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The HESS Experiment

The HESS Experiment. G.Vasileiadis GAM-Univ.Montpellier II For the HESS Collaboration. Outline. HESS Collaboration / Site The Physics Detection Concept Experimental Goals The Instrument Telescope(s) / Camera Electronics / Trigger Data Analysis Physics Results Perspectives.

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The HESS Experiment

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  1. The HESS Experiment G.Vasileiadis GAM-Univ.Montpellier II For the HESS Collaboration

  2. Outline • HESS Collaboration / Site • The Physics • Detection Concept • Experimental Goals • The Instrument • Telescope(s) / Camera • Electronics / Trigger • Data Analysis • Physics Results • Perspectives

  3. HESS Collaboration / Site MPI Kernphysik, Heidelberg Humboldt Univ. Berlin Ruhr-Univ. Bochum Univ. Hamburg Landessternwarte Heidelberg Univ. Kiel LLR, Ecole Polytechnique, Palaiseau PCC, College de France, Paris LPNHE-Paris, Univ. Paris VI-VII CEA Saclay CESR Toulouse LAOG Grenoble Observatoire de Paris GAM, Montpellier Durham Univ. Charles Univ., PragYerewan Physics Inst. Dublin Inst. for Adv. Studies Univ. Namibia, Windhoek Univ. Potchefstroom 3 continents 8 countries 19 institutions 69 physicists 100 engineers and technicians Namibia (Gamsberg) /1800m Alt.

  4. The Physics • Cosmic ray origin and acceleration • Supernova remnants • Starburst galaxies • Unidentified galactic sources/surveys • Clusters of galaxies • Astrophysics of compact objects • AGNs • Micro-Quasars & Stellar-mass black holes • Pulsars • Gamma ray bursts • Cosmology • Diffuse extragalactic radiation fields via cutoff in AGN spectra and AGN halos • Clusters of galaxies • Astroparticle physics • Neutralino annihilation in DM halos

  5. Detection Concept

  6. Experimental Goals • Dynamic Range up to few Tev • Energy threshold from 100 Gev • Energy Resolution 10-20% • Fast Trigger (70 ns actually) • Good Collection Efficiency

  7. Instrumentation / Telescope • Mirror Dishes : 4 x 107 m2 • Diameter 12 m • Focal Length 15 m • Telescope Separation 120 m • Mirror : 380 x 60 circular facets • Ground Glass, Aluminized and Quartz coated • PSF 1.3’ / 0.38 mrad • Pointing Precision 8” • Field View 5o (1.4m) • Pixel Size 2.8 mrad • 960 Photomultipliers • Camera weight 900 kgr • 3-cable control to rest of system

  8. Instrumentation / Camera • 60 Drawers of 16 PMTs each • (photonis XP2960 : QE ~25% borosilicafe window) • Active DC-DC base converters (0-1600V) • Slow Control Card • (HV,Current,Temperature monitoring) • Two R/O Analog Memory Cards (x8 PMTS) • Winston Cone Plate • (~70% Eff.)

  9. Instrumentation / Camera (R/O) ARS0 Fanout signal entry Readout channels Connection to photo-tubes 8 x comparators 12 bits ADC Multiplexor Adder Buffers output local trigger Fpga Enable/disable (4 channels) Amplifications Trigger channels Digital Analogue

  10. Instrumentation / Camera-R/O (cnt.) Analogue MemoryARS0 • Analogue Memory ARS0 built for ANTARES experiment (SEI-Dapnia) • 5 buffers /chip, 128 cells per channel. • Sampling @ 1 GHz • Readout ~ 1 Mhz • Controlled by two parameters • Readout window (~16 ns) • Readout delay (50-70 ns) • Readout : Sampling or integrated charge mode

  11. Instrumentation / Camera-R/O (cnt) • Acquisition Speed limited by : • Readout of the analogue memories+Digi (273ms). • Data transfer on the drawer's busses (141ms). • Readout by the CPU. Single ge determination @ 2x105 of gain

  12. gamma muons hadrons Data Analysis / StereoScopy • Shower detected from different angles:Better discrimination between gammas and hadronic background • Determination of the gamma-ray origin on the sky • Determination of the shower impact parameter on the groundbetter energy resolution • Factor of two less Muon Triggerscompare to single telescope, resulting in lower threshold

