Browsing by Author "Kelley, Richard L."
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Item Characterization of a hybrid array of single and multi-absorber transition-edge sensor microcalorimeters for the Line Emission Mapper(SPIE, 2023-10-20) Wakeham, Nicholas; Adams, Joseph S.; Bandler, Simon R.; Chervenak, James A.; Cumbee, Renata S.; Finkbeiner, Fred M.; Fuhrman, Joshua; Hull, Samuel V.; Kelley, Richard L.; Kilbourne, Caroline A.; Sakai, Kazuhiro; Smith, Stephen J.; Wassell, Edward J.; Yoon, Sang H.The Line Emission Mapper (LEM) is a proposed x-ray probe mission to study the physics of galaxy formation through spectral and spatial measurements of x-rays in the energy band of 0.2 to 2 keV. The LEM Microcalorimeter Spectrometer instrument on LEM will have a hybrid transition-edge sensor (TES) microcalorimeter array made up of an inner array of single-pixels with one x-ray absorber connected to one TES and an outer array of multi-absorber microcalorimeters, or “hydras,” with four absorbers connected to a single TES, each with a different thermal conductance. Here, we characterize the first hybrid array of single-pixel and multi-absorber microcalorimeters designed for LEM. We present the fundamental transition, noise, and detector performance properties to demonstrate their suitability for the mission. We also show that the spectral resolution at the Al Kα line is 1.92 ± 0.02 eV for the 4-pixel hydra (coadded) and 0.90 ± 0.02 eV for the single-pixels. This is significantly better resolution than the LEM mission level requirement. Finally, we demonstrate that the position discrimination between the four pixels of the hydra can be achieved down to 200 eV when measured with a time-division multiplexed readout using timings representative of the anticipated LEM requirements.Item Extended Line Spread Function of TES Microcalorimeters With Au/Bi Absorbers(IEEE, 2019-03-06) Eckart, Megan E.; Adams, Joseph S.; Bandler, Simon R.; Beaumont, Sophie; Chervenak, James A.; Datesman, Aaron M.; Finkbeiner, Fred M.; Hummatov, Ruslan; Kelley, Richard L.; Kilbourne, Caroline A.; Leutenegger, Maurice A.; Miniussi, Antoine R.; Moseley, Samuel J.; Porter, F. Scott; Sadleir, John E.; Sakai, Kazuhiro; Smith, Stephen J.; Wakeham, Nicholas; Wassell, Edward J.Microcalorimeters have the potential to provide line shapes well described by a single Gaussian broadening term of few-eV width. This attribute makes the detectors especially well suited for x-ray astrophysics observations; however, low-level non-Gaussian broadening terms are expected and must be characterized. These terms depend on the composition of the x-ray absorber, the detailed x-ray absorption physics, the device thermalization processes, and the incident x-ray energy. Here we present the first measurements targeted at understanding the extended line-spread function (LSF) of x-ray microcalorimeter pixels under development for the X-ray Integral Field Unit on the Athena X-ray Observatory. These pixels are composed of Mo/Au transition-edge sensors with overhanging electroplated Au/Bi absorbers. We have measured the line shapes using monochromatic x-ray sources with <1-eV width at several x-ray energies (0.85, 0.93, 1.25, 1.5, 5.4, and 8.0 keV) across the instrument bandpass (0.3–12 keV) and have modeled the line profiles. These results are compared to the extended LSF of the Hitomi microcalorimeter pixels that used HgTe absorbers.Item Hitomi (ASTRO-H) X-ray Astronomy Satellite(SPIE, 2018-03-13) Takahashi, Tadayuki; Kokubun, Motohide; Mitsuda, Kazuhisa; Kelley, Richard L.; Pottschmidt, Katja; et alThe Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month.Item Multiabsorber transition-edge sensors for x-ray astronomy(SPIE, 2019-04-08) Smith, Stephen J.; Adams, Joseph S.; Bandler, Simon R.; Chervenak, James A.; Datesman, Aaron M.; Eckart, Megan E.; Finkbeiner, Fred M.; Hummatov, Ruslan; Kelley, Richard L.; Kilbourne, Caroline A.; Miniussi, Antoine; Porter, Frederick S.; Sadleir, John E.; Sakai, Kazuhiro; Wakeham, Nicholas; Wassell, Edward J.We are developing arrays of position-sensitive microcalorimeters for future x-ray astronomy appli cations. These position-sensitive devices commonly referred to as hydras consist of multiple x-ray absorbers, each with a different thermal coupling to a single-transition-edge sensor microcalorimeter. Their development is motivated by a desire to achieve very large pixel arrays with some modest compromise in performance. We report on the design, optimization, and first results from