 215–241, 1983.
[8] Bandstra, M., Bellm, E., Chiu, J.-L., Liang, J.-S., Liu, Z.-K., Perez-Becker, D., Zoglauer, A., Boggs, S., Chang, H.-K., Chang, Y.-H., Huang, M.-H., Amman, M., Chiang, S. J., Hung, W.-C., Jean, P., Lin, C.-H., Luke, P., Run, R.-S., and Wunderer, C., “The spring 2009 balloon flight of the nuclear Compton telescope,” in [Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE], 2131 –2139 (2009).
[9] Bandstra, M., Bowen, J., Zoglauer, A., Boggs, S., Coburn, W., Wunderer, C., Amman, M., and Luke, P., ”Position calibrations and preliminary angular resolution of the prototype nuclear compton telescope,” in [Nuclear Science Symposium Conference Record, 2006. IEEE], 2, 770 –777 (2006).
[10] Bandstra, M., “Observation of the Crab Nebula in Soft Gamma Rays with the Nuclear Compton Telescope,” PhD thesis, U.C. Berkeley, 2010.
[11] Beacom, J.F., Bell, N.F., Bertone, G., “Gamma-ray constraint on galactic positron production by MeV dark matter,” PRL 94, 171301, 2005.
[12] Bellm, E., Boggs, S., Bandstra, M., Bowen, J., Perez-Becker, D., Wunderer, C., Zoglauer, A., Amman, M., Luke, P., Chang, H.-K., Chiu, J.-L., Liang, J.-S., Chang, Y.-H., Liu, Z.-K., Hung, W.-C., Lin, C.-H., Huang, M., and Jean, P., “Overview of the nuclear compton telescope,” Nuclear Science, IEEE Transactions on 56, 1250 –1256 (June 2009).
[13] Bellm, E. C., Chiu, J.-L., Perez-Becker, D., Liang, J.-S., Zoglauer, A., Bandstra, M. S., Liu, Z.-K., Boggs, S. E., Chang, H.-K., Chang, Y.-H., Huang, M. A., Amman, M., Hung, W.-C., Jean, P., Lin, C.-H., Luke, P. N., Run, R.-S., and Wunderer, C. B., “Efficiency and polarimetric calibration of the nuclear compton telescope,” in [Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE], 444 –448 (2009).
[14] Bellm, E. C., Chiu, J.-L., Boggs, S., Chang, H.-K., Chang, Y.-H., Huang, M., Amman, M., Bandstra, M., Hung, W.-C., Jean, P., Liang, J.-S., Lin, C.-H., Liu, Z.-K., Luke, P. N., Perez-Becker, D., Run, R.-S., and Zoglauer, A., “The 2010 balloon campaign of the Nuclear Compton Telescope,” in [Astronomical Telescopes and Instrumentation Conference Record, 2010 SPIE], (2010).
[15] Boehm, C., Hooper, D., Silk, J., et al., “MeV dark matter: has it been detected?” PRL 92, 101301, 2004.
[16] Boggs, S., Bandstra, M., Bowen, J., Coburn, W., Lin, R., Wunderer, C., Zoglauer, A., Amman, M., Luke, P., Jean, P., and von Ballmoos, P., “Performance of the Nuclear Compton Telescope,” Experimental Astronomy, 25–32 (2006).
[17] Boggs, S. E., Coburn, W., Smith, D. M., Bowen, J. D., Jean, P., Kregenow, J. M., Lin, R. P., and von Ballmoos, P., “Overview of the Nuclear Compton Telescope,” New Astron. Rev. 48, 251–255 (2004).
[18] Boggs, S. E. and Jean, P., “Event reconstruction in high resolution Compton telescopes,” Astronomy and Astrophysics Supplement 145, 311–321 (August 2000).
