X-ray Polarimetry - INAF-IASF-Roma

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A high energy polarimeter originally for NHXM A further focal plane polarimeter for even higher energy based on Compton scattering has been investigated. A photon Compton scatters by a low-Z scintillator and it is absorbed by high-Z detector. Efficiency of LEP, MEP and HEP. LEP efficiency arrive at 10 keV. It is smaller than MEP efficiency that arrives at 35 keV compensating the decreasing mirror efficiency to arrive at a similar sensitivity. The HEP efficiency covers the rest of the energy band where the multilayer optics are effective. Simulated modulation curve for 10 cm length BC404 as scatterer (5 mm diameter) and LaBr 3 as the absorber at 5 cm distance at 35 keV. (Soffitta SPIE 2010) Based on simulation MDP 7.2 % for 10 mCrab in 10 5 s (20-80 keV) Paolo Soffitta The Extreme and Variable High Energy Sky Chia Laguna 19-21/09/2011
For a non focal plane experiment to arrive to a large area for sensitive polarimetry with also energy resolution by using Compton scattering, a subdivided and two phase polarimeter [scatterer (low-Z) and absorber (high-Z)] must be devised. Single PM tube for each 5 cm x 5 cm x 4 cm NA102 scatterer and 7 cm x 1 cm x 9 cm NaI(Tl) absorber 25 %, Modular implementation Phoswich-type collimator. Field of View of 14.5 o Gunji et al., 1994 MDP = 7 % in 5.5 hours in 30-700 keV for Crab • The apparatus is divided in an ar<strong>ray</strong> of small detecting units in form of a fiber-like scintillators. • A photon scattered by a low Z-fiber-like scintillator pass across a number of similar fibers until is absorbed by a high- Z fiber. A good sensitiviity can be reached. Single cell: 37-plastic scintillator fibers (2mm large) pins, 5 cm thick, 24-semi-exagonal sticks (CsI or the faster YAP). The system is made by replicas of such cells. (Costa et al., 1993, 1995) •Far-away fibers are fed to a single channel of a multi-wire PM tube to detect coincidence events. • = 50% . MDP = 1.6 % in 20-200 keV in 5.5 hours for Crab A = 1000 cm 2 . • MDP sensitive the low energy threshold. Paolo Soffitta The Extreme and Variable High Energy Sky Chia Laguna 19-21/09/2011
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X-ray Polarimetry - INAF-IASF-Roma

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