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The EEE project The physics and the detector

The EEE project The physics and the detector. F.Riggi, for the EEE Collaboration Department of Physics and Astronomy and INFN, Catania. Lisboa, September 9, 2006. The idea behind the EEE project.

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The EEE project The physics and the detector

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  1. The EEE project The physics and the detector F.Riggi, for the EEE Collaboration Department of Physics and Astronomy and INFN, Catania Lisboa, September 9, 2006

  2. The idea behind the EEE project ●To involve high school teams (students and teachers) in an advanced research work, to allow young fellows to learn about high energy physics, its methods and research tools ●Build and install in a large number of high schools, over an extended area (in the order of 106 km2) a network of cosmic ray telescopes to investigate Extreme Energy Cosmic Ray Events ●Carry out extensive measurements of the muon flux and possible correlations between different telescopes

  3. Physics topics to investigate/1 ● Local measurements, with a single telescope, may give information on atmospheric and solar events Diurnal and long-term variations of atmospheric pressure are anticorrelated with muon flux Muon flux Time correlation analysis of the muon flux exhibit periodic variations Atm. pressure Corrected flux Diurnal variations may be analyzed through harmonic dial analysis

  4. Physics topics to investigate/1 Solar flares may produce strong variations of the cosmic flux (Forbush events) Correlation between 2 distant neutron monitors A Forbush event during November 2004 as seen from neutron monitor stations and muon detectors An educational experiment with a small Geiger during the same event (Nov.2004). Not enough statistics with the Geiger. However a large area muon telescope could see such events.

  5. Physics topics to investigate/2 ● Correlation between telescopes not too far away (i.e. in the same town) may allow the detection of extended showers initiated by high energy primaries. 1013 eV 1014 eV 1015 eV 1016 eV COSMOS Simulations of proton-induced air showers in Catania metropolitan area

  6. 2 high schools in Catania presently involved in EEE INFN & Phys.Dept 3 km

  7. Physics topics to investigate/3 ● Correlations between far telescopes (hundreds km) will allow for further studies which go beyond the physics of single showers Different mechanisms have been discussed to explain possible long-distance correlations between two showers: ● Photodisintegration of heavy primaries in the photon solar field ● Interaction of primaries with cosmic dust grains ● Correlated emission from single sources Such correlations are actively searched for, with no clear results at the moment

  8. CR P(l,q, f) Photodisintegration event r l q f Earth Sun P’ The GZ effect Original paper: Gerasimova & Zatsepin(1960) Recent references: Medina-Tanco & Watson (1999) Epele et al. (1999) A heavy primary may interact with ~eV photons from solar radiation, with a mean free path ( = angle between cosmic and photon) Black body radiation from Sun e<30 MeV . e>150 MeV Photodisintegration cross section

  9. Each fragment is then deflected by the solar magnetic field Approximated by a large number of dipoles located in the equatorial plane

  10. The GZ effect: results within EEE The fragmentation probability vs orientation Contour lines of the fragmentation probability (**106) for He, O and Fe nuclei @1019 eV Evaluation of the yearly event rate over the EEE geographical area depend on several factors: ●Mass composition of high energy primaries ●Detailed acceptance of the array ●Trigger conditions on single showers …

  11. The EEE project: requirements and solution ●Need for an extended array (over a large area, ~106 km2) ●Large number of telescopes (in the order of 100) ●Reasonable cost ●Long term operation required ●Efficiency close to 100 % ●Reconstruction of muon orientation -> at least 3 planes (position sensitive) with good granularity ●Good time resolution CHOICE: Telescopes based on Multigap Resistive Plate Chambers

  12. The MRPC telescopes ●Each telescope is made by 3 MRPC modules, approx. 160 x 80 cm ● Gas mixture of Freon+SF6 ● Special FE cards for readout and trigger ● DC/DC converters for HV (±10 kV) to chambers ●GPS time-stamp of the collected events ●VME-based data acquisition ●Each module provides a two-dimensional position information ● Efficiency close to 100% and excellent time resolution ● Good reconstruction of the muon orientation

  13. Chambers under test @ CERN

  14. Pick-up electrode Mylar Carbon layer Cathode -10 kV glass (-8 kV) glass (-6 kV) glass Gas gaps ~ 300 mm (-4 kV) glass (-2 kV) glass glass Anode 0 V Carbon layer Mylar Pick-up electrode Multi-gap Resistive Plate Chambers The basic working principles Each MRPC is a stack of resistive plates, transparent to the avalanches generated inside the gas gaps. The induced signal on ext.electrodes is the sum over all the gaps Developed by the ALICE TOF group, to achieve excellent time resolution (40 ps) and efficiency

  15. readout pads 15 mm honeycomb 15 mm honeycomb Vetronite panel Anode (resistive layer +HV) Mylar Glass plates (1.1mm) Gas gaps 300 μm Mylar Cathode (resistive layer –HV) Vetronite panel readout pads MRPC for the EEE telescopes

