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Project contact: Mark Pearce.

Brief overview

Left: An overview of the PoGOLite gondola. The polarimeter is the cylindrical object in the centre and is shown in more detail in the right-hand figure (approximately 1 metre long). A one million cubic metre stratospheric balloon connects to the top of the gondola and will lift PoGOLite to an operational altitude of 40 km.

The light-weight Polarized Gamma-ray Observer (PoGOLite) experiment is designed to measure the polarization of soft gamma rays in the 25 keV- 80 keV energy range. Polarized gamma rays are expected from a wide variety of sources including rotation-powered pulsars, accreting black holes and neutron stars, and jet-dominated active galaxies. Polarization has never been measured at soft gamma-ray energies where non-thermal processes are likely to produce high degrees of polarization. The polarization is derived from the azimuthal distribution of Compton scattering angles in the sensitive volume of the instrument. The scattering angle will be measured by detecting coincident Compton scattering and photo-absorption sites in an array of 217 phoswich detectors. Polarization measurement requires high purity coincident signal detection. PoGOLite applies a well-type Phoswich Detector technology for this purpose. The technology has proven to be very effective in reducing source-confusion and cosmic-ray-induced backgrounds. The PoGOLite experiment is being developed by groups in Japan, Sweden, USA and France. Collaboration homepage.

PoGOLite 'pathfinder' mission: a reduced volume instrument (61 detector units) is scheduled to fly from Esrange, northern Sweden in August 2010.

Thanks to an initiative by PoGOLite team member Magnus Axelsson, PoGOLite was featured on stamps issued by the Swedish post office in January 2009 to mark the International Year of Astronomy!
PoGOLite stamps

The stamps also appeared on the front cover of the 2008 annual report for the School of Engineering Sciences at KTH and in articles in 'Populär Astronomi' and 'Forskning och Framsteg'.

Who's who

From Sweden, the Particle and Astroparticle Physics group within the Physics Department at The Royal Institute of Technology (KTH) and the Astronomy Department at Stockholm University participate. The PoGOLite team consists of:

Seniors: Wlodek Klamra (KTH), Stefan Larsson (KTH/SU), Göran Olofsson (SU), Mark Pearce (KTH), Felix Ryde (KTH).
Postdocs: Magnus Axelsson (SU), Miranda Jackson (KTH).
PhD students: Mózsi Kiss (KTH), Cecilia Marini Bettolo (KTH).
Engineering support: Stefan Rydström (KTH), H-G. Florén (SU), Pau Mallol (KTH)

We collaborate with Nikolay Ivchenko from the KTH Alfvén Lab on studies of X-ray auroral backgrounds.We regularly host Master's students, and their theses are listed below.

