1 / 24

Search of High Energy Cosmic Sources with the Plataforma Solar de Almeria: The GRAAL Experiment

Search of High Energy Cosmic Sources with the Plataforma Solar de Almeria: The GRAAL Experiment. Fernando Arqueros Universidad Complutense de Madrid. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources . Frascati Workshop 2001.

hiroko-boyd
Download Presentation

Search of High Energy Cosmic Sources with the Plataforma Solar de Almeria: The GRAAL Experiment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Search of High Energy Cosmic Sources with the Plataforma Solar de Almeria: The GRAAL Experiment Fernando Arqueros Universidad Complutense de Madrid F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  2. Allegorical virgin holding the GRAAL in the form of a Photomultiplier G R A A L amma- ay stronomy at mería F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  3. GRAAL F. Arqueros1, J. Ballestrin2, D.M. Borque1, M. Diaz-Trigo3, H.-J. Gebauer3, R. Enriquez1 and R. Plaga3 1Universidad Complutense de Madrid 2CIEMAT- PSA 3Max-Planck Institut für Physik Also collaboration from: Universidad de Almería Universidad de Sevilla F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  4. GRAAL  Interest of Gamma-ray Astronomy in the energy range around 100 GeV.  Ground-based Cherenkov telescopes is a well established technique in the TeV range.  Sensitivity CTs is limited by the mirror size.  A solar power plant provides the highest available mirrored area. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  5. GRAAL THE SOLAR POWER PLANT TECHNIQUE  Danaher et al. (1982): first proposal  Tumer et al. (1990): secondary optics 1 heliostat  1 PMT  CELESTE and STACEE.  GRAAL follows a different approach. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  6. GRAAL THE PLATAFORMA SOLAR DE ALMERIA  PSA is a CIEMAT centre for the research in thermal solar technologies.  Located in the desert of Tabernas southern Spain at 505 m a.s.l. (37N, 2.4W).  Dark site. Main problem is frequent high humidity. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  7. GRAAL GENERAL PRICIPLES OF OPERATION  Non-imaging optics.  63 heliostats focus the light onto 4 large Winston cones in the central tower. Cone 4 Cone 2 Cone 1 Central tower  Each Winston cone detects light from 13-18 heliostats in one PMT. Cone 3  Heliostats are identified via different arrival times. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  8. GRAAL THE HELIOSTAT FIELD CESA – I  Each one consists of 24 facets (heliostat area of 39.6 m2). Beam spread of 0.25  (1 ).  From a total of 225 heliostats, GRAAL uses 63.  Total mirrored are of GRAAL is 2500 m2. Problem: Dew formation on the mirrors Solution: All mirrors are sprayed every second day with a tensid solution which prevents drop formation. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  9. GRAAL  The GRAAL detector is installed in a dedicated enclosure at the 70 m level of the central tower

  10. C2 C1 C3 C4 64 m GRAAL Let us open the door ! F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  11. GRAAL Direction reconstruction (I)  Direction is inferred from the time pattern of the pulse train.  Digital Scope 1 GHz bandwith 500 ps/bin.  Heliostat identification  front reconstruction   Incomingdirection F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  12. GRAAL Direction reconstruction (II)  Cherenkovfront is spherical with a radius of about 10 km.  The shower axis is assumed to cross the centre of the field.  Angular error related to core position and broadening of the shower extension. Core F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  13. GRAAL Precision in the absolute pointing 32 h of Crab data of Feb/March 2000. ON-source (upper) and OFF-source (lower), including unfavorable conditions.  Reconstruction is independent of heliostat pointing  Deviations smaller than 0.05  F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  14. GRAAL Angular resolution  Reconstructed direction is independent of the assumed pointing direction  MC simulations give for -rays (z=10  , az=45 ) a resolution of (63)  0.35 F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  15. GRAAL Energy Threshold and Detection Area Effective area vs primary energy for -rays (upper) and protons (lower).  Asymptotic detection area of  15000 m2.  MC energy threshold for -rays (250100) GeV  MC trigger rate from cosmic rays background  3 Hz in agreement with real data (2-4 Hz) F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  16. GRAAL GRAAL project development Feb. 99 collaboration agreement with PSA June 99 construction of a new test platform Aug 99 Data acquisition begins Nov 99 Integral trigger in operation Feb. 00 anti-dew spray system in operation Aug 00 remote auto-alarm operational (mobil-phone) F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  17. GRAAL Observation of the Crab nebulae Angular distance of reconstructed directions from the Crab. Upper) ON (continuous) and OFF (dashed) -source. Lower) ON-OFF (normalized) number of events ON-OFF (normalized) number of events vs zenith and azimuth distance. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  18. GRAAL Observation of the Crab nebulae  7 hours of usable ON-source observing time  Significance of the signal 4.5   No evidence for emission of other sources ( 3C 454.3, 3EG 1835+35)  F. Arqueros et al. (submitted to Astroparticle Physics) F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  19. GRAAL Strengths of GRAAL  Highest time resolution than any other Cherenkov experiment.  Largest total mirror area of any current detector.  The tower detector is much less complex than other imaging solar Cherenkov  Smaller costs, fewer systematic errors. Price = higher NSB and thus a higher energy threshold. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  20. GRAAL Difficulties  Field of view restricted to the shower maximum (common to all solar plant experiments) - It biases the direction reconstruction towards the pointing direction. - It leads to a very similar time structure of the shower front for -rays . and protons. Thus:  /p separation is difficult (still much work to do).  Weather conditions. In GRAAL only  4 % of the time (including both weather and moon light) can be used for taking good data.. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

  21. GRAAL Conclusions  GRAAL takes data since Aug. 99. Under remote control since Aug. 00  The experiments performs as planned with lower systematic errors than expected.  The restricted field of view destroys the difference between gamma and hadron showers and worsens the angular resolution. F. Arqueros. Multifrecuency Behaviour of High Energy Cosmic Sources. Frascati Workshop 2001

More Related