devices with small pitch pixels (<75 μm) being developed for a high-angular and energy resolution imaging spectrometer for Lynx. The Lynx x-ray space telescope is a flagship mission concept under study for the National Academy of Science 2020 decadal survey. Broadband full-width-half-maximum (FWHM) resolution measurements on a 9-pixel hydra have demonstrated ΔEFWHM ¼ 2.23 0.14 eV at Al-Kα, ΔEFWHM ¼ 2.44 0.29 eV at Mn-Kα, and ΔEFWHM ¼ 3.39 0.23 eV at Cu-Kα. Position discrimination is demonstrated to energies below <1 keV and the device performance is well-described by a finite-element model. Results from a prototype 20-pixel hydra with absorbers on a 50-μm pitch have shown ΔEFWHM ¼ 3.38 0.20 eV at Cr-Kα1. We are now optimizing designs specifically for Lynx and extending the number of absorbers up to 25/hydra. Numerical simulation suggests optimized designs could achieve ∼3 eV while being compatible with the bandwidth requirements of the state-of-the art multiplexed readout schemes, thus making a 100,000 pixel microcalorimeter instrument a realistic goal.Item Thermal Crosstalk Measurements and Simulations for an X-ray Microcalorimeter Array(Springer, 2020-01-18) Miniussi, Antoine R.; Adams, Joseph S.; Bandler, Simon R.; Beaumont, Sophie; Chang, Meng P.; Chervenak, James A.; Finkbeiner, Fred M.; Ha, Jong Y.; Hummatov, Ruslan; Kelley, Richard L.; Kilbourne, Caroline A.; Porter, Frederick S.; Sadleir, John E.; Sakai, Kazuhiro; Smith, Stephen J.; Wakeham, Nicholas A.; Wassell, Edward J.Arrays of high-density microcalorimeters require careful heat sinking in order to minimize the thermal crosstalk between nearby pixels. For the array of microcalorimeters developed for the Athena X-ray Integral Field Unit instrument, which has more than 3000 pixels on a 275 µm pitch, it is essential to address this problem in order to meet the energy-resolution requirements. The instrument’s energy-resolution budget requires that the impact of the thermal crosstalk on the energy resolution be a contribution that, added in quadrature to other energy-resolution contributions, is less than 0.2 eV. This value results in a derived requirement that the ratio between the amplitude of the crosstalk signal to an X-ray pulse (for example at 6 keV) is less than 1 × 10−3 (for the first neighbor), less than 4 × 10−4 (for the diagonal neighbor) and less than 8 × 10−5 (for the second nearest neighbor). We have measured the thermal crosstalk levels between pixels in various geometries and configurations. The results show a crosstalk ratio which is at least a factor of 4 lower than the derived requirement. We also developed a finite element (FEM) 2D thermal model to predict the thermal behavior of large-scale arrays. This model successfully simulates the measured data in terms of pulse amplitude and time constants.Item Thermal Impact of Cosmic Ray Interaction with an X-Ray Microcalorimeter Array(Springer Nature Switzerland AG., 2020-02-13) Miniussi, Antoine R.; Adams, Joseph S.; Bandler, Simon R.; Beaumont, Sophie; Chang, Meng P.; Chervenak, James A.; Finkbeiner, Fred M.; Ha, Jong Y.; Hummatov, Ruslan; Kelley, Richard L.; Kilbourne, Caroline A.; Porter, Frederick S.; Sadleir, John E.; Sakai, Kazuhiro; Smith, Stephen J.; Wakeham, Nicholas A.; Wassell, Edward J.The X-ray Integral Field Unit (X-IFU) instrument on the Athena mission will be positioned at the Lagrangian point L2 and be subject to cosmic rays generated by astrophysics sources, primarily relativistic protons. Previous simulations have shown that particles of energy higher than 150 MeV will make it through the outer layers of the satellite. They will reach the detector wafer with a rate of 3 cts cm⁻² s⁻¹ and a most probable energy deposited in the Si frame supporting the array at 150 keV. These events can affect the energy resolution of the detectors through the thermal fluctuations that they produce. This study assesses this potential problem and discusses two suggested design approaches to decrease the impact of cosmic ray in order to limit their effect to their allocation of 0.2 eV within the Athena/X-IFU energy-resolution budget. The first is the addition of a coating layer of high heat capacity material (e.g., Pd) and the second is the splitting of this coating into two thermal regions near the TES array to keep the heat away from the array. Implementing these two features is predicted to cause a decrease in the number of events above 1 µK by more than a factor 10 to ~ 1.5 cps when compared to an equivalent design without these features.