[19] Bowen, J., Bandstra, S., Zoglauer, A., Wunderer, C., Amman, M., and Luke, P., “Depth dependent background measurements with NCT,” in [Nuclear Science Symposium Conference Record, 2007. NSS ’07. IEEE], 1, 436 –444 (October 2007).
[20] Bowen, J., “The Prototype Nuclear Compton Telescope: Observations of the Galactic Anticenter Region,” PhD thesis, U.C. Berkeley, 2009.
[21] Cassé, M., Cordier, B., Paul, J., Schanne, S., “Hypernova/gamma-ray bursts in the galactic center as possible sources of galactic positrons.” ApJ 602, L17–L20, 2004.
[22] Chang, H.-K., Boggs, S., and Chang, Y.-H., “The Nuclear Compton Telescope (NCT): Scientific goals and expected sensitivity,” Advances in Space Research 40, 1281–1287 (2007).
[23] Chen, K., Chang, H.-K., Ho, C., “Optical pulse polarization of the Crab pulsar,” ApJ 471, 967–972, 1996.
[24] Cheng, K.S., Chernyshov, D.O., Dogiel, V.A., “Annihilation emission from the galactic black hole,” ApJ 645, 1138–1151, 2006.
[25] Cheng, K.S., Ruderman, M., Zhang, L., “A three-dimensional outer magnetospheric gap model for gamma-ray pulsars: geometry, pair production, emission morphologies, and phase-resolved spectra,” ApJ 537, 964–976, 2000.
[26] Chiu, J.-L., Liu, Z.-K., Bandstra, M., Perez-Becker, D., Bellm, E., Zoglauer, A., Boggs, S., Chang, H.-K., Chang, Y.-H., Huang, M., Amman, M., Hung, W.-C., Liang, J.-S., Lin, C.-H., Luke, P., Run, R.-S., and Wunderer, C., “Energy, depth calibration, and imaging capability of nuclear compton telescope,” in [Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE], 472 –476 (2009).
[27] Chiu, J.-L., Liu, Z.-K., Bandstra, M., Bellm, E., Liang, J.-S., Perez-Becker, D., Zoglauer, A., Boggs, S., Chang, H.-K., Chang, Y.-H., Huang, M., Amman, M., Chiang, S.-J., Hung, W.-C., Lin, C.-H., Luke, P., Run, R.-S., and Wunderer, C., “Ground calibrations of Nuclear Compton Telescope,” in [Astronomical Telescopes and Instrumentation Conference Record, 2010 SPIE], (2010).
[28] Chiu, J.-L., Bellm, E., Boggs, S., Chang, H.-K., Chang, Y.-H., Huang, M., Amman, M., Bandstra, M., Hung, W.-C., Liang, J.-S., Lin, C.-H., Liu, Z.-K., Luke, P., Perez-Becker, D., Run, R.-S., Wunderer, C., and Liu, Z.-K., Bandstra, M., Perez-Becker, D., Zoglauer, A., “Preliminary results from the Spring 2010 balloon campaign of the Nuclear Compton Telescope,” in [Optics+Phontonics Conference Record, 2010 SPIE], (2010).
[29] Coburn, W., Amrose, S., Boggs, S. E., Lin, R. P., Amman, M. S., Burks, M. T., Hull, E. L., Luke, P. N., and Madden, N. W., “3D positioning germanium detectors for gamma-ray astronomy,” in [X-Ray and Gamma-Ray Detectors and Applications IV], James, R. B., Franks, L. A., Burger, A., Westbrook, E. W., and Durst, R. D., eds., Proceedings of the SPIE 4784, 54–63 (2003).
[30] Coburn, W., Boggs, S. E., Kregenow, J. M., Bowen, J. D., Amman, M. S., Burkes, M. T., Craig, W. W., Jean, P., Lin, R. P., Luke, P. N., Madden, N. W., Smith, D. M., von Ballmoos, P., and Ziock, K., “Preliminary laboratory performance of the NCT prototype flight electronics,” in [X-Ray and Gamma-Ray Instrumentation for Astronomy XIII. ], Flanagan, K. A. and Siegmund, O. H. W., eds., Proceedings of the SPIE 5165, 131–138 (February 2004).
[31] Coburn, W., Boggs, S. E., Bowen, J. D., Bandstra, M. E., Amman, M. S., Burks, M. T., Craig, W., Jean, P., Lin, R. P., Luke, P. N., Madden, N. W., Smith, D. M., and von Ballmoos, P., “First results from the balloon flight of the NCT prototype,” in [UV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIV], Siegmund, O. H. W., ed., Proceedings of the SPIE 5898, 13–21 (August 2005)
[32] Cooper, R. J., Boston, A. J., Boston, H. C., Cresswell, J. R., Grint, A. N., Harkness, L. J., Nolan, P. J., Oxley, D. C., Scraggs, D. P., Lazarus, I., Simpson, J., and Dobson, J., “Charge collection performance of a segmented planar high-purity germanium detector,” Nuclear Instruments and Methods in Physics Research Section A 595, 401-409 (2008).
[33] Dean, A. J. et al., “Polarized Gamma-Ray Emission from the Crab,” Science 321, 1183, 2008.
[34] Diehl, R., Halloin, H., Kretschmer, K., et al., "Radioactive 26Al from massive stars in the Galaxy,” Nature 439, 45–47, 2006.
[35] Diehl, R., Timmes, F.X., “Gamma-ray line emission from radioactive isotopes in stars and galaxies,” PASP 110, 637–659, 1998.
[36] Dyks, J., Harding, A.K., Rudak, B., “Relativistic effects and polarization in three high-energy pulsar models,” ApJ 606, 1125–1142, 2004.
[37] Fabris, L., Madden, N. W., and Yaver, H., “A fast, compact solution for low noise charge preamplifiers,” Nuclear Instruments and Methods in Physics Research A 424, 545–551 (March 1999).
[38] Forot, M., Laurent, P., Grenier, I. A., Gouiffès, C., Lebrun, F., “Polarization of the Crab Pulsar and Nebula as Observed by the INTEGRAL/IBIS Telescope,” ApJ 688, L29, 2008.
[39] Geisser, S., “The predictive sample reuse method with applications,” Journal of the American Statistical Association 70, 320–328 (1975).
[40] Gros, S., Hammond, N. J., Lister, C. J., Chowdhury, P., Fischer, S. M., and Freeman, S. J., “Performance tests of large area position-sensitive planar germanium detectors with conventional and amorphous contacts,” Nuclear Instruments and Methods in Physics Research Section A 602, 467-476 (2009).
[41] Harris, M.J., Knödlseder, J., Jean, P., et al., “Detection of gamma-ray lines from interstellar Fe-60 by the high resolution spectrometer SPI,” A&A 433, L49–L52, 2005.
[42] Hirotani, K., Harding, A.K., Shibata, S., “Electrodynamics of an outer gap accelerator: Formation of a soft power-law spectrum between 100 MeV and 3 GeV,” ApJ 591, 334–353, 2003.
[43] Hirotani, Kouichi, “Outer-Gap versus Slot-Gap Models for Pulsar High-Energy Emissions: The Case of the Crab Pulsar,” ApJ 688, L25, 2008.
[44] Hudson, H. M., Hutton, B. F., and Larkin, R., “Accelerated EM reconstruction using ordered subsets,” J.Nucl.Med. 33, p. 960, 1991.
[45] Hudson, H. M. and Larkin, R. S., “Accelerated image reconstruction using ordered subsets of projection data,” IEEE Trans.Med.Im. 13, pp. 601-609, 1994.
