Next Generation Groundbased ray Telescopes

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Next Generation Ground-based ?-ray Telescopes
April, 30 2001

• Frank Krennrich

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Outline

• - Scientific objectives
• - Technique
• - Design considerations
• - Solar arrays
• - Large single imaging telescope
• - Arrays of imaging telescopes
• - Summary

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Early 1990s
Atmospheric Cherenkov (Ground)
Compton, Pair conversion (Satellite)
Whipple
EGRET
10-1
100
101
102
103
104
105
10-2
10-3
GeV
4
Early 1995
Atmospheric Cherenkov (Ground)
Pair conversion (Satellite)
Whipple, CAT, HEGRA
EGRET
10-1
100
101
102
103
104
105
10-2
10-3
GeV
5
2005
Integral
GLAST
Chandra
STACEE, CELESTE
MAGIC
VERITAS, HESS, CANGAROO III
10-1
100
101
102
103
104
105
10-2
10-3
GeV
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Design Goals of New Atmospheric Cherenkov
Telescopes

• - Large effective area
  0.1 km2 (105 GLAST)
• - Low energy threshold
  10 GeV 50 GeV
• - Better flux sensitivity
  5 mCrab (50 hours)
• - Energy resolution ?E/E 10
  - 15
• - Angular resolution ????
  0.02o 0.1o
• - Wide energy range
  10 GeV 100 TeV
• - Large Field of View
  3o 10o (1/80 GLAST)

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Scientific Objectives

• Active Galactic Nuclei

• (Diffuse) Galactic Plane

• Infrared Background

• Pulsars

????????? ? e e -

• Gamma Ray Bursts

• Supernova Remnants

• Neutralino Annihilation,
• Primordial Black Holes,
• Quantum Gravity,

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Existing telescopes
Group/ Location
Reflectors Camera
Threshold Epoch Instrument
Number x Aperture
Pixels (GeV) Beginning
Whipple Arizona, USA
10 m 489
250 1984 Crimea
Crimea, Ukraine 6 x 2.4 m
6 x 37 1000 1985
SHALON Tien Shen, Russia
4 m 244
1000 1994 CANGAROO Woomera,
Aust. 3.8 m
256 500 1994 HEGRA
La Palma, Sp.
5 x 3 m 5 x 271
500 1994 CAT
Pyrenees , Fr. 4 m
600 250
1996 Durham/Mk6 Narrabri/Aust.
3 x 7 m 1 x 109
250 1996 TACTIC
Mt. Abu, India 4 x 3.5 m
1 x 225 300
1997 Seven TA Utah, USA
7 x 2 m 2 x 256
500 1998
STACEE Sandia, New Mexico
32(64) x 7m 32(64) x 1 180(50)
1998
CELESTE Pyrenees, Fr.
40 x 7m 40 x 1
50 2000
Solar-2 Barstow, USA
32x 7m 32 x 1
?? 2000
GRAAL Almeria, Spain
63 x 7m 4
200 1999
Significance (1Crab) gt 5
?????x?????t/hours?1/2
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MAGIC
CELESTE
VERITAS
GRAAL
CangarooIII
STACEE
HESS
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Imaging Atmospheric Cherenkov Telescopes

• Imaging Camera

0.01 100 TeV
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• ?-ray images
• - narrow, short, smooth
• Hadronic images
• - broad, long
• - local muons, patchy
• hadron rejection 99.7 (10-3)

?-ray
proton
Crab Nebula 7 ? in 1hour
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Design Energy Threshold

• - Night Sky Background
• NSB 2 4 x 1012
  photons/sr/m2/s
• ? 1.3 photons/m2
  (5ns, 0.5o aperture)
• - Signal from ?-ray shower
• S 0.1 E /GeV photons/m2
• ? 5 photons/m2
  (50 GeV)
• ? Signal/Noise
  S/NSB1/2
• ?E
  A-1/2

?
mirror
threshold
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Design Energy Threshold

• E (NSB ?????A)1/2

dark site
QE efficiency
threshold
solid angle ? pixel size
electronics optics
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General Strategies

