Generation of flat-laser Compton scattering γ -ray beam

Abstract

To develop an isotope selective computed tomography imaging technique, a flat-laser Compton scattering γ-ray beam (F-LCS) by using a helical undulator installed in a storage ring has been proposed. An LCS beam with a broad energy spectrum and spatial distribution, keeping a small beam size, is preferable for multi-isotope imaging and qualitative evaluation. egs5 simulations assuming the BL1U beamline in UVSOR have been carried out and the result shows that the energy bandwidth of the LCS beam is widened from 2.7% to 22% (FWHM) with a beam size of 2 mm in diameter by varying the undulator K value from 0 to 0.4. A proof of principle (POP) experiment has been carried out in the BL1U, where the APPLE-II undulator has been installed. The K value dependency of the energy spectrum of the generated LCS beam was measured. As a result, a broader energy bandwidth of the LCS beam was observed as the undulator K value increased. The measured energy spectra agreed with the egs5 results.