Transcript NINA: a silicon detector for cosmic ray astrophysics

La missione NINA: misure di
raggi cosmici di bassa energia
in orbita terrestre
Roberta Sparvoli
per la Collaborazione WiZard-NINA*
* Univ. of Tor Vergata and INFN, Rome, Italy
Moscow Engineering Physics Institute, Moscow, Russia
Univ. of Trieste and INFN, Trieste, Italy
Univ. of Bari and INFN, Bari, Italy
Univ. of Firenze and INFN, Firenze, Italy
INFN Laboratori Nazionali di Frascati, Frascati, Italy
IROE CNR, Firenze, Italy
Roberta Sparvoli, Sif 2001 - Milano
Scientific activity
Satellite/Space Station
Balloon
MASS1 (89)
MASS2 (91)
TS93
CAPRICE94
CAPRICE97
CAPRICE98
1990
1995
Life Science
SilEye-1
SilEye-2
2000
Cosmic rays NINA
NINA-2
PAMELA
2005
g rays AGILE
GLAST
ALTEA
Roberta Sparvoli, Sif 2001 - Milano
The Cosmic Ray radiation
Roberta Sparvoli, Sif 2001 - Milano
Galactic Cosmic Rays
GCRs are a directly accessible sample of matter
coming from outside the Solar System.
• The energy spectrum is a power-law for E > 1
GeV/n; at lower energy it is attenuated by the
action of the Solar Wind (solar modulation).
• GCRs are produced in the primordial
nucleosynthesis (light elements) or in explosions
of supernova stars.
At the end of their nuclear
evolution, some stars explode as
violent supernova event, dispersing
most of the star's matter. Some of
this material is accelerated to form
cosmic rays. Particles are most
probably accelerated by interactions
with shocks waves from the
supernova event.
Roberta Sparvoli, Sif 2001 - Milano
Anomalous Cosmic Rays
They represent a sample of the very local interstellar medium. Have a
lower speed and energy than GCRs.
ACRs include He, O, Ne and other elements with high FIP.
While interstellar plasma is kept outside the heliosphere by an
interplanetary magnetic field, the interstellar neutral gas flows through
the solar system. When closer to the Sun, its atoms undergo the loss of
one electron in photo-ionization or by charge exchange. Once these
particles are charged, the Sun's magnetic field picks them up and
carries them outward to the solar wind termination shock.
The ions repeatedly collide with the
termination shock, gaining energy in
the process. This continues until they
escape from the shock and diffuse
toward the inner heliosphere. Those
that are accelerated are then known
as Anomalous Cosmic Rays.
Roberta Sparvoli, Sif 2001 - Milano
Solar Energetic Particles
Particles emitted in SEPS are a sample of matter coming from the solar
corona. They are originated by:
Solar Flares: until the 90ies thought to be
responsible of the most intense SEPs and
geomagnetic storms. The Solar Flare is an
explosive release of energy (both electromagnetic
and charged particles) within a relatively small
(but greater than Earth-sized) region of the solar
atmosphere.
Coronal Mass Ejections (CMEs): violent
eruptions of coronal mass, known to be the very
responsible of particle acceleration. Often, not
always, associated to a flare. The fast CME
explosion in the slow Solar Wind produces a
shock wave which accelerates particles.
Roberta Sparvoli, Sif 2001 - Milano
The influence of the
Earth magnetic field
Originated by electric currents
running inside the Earth core. To a
first approximation it is a dipolar
field:
-> Coordinates: 79°N, 70°W and 79°S, 110°E, reversed with
respect to geographic Poles, about 11° inclined with Earth
axis and shifted by 320 km.
Latitude effect: the CR flux depends on the latitude, is
higher at the poles than at the equator. Each latitude has a
cut-off rigidity (p/z) below which no vertically arriving
particles can penetrate.
Roberta Sparvoli, Sif 2001 - Milano
Trapped particles
Combination of 3 periodic motions:
• Gyration: a helix around the field line;
• Bounce: oscillation around the equatorial plane between
almost symmetrical mirror points. Only small oscillations
are possible, the mirror point cannot hit the Earth surface.
Pitch-angle a0: angle between p and B at the equator.
Condition for trapping: |sin a0| R0-5/4 (4 R0-3)-1/4 ;
• Drift: longitudinal. It is due to
dishomogeneity of the field and
variations of the gyroradius.
Positive particles drift westward,
negative eastward.
Roberta Sparvoli, Sif 2001 - Milano
South Atlantic Anomaly
Above South America, about 200 - 300 kilometers off the
coast of Brazil, and extending over much of South America,
the nearby portion of the Van Allen Belt forms what is called
the South Atlantic Anomaly.
