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The ATIC Experiment ( Exploding Stars, Cosmic Rays and Antarctica)

The ATIC Experiment ( Exploding Stars, Cosmic Rays and Antarctica). John P. Wefel Louisiana State University For the ATIC Collaboration June, 2006. The ATIC Collaboration.

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The ATIC Experiment ( Exploding Stars, Cosmic Rays and Antarctica)

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  1. The ATIC Experiment (Exploding Stars, Cosmic Rays and Antarctica) John P. Wefel Louisiana State University For the ATIC Collaboration June, 2006

  2. The ATIC Collaboration J.H. Adams2, H.S. Ahn3, G.L. Bashindzhagyan4, K.E. Batkov4, J. Chang6,7, M. Christl2, A.R. Fazely5, O. Ganel3R.M. Gunasingha5, T.G. Guzik1, J. Isbert1, K.C. Kim3, E.N. Kouznetsov4, M.I. Panasyuk4, A.D. Panov4, W.K.H. Schmidt6, E.S. Seo3, N.V. Sokolskaya4, J. Watts, J.P. Wefel1, J. Wu3, V.I. Zatsepin4 • Louisiana State University, Baton Rouge, LA, USA • Marshall Space Flight Center, Huntsville, AL, USA • University of Maryland, College Park, MD, USA • Skobeltsyn Institute of Nuclear Physics, Moscow State University, Russia • Southern University, Baton Rouge, LA, USA • Max Plank Institute für Space Physics, Lindau, Germany • Purple Mountain Observatory, Chinese Academy of Sciences, China

  3. Standard Model of Cosmic Ray Acceleration • Supernova shock waves may accelerate cosmic rays via first order Fermi process • Model predicts an upper energy limit Emax ~ Z x 1014 eV  composition growing heavier with increasing energy

  4. Supernovae and Cosmic Rays • Since 1960’s SN associated with CR …….why? • Energetics – take energy density in cosmic rays and a lifetime of 10-100 million years, to obtain the power needed to sustain CR in the galaxy. Ask what objects can produce such a power? Answer was/is Supernovae explosions

  5. Energetics: • CR energy density  1eV/cm3 • Residence time in the galaxy  2.6x107 yrs • Power required ~2.5X1047 ergs/yr • A Type II Supernova yields ~1053ergs • Almost all of it goes into neutrinos • 1051 ergs in the blast wave • SN rate  2/century  2X1049ergs/yr • Blast wave must convert ~1% of its energy into cosmic rays. • Diffusive Shock Acceleration required

  6. Standard picture of cosmic ray acceleration in expanding supernova shocks

  7. Exploding Stars • Novae, Supernovae, Hypernovae/Collapsars …. • Hypernovae/Collapsars may give rise to gamma-ray bursts and may involve a black hole. • Supernovae are explosions of massive stars, say > 5 solar masses which lead to neutron star (pulsar) or black hole remnants. Types I, IA, II, III and variations Classified by Radio emission and Optical spectra • Novae are explosions of small stars leading to ring nebulae, for example. Remnants

  8. Advanced Thin Ionization Calorimeter (ATIC)Science Objectives • Investigate the nature of the cosmic ray accelerator • Look for evidence of more than type of source • Test diffusive shock acceleration models • Investigate galactic confinement • Test “leaky box” and “diffusion” models • Investigate cosmic ray leakage from the Galaxy • Investigate the role of re-acceleration • Examine the electron spectrum for evidence of nearby cosmic ray sources

  9. ATIC energy range

  10. ATIC Instrument Details • Si-Matrix: 4480 pixels each 2 cm x 1.5 cm mounted on offset ladders; 0.95 m x 1.05 m area; 16 bit ADC; CR-1 ASIC’s; sparsified readout. • Scintillators: 3 x-y layers; 2 cm x 1 cm cross section; Bicron BC-408; Hamamatsu R5611 pmts both ends; two gain ranges; ACE ASIC. S1 – 336 channels; S2 – 280 channels; S3 – 192 channels; First level trigger: S1-S3 • Calorimeter: 8 layers (10 for ATIC-3); 2.5 cm x 2.5 cm x 25 cm BGO crystals, 40 per layer, each crystal viewed by R5611 pmt; three gain ranges; ACE ASIC; 960 channels (1200 for ATIC-3). Data System: All data recorded on-board; 70 Gbyte disk (150 Gbyte for ATIC-3); LOS data rate – 330 kbps; TDRSS data rate – 4 kbps (6+ kbps for ATIC-3); Underflight capability (not used). Housekeeping: Temperature, Pressure, Voltage, Current, Rates, Software Status, Disk status Command Capability: Power on / off; Trigger type; Thresholds; Pre-scaler; Housekeeping frequency; LOS data rate, Reboot nodes; High Volt settings; Data collection on / off Geometry Factors: S1-S3: 0.42 m2sr; S1-S3-BGO 6: 0.24 m2sr; S1-S3-BGO 8: 0.21 m2sr

  11. Antarctica • ATIC is constructed as large as possible and must be flown for as long as possible to obtain events in the up to 100 TeV energy region. • Long Duration Ballooning (LDB) from McMurdo Station, Antarctica gives the longest possible flights. • So, take ATIC to the ‘frozen continent’

