Science with Micro-X: the TES Microcalorimeter X-ray Imaging Rocket

Micro-X is a proposed sounding rocket experiment that will combine a transition-edge-sensor X-ray-microcalorimeter array with a conical imaging mirror to obtain high-spectral-resolution images of extended and point X-ray sources. We describe the payload and the science targeted by this mission including the discussion of three possible Micro-X targets: the Puppis A supernova remnant, the Virgo Cluster, and Circinus X-1. For example, a Micro-X observation of the bright eastern knot of Puppis A will obtain a line-dominated spectrum with 90,000 counts collected in 300 seconds at 2 eV resolution across the 0.3-2.5 keV band. Micro-X will utilize plasma diagnostics to determine the thermodynamic and ionization state of the plasma, to search for line shifts and broadening associated with dynamical processes, and seek evidence of ejecta enhancement. For clusters of galaxies, Micro-X can uniquely study turbulence and the temperature distribution function. For binaries, Micro-X's high resolution spectra will separate the different processes contributing to the Fe K lines at 6 keV and give a clear view of the geometry of the gas flows and circumstellar gas

Using ion implantation to adjust the transition temperature of superconducting films

We summarize a continuing investigation into using ion implantation to alter the transition temperature of superconducting thin films. The primary motivation for the work presented here was to study the feasibility of using magnetic ion doping to replace the bi-layer Tc control process currently used for certain cryogenic detector applications at National Institute for Standards and Technology. The results from work with various ion species implanted into aluminum, molybdenum, titanium and tungsten host films are presented

High-resolution calorimetry: limitations of doped semiconductor thermometers

Small thermal calorimeters operating at cryogenic temperatures have achieved an energy resolution for single X-ray photons that is a factor of 20 better than the theoretical limit for a silicon ionization detector. To determine the potential for further improvements and decide on likely routes for achieving them, we discuss detector design optimization, first for an ideal calorimeter, and then for the case where components exhibit non-ideal behavior. Two serious non-ideal properties of doped semiconductor thermometers are electron–phonon decoupling and excess noise. These have been characterized over a range of sensitivity and operating temperature, and their effects on design optimization and ultimate performance can be evaluated

Distributed Transition Edge Sensors for Linearized Position Response in a Phonon-Mediated X-ray Imaging Spectrometer

For future solar X-ray satellite missions, we are developing a phonon-mediated macro-pixel composed of a Ge crystal absorber with four superconducting transition-edge sensors (TES) distributed on the backside. The X-rays are absorbed on the opposite side and the energy is converted into phonons, which are absorbed into the four TES sensors. By connecting together parallel elements into four channels, fractional total energy absorbed between two of the sensors provides x-position information and the other two provide y-position information. We determine the optimal distribution for the TES sub-elements to obtain linear position information while minimizing the degradation of energy resolution

Recent Developments in Transition-Edge Strip Detectors for Solar X-Rays

LMSAL and NIST are developing position-sensitive x-ray strip detectors based on Transition Edge Sensor (TES) microcalorimeters optimized for solar physics. By combining high spectral (E/ delta E approximately equals 1600) and temporal (single photon delta t approximately equals 10 micro s) resolutions with imaging capabilities, these devices will be able to study high-temperature (>l0 MK) x-ray lines as never before. Diagnostics from these lines should provide significant new insight into the physics of both microflares and the early stages of flares. Previously, the large size of traditional TESs, along with the heat loads associated with wiring large arrays, presented obstacles to using these cryogenic detectors for solar missions. Implementing strip detector technology at small scales, however, addresses both issues: here, a line of substantially smaller effective pixels requires only two TESs, decreasing both the total array size and the wiring requirements for the same spatial resolution. Early results show energy resolutions of delta E(sub fwhm) approximately equals 30 eV and spatial resolutions of approximately 10-15 micron, suggesting the strip-detector concept is viable

Micro-X: Mission Overview and Science Goals

Micro-X, the High-Resolution Microcalorimeter X-ray Imaging Rocket, is a sounding rocket space telescope that will combine a transition-edge-sensor (TES) X-ray microcalorimeter array with a conical imaging mirror to obtain high spectral resolution images of extended and point X-ray sources. Microcalorimeters measure the energy of an absorbed photon by sensing the increase in temperature of the sensor from the thermalization of the absorbed photon’s energy. The advantages and scientific promise of this technology have fueled active development for the past 20 years. We will leverage this development and take the next step by producing a flight-qualified system that will serve as a pathfinder for future missions. Our scientific program will initially focus on extended sources, for which our high-spectral-resolution observations have distinct advantages over other technologies. For our initial flight, we will observe the bright eastern knot in the Puppis A remnant, a site of complex cloud-shock interactions and ejecta enrichment. A Micro-X observation of the bright eastern knot of Puppis A will obtain a line-dominated spectrum with 90,000 counts collected in 300 seconds at 2 eV resolution across the 0.3–2.5 keV band