1. Comparison of GAMMA-400 and Fermi-LAT telescopes
Barcelona, June, 2015

2. Next gamma-telescope after Fermi-LAT
Gamma telescope - pair-conversion telescope with a precision tracker and calorimeter.
Fermi-LAT - the design approach (Atwood et al. 1994) launched by NASA on 2008 June 11
main mode - sky survey
GAMMA the design approach 2011 (2012) arXiv:
main mode – continuous long time point source observations (>100 days)
Barcelona, June, 2015

3. Fermi-LAT main mode - sky survey
wide field-of-view (FoV) sr effective area ~ 0,8 m2 (total) ~ 0,45 m2 (front) angular resolution (100 GeV) ~ 0,1° energy resolution (100 GeV) ~ 10% The 3FGL catalog includes 3033 sources The first Fermi -LAT catalog of >10 GeV sources (1FHL) has 514 sources
Barcelona, June, 2015

4. GAMMA-400 main mode – point source observation
field-of-view ~ 120°
effective area ~ 0,4 m2
angular resolution (100 GeV) ~ 0,01°
energy resolution (100 GeV) ~ 1%
Barcelona, June, 2015

5. TKR Fermi-LAT GAMMA-400 The single-sided SSDs strips 228 μm pitch.
18 pair SSD (X, Y)
Front converter - 12 paired layers (W 0,03 radiation lengths),
Back converter paired layers (W 0,18 r.l.)
Last 2 paired layers no W.
Digital readout
GAMMA-400
The single-sided SSDs strips 80 μm pitch,
10 pair SSD (X, Y)
8 paired layers (W 0,1 radiation lengths) ,
Last 2 paired layers no W.
Analog readout
Barcelona, June, 2015

6. Calorimeter Fermi-LAT imaging calorimeter,
“The Calorimeter for the GLAST Large Area Telescope” Grove 2007
By 1995 it was clear that the launch vehicle would be a Delta-II (5). The latter choice limits the total satellite weight to about 3 tons…The mass allotted to the calorimeter design was set at < 1440 kg.
in each tower 8 layers, each with 12 crystal
logs (with dimensions 326 mm26:7 mm19:9 mm).
Each calorimeter module layer is aligned 90◦with
respect to its neighbors, forming an (x, y)
(hodoscopic) array.
The light yield tapering along the length of the
crystal is monotonic, the ratio of the light collected from the far end of the crystal is 60% of that from the near end for all crystals.
Position resolution < 3 cm.
The total vertical depth of the calorimeter is 8.6 radiation lengths.
e/p rejection 103
Barcelona, June, 2015

7. Calorimeter GAMMA-400 Two part imaging calorimeter CC1 Preshower
Two super layers
CsI(TL) 333×50×20 mm – 60 crystal plus Si strip detectors (analog last layer TKR – X,Y SSD pitch 80 μm)
CC2 imaging calorimeter 12 layers 27×27
cubic crystal 36×36×36mm.
The total vertical depth of the calorimeter is
23 radiation lengths
e/p rejection 105
Barcelona, June, 2015

8. Calorimeter GAMMA-400 more deep calorimeter allow
significantly improve angular resolution (0,01°)
allows more precisely determine the shower axis and, therefore, in the reconstruction of the track to reduce the number of hits strips (noise) - and thereby improve the angular resolution
improve energy resolution (1%)
improve proton rejection (105)
additional possibilities – observations lateral direction
Barcelona, June, 2015

9. Backsplash influence
Distance from calorimeter crystal CsI to bottom tracker SSD
Fermi-LAT 10 сm, GAMMA cm.
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10. The ghost events have been the largest detrimental effect observed in flight data. They affect all of the subsystems, significantly complicate the event reconstruction and analysis, and can cause serious errors in event classification (Ackermann et al. 2012, ApJS, 203, 4)
Event display of a simulated 27 GeV ray (Arxiv: )
Barcelona, June, 2015

11. GAMMA GeV
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12. AC
Fermi-LAT
The ACD plastic tiles covering the top of the instrument and 16 tiles covering each of the four sides (89 in all). The dimensions of the tiles between 561 and 2650 cm2 in geometrical surface and between 10 and 12 mm in thickness. Tiles overlap in one dimension, leaving gaps between tile rows in the other. The gaps are ~ 2,5 mm
Efficiency of
GAMMA-400
AC double layer thickness 10×2 mm, overlay 5 –10mm
Efficiency of
Backsplash rejection (false vetoes caused by backsplash)
Fermi-LAT - segmentation (<20% 300GeV false vetoes caused by backsplash)
GAMMA segmentation,
double layer coincidence, time of flight (AC – S1) (<3% 1000GeV)
Barcelona, June, 2015

13. GAMMA-400 backsplash rejection
Normal AC layers operation OR mode
200 GeV photons, energy consumption S3 280 MeV, 10% photons can be lost via false vetoes caused by backsplash
up to 100 GeV energy consumption S3 < threshold (150 MeV) segmentation, <3% photons can be lost via false vetoes caused by backsplash
TRIGGER for signal S3 > threshold (150 MeV) AC layers operate in AND mode <3% photons losses via false vetoes caused by backsplash (even at 1000 GeV were 27% hits in single layer)
Time of flight (AC – S1) method <5% can be lost via false vetoes caused by backsplash (all energy range)
Barcelona, June, 2015

14. Trigger (gamma) Fermi-LAT GAMMA-400 (only fast signal)
TKR (also known as “three-in-a-row“) slow signal
CAL (LO or HI) slow signal
VETO ACD
The time between a particle interaction in the LAT that causes an event trigger and the latching ∼2.5 μs)
GAMMA (only fast signal)
TOF
S3 (LO or HI)
The time between a particle interaction in the LAT that causes an event trigger and the latching ∼50 ns)
Barcelona, June, 2015

15. Additional apertures GAMMA-400
1 – gamma quantum
2 – cosmic rays +diffuse gamma
X0 = 25 r.l., λ0 = 1.2 i.l.
(vertical directions)
3 – cosmic rays
X0 = 54 r.l, λ0 = 2.5 i.l.
(lateral direction)
Barcelona, June, 2015

16. GAMMA-400 and CTA
S.Funk, J.A. Hinton/ Astroparticle Physics 43(2013)
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17. summary
Gamma further development of gamma-ray telescopes after Fermi-LAT.
Do not repeat the measurement Fermi-LAT allow to measure astrophysical objects with qualitatively new parameters in the field of high-energy (> 10 GeV GeV), the angular resolution of times better energy resolution of times better,
Is intended for long-term continuous measurement
In this range parameters Gamma-400 is also superior being developed ground gamma telescopes CTA angular resolution 10 times, energy resolution times.
Allow a search for traces of decay and annihilation of particles of dark energy
Barcelona, June, 2015

18. Barcelona, June, 2015