  16. Fishing line is used to create uniform small gaps (300 microns) between glasses

  17. Gas flow in the chambers Several gas mixtures have been tried by the TOF group for optimal performances, without the need for flammable components A mixture of Freon + SF6 (95% + 5%) is normally used, with continuous flow in the order of 40 cc/min Preliminary tests point out that the chambers may be operated even in static mode for long periods, with no dramatic worsening of the performance The final design of the gas mixing station

  18. 180 cm 90 cm Front-End electronics The detector is able to give 2-dimensional position information through individual (24) 2.5 cm strips with 7 mm spacing in one direction and right-left time comparison in the other direction. FE cards (24 channels) Tot. # of readout channels = 144 An ultra-fast and low power front-end amplifier/discriminator ASIC specifically designed for the MRPC is being used. This good space resolution can be achieved due to the low jitter electronics. No slewing corrections applied

  19. GPS time stamping of events Distant telescopes will be synchronized through GPS time stamping of individual events Commercial GPS units are used for the first telescopes. Future installations could use integrated GPS cards EventTime_2: Year, Day, s, ns EventTime_1: Year, Day, s, ns

  20. Trigger and data acquisition 144 channels TDC Trigger unit GPS Unit VME crate USB connection to PC VME Bridge from FE cards Acquisition and control software based on Labview is being exploited Future developments will include integrated, low-cost electronics MRPC Telescope

  21. Data collection and distribution GRID facilities will be used to distribute and share data and simulations User-friendly Web interfaces will allow to search and retrieve data among different sites Some of the involved sites will benefit from being a pole of the GRID network for LHC experiments

  22. Acceptance The acceptance depends on the assumed geometry (distance between chambers) For typical distances in the order of 1 m Frascati installation

  23. Angular resolution: muon and shower reconstruction Difference between generated and reconstructed muon zenithal angle (RMS ~0.3°) ~7° ~3° A single muon Average from 3 muons Capability to reconstruct the shower axis direction with 3 non-aligned telescopes

  24. The present status of the project: installation of first telescopes and preliminary tests

  25. Construction of chambers started in 2005 at CERN by teams including high-school teachers and students More than 70 chambers built so far

  26. First 7 telescopes sent out to italian sites On going installation and tests in progress

  27. (CH1)AND(CH2)AND(CH3) 6-fold coincidence MRPC’s SC1 (SC1) AND (SC2) 2-fold coincidence SC2 (SC) AND (Chambers) 8-fold coincidence Extensive tests of the chambers efficiency and response uniformity were carried out in several laboratories involving high school students Catania present installation

  28. y x Sc Efficiency of the chambers Efficiency vs HV Catania set-up Probing the response uniformity

  29. Frascati set-up • without gas flow with gas • MRPC#15 96,0% 96% • MRPC#13 94,4% 97% • MRPC#19 92,3% 96% Tests carried out for about 3 weeks point out that chambers may be operated even without gas flow without large performance degrading

  30. Catania set-up About 1.7 % reduction in efficiency after ~ 3 days without gas flow 70 hours later Gas flow closed

  31. Measure coordinate along strip by time difference from the two ends Moving external trigger scintillators, extract time calibration: 114 ps/cm With angle cut on the vertical orientations, extract position resolution: (171 / 114)/√2 = 1.06 cm Measurements and analysis carried out at CERN

  32. The GPS event time-stamp Tests of the cross correlation between two independent GPS units GPS/A GPS/B Antenna Trigger Unit EVENT Input GTS8000 GDG 40 ns time resolution achievedin standard mode

  33. Scatter plot of the geographical position over extended periods Comparison between position information provided by 2 GPS Checking fluctuations in position information over several days

  34. A first physics measurement of the muon flux and atmospheric pressure Muon count rate and atmospheric pressure monitored for a few days with one of the EEE telescopes in Catania (May 2006) ~ 7 x 107 events collected Barometric coefficient ~ 0.13 %/mbar

  35. Conclusions and outlook Present status Preliminary set of EEE telescopes installed and tested Time-scale: Before the end of 2006 EEE could start to collect first data Additional telescopes will be installed and tested Technical developments: Upgrading of integrated electronics/acquisition Use of distributed computing for data access Dissemination of results: Involvement of teams for measurements and analysis Remote access and distribution of data Physics results

  36. Back-up slides

  37. Background rejection in a single EEE telescope • MRPC background rate: 1-3 Hz/cm2 (13-40 KHz) • Spurious rate between 3 MRPC = 0.02 – 0.6 Hz • Expected muon count rate (1 m distance) = 30 Hz • Not negligible, but… 2 additional constraints: • The 3 space points in the 3 MRPC must be aligned • The time-of-flight between the chambers must fit muon speed and orientation

  38. Background rejection between distant EEE telescopes Single telescope rate: 36 Hz Spurious rate between 2 telescopes ~ 1.3 x 10-3Δt (μs) Time window Δt (μs) Spurious rate between 3 telescopes (in 1 μs time window) = ~ 10-7 Hz (1 in 100 days) Additional constraints on relative muon orientation (θrel <10°) reduce further ~2 orders of magnitudes

  39. COSMOS Simulation Code A Monte Carlo simulation code for the propagation of cosmic rays in the atmosphere and near Earth regions COSMOS employs several nuclear interaction models

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