  13. Data Analysis / Reconstruction Source Position on the Camera ( Angular resolution from 0.1o to 0.06o) Geometrical Determination of the Shower Impact point on the ground

  14. Data Analysis / Muon Rejection

  15. H.E.S.S. Crab Nebula preliminary q Source Reconstructed Shower Axis 0.2o CoG q2(Degr.2) Background flat in q2 Data Analysis / Interpretation • Angle a between image axis and source image; signal has a < 10-20o • Sky plot or angle q between shower axis and direction to source; signal has q < 0.1-0.2o a Source

  16. Time Telescopes Telescope rate System rate July 2002 – Feb. 2003 CT 3 ~ 250 Hz - Mar. – July 2003 CT 2 , 3 (independent) ~ 250 Hz ~ 30 Hz Aug. – Sept. 2003 CT 2, 3 (coincidence) ~ 2 kHz ~ 110 Hz Oct. – Nov. 2003 CT 2, 3, 4 (2 out of 3) ~ 2 kHz ~ 210 Hz Since Dec. 2003 CT 1, 2, 3, 4 (2 out of 4) ~ 2 kHz ~ 350 Hz Data Analysis / DataSets Increased Single-telescope rate  decreased threshold Increased System rate  increased collection area

  17. Physics Results / CRAB Nebula • October 2003 (3 telescopes) • Live time: 4h1m53s • Mean zenith angle (Z): 47° • Energy Threshold: 325 GeV (at this Z) • Standard Analysis: • Significance: 53.5 s (26.6 s/hr-0.5) • Excess: 10.8 ± 0.2 s.min-1 • Signal easily detected, stable in time Preliminary Preliminary

  18. Physics Results / Sensitivity At 20º zenith angle, full array, after selection cuts Sensitivity:: 0.01 Crab in ≈25 hrs 0.05 Crab in ≈1 hr 0.10 Crab in ≈20 min 0.50 Crab in ≈75 sec 1.00 Crab in ≈30 sec Threshold (trigger, selected): (105,125) GeV at 0º (115,145) GeV at 20º (265,305) GeV at 45º (785,925) GeV at 60° with current standard analysis (threshold = peak in event rate for Crab-like spectrum) Crab: F(>1 TeV) = (1.35±0.45) ×10-8 m-2 s-1

  19. Physics Results / RXJ 1713.7-3946 • 2003: 18.1 hrs with 2 tels • (250 GeV thres) • 2004 data (under analysis) • Skymap • Hard cuts (background-free) • 800 GeV Threshold • --> 20 Sigma • First resolved TeV source!

  20. ASCA HESS Courtesy of Y. Uchiyama Physics Results / RXJ 1713.7-3946 (X-Ray correlation)

  21. Physics Results / RXJ 1713.7-3946 (Spectra) Hard Spectrum from WHOLE SNR (H.E.S.S.) (cf. CANG spectrum for NW rim) dN/dE ~ E-2.19+/-0.1+/0.15 F(1-10TeV) ~ 3x10-11 erg/cm2/s (~1 Crab) Extends to 10 TeV --> 100 TeV particles Clouds (n~100 cm-3) NW region --> Ep ~ 10-49/n erg --> 2004 data (>50h) ....spectral imaging, energy resolved morphology

  22. Physics Results / Galactic Center (1) Aharonian et al. (2004) astro-ph//0408145 Observations with 2 tels (2003 ~16h) Tight cuts (600 GeV) Count map (back. free) - Steady emission - Point src. Size < 4.2 arcmin - Position consistent with SgrA* < 20 arcsec - No E-dependence on position

  23. 21cm Radio Physics Results / Galactic Center (2)

  24. Physics Results / Galactic Center (3) Aharonian & Neronov 2004 [astro-ph/0408303] Rate: 0.3 ph/min Rate: 0.34 ph/min HESS: F ~ E-2.11+-0.19 (Jun/Jul 03) E-2.21+-0.09 (Jul/Aug 03)

  25. Perspectives / HESS II ?! • 28m telescope • Centre of Phase I array • Push threshold --> 10 GeV • Development underway

  26. Summary • H.E.S.S. Phase I (4-tel) operational (since Dec. 2003) • Most sensitive Gamma-ray detector: 0.05 Crab in 1 hour (5s) • First resolved Gamma-image: RXJ 1713-3946 • Discovery of Gamma-rays from the Galactic center • Great potential for a census of Galactic sources • H.E.S.S. Phase II & 5@5.....

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