PAMELA: a Satellite Experiment for Antiparticles Measurement in

NUCLEAR SCIENCE SYMPOSIUM - Portland, OR - October 20-24, 2003 Massimo Bongi

PAMELA: a Satellite Experiment for PAMELA: a Satellite Experiment for Antiparticles Measurement in Antiparticles Measurement in

Cosmic Rays Cosmic Rays

Massimo BongiUniversita’ degli Studi di Firenze and INFN Sezione di Firenze

The PAMELA collaboration

• PAMELA scientific objectives• Detector’s overview• Subsystems’ description• PAMELA status


The PAMELA CollaborationThe PAMELA Collaboration

Bari Florence Frascati

Italy:TriesteNaples Rome CNR, Florence

Russia:

Moscow St. Petersburg

India:

Bombay

Germany:Siegen

Sweden:KTH, Stockholm

NMSU

GSFC

USA:


STUDY OF ANTIMATTER IN COSMIC RAYS

AntiprotonsAntiprotons spectrum

PositronsPositrons spectrum

Search for light antinucleiantinuclei

SECONDARY GOALS

•Modulation of GCRs in the Heliosphere

•Solar Energetic Particles (SEP)

•Earth Magnetosphere

PAMELA scientific objectivesPAMELA scientific objectives

Antiproton flux






SECONDARY GOALS





Positron charge ratio






SECONDARY GOALS





Earth magnetosphere

PAMELA

70.4o

300-600 km

PAMELA will fly on board of RESURS DK1

satellite, which will be launched by a

Soyuz 2 rocket from Baikonur launch site in the

first half of 2004 for a 3 years long mission






SECONDARY GOALS





Earth magnetosphere

PAMELA

70.4o

300-600 km

80 MeV/n – 30 GeV/n7•10-8He/He limit

50 MeV – 270 GeV> 3•105Positrons

50 MeV – 2 TeV6•106Electrons

80 MeV – 190 GeV> 3•104Antiprotons

80 MeV – 700 GeV3•108Protons

Energy rangeNumber (3 years)Particle


Detector’s structureDetector’s structureTRANSITION RADIATION DETECTOR

MAGNETIC SPECTROMETER

ELECTROMAGNETIC CALORIMETER

NEUTRON DETECTOR

TIME-OF-FLIGHT SCINTILLATORS

ANTICOUNTER SYSTEM

BOTTOM SCINTILLATOR


AC

Neutron detectorBottomscintillator

Detector’s principle of operationDetector’s principle of operation• Trigger and

Time-of-Flight Measurement

• γ Measurement

• Momentum Measurement

• Energy Measurement and

Particle Identification


TimeTime--ofof--Flight SystemFlight System3 double layers of Bicron BC-404 plastic scintillatorread by Hamamatsu R5900 PMTs

• 110 ps transit time spread

• high gain (~106) at 800 V


TimeTime--ofof--Flight SystemFlight System3 double layers of Bicron BC-404 plastic scintillatorread by Hamamatsu R5900 PMTs

• 110 ps transit time spread

• high gain (~106) at 800 V

•• Trigger signalTrigger signal

•• Detects Detects albedoalbedo particlesparticles

•• dEdE//dxdx measurementmeasurement

•• Particle identificationParticle identification

up to up to ~~1 GeV/c1 GeV/c

~130 ps time resolution


Transition Radiation DetectorTransition Radiation Detector9 planes of 1024 straw tubesstraw tubes each (4 mm ∅) interleaved with carbon carbon fibres radiatorsfibres radiatorsstraw tubes use a Xe-CO2 (80-20)% gas mixture and work at ~ 1400 V


Transition Radiation DetectorTransition Radiation Detector9 planes of 1024 straw tubesstraw tubes each (4 mm ∅) interleaved with carbon carbon fibres radiatorsfibres radiatorsstraw tubes use a Xe-CO2 (80-20)% gas mixture and work at ~ 1400 V

Threshold device:

