CANGAROOIII and beyond

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CANGAROO-III and beyond

• Masaki Mori
• for the CANGAROO team
• ICRR, The University of Tokyo

Pre-ICRC workshop New Generation Cherenkov
Imaging Telescopes Aug 1-2, 2005, Mumbai, India
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CANGAROO Collaboration of Australia and
Nippon for a GAmma Ray Observatory in the Outback
Woomera, South Australia
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CANGAROO team

• University of Adelaide
• Australian National University
• Ibaraki University
• Ibaraki Prefectural University
• Konan University
• Kyoto University
• STE Lab, Nagoya University
• National Astronomical Observatory of Japan

• Kitasato University
• Shinshu University
• Institute of Space and Astronautical Science
• Tokai University
• ICRR, University of Tokyo
• Yamagata University
• Yamanashi Gakuin University

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Brief history of CANGAROO

• 1987 SN1987A
• 1990 3.8m telescope
• 1990 ICRR-Adelaide Physics agreement
• 1992 Start obs. of 3.8m tel.
• 1994 PSR 1706-44
• 1998 SNR1006
• 1999 7m telescope
• 2000 Upgrade to 10m
• 2001 U.Tokyo-U.Adelaide agreement
• 2002 Second and third 10m tel.
• 2004 Four telescope system

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Why Woomera?

• NZ too wet, not many clear nights
• Woomera
• Former rocket range and prohibited
  areainfra-structure and support
• Adelaide group was operating BIGRAT

ELDO rocket Launch site in 60s
BIGRAT (BIcentennial Gamma RAy Telescope)
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3.8m telescope ex. Lunar ranging
Imaging camera at the prime focus
Tadashi Kifune John Patterson
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CANGAROO-II telescope

• Upgraded in 2000 from 7m telescope completed in
  1999
• 114 x 80cm CFRP mirror segments in
  parabola(first plastic-base mirror in the
  world!)
• Focal length 8m
• Alt-azimuth mount
• 552ch imaging camera
• Charge and timing electronics

(March 2000)
Tanimori et al., ICRC 1999
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CFRP mirror tuning system
80cm?, 5.5kg
Kawachi et al., Astropart.Phys. 14, 261 (2001)
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CANGAROO-II camera

• 3? FOV
• R4124UV(Hamamatsu)
• 0.115? pixel
• Lightguide
• 16PMTs/module

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CANGAROO-II Electronics
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CANGAROO-II -III
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Woomera 2004 March
T2 T4 T3 T1
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Basic specifications of telescopes

• Location
• 31?06S, 136?47E
• 160m a.s.l.
• Telescope
• 114? 80cm? FRP mirrors
• (57m2, Al surface)
• 8m focal length
• Alt-azimuth mount
• Camera
• T1 552ch (2.7? FOV)
• T2,T3,T4 427ch (4? FOV)
• Electronics
• TDCADC

T2
Mori et al., Snowbird WS (1999)
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GFRP mirrors and tuning system
Tuning using star images via a CCD camera
Ohishi et al., ICRC 2003
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Spot size
T4
0.7?
Point Spread Function (FWHM) T1 0.20? T2
0.21? T3 0.14? T4 0.16?
Y (vertical)
(measured at construction time)
Image of a star on camera observed by a CCD camera
X (horizontal)
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CANGAROO-III camera
R3479 (Hamamatsu)
Lightguide (T1/T234)
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PMT gain uniformity and linearity
Kabuki et al., Nucl. Instr. Meth. A500, 318-336
(2003)
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Lightguide design
Winstone cone cross section
Efficiency vs. incident angle
Kajino et al., ICRC2001
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High voltage control monitor
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Camera calibration
Blue LED flasher at the reflector center
Blue LED flasher in the camera box
Patterned screen
Yamaoka et al., ICRC2003
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CANGAROO-III Electronics (1)
Kubo et al., ICRC 2003
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CANGAROO-III Electronics (2)
Discriminator and summing module (DSM)
Trigger logic
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CANGAROO-III Electronics (3)
Single photoelectron spectrum measured with DSM
and ADC
ADC linearity
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Telescope control
Telescope control unit
GPS
Position data (every 100ms)
Position command (alt-azimuth)
RS-232C
Driving control PC
Remote command/position data/NTP
Hayashi et al., ICRC2003
Local area network
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Star tracking
Star position error observed by a CCD camera
T3
PMT size
RMS deviation 0.013 degree
CCD Y-axis (degree)
Hear Kiuchis talk!
CCD X-axis (degree)
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Construction of CANGAROO-III
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Sample of 4-fold stereo events
Data 2004 March
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Global trigger system
d

