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SUMMARY:PoGOLite: a balloon-borne soft gamma-ray polarimeter.
DTSTART;VALUE=DATE-TIME:20070706T170500Z
DTEND;VALUE=DATE-TIME:20070706T171700Z
DTSTAMP;VALUE=DATE-TIME:20260308T203945Z
UID:indico-contribution-1177@cern.ch
DESCRIPTION:Speakers: Prof. PEARCE\, Mark (KTH\, Department of Physics\, S
 tockholm)\nPolarized gamma-rays are expected from a wide variety of source
 s including \nrotation-powered pulsars\, accreting black holes and neutron
  stars\, and jet-\ndominated active galaxies. Polarization measurements pr
 ovide a powerful \nprobe of the gamma-ray emission mechanism and the distr
 ibution of magnetic \nand radiation fields around the source. No measureme
 nts have been performed \nin the soft gamma-ray band where non-thermal pro
 cesses are expected to \nproduce high degrees of polarization. The PoGOLit
 e experiment applies well-\ntype phoswich detector technology to polarizat
 ion measurements in the 25 - \n100 keV energy range. The instrument uses C
 ompton scattering and \nphotoabsorption in an array of 217 phoswich detect
 or cells made of plastic and \nBGO scintillators\, and surrounded by activ
 e BGO shields. A prototype of the \nflight instrument has been tested with
  polarized gamma-rays and background \ngenerated with radioactive sources.
  The test results and computer simulations \nconfirm that the instrument c
 an detect 10% polarization of a 100 mCrab source \nin one 6 hour balloon o
 bservation. In flight\, targets are constrained to within \nbetter than 5%
  of the field-of-view (~5 degrees squared) in order to maximize \nthe effe
 ctive detection area during observations. The pointing direction on the \n
 sky is determined by an attitude control system comprising star trackers\,
  \ndifferential GPS receiver system\, gyroscopes\, accelerometers and \nma
 gnetometers which provide correction signals to a reaction wheel and \ntor
 que motor system. Additionally\, the entire polarimeter assembly rotates \
 naround its viewing axis to minimize systematic bias during observations. 
 Flights \nare foreseen to start in 2009 and will target northern sky sourc
 es including the \nCrab pulsar/nebula\, Cygnus X-1\, and Hercules X-1. The
 se observations will \nprovide valuable information about the pulsar emiss
 ion mechanism\, the \ngeometry around the black hole\, and photon transpor
 tation in the strongly \nmagnetized neutron star surface\, respectively. F
 uture goals include a long \nduration balloon flight from the Esrange faci
 lity in the North of Sweden to \nCanada.\n\nhttps://indico.nucleares.unam.
 mx/event/4/session/93/contribution/1177
LOCATION:Merida\, Mexico Kabah (Holiday Inn)
URL:https://indico.nucleares.unam.mx/event/4/session/93/contribution/1177
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