Astrofisica e particelle elementari

aa 2010-11Lezione 7

• Esperimenti su satellite per radiazione gamma

• Cerenkov in atmosfera, esperimenti a terra per radiazione gamma

Bruno Borgia

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Prossime conferenze

• 2011 Fermi Symposium 9-12 May 2011 Rome,http://fermi.gsfc.nasa.gov/science/symposium/2011/

• 3rd Roma International Conference on Astro-Particle Physics 25-27 May Romehttp://ricap11.roma3.infn.it/

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FERMI SYMPOSIUMLUNEDI 9 SESSIONE PLENARIA

Esperimenti nello spazio

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CONVERSIONE γ→e+ e-

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γ → e+ + e-

angolo di apertura θ(e+ e-) ≈ me/kγ

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DISTRIBUZIONE θP

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ATIC4 lanci dal 2000

ATIC must be capable of measuring theincident cosmic ray charge and energy over anenergy range of 50 GeV to >100 TeV.

The fully active ATIC calorimeter is composedof 10 layers of Bismuth Germanate (BGO)scintillating crystals and is located on thebottom of the instrument. Above thecalorimeter is the target section consisting ofthree plastic scintillator strip hodoscopes todefine the instrument aperture and provideredundant charge and trajectorymeasurements, as well as layers of inertcarbon (between hodoscopes) to provide avolume for the incident particles to interact.

On the top of the detector stack is the highlysegmented silicon matrix detector thatprovides an accurate measure of the incidentparticle charge. Surrounding the detectorstack, electronics bays hold the flightcomputers, readout electronics, power systemboards and other instrument electronics. Thetotal weight of ATIC is about 1,500 kg (3,300lbs), the total power consumed is less than350 Watts.

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EGRET

EGRET- 1991-2000- 30 MeV - 30 GeV- AGN, GRB, Unidentified Sources, Diffuse Bkg

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AGILE

LANCIATO NEL 2007 DA UN RAZZO INDIANO DALLA BASE DI SRIHARIKOTA

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AGILE

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AGILE

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AGILE

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GLAST/FERMI

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FERMI Key-Features• Two GLAST instruments:

– LAT: 20 MeV - >300 GeV– GBM: 10 keV - 25 MeV– Launch: 11 June 2008.– 565 km, circular orbit– 5-year mission (10-year goal)– International Collaboration

• Huge field of view:– LAT: 20% of the sky at any instant; in sky survey mode, expose all

parts of sky for ~30 minutes every 3 hours.– GBM: whole unocculted sky at any time.

• Huge energy range, including largely unexplored band 10 GeV- 100GeV

• LAT: Large Area Telescope• GBM: Gamma ray Burst Monitor

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FERMI

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FERMI Large Area TelescopeFERMI Large Area Telescope

e+ e–

g

Calorimeter

Tracker

ACD[surrounds4x4 array ofTKR towers]

• Precision Si-strip Tracker (TKR)

18 XY tracking planes. 228 mm pitch). Highefficiency. Good position resolution (ang. resolutionat high energy) 12 x 0.03 X0 front end => reducemultiple scattering. 4 x 0.18 X0 back-end =>increase sensitivity >1GeV . Tot t ≈ 1X0

• CsI Calorimeter(CAL) Array of 1536 CsI(Tl) crystals in 8 layers.

Hodoscopic => Cosmic ray rejection. => shower leakage correction. 8.5 X0 => Shower max contained <100 GeV

• Anticoincidence Detector (ACD) Segmented (89 plastic scintillator tiles) => minimize self veto, Reject background of charged cosmic rays;

• Electronics System Includes flexible, robusthardware trigger and software filters.

Systems work together to identify and measure the flux of cosmic gammarays with energy 20 MeV - >300 GeV.

Height/Width = 0.4 => Large field of view

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GBM

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FERMI

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FERMI: RISOLUZIONE E

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PAMELA

• Costruito in granparte in Italia

• Lanciato nel 2006con un razzo russo

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PAMELA

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PAMELA-MAGNETE

• The magnetic material used is the

sintered Nd-Fe-B with a large residual

magnetic induction (1.3T). The average

field inside the magnet is 0.4 T, with a

good homogeneity.

• The combined characteristics of the

magnet and of the Si tracker will allow a

Maximum Detectable Rigidity (MDR)

greater than 740 GV/c.

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PAMELA- CALORIMETRO EM

• The total thicknesscorresponds to 0.9 interactionlengths and 16 radiationlengths.

• The energy resolution for highenergy electrons is better than10% .

