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Title: Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)

Abstract

We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (25-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO will detect 10% polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter technology used in balloon-borne experiments (Welcome-1) and AstroE2 Hard X-ray Detector. PoGO consists of close-packed array of 397 hexagonal well-type phoswich counters. Each unit is composed of a long thin tube (well) of slow plastic scintillator, a solid rod of fast plastic scintillator, and a short BGO at the base. A photomultiplier coupled to the end of the BGO detects light from all 3 scintillators. The rods with decay times < 10 ns, are used as the active elements; while the wells and BGOs, with decay times {approx}250 ns are used as active anti-coincidence. The fast and slow signals are separated out electronically. When gamma rays entering the field-of-view (fwhm {approx} 3deg{sup 2}) strike a fast scintillator, some are Compton scattered. A fraction of the scattered photonsmore » are absorbed in another rod (or undergo a second scatter). A valid event requires one clean fast signal of pulse-height compatible with photo-absorption (> 20keV) and one or more compatible with Compton scattering (< 10keV). Studies based on EGS4 (with polarization features) and Geant4 predict excellent background rejection and high sensitivity.« less

Authors:
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC), Menlo Park, CA
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
839830
Report Number(s):
SLAC-PUB-11083
TRN: US0503356
DOE Contract Number:  
AC02-76SF00515
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; BLACK HOLES; COMPTON EFFECT; DECAY; DIMENSIONS; DISTRIBUTION; NEUTRON STARS; PHOSPHORS; PHOTOMULTIPLIERS; PHOTONS; PLASTIC SCINTILLATORS; POLARIZATION; PULSARS; SENSITIVITY

Citation Formats

Blanford, R. Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO). United States: N. p., 2005. Web. doi:10.2172/839830.
Blanford, R. Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO). United States. doi:10.2172/839830.
Blanford, R. Wed . "Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)". United States. doi:10.2172/839830. https://www.osti.gov/servlets/purl/839830.
@article{osti_839830,
title = {Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)},
author = {Blanford, R},
abstractNote = {We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (25-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO will detect 10% polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter technology used in balloon-borne experiments (Welcome-1) and AstroE2 Hard X-ray Detector. PoGO consists of close-packed array of 397 hexagonal well-type phoswich counters. Each unit is composed of a long thin tube (well) of slow plastic scintillator, a solid rod of fast plastic scintillator, and a short BGO at the base. A photomultiplier coupled to the end of the BGO detects light from all 3 scintillators. The rods with decay times < 10 ns, are used as the active elements; while the wells and BGOs, with decay times {approx}250 ns are used as active anti-coincidence. The fast and slow signals are separated out electronically. When gamma rays entering the field-of-view (fwhm {approx} 3deg{sup 2}) strike a fast scintillator, some are Compton scattered. A fraction of the scattered photons are absorbed in another rod (or undergo a second scatter). A valid event requires one clean fast signal of pulse-height compatible with photo-absorption (> 20keV) and one or more compatible with Compton scattering (< 10keV). Studies based on EGS4 (with polarization features) and Geant4 predict excellent background rejection and high sensitivity.},
doi = {10.2172/839830},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2005},
month = {4}
}

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