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The past 5 months when I was in SSL @ UCB…
Jeng-Lun Chiu (Alan)Department of Physics, NTHU /
SSL, UCB2006/12/19
Outline
• Introduction to NCT
• Data & simulation formats
• Charge sharing & Energy Loss
• Mgeant & MEGAlib
• Image Reconstruction
• PIXON algorithm
• Future Work
NCTNuclear Compton Telescope• 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 th
e 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
( S. E. Boggs, CIS workshop 2005 @ NTHU )
( M. E. Bandstra, 2006 IEEE )
( E, x, y, z, t )
Simulation
Data
.out [9]
.txt [7]
.bin
.str
.dat [15]
.gif
mgeant sharexi
nt
wrfile
reconstruct
IDL
prbin
(bin)
(bin)
(..etc)
Procedure for analysis
“Readme.txt” by J. D. Bowen, Jul 14, 2006
Event number
Energy
X DSP
Multi. # /
order
Y Z veto
Simulation(/data) formats
Event number
Event clock
E (DC)
E (AC)
X-strip
Y-strip
Sharing flag - X
Sharing flag - Y
DSP
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
Simulation
Data
.out [9]
.txt [7]
.bin
.str
.dat [15]
.gif
mgeant sharexi
nt
wrfile
reconstruct
IDL
prbin
(bin)
(bin)
(..etc)
Procedure for analysis
“Readme.txt” by J. D. Bowen, Jul 14, 2006
Imakefile
input.dat( simulation param
eters )
mgeantexcuta
ble
usrinp.F
gmake
SCAN2
INTER BATCH
output
others...
version, format,beam, spec, ( hadronic inter. )
Kine, Trig, Beam, Spec, Threshold, output filename, etc..
setup.geo( creation of geome
tries )
media.med
( define material types )material.mat
( define materials )
Information on the header of output file ..etc
GEANTGEANT3 3
mgeantmgeant
Interface for “Geant3” simulation
http://astrophysics.gsfc.nasa.gov/astroparticles/programs/mgeant/
MEGAlib picture
MEGAlib: completely object-oriented (written in “C++ & ROOT”)
Geomega: providing geometry & detector description module
Compton, Pair, etc.. Unsequenced hits
MGGPODConvert-
MGGPOD RevanEvent
Reconstruction
MimrecHigh-level
data analysis & Image
reconstruction
tra
Responsegenerator
GMegaGeant3
simulation
CosimaGeant4
simulation
sim
Detector(real data)
SivanSimulation verification
MEGAlyzeData acquisition
& calibration
Geant3
Geant4 fits
fits
fits
evta
bin
A. C. Zoglauer, 2006
GeoMega – Geometry for Mega
Revan – Real event analyzer
Mimrec – Mega image reconstruction
( http://www.mpe.mpg.de/MEGA/megalib.html )
Image Reconstruction
• Instrumental and atmospheric limitations blurring of the image
• But deblurring (deconvolution) techniques tend to amplify the noise
( D: data ; H: PSF ; I: image ; N: 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
Pixon method demands minimum complexity, or Algorithmic Information Content (AIC)
It selects the smallest number of basis functions that still adequately fit the data.
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)
Innovation: Pixon-element (each basis function) minimum parameterization
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 order
s of magnitude (3) Ensure robust rejection of spurious sources
PIXONPIXON
Quick PIXON
Summary
• 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
• Ground Support Equipment (with Mark)
• Pointing & Aspect (with Mark)
• Calibrations (all)
• Data archiving (with Andreas)
• Analysis Software (Andreas leads all)
Reference• 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).
• Andreas Zoglauer, "First Light for the Next Generation of Compton and Pair Telescopes", TU Munich, 12/2005
• Talks in CIS workshop @ NTHU, Nov. 15-17, 2005• Talks in NCT workshop @ NTHU, Sep. 11-12, 2006
• http://universe.gsfc.nasa.gov/astroparticles/programs/mgeant/ ( mgeant ) • http://www.mpe.mpg.de/MEGA/megalib.html ( MEGAlib )
• 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)
~ Thank you ~