Fabrication process responsible for fundamentally improving Silicon X-ray microcalorimeter arrays

We have developed an improved microcalorimeter array that will be used on the AstroE-2 satellite mission. The 6×6 array consists of a grid of 36 suspended pixels. Each 1.5μm thick pixel has an ion-implanted thermometer, four thermal links (support beams), and four X-ray absorber support tabs. Improvements in Silicon micro-machining capabilities and the availability of custom Silicon-on-Insulator (SOI) wafers has enabled us to precisely control pixel geometry, lead widths, and develop a more compact array. Knowing the silicon thickness, we can calculate a precise implant dose for the thermometer. Using a high-temperature anneal, we can uniformly diffuse the implant throughout the depth of the top layer of the SOI wafer. Defining the length, width, and thickness of the support beams, we can control the thermal conductance of the pixel. Advancements in polymer-photo resists have enabled us to develop a new absorber support tab attachment scheme resulting in more controlled heat dissipation from the absorber to the thermometer on the pixel. An overview of fabrication improvements focusing on these topics will be discussed

Laboratory Astrophysics Using a Spare XRS Microcalorimeter

The XRS instrument on Astro-E is a fully self-contained microcalorimeter x-ray instrument capable of acquiring optimally filtering, and characterizing events for 32 independent pixels. With the launch of the Astro-E spacecraft, a full flight spare detector system has been integrated into a laboratory cryostat for use on the electron beam ion trap (EBIT) at Lawrence Livermore National Laboratory. The detector system contains a microcalorimeter array with 32 instrumented pixels heat sunk to 60 mK using an adiabatic demagnetization refrio,erator. The instrument has a composite resolution of 8eV at 1 keV and 12eV at 6 keV with a minimum of 95% quantum efficiency. This will allow high spectral resolution, broadband observations of collisionally excited plasmas which are produced in the EBIT experiment. Unique to our instrument are exceptionally well characterized 1000 Angstrom thick aluminum on polyimide infrared blocking filters. The detailed transmission function including the edc,e fine structure of these filters has been measured in our laboratory using an erect field grating spectrometer. This will allow the instrument to perform the first broadband absolute flux measurements with the EBIT instrument. The instrument performance as well as the results of preliminary measurements will be discussed. Work performed under the auspices of the U.S. D.o.E. by Lawrence Livermore National Laboratory under contract W-7405-ENG-48 and was supported by the NASA High Energy Astrophysics Supporting Research and Technology Program

The next-generation microcalorimeter array of XRS on Astro-E2

The square-format 32-pixel microcalorimeter array at the focal plane of the high-resolution X-ray spectrometer on the Astro-E2 X-ray Observatory is the first of a new generation of silicon-based microcalorimeters. This array has numerous advantages over its predecessor, the bilinear array that was launched on Astro-E. Foremost among its benefits are: (1) the energy resolution is improved by a factor of two at 6keV (now 6eV FWHM), (2) the thermal time constant is a factor of two faster, and (3) each pixel has a Gaussian line response. We will discuss the design changes that have led to these and other advantages