• - increase mirror area
• 250 GeV ? 50 GeV

10m
50m
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General Strategies

• - increase mirror area
• 250 GeV ? 50 GeV

10m
50m
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Solar Arrays

• heliostats reflect light onto secondary optics
  (tower)
• wavefront sampling (light density profile)
• rejection of hadrons in trigger

• mirror area 1200 - 2000 m2
• energy threshold 50 GeV

Significance (1Crab) 1.0 1.6
?????x?????t/hours?1/2
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Solar Arrays
Parameter CELESTE
GRAAL Solar-1
STACEE

Base Ecole Polytechnique
MPI, Munich UC, Riverside
UCLA Location Pyrenees, Fr.
Almeria, Spain
Barstow, CA Sandia, NM of heliostats
40 (54)
63 32
32(48) Mirror area
2160 m2 2520
m2 1200 m2
1200 (1800) m2 Pixels
40 4
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32(48) Energy threshold 50
GeV 100 GeV
? 190 GeV (50
GeV)
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Single Large Imaging Telescope

• - parabolic reflector
  236 m2
• - focal length 17 m
• - carbon fiber space
  frame
• - diamond-milled
  aluminum mirrors
• - swift slew speed
  3o/s
• - 800 pixels
  0.1o
• - fast electronics ? 5
  ns trigger, FADCs
• - future (high QE
  detectors 45)
• - E 30 GeV

MAGIC
threshold
- First light 2002
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Arrays of Imaging Telescopes I
VERITAS

• - 50 GeV 50 TeV
• - ???? 0.03o _at_1TeV
• 0.09o _at_100GeV
• - Flux sensitivity
• 15 mCrab _at_100GeV
• 5 mCrab _at_300GeV

80 m
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Arrays of Imaging Telescopes I
VERITAS

• - 50 GeV 50 TeV
• - ???? 0.03o _at_1TeV
• 0.09o _at_100GeV
• - Flux sensitivity
• 15 mCrab _at_100GeV
• 5 mCrab _at_300GeV

80 m
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Arrays of Imaging Telescopes II

• Stereoscopic detection - reduction of energy
  threshold
• -
  improved angular resolution

• - rejection of local muons
• - shower core reconstruction
• - analysis of faint images

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Arrays of Imaging Telescopes III

• - Science topics with NGGGRT

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HESS

• - 4 x Davis-Cotton
  120 m2
• - focal length 15 m
• - steel space frame
• - ground-glas mirrors
• - 960 pixels
  0.16o
• - distance 120 m

First light 2002
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CANGAROO III

• - 4 x parabola 80
  m2
• - focal length 8 m
• - composite mirrors
• - 552 pixels
• -
  distance 100 m

First light 2004
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VERITAS

• - 7x Davis-Cotton
  100 m2
• - focal length 12 m
• - steel structure
• - ground-glas mirrors
• - 499 pixels
  0.15o
• - distance 80 m
• - 300 MHz FADC
• - Sub-arrays
• - mirror covers

First light 2003/2005?
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VERITAS
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Overview of Future Telescopes
Parameter MAGIC
HESS CANGAROO-III
VERITAS

Base MPI, Munich
MPI, Heidelberg Tokyo, Japan
SAO, Arizona Location La
Palma Namibia
Woomera, Australia Arizona of
telescopes 1
4(16)
4 7 Mirror
area/tel. 236 m2
120 m2
80 m2 100
m2 Elevation 2.3 km
1.8 km
S.L. 1.3 km
Energy threshold 30 GeV
40 GeV 100 GeV
50 GeV of pixels
800 960 x 4
552 x 4
499 x 7 Sub-arrays


First light 2002
2002
2004 2003/2005?

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Point Source Sensitivity
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Sensitivity of Telescope Arrays
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CELESTE Crab at 50 GeV
de Naurois et al., Proceed. of Gamma Ray
Astrophysics workshop, in press (Heidelberg)
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Sensitivity to flares

• 5 mCrab (50 h)
• 20 x Whipple
• ? second time scale
• for flares
• ? Good match with
• X-ray satellites

hypothetical lightcurve
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Status of Projects?
Astronomy Astrophysics in the New Millenium
NRC 10-year Report
Very Energetic Radiation Imaging Telescope
Array System (VERITAS)