The past 5 months when
I was in SSL @ UCB…
Jeng-Lun Chiu (Alan)
Department of Physics, NTHU / SSL, UCB
2006/12/19
Outline
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Introduction to NCT
Data & simulation formats
Charge sharing & Energy Loss
Mgeant & MEGAlib
• Image Reconstruction
• PIXON algorithm
• Future Work
NCT
Nuclear Compton Telescope
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Sources: Nuclear line emission & polarization
Energy-band: Soft gamma-ray (0.2-10 MeV) & hard X-ray (8-100 keV)
Targets: GRB (monitor), solar flares, TGFs (Terrestrial Gamma-ray Flashes),
Interest: 511-keV galactic emission line, emission and acceleration mechanisms in
the magnetospheres of gamma-ray pulsars, sources of 26Al as being core-collapsed
supernovae or Wolf-Rayet stars
Scientific goal: (1) MeV gamma-ray all-sky survey, (2) hard X-ray all-sky survey, (3)
Gamma-Ray Bursts (GRBs), (4) cosmic rays, (5) Active Galactic Nuclei (AGN), (6)
supernovae and supernova remnants, (7) X-ray binaries, (8) Soft Gamma Repeaters
(SGRs) and Anomalous X-ray Pulsars (AXPs), (9) gamma-ray pulsars, (10) galactic
0.511-MeV lines, (11) solar flares, and (12) Terrestrial Gamma-ray Flashes (TGFs)
Calibration Lines (keV): 59.5 (241Am); 81.0, 356 (133Ba); 122, 136 (57Co); 662
(137Cs); 1173, 1333 (60Co).
Pre-flight in 2005
Present status
Nuclear Compton Telescope
( M. E. Bandstra, 2006 IEEE )
( E, x, y, z, t )
( S. E. Boggs, CIS workshop 2005 @ NTHU )
Procedure for analysis
mgeant
Simulation
sharexint
reconstruct
.out [9]
.txt [7]
Data
(bin)
(bin)
.bin
.str
.dat [15]
IDL
.gif
(..etc)
wrfile
prbin
“Readme.txt” by J. D. Bowen, Jul 14, 2006
Simulation(/data) formats
Event
number
Energy
X
Y
Z
DSP
Multi.
# / order
veto
Event
number
Event
clock
E (DC)
E (AC)
X-strip Sharing
flag - X
Y-strip Sharing DSP
flag - Y
Multi.
# | order
……………………………
Energy loss & charge sharing (AC)
by Zong-Kai Liu
Energy loss & charge sharing (DC)
by Zong-Kai Liu
Energy loss & charge sharing
W. Coburn, et al., 2002, SPIE
Procedure for analysis
mgeant
Simulation
sharexint
reconstruct
.out [9]
.txt [7]
Data
(bin)
(bin)
.bin
.str
.dat [15]
IDL
.gif
(..etc)
wrfile
prbin
“Readme.txt” by J. D. Bowen, Jul 14, 2006
Kine, Trig,
Beam, Spec,
Threshold,
output filename,
etc..
version, format,
beam, spec,
( hadronic inter. )
others...
Imakefile
mgeant
usrinp.F
input.dat
Information on
the header of
output file ..etc
media.med
gmake
( simulation parameters )
( define material types )
setup.geo
material.mat
( creation of geometries )
( define materials )
mgeant
excutable
INTER
Interface for
“Geant3” simulation
BATCH
GEANT3
SCAN2
output
http://astrophysics.gsfc.nasa.gov/astroparticles/programs/mgeant/
MEGAlib picture
GMega
Geant3
MGGPOD
Geant4
Detector
(real data)
fits
fits
fits
bin
Geant3
simulation
ConvertMGGPOD
Sivan
Simulation
verification
sim
Cosima
Responsegenerator
Mimrec
Revan
Event
Reconstruction
tra
High-level
data analysis
& Image
reconstruction
Geant4
simulation
MEGAlyze
Data acquisition
& calibration
evta
GeoMega – Geometry for Mega
Revan – Real event analyzer
Mimrec – Mega image reconstruction
( http://www.mpe.mpg.de/MEGA/megalib.html )
Compton, Pair, etc..