  12. Antarctica is a continent for Science • Geology / Geophysics • Marine Biology • Glaciology • Volcanology • Life in Extreme Environments • Environmental / Atmospheric Science • Astrophysics

  13. Astrophysics (Long History) • McMurdo Neutron Monitor Station • IR Telescope at Pole (upgrade to 10 m) • Meteorite collection • Spase/Amanda  IceCube/IceTop • Long Duration Balloon Flights • Cosmic Microwave Background • Solar Observations • Infrared Astronomy • Cosmic Ray Studies

  14. LDB Facilities (new)

  15. Flight and Recovery The good ATIC-1 landing on 1/13/01 (left) and the not so good landing of ATIC-2 on 1/18/03 (right) Launch of ATIC-2 in Dec. 2002 ATIC is designed to be disassembled in the field and recovered with Twin Otters. Two recovery flights are necessary to return all the ATIC components. Pictures show 1st recovery flight of ATIC-1

  16. All particle spectrum: ATIC, emulsion, and EAS data RUNJOB JACEE CASA-BLANCA Tibet KASKADE TUNKA ATIC-2

  17. Charge resolution in the p-He group EBGO > 50 GeV EBGO > 500 GeV EBGO > 5 TeV

  18. Deconvolution Primary Energy Spectra (E0) Instrument Response Measured Energy Deposit Spectra (Ed) + = (must solve the inverse problem) A(E0,Ed) = response matrix Obtained from FLUKA model of instrument

  19. Cosmic Ray Propagation Leaky Box Model: where from HEAO-3-C2: for R > 4.4 GV with  = 2.23 for Z > 2 But, at high energy leads to conflict with anisotropy measurements And, Some weak re-acceleration in turbulent magnetic fields seems likely

  20. Cosmic Ray Propagation Diffusion Model: Osborne and Ptuskin (1988) proposed: where R0 = 5.5 GV  Spectral index ~2.6 at high energy

  21. Charge resolution in the CNO-group EBGO > 1 TeV EBGO > 250 GeV EBGO > 50 GeV O C

  22. Charge resolution in the Ne-Si group EBGO > 250 GeV EBGO > 1 TeV EBGO > 50 GeV Mg Ne Si S

  23. Charge resolution in the Fe group EBGO > 50 GeV EBGO > 250 GeV EBGO > 1 TeV Fe S Ca

  24. Energy spectra of abundant nuclei C Mg O/10 Si/10 Mg C Fe/100 O Si Ne/100 Fe Ne HEAO-3-C2 CRN Leaky Box Model ATIC-2

  25. Energy spectra of abundant nuclei Mg C O/10 Si/10 Fe/100 Ne/100 HEAO-3-C2 ATIC-2 CRN

  26. Electrons ( negatrons + positrons ) • Electrons are both Primary (source produced) and secondary (produced by interactions in ISM • Electrons are accelerated in Supernovae Remnants (SNR) • Electrons lose energy by Synchrotron Radiation, Compton collisions and Bremstrahlung • Electron Energy Loss proportional to E^2 • Protons, in comparison, lose E proportional to log E • Thus, at very high Energy, electrons do not last a long time • Cannot get here from very far away (‘local source’) • Source (accelerator) must be relatively young • High energy (TeV) electrons may show nearby SN source(s)

  27. ATIC can Measure High Energy Electrons Typical (p,e,γ) Shower image in ATIC (from Flight data) 3 events, energy deposit in BGO is about 250 GeV Electron and gamma-ray showers are narrower than the proton shower Gamma-ray shower: No hits in the top detectors around the shower axis electron gamma Proton

  28. Shower width (r.m.s. ) distribution of protons and electrons in BGO2 Solid line from 150 GeV electrons, Dashed line from protons with comparable energy deposit in the BGO block Simulation CERN calibration

  29. F= (E10/Sum)*(r.m.s.)2 distribution in BGO10 Solid line is from 150 GeV electrons Dashed line is from protons with comparable E deposit in BGO Simulation CERN

  30. Background Level (inferred from the CERN beam test) • 8741 proton events with energy deposit comparable to that of the electron events: Only 3 protons mimic electrons for a cut at 80% of the electrons. • A proton deposits on average about 40% of its energy in ATIC • Rejection power = 8741/3*2.5^1.7 ~ 13000 (for a proton spectral index of –2.7) Expected Balloon Observation

  31. Single charge good geo. >50GeV After step 1 • The method to select electron events: • 1. Rebuild the shower image, get the shower axis, and get the charge from the Si-detector • (χ2<1.5) • 2. Shower axis analysis • In Carbon to reject γ and • Proton (its first interaction point is not in carbon) • 3. Shower width analysis in BGO1 and BGO2 • 4. Shower F value analysis in BGO7 and BGO8 After step 2 After step 2 After step 3 4 After step 3 4

  32. Electron Spectrum from ATIC-2

  33. Comparing with electron models Absolute electron spectrum spectrum comparison with calculated model by a diffusion coefficient of D=2.0X1029(E/TeV)0.3cm2s-1 and a power index of injection spectrum 2.4 T. Kobayashi, et al.; Astrophys. J. 601 , 340 (2004)

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