Development of microcalorimeters for observing large-scale motion in the universe

我们正在开发高能量分辨率的X射线微量热计，以观察宇宙中扩展的热等离子体的X射线发射，并研究它们的动力学演化。我们已经提出了一项专门的小型X射线任务，利用带有TES微热量计阵列的氧发射线来探测温热的星际介质。我们与早稻田大学、精工仪器和三菱重工合作开发了TES微卡尺阵列。对于单像素TES，我们获得了~6 eV的能量分辨率，接近世界纪录。研究了其性能，包括噪声和灵敏度对电流和磁场的依赖性。发展了锡或铋的电沉积技术，并成功地在TES微量热计上制作了蘑菇状的X射线吸收元件。要获得大的填充因子、足够的量子效率和均匀的响应，这是天文应用的强烈要求。热容低、升温快、Z值高的材料适合作为吸收塔，因此选择了锡或铋。我们最近制作了256个像素的阵列传感器的测试模型，成功地产生了X射线信号。我们还开发了一种小型绝热退磁制冷系统，能够在实验室外进行微量热计测试。另一种新型仪器，磁力量热计，也被开发出来，可以产生5.5 MeV阿尔法粒子的信号。

We are developing high-energy-resolution X-ray microcalorimeters to observe X-ray emission from extended hot plasmas in the universe and to study their dynamical evolution. We have proposed a dedicated small X-ray mission to survey warm-hot intergalactic medium using oxygen emission lines with an array of TES microcalorimeters. We developed TES microcalonmeter array in collaboration with Waseda University, Seiko Instruments and Mitsubishi Heavy Industory. For a single pixel TES, we achieved energy resolution of 〜6 eV, close to the world record. Its performance including noise- and sensitivity-dependence on current and magnetic field was investigated. The electrodeposition technique of Sn or Bi was developed, and we successfully fabricated mushroom-shaped X-ray absorbers on TES microcalorimeters as an pixel array. It is essential to achieve large filling factor, adequate quantum efficiency, and uniform response, which is strongly required for the astronomical applications. Low heat capacity, fast thermalization, and high-Z material is suitable for an absorber, so that Sn or Bi are chosen. We recently fabricated a test model of the array sensor with 256 pixels, which produced X-ray signals successfully. We also developed a small adiabatic demagnetization refrigerator system capable for microcalorimeter testings outside of our laboratory. Another new type of instrument, magnetic calorimeters, was also developed and produced signals to 5.5 MeV alpha particles.