We are developing small-pixel transition-edge sensor microcalorimeters for solar physics and astrophysics applications. These large format close-packed arrays are fabricated on solid silicon ...substrates and are designed to have high energy resolution, and also accommodate count-rates of up to a few hundred counts per second per pixel for X-ray photon energies up to ~ 8 keV. We have fabricated kilo-pixel versions that utilize narrow-line planar and stripline wiring. These arrays have a low superconducting transition temperature, which results in a low heat capacity and low thermal conductance to the heat sink. We present measurements of the performance of pixels with single 65-μm absorbers on a 75-μm pitch. With individual single pixels of this type, we have achieved a full-width at half-maximum energy resolution of 0.9 eV with 1.5 keV Al K X-rays, to our knowledge the first X-ray microcalorimeter with sub-eV energy resolution. We will discuss the properties of these arrays and their application to new solar and astrophysics mission concepts.
The Micro-X sounding rocket program will fly a 128-pixel array of transition-edge-sensor microcalorimeters to enable high-resolution X-ray imaging spectroscopy of supernova remnants. To match the ...angular resolution of the optics while maximizing the field-of-view and retaining a high energy resolution (2-4 eV at 1 keV), we have designed the pixels using 590 × 590 μm 2 Au/Bi absorbers, which overhang 140 × 140 μm 2 Mo/Au sensors. Here we report experimental results from flight-candidate arrays, including measurements of energy resolution, uniformity, and absorber thermalization. We describe the reduction in pixel-to-pixel crosstalk afforded by an angle-evaporated Cu backside heatsinking layer, which provides Cu coverage on the four sidewalls of the silicon wells beneath each pixel. In addition, we present measurements of devices that have an identical pixel architecture but were fabricated with thin (sub-micron) all-Au absorbers.
Athena is a European X-ray observatory, scheduled for launch in 2028. Athena will employ a high-resolution imaging spectrometer called X-ray integral field unit (X-IFU), consisting of an array of ...4000 transition edge sensor (TES) microcalorimeter pixels. For the readout of X-IFU, we are developing frequency domain multiplexing, which is the baseline readout system. In this paper, we report on the performance of a TES X-ray calorimeter array fabricated at Goddard Space Flight Center (GSFC) at MHz frequencies for the baseline of X-IFU detector. During single-pixel AC bias characterization, we measured X-ray energy resolutions (at 6 keV) of about 2.9 eV at both 2.3 and 3.7 MHz. Furthermore, in the multiplexing mode, we measured X-ray energy resolutions of about 2.9 eV at 1.3 and 1.7 MHz.
Arrays of superconducting transition-edge sensors (TES) can provide high spatial and energy resolution necessary for X-ray astronomy. High quantum efficiency and uniformity of response can be ...achieved with a suitable absorber material, in which absorber X-ray stopping power, heat capacity, and thermal conductivity are relevant parameters. Here we compare these parameters for bismuth and gold. We have fabricated electroplated gold, electroplated gold/electroplated bismuth, and evaporated gold/evaporated bismuth 8×8 absorber arrays and find that a correlation exists between the residual resistance ratio (RRR) and thin film microstructure. This finding indicates that we can tailor absorber material conductivity via microstructure alteration, so as to permit absorber thermalization on timescales suitable for high energy resolution X-ray microcalorimetry. We show that by incorporating absorbers possessing large grain size, including electroplated gold and electroplated gold/electroplated bismuth, into our current Mo/Au TES, devices with tunable heat capacity and energy resolution of 2.4 eV (gold) and 2.1 eV (gold/bismuth) FWHM at 5.9 keV have been fabricated.
In a large close-packed array of x-ray microcalorimeters, sufficient heat sinking is important to minimize thermal crosstalk between pixels and to make the bath temperature of all the pixels uniform. ...We have measured crosstalk in our 8 times 8 pixel arrays. The shapes of the thermal crosstalk pulses are reproduced well as a convolution of heat input from the source pixel and the thermal decay in the receiver pixel. The amount of the thermal crosstalk is clearly dependent on the degree of electrothermal feedback. We have compared the magnitude of thermal crosstalk with and without a heat-sinking copper layer on the backside of the silicon frame as a function of distance between the source and receiver pixels. Using the results obtained, we have estimated the degradation of energy resolution that is expected as a function of count rate. We have also studied the temperature distribution within an array due to continuous heating from the TES bias to estimate impacts on the uniformity of the pixel performance.
Mo/Au transition-edge sensors exhibit weak-link behavior in the measured temperature,
T
and field,
B
dependence of the critical current
I
C
(
T
,
B
)
. This is a consequence of the longitudinal ...proximitization between the Nb electrical bias contacts and the bilayer. Understanding how weak-link superconductivity impacts the resistive transition and the detector energy resolution is of great interest. In this contribution we present studies of
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C
(
T
,
B
)
for three devices that have different geometries of metallic depositions on top of the sensor used for noise mitigation and X-ray absorption. Results show that these features change the measured
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C
(
T
,
B
)
compared to the previously seen measurements on devices without additional deposition layers. Measurements of the small signal transition parameters
α
and
β
also reveal differences between designs that impact the measured response to X-rays and energy resolution.
Episialin, which is found on the apical membrane of human endometrial epithelium, has been postulated to act as an antiadhesive factor through the steric hindrance generated by its extensively ...glycosylated structure. The present studies were designed to test this hypothesis in an in vitro model of endometrial-blastocyst attachment. Episialin was expressed in human endometrial carcinoma cells (HEC-1A > RL95-2), and attachment of JAr choriocarcinoma cells to the endometrial cell monolayers was inversely related to episialin expression. Treatment of endometrial monolayers with type III sialidase increased JAr binding, and this increase was suppressed by HMFG1, a monoclonal antibody specific for episialin. The effects of sialidase appear to have resulted from a contaminant protease rather than from a loss of sialic acid residues, because sialidase preparations other than type III were ineffective. After sialidase treatment, conditioned medium from cells treated with type III sialidase contained more episialin than medium from cells treated with other sialidase preparations. Similar attachment-assay results were obtained using O-sialoglycoprotein endopeptidase; after treatment, the increase in JAr binding (>50%) was suppressed by the antiepisialin antibody. These results demonstrate for the first time that episialin acts as an antiadhesive agent in a model of human endometrial-blastocyst attachment.
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