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A fast online and trigger-less signal reconstruction. Arno Gadola Physik-Institut Universität Zürich Doktorandenseminar 2009. Outline. Introduction into γ -ray astronomy Characteristics and detection of γ -ray induced Cherenkov pulses Reconstruction of detected Cherenkov pulses

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A fast online and trigger less signal reconstruction

A fast online and trigger-less signal reconstruction

Arno Gadola

Physik-Institut Universität Zürich

Doktorandenseminar 2009


Outline
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


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


Cherenkov light production
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


Cherenkov light production1
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


Cherenkov telescope
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


Camera readout chain
Camera readout chain

Physik-Institut Universität Zürich

Winterthurerstr. 190, 8057 Zürich


Cross correlation

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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


Simulation

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Simulation

Simulated measurement

fNSB= 3000 MHz (full moon)

Template

Physik-Institut Universität Zürich

Winterthurerstr. 190, 8057 Zürich


Reconstruction
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


Results
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


Summary outlook
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


Questions
Questions

?

Physik-Institut Universität Zürich

Winterthurerstr. 190, 8057 Zürich


Backup slides
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


Ray sources
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


Shower development
Shower development

Astroparticle Physics, Claus Grupen

Physik-Institut Universität Zürich

Winterthurerstr. 190, 8057 Zürich


Shower development1
Shower development

Very High Energy Gamma-ray Astronomy, T.C. Weekes

Physik-Institut Universität Zürich

Winterthurerstr. 190, 8057 Zürich


Properties of cherenkov light
Properties of Cherenkov light

Astroparticle Physics, Claus Grupen

Physik-Institut Universität Zürich

Winterthurerstr. 190, 8057 Zürich


Properties of the atmosphere
Properties of the atmosphere

Astroparticle Physics, Claus Grupen

Physik-Institut Universität Zürich

Winterthurerstr. 190, 8057 Zürich


Photon interactions
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


Simulation examples

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


Time resolution
Time resolution

Physik-Institut Universität Zürich

Winterthurerstr. 190, 8057 Zürich


Amplitude resolution
Amplitude resolution

Physik-Institut Universität Zürich

Winterthurerstr. 190, 8057 Zürich


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