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Purpose An estimated 377 million diagnostic and interventional radiological exams are performed annually in the United States and approximately 4 to 5 billion globally. All use x-ray tubes that emit x-rays over a broad energy band, a technology that is more than a century old. Only a small fraction of the radiation is useful for imaging while the remaining fraction either increases the radiation dose received by the patient or degrades the image. Monochromatic x-rays can provide lower dose images in many of these radiological applications while maintaining or improving image quality. We report the development of the first monochromatic x-ray source suitable for low-dose, high-quality imaging in the clinic and demonstrate its first application and performance with mammography phantoms. Methods X-ray fluorescence was used to generate monochromatic x-rays with selectable energies from 18 to 60 keV. This patented technology was incorporated into a laboratory prototype of a monochromatic x-ray mammography system. Image quality was evaluated as a function of radiation dose in standard breast phantoms using the signal-to-noise ratio (SNR) measured for high and low contrast masses and microcalcifications. Spatial imaging properties were assessed from these images as well as from modulation transfer function (MTF) analysis. Measurements using an iodine contrast agent were also performed. The results were compared to those obtained using a commercially available, conventional x-ray mammography system. Results Our prototype system reduced radiation dose by factors of five to ten times for the same SNRs as obtained from the conventional system. This performance was demonstrated in phantoms simulating a wide range of lesion sizes and microcalcifications in a variety of breast thicknesses. The high SNRs for very thick breast phantoms provide evidence that screening with less breast compression is possible while maintaining image quality. Contrast-enhanced digital mammography (CEDM) with monochromatic x-rays was shown to provide a simpler and more effective technique at substantially lower radiation dose. The MTF value at 20% was 9 lp/mm. Conclusions The monochromatic x-ray system is more sensitive for imaging a wide range of breast sizes and compositions than conventional broadband mammography. High image quality and lower dose are its hallmarks. It also makes CEDM much more effective than current methods developed for use with conventional broadband mammography systems.

This paper reports recent advances in our microcalorimeter spectrometer that result in an energy resolution of 3.1 eV FWHM for 6 keV X-rays. We have developed a detailed model that indicates that further minor improvements will realize 2 eV FWHM at 6 keV and well under 2 eV at 1 keV. The results demonstrate the value of the microcalorimeter for many applications where a premium exists for very fine resolution in the 0.2–10 keV energy band.

An EBIT can selectively create, in principle, any charge state of every naturally occurring element, has good control on atomic collision processes, and can produce nearly ideal conditions for the analysis of highly ionized plasmas of astrophysical importance. A microcalorimeter enables the broadband detection of x-ray emission with high energy resolution and near-unity quantum efficiency in the energy range wherein many cosmic x-ray sources emit the bulk of their energy (0.2 keV–10 keV). The combination (EBIT+ microcalorimeter) provides a powerful tool for laboratory studies of the atomic/plasma processes underlying the energy release mechanisms in cosmic x-ray sources. We briefly describe some early experiments with a microcalorimeter built by the Smithsonian Astrophysical Observatory (SAO) and deployed on the NIST EBIT. We also present some very recent observations with a more advanced microcalorimeter built by SAO that can obtain an energy resolution of 4.5 eV. The higher spectral quality produced by the new system will be useful in laboratory measurements of interest in x-ray astronomy.

We discuss how the sensitivity to the position of absorption of the photons can affect the spectral resolution of X-ray microcalorimeters with superconducting Sn absorber and NTD-Ge thermal sensor. Data obtained through the computer simulations are reported for microcalorimeters with different geometries and phonon transmission probabilities at the interface between the absorber and thermistor.

Long-living quasiparticles can pile-up in a superconducting absorber of an X-ray microcalorimeter when photons are detected at high count rate. These quasiparticles can give a non-negligible contribution to the total heat capacity of the detector thus affecting the pulse height spectrum of detected photons. We investigated this effect with numerical simulations and evaluated the resulting spectral broadening as a function of the photon absorption rate, and the heat capacity of the detector for a NTD germanium microcalorimeter with pure Sn absorber.

The importance of the combination of electron beam ion trap (EBIT) spectroscopy with X-ray microcalorimeters in the field of astrophysics was discussed. X-ray astronomy involves heavily charged ion instruments , especially EBIT, to obtain improved quality atomic data. In this regard, the research program at the National Institute of Standards and Technology, which uses X-ray spectroscopic methods to study plasma and atomic physics, was also discussed.

