Large Area Telescope (LAT)
GLAST Burst Monitor (GBM)
Gamma-ray Large Area Space Telescope
-France -Germany
-Italy -Japan
-Sweden -USA
Energy Range 10 keV-300 GeV.
GLAST :
- An imaging gamma-ray telescope (LAT)
- A second instrument for the study of Gamma Ray Bursts (GBM).
Omar Tibolla. ISAPP. Belgirate (Italy) 30 June - 9 July 2005
ACD contains 16 towers and each tower is divided in two parts:
-the TRACKER (TKR): 18 layers in each tower -Tungsten converters (1.08 χ0 : 78% prob) -2 orthogonal SSD planes of silicon microstrip sensors for detecting the electromagnetic shower
-a CALORIMETER (CAL) of CsI crystals dopped by Tl; so the energy deposited by the EM shower is converted in light signal. CAL is characterized by fast decaying fluorescent light (~ns) and a long decaying afterglow (~ms).
e+ e–
e+ e–e+ e–
The main instrument of GLAST is the Large Area Telescope (LAT): a pair conversion telescope:
Anticoincidence Shield (ACD) made of plastic scintillator (Bicron-408) sensitive to charged particles; ACD is segmented to avoid self veto from Calorimeter backsplash and also for micrometeorites.
TRACKER
CALORIMETER
ANTICOINCIDENCESHIELD
Omar Tibolla. ISAPP. Belgirate (Italy) 30 June - 9 July 2005
Quantity EGRET LAT (Minimim Spec.)
Energy Range 20 MeV - 30 GeV 20 MeV - 300 GeV
Peak Effective Area
(after background rejection)
1500 cm² > 8000 cm²
Field of View 0.5 sr > 2 sr
Angular Resolution 5.8° (100 MeV) < 3.5° (100 MeV) < 0.15° (>10 GeV)
Energy Resolution 10% < 10%
Deadtime per Event 100 ms < 100 μs
Source Location Determination 15' < 0.5'
Point Source Sensitivity ~ 10-7 cm-2 s-1 < 6 x 10-9 cm-2 s-1
LAT Specifications and Performance Compared with EGRET
Omar Tibolla. ISAPP. Belgirate (Italy) 30 June - 9 July 2005
The Glast Burst Monitor (GBM) will include two sets of detectors:
-12 sodium iodide (NaI) scintillators -2 cylindrical bismuth germanate (BGO)
scintillators
The NaI detectors are sensitive in the lower end of the energy range, from a few
keV to about 1 MeV and provide burst triggers and locations.
The BGO detectors cover the energy range ~150 keV to ~ 30 MeV, providing a
good overlap with the NaI at the lower end and with the LAT at the higher end.
Schematic layout of the 12 NaI and two BGO detectors on the GLAST spacecraft
Omar Tibolla. ISAPP. Belgirate (Italy) 30 June - 9 July 2005
Quantity BATSE GBM (Minimum Spec.)
Energy Range 25 keV - 10 MeV < 10 keV - > 25 MeV
Field of View 4π sr all sky notocculted by the Earth
Energy Resolution < 10% < 10%
Deadtime per Event < 15 μs
Burst Sensitivity 0.2 cm-2 s-1 < 0.5 cm-2 s-1
GRB Alert Location ~ 25° < 15°
GRB Final Location 1.7° < 1.5°
GBM Specifications and Performance Compared with BATSE
Omar Tibolla. ISAPP. Belgirate (Italy) 30 June - 9 July 2005
AGN/BLAZARS
UNIDENTIFIED EGRET SOURCES
NEW PARTICLE PHYSICS
EXTRAGALACTIC BACKGROUND LIGHT
GAMMA-RAY BURSTS
PULSARS
COSMIC RAYS AND INTERSTELLAR EMISSION
SOLAR FLARES
And other extremely important features are the COMPLEMENTARITY WITH GROUND-BASED GAMMA-RAY TELESCOPES and that GLAST will study the Universe in UNEXPLORED REGIONS OF EM SPECTRUM.
Scientific purposes
Omar Tibolla. ISAPP. Belgirate (Italy) 30 June - 9 July 2005
Background rejection with Classification Trees using R .-Signal file (ag-v3r3p7-merituple-prune20031218-fulltup.root)
722594 γ (power law, isotropic 4)
-27 BKG files (ntuple_prune*.root)
5551326 events : p, e- , e + , albedo γ
Before bkg rejection with R CT was made in a single step:0signal1bkg
A day of “real” data (part of Data Challenge 1).
Omar Tibolla. ISAPP. Belgirate (Italy) 30 June - 9 July 2005
I tried to do it in 2 steps: 1º: separate from charged particles. 2º: separate with the same method signal and albedo
0 charged particle1 γ 2 γ sign 3 γ albedo
Conclusions
-Big improvements using matrix of costs, expecially in high energy bins.-Problems with second steps.
Omar Tibolla. ISAPP. Belgirate (Italy) 30 June - 9 July 2005
Conclusions (2)
Omar Tibolla. ISAPP. Belgirate (Italy) 30 June - 9 July 2005