• Before software trigger
• Each telescopes triggered independently
• Now hardware stereo
• Requires at least 2 telescopes
• If no coincidence ? Reset
• Dead time ?1/100

100m
?td/c lt 500ns variable
Opt.fiber
650ns
150m
Telescopes
Telescopes
Opt.fiber
Turnaround 2.5?s
Trigger
Wait time 5?s
Trigger
Event number
Coincidence
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Effect of global triggers
without global trigger
muon
hadron
with global trigger
with global trigger
without global trigger
Length/size
Muon events are removed!
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Beyond CANGAROO-III

• In the near future
• Improvement of old T1 and others
• In the long range
• No unified plan yet
• Started brainstorming, technical and physical
  considerations

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Where should we go?
Wide FOV camera
Lower Energy
Wider coverage
Large reflector/high altitude
Higher Energy
Large effective area
Higher sensitivity
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A case study array of telescopes

• How to achieve large effective area in modest
  cost?
• Large span array with wide cameras?

SPAN
Yoshikoshi et al. Paleiseau WS (2005)
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Lateral distribution of light

• Tail is extended beyond 150m!

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Array span vs. effective area

• 6? FOV camera
• Gamma-ray energy100 GeV, 1 TeV, 10 TeV

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Summary

• CANGAROO-III is a system of 10m imaging Cherenkov
  telescope build by Japanese-Australian
  collaboration.
• We have been carrying out 4-telescope stereo
  observations of sub-TeV gamma-rays since 2004
  March. Now we have incorporated a global trigger
  system to reduce muons.
• We are studying the next-generation telescopes.
  One option could be a large-span array of
  telescopes to increase the effective area.

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End
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Stereo analysis still underway in progress

• Inconsistency with H.E.S.S results on some
  sources? New observations with CANGAROO III
  Efforts for advanced analysis procedures
• Measure more optical parameters
• CCD measurements of spotsizes and stars
• Use muons for calibration
• Tune Monte Carlo simulation
• Use the Crab as the standard candle
• Flux obtained with Monte Carlo simulation is
  compared with those reported by other groups
• Independent teams within the collaboration are
  working
• Hereafter, referred to as Teams A, B, C
• Results, especially detections, are double-checked

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Muon events (1)

• Selected by 1) clustering2) R?? (arc length)
  gt2deg?rad3) Small ?2 (good fit)

Data 2004 March
T2 T3 T4
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Muon events (2)

• T4

Curvature Distribution 1-7GeV 1/r gt 1.0
1/deg gt 7GeV 1/r lt 1.0 1/deg
Length/size Distribution
Monte Carlo simulation
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Muon parameters compared with Monte Carlo
Histogram data Hatched M.C.
T2 T3 T4
?2 for ring fitting (sensitive to spot size) r
curvature radius (0.8 for v/c1) Size/arclength
? total light collection efficiency
?2 1/r size/arclength
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Time variation of Size/Arclength

• Monitor of total light conversion efficiency
• Gradually,
• Size/Arclength is decreasing
• (5 / year)
• Mirror degradation due to dust etc.

T2 start
T3 start
T4 start
T2
T3
T4
2003
2004
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Stereo observation
Angular resolution 0.25deg ? 0.1 deg Energy
resolution 30 ? 15 Better S/N (no local
muons)
?2 distribution
Intersection point
(Simulation)
Target
Entries/bin
(qx, qy)
0 0.25 0.5
?2 deg2
?2 ?x2 ?y2
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Unfortunate situation for the Crab
Showers from the Crab

• The oldest T1 has higher energy threshold and bad
  efficiency for stereo observation
• Only T2/T3/T4 are used for stereo analysis
• Stereo baseline becomes short for the Crab
  observation at large zenith angles

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Large zenith angle observation of the Crab

Higher energy threshold 1TeV Bad intersection
accuracy
Narrower
Far core?small angle?bad accuracy
h?30?
Entries/bin
h?60?
Accept 15?lt?lt165? only
0 90 180?
?
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Crab signal (1)
Team A
(simple square cuts)
Nov 2003
On
Preliminary
Preliminary
Off
(On-Off)/bin
Entries/bin
?2 deg2
?2 deg2
Sigma 6.19 Excess 258?42 event Angular
Resolution 0.16? (HWHM)

• T2 T3
• ON 7.5hr
• OFF 7.0hr

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Crab signal (2)
Team A

• Significance map

• Differential flux

Preliminary
Preliminary
Angular resolution for the Crab (h35?) 0.17?
(RA) / 0.14 ? (Decl)