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AMS

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AMS con magnete permanenteBL2=0.14 Tm2

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Risoluzione dello spettrometro

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AMS2

EM sampling calorimeter

18.5mm

p± e±⇒ High granularity :

-0.5 Molière radius in X-Y-18 samplings, 0.9 X0 in depth

why spaghetti?⇒ best longitudinal & lateral shower

reconstruction⇒ energy correction⇒ p/e separation

⇒ best γ angular resolution

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Calorimetro Elettromagnetico

# fotoni ∝ E ∆E/E = (a/√ E) + b

1X0: probabilità 1/e di emettere 1γ o e+e-

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Alcune prestazioni degli esperimenti

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SENSIBILITA`

H/L = 0.4

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AGILE

Area effettiva di AGILE a 100 MeV confrontata con EGRET in funzione delladirezione di incidenza del fotone.

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AGILE

Area effettiva in funzione dell’energia del fotone per diversi angoli di incidenza

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AMS02 Gamma

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GLAST: PRESTAZIONI

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GLAST

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PULSAR: POLAR CAP

EsperimentiTelescopi Cerenkov

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SCIAMI IN ATMOSFERA

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CERENKOV IN ATMOSFERA• A livello del mare (n - 1) = ε ≈ 3 10-4.

• Per v ≈ c, cosθ = 1/βn ≈ 23 mrad ≈ 1.3°

• Energia di soglia per l’effetto Cerenkov: cosθ = 1 = 1/βn ; β > 1/n

E= γmc2=mc2/(1- β2)1/2 ; (1- β2)1/2 = (1-1/n2)1/2 = [(n2-1)/n2]1/2

E=mc2/√(2ε) 1/√2ε ≈ 41

• La soglia per elettroni: E ≈ 21 MeV

muoni: E ≈ 4.4 GeV

• Il massimo di produzione di particelle si ha a 10 km di quota (massimo di produzione Cerenkov).

• L’area illuminata a terra è un ellisse, o un cerchio di raggio r = h⋅θ = 104 23 10-3 = 230 m con unasuperficie di 1.6 105 m2.

• Il numero di fotoni prodotti nel visibile, 350—500 nm, da un gamma di 1 TeV è

Nγ ≈ 8.2 103 fotoni/λ

pari a circa 30—50 fotoni/m2in un’area entro ≈100m dall’asse dello sciame.

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MAGIC

230 m2

E: 10-300 GeVLa Palma

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MAGIC

17 m

17 m

ReflRefl. . surfacesurface::236 m236 m22, F/1, 17 m , F/1, 17 m ÆÆ

–– 964 964 heated mirrors heated mirrors on 247 on 247 panelspanels–– LasersLasers++mechanisms for mechanisms for AMCAMC

CameraCamera::~ 1 m ~ 1 m ÆÆ , 3.5°FoV, 3.5°FoV576 PMT (QE576 PMT (QEMAXMAX ~ 30%) ~ 30%)

AnalogicalAnalogicalTransmissionTransmission((opticaloptical fiberfiber))

2-level Trigger:2-level Trigger:1º 1º levellevel: : coincidencecoincidence2º level: pattern recognition2º level: pattern recognition300 300 MHzMHz DAQ DAQ

RapidRapid pointingpointing –– Carbon fiber structure Carbon fiber structure –– Active Mirror ControlActive Mirror Control

20÷30 20÷30 secondsseconds

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MAGIC IISeptember 21, 2008

MAGIC 24 APRILE 2009

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I quattro telescopi della Fase I sono stati completati nel dicembre 2003

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HESSA ≈ 100 m2

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HESS

Le immagini di HESS mostrano chiaramente la shell dellesupernove dove hanno originei gamma

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HESS: CENTAUROS A

Spectral distribution of the emission fromCentaurus A, from X-rays to the VHEgamma-ray energy band. Archival X-rayand EGRET gamma-ray data are shownin grey, previous VHE upper limits andthe tentative early detection in purple.

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MSH 15-52

VERITAS

CANGAROO

The High Energy Stereoscopic System (H.E.S.S.)

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The “Big Four”

Roque delos Muchachos,Canary Islands

VERITAS (USA,UK1…)1: Oct ’034: 2007100 m2

FLWO,Mt. Hopkins,Arizona

Windhoek,Namibia

HESS (Germany & France)2: Sum ’024: Early ’04100 m2

Woomera,Australia

CANGAROO III(Japan & Australia)2: Dec. ’02, 3: Early ’0457 m2

MAGIC MAGIC (Germany, Italy & Spain)(Germany, Italy & Spain)1: Autumn 1: Autumn ‘‘0303236 m236 m22

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TELESCOPI CERENKOV

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OSSERVAZIONE SPAZIO-TERRA

• Gli esperimenti nellospazio e a Terra sonocomplemetari fra di loro.Nella figura è mostrata lasensibilità al flusso digamma vs l’energia diGLAST e di HESS. Lelinee blu rappresentanorispettivamente il flusso difotoni dalla Crab Nebula elo stesso flusso ridotto perun fattore 10 e 100.

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RIVELATORI GAMMA

AMS