Selected publications / talks

M. Pearce, M. Jackson, et al., "PoGOLite - a high sensitivity balloon-borne soft gamma-ray polarimeter". IEEE Nuclear Science Symposium, Orlando, USA, 25-31 October 2009. [poster] [paper]
M. Pearce. "PoGOLite - a high sensitivity balloon-borne soft gamma-ray polarimeter". The coming age of X-ray polarimetry, Rome, April 2009. [talk] [paper]
M. Kiss. "Studies of neutron background rejection in the PoGOLite balloon-borne polarimeter". The coming age of X-ray polarimetry, Rome, April 2009.
M. Jackson. "Pre-flight tests of the PoGOLite detector system". The coming age of X-ray polarimetry, Rome, April 2009.
M. Axelsson. "Observing polarised X-rays with PoGOLite". The coming age of X-ray polarimetry, Rome, April 2009.
T. Mizuno et al., "A Monte Carlo method for calculating the energy response of plastic scintillators to polarized photons below 100 keV". Nucl. Instr. and Meth. A 600 (2009) 609.
M. Pearce, "PoGOLite - a high sensitivity balloon-borne soft gamma-ray polarimeter". IEEE Nuclear Science Symposium, Dresden, Germany. October 2008.
C. Marini Bettolo. "The PoGOLite star tracker system". IEEE Nuclear Science Symposium, Dresden, Germany. October 2008.
W. Klamra. "Performance of BGO crystals for the PoGOLite gamma-ray polarimeter". IEEE Nuclear Science Symposium, Dresden, Germany. October 2008.
T. Kamae et al., "PoGOLite - A High Sensitivity Balloon-borne Soft Gamma-ray Polarimeter". Astroparticle Physics 30 (2008) 72. arXiv:0709.1278v2
M. Kiss, "The PoGOLite balloon-borne soft gamma-ray polarimeter. Proc. Cool discs, hot flows: The varying faces of accreting compact objects, Funäsdalen, Sweden, March 2008. AIP proceedings series, to appear.
PoGO ska studera röntgenstrålning på ett nytt sätt, ESA news item, 6th September 2007.
M. Kiss, ‘The PoGOLite balloon-borne soft gamma-ray polarimeter’. Proc. International Conference on Advanced Technology and Particle Physics (ICATPP), Como, Italy, October 2007. World Scientific.
M. Pearce et al., "PoGOLite: a balloon-borne soft gamma-ray polarimeter". Proceedings of 30th International Cosmic Ray Conference, Mérida, Mexico. June 2007. [talk]
C. Marini Bettolo et al., "The BGO anticoincidence system of the PoGOLite balloon-borne soft gamma-ray polarimeter". Proceedings of 30th International Cosmic Ray Conference, Mérida, Mexico. June 2007. [poster]
S. Larsson et al., "Studies of Auroral X-ray Backgrounds for high latitude balloon astrophysics experiments". Proc. Proc. 18th ESA Symposium on European Rocket and Balloon Programmes and Related Research. Visby, Sweden. 3-7 June 2007. [talk] [related interview]
T. Mizuno et al., "High Sensitivity Balloon-Borne Hard X-Ray/Soft Gamma-Ray Polarimeter PoGOLite". Submitted (summary) to IEEE Nuclear Science Symposium, Honolulu, Hawaii. October 2007.
T. Tanaka et al., "Data Acquisition System for the PoGOLite astronomical hard X-ray polarimeter". Submitted (summary) to IEEE Nuclear Science Symposium, Honolulu, Hawaii. October 2007.
M. Axelsson et al., "Measuring energy dependent polarisation in soft gamma-rays using Compton scattering in PoGOLite". astro-ph/07041603. Astroparticle Physics 28 (2007) 327. [newsflash]
M. Kiss and M. Pearce, "PoGOLite: Opening a new window on the Universe with polarised gamma-rays". Proceedings of 'Imaging 2006', Stockholm, June 2006. Nucl. Instr. and Meth. A.
F. Ryde, Stefan Larsson, Nickolay Ivchenko, and Mark Pearce, "Auroral X-ray emission". November 2006. Internal note.
Y. Kanai et al., "Beam test of a prototype phoswich detector assembly for the PoGOLite astronomical soft gamma-ray polarimeter". Nucl. Instr. and Meth. A570 (2007) 61.
J. Kataoka et al., ‘Low energy response of a prototype detector array for the PoGO Astronomical Hard X-ray Polarimeter’. Proc. Photonics for Space Environments X. SPIE, Volume 5898 (2005).
V. Andersson et al., "Large area balloon-borne polarised gamma-ray observer (PoGO)". Proceedings of the 22nd Symposium on Relativistic Astrophysics at Stanford University, December 2004.
Stefan Larsson and Mark Pearce, "PoGO: The polarised gamma-ray observer". Nucl. Instr. and Meth. A 525 (2004) 148. Proceedings of 'Imaging 2003', Stockholm, June 2003. Nucl. Instr. and Meth. A.

Postgraduate Theses

C. Marini Bettolo, licentiate thesis (April 2008).
M. Kiss, licentiate thesis (June 2008).

Master's Theses

Nick Barkas, in progress (2009)
Pau Mallou, KTH, 'A cooling system for PoGOLite - a balloon-borne soft gamma-ray polarimeter' (2009).
Daniel Walldin, in progress (2009).
Erik Brandrup-Wognsen, in progress (2009).
Kristoffer Myrsten, KTH, 'PoGOLite pathfinder experiment: neutron shield design and limits on polarisation measurements' (2008).
Jaroslav Kazejev, KTH, 'Neutron background studies for PoGOLite' (2007).
Tomas Ekeberg, KTH, 'Polarimetry measurements with the PoGOLite prototype and simulations of polarisation in inverse Compton scattering processes' (2007).
Bianca Iwan, KTH, 'Development of the PoGOLite Star Tracker System and construction of detector units for the Polarimeter Telescope Assembly' (2007).
Olle Engdegård, KTH/SU, 'Studies of energy dependent polarisation with PoGOLite' (2006).
Mózsi Kiss, KTH, 'Construction and laboratory tests of the PoGOLite prototype' (2006).
Tomi Ylinen, KTH, 'Constrcution and accelerator-based tests of the PoGOLite prototype' (2006).
Viktor Andersson, KTH, 'Tests of scintillators and PMTs for the Polarised Gamma-ray Observer (PoGO)' (2005).
Markus Suhonen, KTH, 'Tests of PoGO calorimeters' (2003).

If you are interested in performing your Master's Thesis on PoGOLite, please contact Mark Pearce.

Funding

Our participation in PoGOLite was made possible through a substantial grant in 2005 from The Knut and Alice Wallenberg Foundation. We receive programmatic support from The Swedish National Space Board, who also fund the pathfinder flight in 2010. The Swedish Research Council (Committee for research infrastructure) funds our work on the attitude control and gondola systems. Several PoGOLite team members receive support ('friköp') from The Swedish Research Council or The Swedish National Space Board. The Göran Gustafsson Foundation is funding work on the star tracker systems.

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