This is an area of enhanced radiation caused
by the offset and tilt of the geomagnetic axis
with respect to the Earth's rotation axis,
which brings part of the radiation belt to
lower altitudes.
The inner edge of the proton belt dips below the line
drawn at 500 km altitude.
Roberta Sparvoli, Sif 2001 - Milano
Albedo particles
Albedo particles are produced by cosmic ray interactions in
atmosphere (40 km). They are rebound to space by the Earth
magnetic field and have energies below the cut-off.
According to pitch-angle, we can have:
•1. Only one bounce: albedo
•2. More than one bounce: quasi-trapped
•3. Trapped
with almost equal fluxes (Grigorov, 1977).
Differences between albedo and trapped:
- the origin traces back into atmosphere or ground level;
- shorter flight time (from source to sink).
- energy up to GeV.
Roberta Sparvoli, Sif 2001 - Milano
Objectives of the mission NINA
• Study of the nuclear and isotopic component of Galactic
Cosmic Rays (GCR):
H-Fe --> 10-200 MeV/n in full containment
H-Fe --> 10-1 GeV/n
out of containment
• Study of Solar Energetic Particles (SEPs) in a long portion
of the 23 solar cycle, and transient solar phenomena
• Study of particles trapped in the magnetosphere (in SAA)
and albedo particles
• Study of Anomalous Cosmic Rays (ACRs)
Mission organized in two steps
Roberta Sparvoli, Sif 2001 - Milano
The mission NINA-1
Collaboration WiZard-NINA: Italy (INFN) - Russia (MEPhI)
Russian satellite
RESURS-01 n.4:
PERIOD
ALTITUDE
INCLINATION
MASS
~ 100 min
~ 840 km
98.7 deg.
2500 kg
Launch: 10 July 1998
Base Baikonur (Kazakhstan)
Zenith launcher
First scientific data:
31st August 1998.
End of the mission:
13th April 1999.
2.000.000 events taken
Roberta Sparvoli, Sif 2001 - Milano
The instrument NINA
The detector (D1)
Basic element:
a silicon wafer 6x6 cm2, 380 mm thick
with 16 strips, 3.6 mm wide in two
orthogonal views X -Y.
32 wafers arranged in 16 planes, 1.4 cm
apart.
The first two 150 mm thick (to lower the
energy threshold) and 8.5 cm apart (to
improve the trajectory reconstruction).
Roberta Sparvoli, Sif 2001 - Milano
Total weight = 40 kg
Power = 40 W
Internal structure:
Whole structure is housed in a
cylindrical aluminum vessel (300 mm
thick), filled up with N at 1.2 atm.
Roberta Sparvoli, Sif 2001 - Milano
Positioning into Resurs
D1:
the detector, composed of 32
silicon layers and the electronics for
signal processing;
D2:
the on-board computer, a
dual microprocessor dedicated to
data processing and to the selection
of the trigger and the acquisition
mode configuration;
E:
the interface computer, which
rearranges the data coming from box
D2 and delivers them to the satellite
telemetry system;
P:
the power supply, which
distributes the power supply to the
different subsystems.
Roberta Sparvoli, Sif 2001 - Milano
Operating Modes
Containment:
- the strips 1 and 16 of each plane form the Lateral AC,
always ON;
- Plane 16 forms the Bottom AC, ON in normal
operations.
NINA-1 worked always in Full Containment, whereas NINA-2 adopted
also the Non-Containment operating mode.
Trigger:
- the main trigger requires a particle to reach the first
view of the second silicon plane, i.e. requires a particle
to hit at least 3 silicon detectors.
Roberta Sparvoli, Sif 2001 - Milano
Performance of NINA-1
Geometrical factor
10 cm2sr
Maximum aperture
± 34º
Pointing accuracy
5º
Time resolution
2 ms
Energy resolution
(containment)
1 MeV
Mass resolution
H --> 0.1 amu
He --> 0.15 amu
Roberta Sparvoli, Sif 2001 - Milano
Isotope identification
Method of the Residual Range:
the mass M of the isotope with
charge Z is given by:
1/(b-1)
M = a[Eb - (E - DE)b]
Z2 Dx
with E the total energy released in
the detector, and a and b
parameters optimized by fit. Dx is a
particle path opportunely tuned,
with energy deposit DE.
Flight data in agreement with
data taken on ground
Roberta Sparvoli, Sif 2001 - Milano
Orbit analysis
Polar regions:
GCR
SEP
ACR
Mid-latitudes:
Trapped
Albedo
Roberta Sparvoli, Sif 2001 - Milano
GCR flux measurements
Performed in the solar quiet period:
December 1998-March 1999,
during passages over the
polar cups.
- Particle relative abundances estimated;
- Spectra of 4He, 12C and 16O reconstructed.
