A fast online and trigger-less signal reconstruction

1. A fast online and trigger-less signal reconstruction Arno Gadola Physik-Institut Universität Zürich Doktorandenseminar 2009

2. Outline • Introduction intoγ-ray astronomy • Characteristics and detection of γ-ray induced Cherenkov pulses • Reconstruction of detected Cherenkov pulses • Results of reconstruction algorithm • Summary and Outlook Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

3. γ-rays AGNs • Energy range:103 – 1020 eV • HE and VHE: 107 – 1012 eV • Wavelength: 10-13 – 10-18 m • Visible light: 3.2 – 1.6 eV 380 – 750 nm • Production mechanisms: inverse Compton, π0 → γγ, decay of heavy particles, etc. • Low rates: 1γ/min (Vela pulsar) • Not affected by magnetic fields • Probing non-thermal universe GRBs Dark Matter SNR Pulsars PWN Micro quasars x-ray binaries Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

4. Cherenkov light production ve>c/n=cn Bremsstrahlung E0 e ½E0 ¼E0 θ≈1˚ 45‘000m2 illuminated on sea level, but θ(n)! X0 = typically 330m in atmosphere Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

5. Cherenkov light production Some values for relativistic electrons: Characteristics of Cherenkov pulses: • Duration: ≈ 5ns • Time spread: 0 – 10ns • Intensity: 4.6 – 74γ/m2 for Eγ= 0.1 – 1TeV (A. M. Hillas, 2002) • i.e. for a 12m telescope = 110m2 mirror = 500 – 8’140 γ • Wavelength: 300 – 600 nm Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

6. Cherenkov telescope MAGIC I camera ø 1.5m, 450kg MAGIC I, La Palma Mirror ø 17m Signal: □ γ-rays □ protons □ muons Noise: □ stars □ airplanes □ cities       H.E.S.S., Namibia Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

7. Camera readout chain Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

8. ¥ ò º t + t t * ( f * g )( t ) f ( ) g ( t ) d - ¥ ¥ å º + * ( f * g )[ n ] f [ m ] g [ n m ] = -¥ m Cross-Correlation For two continuous functions: For two discrete functions: The second derivative:  Better resolution of pile-up Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

9. ¥ å º + * ( f * g )[ n ] f [ m ] g [ n m ] = -¥ m Simulation Simulated measurement fNSB= 3000 MHz (full moon) Template ≈ Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

10. Reconstruction Input sample Signal: A=5γ @ t=250ns NSB: 60MHz (After ADC): Second derivative of the discrete cross-correlation Reconstruction of sample with time and amplitude stamps Output at threshold of 2γ Signal: 4.6γ @ t=250ns Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

11. Results • Time resolution: (0.0 ± 0.4)ns for 12bits, 1000MHz ADC (-0.5 ± 1.5)ns for 10bits, 250MHz ADC • Amplitude resolution: (0.7 ± 1.5)γ for 12bits, 1000MHz ADC (1.5 ± 2.0)γ for 10bits, 250MHz ADC • Reconstruction efficiency increases with: • higher ADC resolution or higher ADC sampling rate • higher Cherenkov signal amplitude • higher NSB frequency • Noise rate for 3000 MHz NSB and sampling rate fs = 1 GHz: 8 bits → noise rate = 360 MHz 10 bits → noise rate = 240 MHz 12 bits → noise rate = 125 MHz • Simulation parameters: • ADC resolutions: 8 – 12bit • ADC sampling rates: 250 – 1000 MHz • NSB: 40 – 3000MHz • Cherenkov signal amplitudes: 1 – 100γ This ratio of 3:2:1 shows up for all sampling rates fs Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

12. Summary & Outlook • Good reconstruction efficiency for an ADC setup with 300 MHz and 9 - 10 bit sampling: • 5γ pulse @ noise rate < 100 kHz for low NSB (100 MHz) • 5γ pulse @ noise rate < 5 MHz for large NSB (3000 MHz) • Further investigations on reconstruction algorithm behavior (time jitter, real data) • Investigation of a hardware based implementation of the reconstruction algorithm • Designing a toy camera readout chain for testing the signal reconstruction algorithm • Research on “new” light collector design together with ETHZ Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

13. Questions ? Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

14. Backup Slides • Shower development • Propertier of Cherenkov light • Propertier of the atmosphere • Photon interactions • Simulation examples • Time resolution • Amplitude resolution Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

15. γ-ray sources • Supernova remnants (SNRs) • A supernova is the explosion of a massive star (mass of 8 to 150 solar masses) at the end of • its life. Cosmic-rays are accelerated in the supernova explosion shocks which are non thermal processes. The gamma-ray energies reach well beyond 1013 eV. • • Pulsars and associated nebulae • Pulsars are rotating neutron stars with an intense magnetic field. The pulsar’s magnetosphere • is known to act as an efficient cosmic accelerator with gamma-ray emission in the range of 10 • to 100 GeV. • Pulsar wind nebulae are synchrotron nebulae powered by the relativistic winds of energetic • pulsars. Their VHE gamma-ray emissions originate most probably from electrons accelerated • in the shock formed by the interaction of the pulsar wind with the supernova ejecta. The most • famous pulsar wind nebula is the Crab Nebula which, due to its strong and steady • emission of gamma-rays, is used as calibration candle for almost all VHE gamma-ray detectors. • • Binary systems • A binary system contains a compact object like a neutron star or a black hole orbiting a massive • star. Such objects emit mostly VHE gamma-rays. • • Active galactic nuclei (AGNs) • An AGN is a galaxy with a super massive black hole at the core. AGNs are known to produce • outflows which are strong sources of high energy gamma-rays. Other possible sources of • gamma-rays are synchrotron emission from populations of ultra-relativistic electrons and inverse • Compton emission from soft photon scattering. • • Gamma ray bursts (GRBs) • GRBs are still a not completely resolved phenomenon. Their pulses are extremely intensive and • have a duration of about 0.1 seconds to several minutes. They are known as the most luminous • electromagnetic events occurring in the universe since the Big Bang and they all originate from • outside our galaxy (as known so far). Investigation of gamma-rays coming from GRBs would • help to establish a reliable model for GRBs. • • Dark matter • Dark matter particles accumulate in, and cause, wells in gravitational potential, and with high • enough density they are predicted to have annihilation rates resulting in detectable fluxes of • high energy gamma-rays. Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

16. Shower development Astroparticle Physics, Claus Grupen Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

17. Shower development Very High Energy Gamma-ray Astronomy, T.C. Weekes Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

18. Properties of Cherenkov light Astroparticle Physics, Claus Grupen Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

19. Properties of the atmosphere Astroparticle Physics, Claus Grupen Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

20. Photon interactions Observation of UHE gamma-rays only possible for near sources due to attenuation through γ + γ e+ + e- (e.g. cosmic background γ’s) Dominations of photon interactions Astroparticle Physics, Claus Grupen Astroparticle Physics, Claus Grupen Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

21. ≈ Simulation examples NSB of frequency fNSB superposed by two 5γ showers fNSB= 40 MHz (newmoon) fNSB= 3000 MHz (full moon) Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

22. Time resolution Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich

23. Amplitude resolution Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich