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Precise measurement of neutron beta decay tests predictions of the Standard Model of electroweak interaction. The coefficient a of the antineutrino/electron angular correlation is determined by measuring the energy spectrum of the recoil protons generated in the neutron beta decay. A proton spectrometer required for this measurement demands high detection efficiency, high energy resolution and a large detection area. We have begun development of a transition edge sensor (TES) microcalorimeter for use as a low energy particle detector. To realize the large detection area we have designed a pixelated TES array incorporating a parallel biasing scheme. Our TES device consists of 4-pixels using a Au/Ti/Au trilayer film adjusted to a superconducting transition temperature of Tc ~ 380 mK. This temperature is convenient for use in a 3He cryostat with a pulse tube refrigerator. The Au films improve thermal conductivity, thereby reducing position dependent effects and allow an increased detector area.