Roberta Sparvoli, Sif 2001 - Milano
Particle relative abundances
Particle fluxes
The comparison with other instruments is consistent
Roberta Sparvoli, Sif 2001 - Milano
SEP events observations
Period of observation:
November 1998 -- April 1999.
SEP events are identified by
increases of at least one order of
magnitude in the counting rate.
9 such increases have been
recorded in this period.
Other space instruments
confirm the SEP detection.
Some events are very close
in time but show different
characteristics.
Protons E>10 MeV
Roberta Sparvoli, Sif 2001 - Milano
4He
energy spectra
NINA energy window for 4He: 10--50 MeV/n.
Flux (E): A E-g + B(E)
Galactic
background
Power-law
spectrum
Roberta Sparvoli, Sif 2001 - Milano
3He/4He
3He
ratio
Background subtraction:
• Solar quiet BG: measured
during passages over the polar
cups in solar quiet periods.
• Secondary production: in the
Al cover. About 10% of the solar
quiet BG (estimations).
SEP events with 3He/4He ratio 3 s greater
than the solar coronal value (~4x10-4).Roberta Sparvoli,
Sif 2001 - Milano
2H/1H
and 3H/1H ratio
NINA energy window for H isotopes: 9--12 MeV/n.
2H/1H
ratio: (3.9 ± 1.4) x 10-5
averaged over all events,
consistent with solar
abundances.
In a previous measurement (IMP-5)
2H/1H ratio: (5.4 ± 2.4) x 10-5,
in [10.5--13.5 MeV/n], averaged
over several events [Anglin, ApJ,
198, 733, 1975].
Only upper limits for the
3H/1H ratio.
Roberta Sparvoli, Sif 2001 - Milano
Particles trapped in the SAA
Period of observation: November 1998--April 1999
Passages into SAA: 7 revolutions/day
SAA  L-shell<1.2 and B<0.22 G
Local pitch-angle aloc in SAA
corresponds to an equatorial
pitch-angle < a0 >  75°.
At Resurs altitudes particles
detected are permanently trapped
(mirror points higher than
atmosphere).
|sin a0| R0-5/4 (4 R0-3)-1/4
Roberta Sparvoli, Sif 2001 - Milano
E1-Etot and mass reconstruction
The E1 vs. Etot graph shows
presence of H and He isotopes
in SAA. Also 6Li is visible.
The mass reconstruction algorithm,
after
background
subtraction,
confirms the presence of ‘real’ H
and He isotopes in Radiation Belts.
3He is more abundant than 4He [see
also Wefel et al., 24th ICRC 1995].
Roberta Sparvoli, Sif 2001 - Milano
3He
and
4He
flux in SAA
g (3He) = 2.30 ± 0.08 in [10--50 MeV]
g (4He) = 3.4 ± 0.2 in [10--40 MeV]
Reasonable agreement with data from MAST on SAMPEX [Cummings et al.,
AGU Fall Meeting, 1995] at L-shell=1.2, all averaged over local pitch-angles.
Data are in agreement with
models
of
proton
interaction
with
the
residual
atmospheric
helium [Selesnick and Mewaldt,
1996, JGR, 101, 19745].
The sum of He and O
interaction
sources
in
atmosphere
seems
to
3He
overestimate
the
content.
L-shell 1.18—1.22, B<0.22 G
Roberta Sparvoli, Sif 2001 - Milano
2H
and
3H
flux in SAA
The 2H and 3H fluxes are compared with models based on atmospheric
interaction and models combining the effect of atmospheric
interaction and radial diffusion [Spjeldvik et al, 1997, 25th ICRC]. The global
agreement is quite good.
Nevertheless a more detailed
abundance analysis is not
consistent with the existing
models. For L-shell=1.2:
2H/1H
~ 0.01
2H/1H ~ 10-3
NINA 10 MeV/n
[Selesnick & Mewaldt,
1996]
3H/2H
~ 0.2
NINA 10 MeV/n
3H/2H ~ 0.05
[Spjeldvik et al, 1997].
SAMPEX results on deuterium
[Looper et al., Radiation Measurements,
1996] were also higher than
calculations.
L-shell 1.18—1.22, B<0.22 G
Roberta Sparvoli, Sif 2001 - Milano
Conclusion
• NINA-1 flew one year in space with performance
according to expectations;
• The analysis of Galactic Cosmic Rays, SEP events and
particles in the SAA provided excellent results;
• Anomalous Cosmic Rays could not be detected owing
to the solar modulation;
• The albedo particle analysis is still in progress;
• NINA-2 is continuing NINA-1 observations in a
different period of the 23rd solar cycle;
• PAMELA will complement the NINA observations
extending the energy range.
Visit our web site http://wizard.roma2.infn.it/nina
Roberta Sparvoli, Sif 2001 - Milano