• signal from e+ and e-

• no signal from p and p

A pion contamination of 5% at an

electron discrimination efficiency of

~ 90% has been obtained


Magnetic SpectrometerMagnetic SpectrometerSilicon Tracker inside a Permanent MagnetSilicon Tracker inside a Permanent Magnet

Measures particles’ rigidity: R=Measures particles’ rigidity: R=p/qp/q

• 5 Nd-Fe-B alloy magnetic modules in an aluminum structure

• (132 x 162 x 445) mm3 cavity

• 20.5 cm2sr geometric factor

• B = 0.48 T in the center





• (132 x 162 x 445) mm3 cavity



• 6 planes of 300 µm thick silicon

sensors

• 6 microstrip silicon sensorsmicrostrip silicon sensors in

each plane

• double sided sensors, with

double metalization and

integrated decoupling capacitance

• strip pitch: 50 µm on X side

(bending view), 67 µm on Y side





• (132 x 162 x 445) mm3 cavity



• 6 planes of 300 µm thick silicon

sensors

• 6 microstrip silicon sensorsmicrostrip silicon sensors in

each plane

• double sided sensors, with

double metalization and

integrated decoupling capacitance

• strip pitch: 50 µm on X side

(bending view), 67 µm on Y side

s

e

d


Signal / Noise ratioSignal / Noise ratioY: S/N ~ 26 X: S/N ~ 52

300 GeV/c electron event300 GeV/c electron eventJune 2002 SPS beam test

non-bending view bending view

Magnetic SpectrometerMagnetic Spectrometer


Signal / Noise ratioSignal / Noise ratioY: S/N ~ 26 X: S/N ~ 52

300 GeV/c electron event300 GeV/c electron eventJune 2002 SPS beam test

non-bending view bending view

Magnetic SpectrometerMagnetic SpectrometerSpatial resolutionSpatial resolution

σX ~ 3 µm, σY ~ 13 µm

Maximum Detectable Maximum Detectable Rigidity:Rigidity:

MDR > 740 GV/cMDR > 740 GV/c


Electromagnetic CalorimeterElectromagnetic CalorimeterSampling calorimeter made of 22 planes: 16 radiation lengths, 0.9 interaction lengths

2.6 mm thick tungsten absorber between two 380 µm thick macrostrip silicon detector layers

Measures energy of e+ and e- with ∆E/E = 15% / E 1/2 + 5.5%

Reconstructs shower profile both in the longitudinal and in the transverse

direction: 10-4 hadron/leptonrejection power

Electrons’ energy up to 2 TeV in self-trigger mode


(x4)

CASCAT

AnticounterAnticounter SystemSystem4 panels (CAS) of Bicron BC-448 plastic scintillator surrounding the sides of the spectrometer + 1 panel (CAT) on top of it, read by Hamamatsu 5900 PMTs


(x4)

CASCAT

AnticounterAnticounter SystemSystem4 panels (CAS) of Bicron BC-448 plastic scintillator surrounding the sides of the spectrometer + 1 panel (CAT) on top of it, read by Hamamatsu 5900 PMTs

•Defines the spectrometer acceptance•Helps in rejecting spurious triggers


BottomBottom ScintillatorScintillator and Neutron Detectorand Neutron DetectorBottom Scintillator

10 mm thick scintillator

read by 6 MELZ FEU-85 PMTs

Neutron Detector

36 3He proportional counters + lowZ moderator enveloped in a thin cadmium layer

n + 3He p + 3H + 765 keV

lot

The Bottom Scintillator triggers the Neutron Detector, which helps in hadron/lepton identification


PAMELA statusPAMELA statusAll the subdetectors are nearly ready and fulfill

the requirements

Intense simulation and beam test activities have been performed




the requirements




the requirements


Integration of the detector is in progress



the requirements


Integration of the detector is in progress

Launch from Baikonur on next

year

PAMELA: a Satellite Experiment for Antiparticles Measurement in

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