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

2. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 2 Outline  Introduction into γ -ray astronomy  Characteristics and detection of γ -ray induced Cherenkov pulses  Reconstruction of detected Cherenkov pulses  Results of reconstruction algorithm  Summary and Outlook

3. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 3 γ -rays SNR Dark Matter GRBs AGNs Pulsars PWN Micro quasars x-ray binaries  Energy range:10 3 – 10 20 eV  HE and VHE: 10 7 – 10 12 eV  Wavelength: 10 -13 – 10 -18 m  Visible light: 3.2 – 1.6 eV 380 – 750 nm  Production mechanisms: inverse Compton, π 0 → γγ, decay of heavy particles, etc.  Low rates: 1 γ /min (Vela pulsar)  Not affected by magnetic fields  Probing non-thermal universe

4. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 4 Cherenkov light production X 0 = typically 330m in atmosphere Bremsstrahlung v e >c/n=c n E0E0 ½E 0 ¼E 0 θ≈1˚  45‘000m 2 illuminated on sea level, but θ(n)! e

5. 05.06.09, Arno Gadola Doktorandenseminar 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 – 74 γ /m 2 for E γ = 0.1 – 1TeV (A. M. Hillas, 2002) i.e. for a 12m telescope = 110m 2 mirror = 500 – 8’140 γ  Wavelength: 300 – 600 nm WaterAtmosphere @ sea level n1.331.00029 θ max 40°1.3° E Tresh 260 keV21’000 keV X0X0 430 m330 m # γ /m250030 # γ /X 0 1’075’00010’000

6. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 6 Cherenkov telescope MAGIC I, La Palma Mirror ø 17m Noise:□ stars □ airplanes □ cities Signal:□ γ -rays □ protons □ muons H.E.S.S., Namibia MAGIC I camera ø 1.5m, 450kg     

7. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 7 Camera readout chain

8. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 8 Cross-Correlation     m mngmfngf][][])[*( *     dtgftgf)()())(*( * For two continuous functions: For two discrete functions: The second derivative:  Better resolution of pile-up

9. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 9 Simulation ≈ TemplateSimulated measurement f NSB = 3000 MHz (full moon)     m mngmfngf][][])[*( *

10. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 10 Reconstruction Output at threshold of 2 γ Signal:4.6 γ @ t=250ns Input sample Signal: A=5 γ @ t=250ns NSB:60MHz (After ADC): Second derivative of the discrete cross-correlation Reconstruction of sample with time and amplitude stamps

11. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 11  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 f s = 1 GHz: 8 bits → noise rate = 360 MHz 10 bits → noise rate = 240 MHz 12 bits → noise rate = 125 MHz Results  Simulation parameters: ADC resolutions:8 – 12bit ADC sampling rates:250 – 1000 MHz NSB:40 – 3000MHz Cherenkov signal amplitudes:1 – 100 γ This ratio of 3:2:1 shows up for all sampling rates f s

12. 05.06.09, Arno Gadola Doktorandenseminar 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: 5 γ pulse @ noise rate < 100 kHz for low NSB (100 MHz) 5 γ 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

13. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 13 Questions ?

14. 05.06.09, Arno Gadola Doktorandenseminar 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

15. 05.06.09, Arno Gadola Doktorandenseminar 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.

16. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 16 Shower development Astroparticle Physics, Claus Grupen

17. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 17 Shower development Very High Energy Gamma-ray Astronomy, T.C. Weekes

18. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 18 Properties of Cherenkov light Astroparticle Physics, Claus Grupen

19. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 19 Properties of the atmosphere Astroparticle Physics, Claus Grupen

20. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 20 Photon interactions Astroparticle Physics, Claus Grupen Dominations of 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)

21. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 21 Simulation examples ≈ NSB of frequency f NSB superposed by two 5 γ showers f NSB = 40 MHz (newmoon) f NSB = 3000 MHz (full moon)

22. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 22 Time resolution

23. 05.06.09, Arno Gadola Doktorandenseminar Physik-Institut Universität Zürich Winterthurerstr. 190, 8057 Zürich 23 Amplitude resolution