[46] Hung, W.-C., Chang, Y.-H., Lin, C.-H., Boggs, S., Chang, H.-K., Bandstra, M., Bellm, E., Chiu, J.-L., Liang, J.-S., Liu, Z.-K., Perez-Becker, D., Wunderer, C., Zoglauer, A., Huang, M.-H., Amman, M., and Luke, P., “The data readout system of the nuclear compton telescope (nct),” Nuclear Science, IEEE Transactions on 56, 2303 –2308 (August 2009).
[47] Jean, P., Knödlseder, J., Gillard, W., Guessoum, N., Ferriére, K., Marcowith, A., Lonjou, V., Roques, J.P., “Spectral analysis of the Galactic e+e- annihilation emission.” A&A 445, 579–589, 2006.
[48] Kanbach, G., Kellner, S., Schrey, F.Z., et al., “Design and results of the fast timing photo-polarimeter OPTIMA,” SPIE 4841, 82–93, 2003.
[49] Kalemci, E., Boggs, S.E., Milne, P.A., Reynolds, S.P, “Searching for annihilation radiation from SN 1006 with SPI on INTEGRAL,” ApJ 640, L55–L57, 2006.
[50] Knödlseder, J., Bennett, K., Bloemen, H., et al., “A multiwavelength comparison of COMPTEL 1.8 MeV Al-26 line data,” A&A 344, 68–82, 1999.
[51] Knödlseder, J., Jean, P., Lonjou, V., et al., “The all-sky distribution of 511 keV electron–positron annihilation emission,” A&A 441, 513–532, 2005.
[52] Lei, F., Dean, A. J., and Hills, G. L., “Compton Polarimetry in Gamma-Ray Astronomy,” Space Science Reviews 82, 309–388 (November 1997).
[53] Liang, J.-S., “Nuclear Compton Telescope: data analysis and polarization determination,” PhD thesis, National Tsing Hua University, 2010.
[54] Luke, P. N., Cork, C. P., Madden, N. W. Rossington, C. S., and Wesela, M. F., “Amorphous Ge bipolar blocking contacts on Ge detectors,” IEEE Trans. Nucl. Sci. NS-39, 590–594 (August 1992).
[55] Martin, P., Knödlseder, J., Diehl, R., & Meynet, G., “New estimates of the gamma-ray line emission of the Cygnus region from INTEGRAL/SPI observations,” A&A 506, 703, 2009
[56] Milne, P.A., The, L.S., Leising, M.D., “Positron escape from type Ia supernovae,” ApJS 124, 503–526, 1999.
[57] Muslimov, A.G., “Harding, A.K. Extended acceleration in slot gaps and pulsar high-energy emission,” ApJ 588, 430–440, 2003.
[58] Naya, J.E., Barthelmy, S.D., Bartlett, L.M., et al., “Gamma-ray limits on galactic Fe-60 nucleosynthesis and implications on the origin of the Al-26 emission,” ApJ 499, L169–L173, 1998.
[59] Oberlack, U., Bennett, K., Bloemen, H., et al., “The COMPTEL 1.809 MeV all-sky image,” A&AS 120, C311–C314, 1996.
[60] Parizot, E., Cassé, M., Lehoucq, R., Paul, J., “GRBs and the 511 keV emission of the Galactic buldge.” A&A 432, 889–894, 2005
[61] Prantzos, N., “Radioactive 26Al and 60Fe in the Milky Way: implications of the RHESSI detection of 60Fe,” A&A 420, 1033–1037, 2004.
[62] Purcell, W.R., Cheng, L.X., Dixon, D.D., et al., “OSSE mapping of galactic 511 keV positron annihilation line emission,” ApJ 491, 725–748, 1997.
[63] Schönfelder, V., Aarts, H., Bennet, K., et al., “Instrument description and performance of the imaging gamma-ray telescope COMPTEL aboard the Compton Gamma-Ray Observatory,” ApJS 86, 657–692, 1993.
[64] Smith, F.G., Jones, D.H.P., Dick, J.S.B., et al., “The optical polarization of the Crab pulsar,” MNRAS 233, 305–319, 1988.
