Roma May 7, 2007 1Observation of the Universe from the Moon: PIM
Plastic Imager on the Moon
Claudio LabantiClaudio Labanti IASF Bologna
Moon based -ray observatory:
range 50 MeV – 200 GeV
large FOV (~ 3 sr)
sensitivity one order of magnitude greater than GLAST
Roma May 7, 2007 2Observation of the Universe from the Moon: PIM
SAS-2 (1972 - 1973) 20 MeV – 1 GeV spark-chamber
COS-B (1975 - 1982) 30 MeV – 3 GeV spark-chamber 50 cm2
EGRET (1991 - 2000) 100 MeV – 30 GeV spark-chamber ~1000 cm2
AGILE 23.4.2007 - 30 MeV – 50 GeV Si-tracker & MCAL ~1000 cm2
GLAST (~2007 - 30 MeV – 50 GeV Si-tracker & CAL ~8000 cm2
Gamma ray experiments history
Roma May 7, 2007 3Observation of the Universe from the Moon: PIM
Gamma ray Science
• Galactic topics
(SuperNova Remnants, Pulsars, Unidentified AGILE and GLAST sources). To understand the mechanisms of particle acceleration in Pulsars, and SNRs.
• Detailed study of the spectral phase variations of Pulsar emission will be used to determine the physics of the particle accelerator associated with these objects.
• Study of the dynamics of shocks in SNRs. • Constraining the contribution of unidentified sources to the diffuse emission from
the Milky Way. Through observations of diffuse gamma-ray emission produced by interactions of Cosmic-Rays with interstellar gas and photons it could be possible to verify the actual models describing CRs as accelerated in the shocks of SNR.
• The detection in the Milky Way of a broad spectral feature centered at 68 MeV signaling the decay of neutral pion, has escape detection so far. This feature can be searched next to SNR.
Roma May 7, 2007 4Observation of the Universe from the Moon: PIM
Gamma ray Science• Extragalactic topics
(Active Galactic Nuclei, Gamma Ray Bursts).
• Gamma-ray observations of AGNs will probe supermassive black holes through jet formation and evolution studies, and provide constraints on the star-formation rate at early epochs through photon-photon absorption over extragalactic distances.
• Understanding the particle acceleration in AGNs and the formation of jets. • Determine the high-energy behavior of Gamma-Ray Bursts. • Study of the extragalactic diffuse background. Isotropic diffuse gamma-ray flux
above 30 MeV has been observed. It can be interpreted either as the superposition of faint point sources or as the relic radiation from some high energy process in the early Universe, such as neutralino decay. The test of the models will require removal of the contribution from the resolved point sources and of the foreground Galactic flux.
• Fundamental physics
(Dark Matter, Test of Quantum gravity models with other lower energy instruments).
• Observing monoenergetic gamma-ray "lines" above 30 GeV from super-symmetric dark matter interaction; detecting decays of relics from the very early Universe, (cosmic strings or evaporating primordial black holes).
• Using GRB to detect quantum gravity effects.
Roma May 7, 2007 5Observation of the Universe from the Moon: PIM
Tracker telescope concept
-rays passing through an Anticoincidence shield (sensitive to charge particles) interacts with a moderator, producing electrons and positrons.The trajectories of these particles are determined in a stack of position sensitive detectors (Tracker); a Calorimeter will measure their energies.
courtesy AGILE team
Roma May 7, 2007 6Observation of the Universe from the Moon: PIM
PIM concept
TRACKER ASSEMBLY
CALORIMETER ASSEMBLY
ANTENNA
Equator line
North/South direction
radiatorsolar array
detection area
1200 mm
2200 mm
3500 mm
3600 mm
courtesy AAS-I LABEN
Roma May 7, 2007 7Observation of the Universe from the Moon: PIM
Tungsten plate
Y
X
Photodiode array with its connector
Tracker assemblyTop cover panel
External frame layersPhotodiodes electronics connector side Bottom panel
20LAYERS
Each layer is composed by:• two layers of parallel scintillator
fibers, 1 mm thick (TBD), placed at 90°, (2000 fibers for both directions X and Y).
• a tungsten plate 0.3 mm thick (TBD) on top of the fiber layers
• a 10 mm (TBD) CFRP honeycomb panel acting as structural element
Layers distance: 50 mm (TBD)
courtesy AAS-I LABEN
Each scintillanting fiber will deliver at the photodetector a ‘digital’ signal when passed by a MIP particle.There is no need of a linear amplifying photodetector.
