Design and Performance of the XENON10 Dark Matter Experiment E. Aprile, 1, ∗ J. Angle, 2, 3 F. Arneodo, 4 L. Baudis, 2, 3 A. Bernstein, 5 A. Bolozdynya, 6 P. Brusov, 6 L.C.C. Coelho, 7 C.E. Dahl, 6, 8 L. DeViveiros, 9 A.D. Ferella, 3, 4 L.M.P. Fernandes, 7 S. Fiorucci, 9 R.J. Gaitskell, 9 K.L. Giboni, 1 R. Gomez, 10 R. Hasty, 11 L. Kastens, 11 J. Kwong, 6, 8 J.A.M. Lopes, 7 N. Madden, 5 A. Manalaysay, 2, 3 A. Manzur, 11 D.N. McKinsey, 11 M.E. Monzani, 1 K. Ni, 11, † U. Oberlack, 10 J. Orboeck, 3 D. Orlandi, 4 G. Plante, 1 R. Santorelli, 1 J.M.F. dos Santos, 7 P. Shagin, 10 T. Shutt, 6 P. Sorensen, 9 S. Schulte, 3 E. Tatananni, 4 C. Winant, 5 and M. Yamashita 1 (XENON Collaboration) $^{1}$Department of Physics, Columbia University, New York, NY 10027, USA $^{2}$Department of Physics, University of Florida, Gainesville, FL 32611, USA $^{3}$Physik-Institut, Universit¨ at Z¨ urich, Z¨ urich, 8057, Switzerland $^{4}$INFN - Laboratori Nazionali del Gran Sasso, Assergi, 67010, Italy $^{5}$Lawrence Livermore National Laboratory, Livermore, CA 94550, USA $^{6}$Department of Physics, Case Western Reserve University, Cleveland, OH 44106, USA $^{7}$Department of Physics, University of Coimbra, R. Larga, 3004-516, Coimbra, Portugal $^{8}$Department of Physics, Princeton University, Princeton, NJ 08540, USA $^{9}$Department of Physics, Brown University, Providence, RI 02912, USA $^{10}$Department of Physics and Astronomy, Rice University, Houston, TX, 77251, USA $^{11}$Department of Physics, Yale University, New Haven, CT 06511, USA (Dated: January 16, 2010) XENON10 is the first two-phase xenon time projection chamber (TPC) developed within the XENON dark matter search program. The TPC, with an active liquid xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground laboratory (LNGS) in Italy, and operated for more than one year, with excellent stability and performance. Results from a dark matter search with XENON10 have been published elsewhere. In this paper, we summarize the design and performance of the detector and its subsystems, based on calibration data using sources of gamma-rays and neutrons as well as background and Monte Carlo simulations data. The results on the detector’s energy threshold, energy and position resolution, and overall efficiency show a performance that exceeds design specifications, in view of the very low energy threshold achieved ( < 10 keVr) and the excellent energy resolution achieved by combining the ionization and scintillation signals, detected simultaneously. PACS numbers: 95.35.+d, 29.40.Mc, 95.55.Vj Contents I. Introduction 2 II. The XENON10 Detector 2 A. Principle of Operation 2 C. PMTs and Calibration System 5 B. Electrodes Assembly and Electric Fields 3 D. Cryogenic System 6 E. Xe Purification and Recirculation System 7 F. Slow Control System 8 III. The XENON10 Shield 8 IV. The XENON10 Data Acquisition System 9 V. The XENON10 Data Processing and Analysis 10 A. S1 & S2 Pulse Identification 10 B. Event Position Reconstruction 11 C. Basic Quality Cuts 12 VI. The XENON10 Calibration Data Results 13 A. Gamma Calibration 13 1. S1 light yield and energy scale 13 2. S2 yield and liquid xenon purity 14 3. Position-dependence of S 1 and S 2 Signals 14 4. Combined energy scale 15 B. Neutron Calibration 16 C. Nuclear/Electron Recoil Discrimination 17 VII. The XENON10 Dark Matter Search Data 19 A. Background reduction with fiducial volume selection 19 B. Definition of anomalous events and cuts 20 A. The XENON10 Backgrounds 21 1. Gamma and Neutron Backgrounds from Data and MC Simulations 22 2. Intrinsic backgrounds in LXe 23 Acknowledgments 24 arXiv:1001.2834v1 [astro-ph.IM] 16 Jan 2010 $^{∗}$XENON Spokesperson (E. Aprile). Phone: +1-212-854-3258. E-mail address: age@astro.columbia.edu. $^{†}$Corresponding author (K. Ni). Now at Physics Department, Shanghai Jiao Tong University, China. Phone: +86-21-34202904. E-mail address: nikx@sjtu.edu.cn.