[65] Smith, D.M., “The Reuven Ramaty High Energy Solar Spectroscopic Imager observation of the 1809 keV line from galactic 26Al,” ApJ 589, L55–L58, 2003.
[66] Stone, M., “Cross-validatory choice and assessment of statistical predic-ations,” Journal of the Royal Statistical Society. Series B 3, 111–147 (1974).
[67] Sturner, S. J., Seifert, H., Shrader, C., and Teegarden, B.J., “MGEANT - A GEANT-based multi-purpose simulation package for gamma-ray astronomy missions,” Proc. AIP Conf. 510, 814-818 (2000).
[68] Takata, J., Shibata, S., Hirotani, K., Chang, H.-K., “A two-dimensional electrodynamical outer gap model for gamma-ray pulsars: gamma-ray spectrum,” MNRAS 366, 1310–1328, 2006.
[69] Takata, J., Chang, H.-K., Cheng, K.S., “Polarization of high-energy emissions from the Crab pulsar,” ApJ 656, 1044–1055, 2007.
[70] Takata, J., Chang, H.-K., “Pulse Profiles, Spectra and Polarization Characteristics of Non-thermal Emissions from the Crab-like Pulsars,“ ApJ 670, 677, 2007.
[71] Thompson, D.J., “Gamma ray pulsars – Multiwavelength observations,” Available from: astro-ph/0312272, 2003
[72] Wang, W., Pun, C.S.J., Cheng, K.S., “Could electron–positron annihilation lines in the galactic center result from pulsar winds?” A&A 446, 943–948, 2006.
[73] Wang, W., Lang, M. G., Diehl, R., et al., “Spectral and intensity variations of Galactic 26Al emission,” A&A 496, 713, 2009
[74] Weidenspointner, G., Harris, M.J., Sturner, S., et al., “MGGPOD: a Monte Carlo suite for modeling instrumental line and continuum backgrounds in gamma-ray astronomy,” ApJS 156, 69–91, 2005.
[75] Wilderman, S., Clinthorne, N., Fessler, J., and Rogers, W., “List-mode maximum likelihood reconstruction of Compton scatter camera images in nuclear medicine,” Nuclear Science Symposium Conference Record. 1998 IEEE vol. 3, pp. 1716–1720, Nov 1998.
[76] Zhang, B., Harding, A.K., “Full polar cap cascade scenario: gamma-ray and X-ray luminosities from spin-powered pulsars,” ApJ 532, 1150–1171, 2000.
[77] Zoglauer, A., Andritschke, R., and Schopper, F., “MEGAlib — The Medium Energy Gamma-Ray Astronomy Library,” New Astron. Rev. 50, 629–632 (2006).
[78] Zoglauer, A., Andritschke, R., Boggs, S., Schopper, F., Weidenspointner, G., and Wunderer, C., “MEGAlib: simulation and data analysis for low-to-medium-energy gamma-ray telescopes,” Space Telescopes and Instrumentation 2008: Ultraviolet to Gamma Ray. Edited by Turner, vol. 7011, p. 101, Jul 2008.
[79] Zoglauer, A., Andritschke, R., Kanbach, G., and Boggs, S., “A Bayesian-based Method for Particle Track Identification in Low-energy Pair-creation Telescopes,” AIP Conference Proceedings 921, 584-585, Jan 2007.
[80] Zoglauer, A., and Boggs, S., “Application of Neural Networks to the Identification of the Compton Interaction Sequence in Compton Imagers,” in [Nuclear Science Symposium Conference Record (NSS/MIC), 2007 IEEE], 4436-4441, Jan 2007.
[81] Zoglauer, A., Weidenspointner, G., Galloway, M., Boggs, S. E., and Wunderer, C. B., “Cosima – the Cosmic Simulator of MEGAlib,” in [Nuclear Science Symposium Conference Record (NSS/MIC), 2009 IEEE], 2053–2059 (2009).