Noise and Signal Analysis of Ir/Au TES With Asymmetrical Slits Parallel to the Electric Current
A multi-pixel TES array is one of the attractive methods to read-out the incident x-ray position, which simplifies a read-out circuit for imaging applications. We fabricated a ten-pixel Ir/Au TES microcalorimeter with asymmetrical slits parallel to the electric current, and analyzed its noise and signal characteristics. The device was successfully operated in a strong electro-thermal feedback (ETF) mode. However, very large excess noise is observed, which cannot be explained by the noise theory for a single pixel TES. We have modeled the multi-pixel TES array as separated thermal group components, and analyzed noise performance theoretically. As a result, the current noise in our theory is well agreed with the measured noise at a low frequency below 3 kHz. From the x-ray irradiation measurements, ten divided signal groups are observed, which will be associated with the incident x-ray position pixel. The best energy resolution was 18 eV (FWHM) for 5.9 keV x-rays at 0.5 μV bias voltage.