Response of a superconducting transition-edge sensor microcalorimeter with a mushroom-shaped absorber to L X-rays emitted by transuranium elements

Maehata, Keisuke*; Maeda, Makoto  ; Iyomoto, Naoko*; Ishibashi, Kenji*; Nakamura, Keisuke  ; Aoki, Katsunori ; Takasaki, Koji  ; Mitsuda, Kazuhisa*; Tanaka, Keiichi*

A four-pixel-array superconducting transition-edge sensor (TES) microcalorimeter with a mushroom-shaped absorber was fabricated for the energy dispersive spectroscopy performed on a transmission electron microscope. The TES consists of a bilayer of Au/Ti with either a 120-nm or 50-nm thickness. The absorber of 5.0 m thick is made from a Au layer and its stem is deposited in the center of the TES surface. A TaO insulating layer of 100-nm thickness is inserted between the overhang region of the absorber and the TES surface. A selected pixel of the TES microcalorimeter was operated for the detection of L X rays emitted from an Am source. A response of the TES microcalorimeter to L X rays was obtained by analyzing detection signal pulses with using the optimal filter method. An energy resolution was obtained to be 33 eV of the full width at half maximum value at 17.751 keV. Response to L X rays emitted from a mixture source of Pu, Pu and Am was obtained by operating the selected pixel of the TES microcalorimeter Major L X-ray peaks of progeny elements of decay of Pu and Am isotopes were clearly identified in the obtained energy spectrum. The experimental results demonstrated the separation of Am and plutonium isotopes by L X-ray spectroscopy.