Unsequenced hits
Geomega: providing geometry & detector description module
A. C. Zoglauer, 2006
MEGAlib: completely object-oriented
(written in “C++ & ROOT”)
Image Reconstruction
( D: data ; H: PSF ; I: image ; N: noise )
• Instrumental and atmospheric limitations
 blurring of the image
• But deblurring (deconvolution) techniques
tend to amplify the noise
PIXON - Basic Concepts
• Information theory: the most efficient (minimal
description) model of the signal also does the
best job of separating it from noise
Innovation: Pixon-element (each basis function)
 minimum parameterization
PIXON: (1). A picture element (2). A fundamental unit of information in the image
The smallest groupings of signal warranted by the quality of the data, and they
are fundamental and indivisible units of picture information. An image’s pixon
represent the minimum set of degrees of freedom necessary to describe the
image. (PP93)
 Pixon method demands minimum complexity, or Algorithmic
Information Content (AIC)
 It selects the smallest number of basis functions that still
adequately fit the data.
Solution: Pixon method provides a solution:
(1) It assigns a priori probabilities to different signal models,
so a function that zigzags through noisy data has low
probability, while a smooth function has a high a priori
probability.
(2) In Bayesian fashion, it maximizes not the usual
maximum likelihood of the data, given the model, but
the product of that likelihood and the prior
probability of the model.
Benefit:
(1) Increase the spatial resolution by factors of several
(2) Increase the sensitivity to low contrast sources by
orders of magnitude
(3) Ensure robust rejection of spurious sources
PIXON
Quick PIXON
Summary
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Data formats and processing procedures
Simulation – mgeant to geant3
MEGAlib package
PIXON algorithm
C++ for object-oriented programming
LM-ML algorithm
GSE codes…
Starting…
Future Work
• Image reconstruction – PIXON
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Ground Support Equipment (with Mark)
Pointing & Aspect (with Mark)
Calibrations (all)
Data archiving (with Andreas)
• Analysis Software (Andreas leads all)
Reference
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W. Coburn, S.E. Boggs, S. Amrose, R.P. Lin, M.T. Burks, M. Amman, P.N. Luke, N.W. Madden,
and E.L. Hull. Results of charge sharing tests in a Ge-strip detector. In 2001 IEEE Nuclear
Science Symposium Conference Record. IEEE, New York, NY, Vol. 1, pp. 226-229 (2002).
W. Coburn, S. Amrose, S.E. Boggs, R.P. Lin, M.S. Amman, M.T. Burks, E.L. Hull, P.N. Luke, and
N.W. Madden. 3D positioning germanium detectors for gamma-ray astronomy. In SPIE-Int. Soc.
Opt. Eng. Proceedings of Spie - the International Society for Optical Engineering, Bellingham, WA,
Vol. 4784, pp. 54-63 (2002).
J.D. Bowen, M.E. Bandstra, S.E. Boggs, W. Coburn, C.B. Wunderer, R.P. Lin, M. Amman, P.N.
Luke, M.T. Burks, W. Craig, N.W. Madden, D.M. Smith, P. von Ballmoos, P. Jean. Pre-flight
calibration of the prototype Nuclear Compton Telescope. In SPIE-Int. Soc. Opt. Eng. Proceedings
of Spie - the International Society for Optical Engineering, Bellingham, WA, Vol. 6266, pp. (2006).
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Andreas Zoglauer, "First Light for the Next Generation of Compton and Pair
Telescopes", TU Munich, 12/2005
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Talks in CIS workshop @ NTHU, Nov. 15-17, 2005
Talks in NCT workshop @ NTHU, Sep. 11-12, 2006
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http://universe.gsfc.nasa.gov/astroparticles/programs/mgeant/
http://www.mpe.mpg.de/MEGA/megalib.html ( MEGAlib )
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Piña R. K. & Puetter R. C., 1993, PASP, 105, 630
R. C. Puetter, Ann. N.Y Acad. Sci., 808, pp. 160-183 (1997).
http://casswww.ucsd.edu/personal/puetter/pixonpage.html (The Pixon PAGE in UCSD)
http://www.pixon.com/brochure.html (The PIXON method @ www.pixon.com)
( mgeant )
~ Thank you ~