title: Polarimetry of short-pulse gamma rays produced through inverse Compton scattering of circularly polarized laser beams.
abstract: We have developed a polarimetry of ultrashort pulse gamma rays based on the fact that gamma rays penetrating in the forward direction through a magnetized iron carry information on the helicity of the original gamma rays. Polarized, short-pulse gamma rays of (1.1+/-0.2)x10(6)/bunch with a time duration of 31 ps and a maximum energy of 55.9 MeV were produced via Compton scattering of a circularly polarized laser beam of 532 nm off an electron beam of 1.28 GeV. The first demonstration of asymmetry measurements of short-pulse gamma rays was conducted using longitudinally magnetized iron of 15 cm length. It is found that the gamma-ray intensity is in good agreement with the simulated value of 1.0x10(6). Varying the degree of laser polarization, the asymmetry for 100% laser polarization was derived to be (1.29+/-0.12)%, which is also consistent with the expected value of 1.3%.
authors: Department of Physics, Tokyo Metropolitan University, Minami-Osawa, Hachioji-shi Tokyo 192-0397, Japan.
authors: M
authors: M
authors: Fukuda
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authors: T
authors: Aoki
authors: K
authors: K
authors: Dobashi
authors: T
authors: T
authors: Hirose
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authors: Iimura
authors: Y
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authors: Kurihara
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authors: Okugi
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authors: Omori
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authors: Sakai
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authors: Urakawa
authors: M
authors: M
authors: Washio