Roma May 7, 2007 8Observation of the Universe from the Moon: PIM
PIM basic technologyScintillating fibers:
Core material: Polystyrene
Multi-Clad Fibers
(thickness: 2% of fiber size)
Trapping efficiency, square fibers: >7 %
No. of H atoms per cc (core): 4.82 x 1022
Radiation length: 40 - 100 cm
from: http://www.detectors.saint-gobain.com/
Light output for a MIP: > 50 ph
@ 20 cm from photodetector in a 0.75 mm square fiber
K. Rielage et. al: “The FiberGLAST detector…” Proc. 26th ICRC Conference, 5, 152, 1999
Roma May 7, 2007 9Observation of the Universe from the Moon: PIM
PIM basic technologyPhotodetectors for fiber readout: Si-PMT or Single Photon Avalanche Diode (SPAD)
SPAD operated at voltage biases above the breakdown voltage (Geiger mode) so that a single incident photon give rise to a macroscopic current pulse.
The avalanche process is then stopped by a current quenching circuit
Technology status @ today:
Dimensions from 20 to 200 m Ø
Q E @ 550 nm 48 %
Output pulse rise and fall time < 2ns on 10 pF load
Output pulse duration 20 ns
Dead time 65 ns
Dark counts @ 20 °C <250 (20 m Ø), < 20.000 (100 m Ø)
@ 0 °C < 25 (20 m Ø), < 500 (100 m Ø)
from: http://www.micro-photon-device.com/
2 SPAD, one at each end of a fiber, will be used for read-out.
A coincidence logic on the 2 SPAD signals will eliminate the dark counts of the photodetectors.
Micro lenses will focus the light from the fiber into the SPAD
Roma May 7, 2007 10Observation of the Universe from the Moon: PIM
Calorimeter assembly
The calorimeter is composed by three layers of plastic scintillator sheets, laying on a CFRP honeycomb structural panel 25 mm thick on the top (TBD), 40 mm thick on the bottom.
Each plane is composed by four sectors attached to the main structure frame.
Each sector has two phototubes on each side (for a total of 16 phototubes per each layer).
Calorimeter concept:
The particles detected on the tracker loose their energy on interacting with the regolite powder extracted from the Moon surface that fills the Calorimeter structure.
The EM shower shape and the number of its particles is measured by layers of plastic scintillator with PMT read-out
courtesy AAS-I LABEN
Roma May 7, 2007 11Observation of the Universe from the Moon: PIM
Regolite Loading Unit
1. Storing device
2. Pressurization device
3. Compressor
4. Pressurized inlet circuit
5. Filters
6. Pressurized outlet circuit
12
3
4
456
courtesy AAS-I LABEN
Roma May 7, 2007 12Observation of the Universe from the Moon: PIM
PIM mass and power budgetITEM Q.ty kg total [kg] total [kg]
TRACKER 1202
Scintillator fibers 80000 0.0037 296
Tungsten plate 20 21 420
Honeycomb panel 20 7 140
Photodiode 1600 0.01 16
External frame 180
Anti-coincidence 150
CALORIMETER 970
Plastic scintillator 270
Structure 700
EQUIPMENTS 1570
Electronics 210
Solar array 500
Radiator and Antenna 60
Battery pack 800
RLU 500
TOTAL ~ 4250
ITEM [W]
photodiodes 160
electronics 160
anti-coincidence 20
phototubes 20
panels 5
antenna 15
DC/DC 80
heaters 50
TOTAL [W] 510
Roma May 7, 2007 13Observation of the Universe from the Moon: PIM
PIM at a glance-ray observatory-ray observatory
Range 50 MeV – 200 GeV
FoV ~ 3 sr
Sensitivity 1.0 x 10-10 photons cm-2 s-1 (3 , at E > 100 MeV)
source detection for 107 sec. observation time
Angular resolution some arc second @ 1 GeV
Energy resolution > 10% (1 )
Time resolution some tenth of nsec
Measurements continuous
Site Equatorial belt. Moon side facing the Earth to ease communications
Operating temp. -30 to +50 °C Moderate temperature control on the SPAD detectors
Size ~ 3 x 3 x 3 m Mass ~ 4300 kg Power ~ 500 W
Technology objectivesTechnology objectives
- a particle Tracker based on scintillating fibre
- tracker read-out system based on Single Photon Avalanche Diodes (SPAD)
- calorimeter for high energy particles build with material collected on the Moon surface and plastic scintillators detectors
Technology status: mature
Science objectiveScience objective
- Galactic diffuse emission.
- Galactic sources (SNR, Pulsars, Unidentified sources).
- Extragalactic sources (AGN, GRB).
- Fundamental physics (Quantum gravity models, Dark matter)