The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA's scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe Kα region (1100 cm2). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin2 . A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations.

We report new observations of emission line intensity ratios of Fe XVII under controlled experimental conditions, using the National Institute of Standards and Technology electron beam ion trap (EBIT) with a microcalorimeter detector. We compare our observations with collisional-radiative models using atomic data computed in distorted wave and R-matrix approximations, which follow the transfer of the polarization of level populations through radiative cascades. Our results for the intensity ratio of the 2p6 1S0-2p53d 1P1 15.014 A line to the 2p6 1S0-2p53d 3D1 15.265 A line are 2.94 ± 0.18 and 2.50 ± 0.13 at beam energies of 900 and 1250 eV, respectively. These results are not consistent with collisional-radiative models and support conclusions from earlier EBIT work at the Lawrence Livermore National Laboratory that the degree of resonance scattering in the solar 15.014 A line has been overestimated in previous analyses. Further observations assess the intensity ratio of the three lines between the 2p6-2p53s configurations to the three lines between the 2p6-2p53d configurations. Both R-matrix and distorted wave approximations agree with each other and our experimental results much better than most solar and stellar observations, suggesting that other processes not present in our experiment must play a role in forming the Fe XVII spectrum in solar and astrophysical plasmas.

With the ability to create cosmic plasma conditions in the laboratory it is possible to investigate the dependencies of key diagnostic X-ray lines on density, temperature, and excitation conditions that exist in astrophysical sources with X-ray optics and a high-resolution X-ray microcalorimeter. The same instrumentation can be coupled to scanning electron microscopes or X-ray fluorescence probes to analyze the elemental and chemical composition of electronic, biological, geological and particulate materials. We describe how our microcalorimeter and X-ray optics provide significantly improved capabilities for laboratory astrophysics and microanalysis.

Our group has been developing x-ray microcalorimeters consisting of neutron transmutation doped (NTD) germanium thermistors attached to superconducting tin absorbers. We discuss the performance of single pixel x-ray detectors, and describe an array technology. In this paper we describe the read-out circuit that allows us to measure fast signals in our detectors as this will be important in understanding the primary cause of resolution broadening. We describe briefly a multiplexing scheme that allows a number of different calorimeters to be read out using a single JFET. We list the possible causes of broadening and give a description of the experiment which best demonstrates the cause of the primary broadening source. We mention our strategy for finding a suitable solution to this problem and describe briefly a technology for building arrays of these calorimeters.

Broadband, high-resolution x-ray spectra from samples excited by the electron beam of a scanning electron microscope were obtained with an NTD germanium-based microcalorimeter. An energy resolution of 8 eV was used to resolve completely the silicon Kα from the tungsten Mα x-rays. This performance will make it possible to analyze efficiently the composition of thin films and surface contaminants by using low electron excitation energies.

Scanning electron microscope (SEM)-based x-ray analyzers have employed wavelength-dispersive x-ray (WDX) diffractometers or energy-dispersive x-ray (EDX) detectors as the spectrally resolving elements. In spite of their relatively poor energy resolution (ΔE = 130 eV at 6 keV), the solid-state EDX instruments have enjoyed much wider use than the WDX systems (ΔE = 1-10 eV) because of their convenience and efficiency. A microcalorimeter detector with 95% quantum efficiency at 6 keV has been developed that can produce spectra with an energy resolution of 7 eV over the broad energy band of 0.2-20 keV. This performance will advance the state-of-the-art for elemental analysis by virtue of its 20-fold increase in x-ray energy resolution. When coupled to an SEM it will permit the evolution of a new generation of microanalysis tools with greatly improved spatial resolution and increased sensitivity for minor elemental constituents. Since it will allow the SEM to operate at low electron energies, it will provide the ability to identify unambiguously x-ray signatures from a mixture of light and heavy elements. The latest performance of these detectors is presented along with a discussion of how they will eventually improve SEM-based microanalysis for small particle defect review and sub-micron depth studies.

A precise determination of the Lamb shift from photons emitted by highly charged, one electron ions represents one of the most sensitive tests of QED in strong electromagnetic fields. Recent progress in the production and cooling of intense beams of fully stripped Au and U in the SIS/ESR synchrotron storage ring at GSI, Darmstadt has made it possible to obtain precision spectroscopy of these ions. A fully stripped beam of either Au 79+ or U 92+ ions is injected, stored and cooled in the ESR and interacts with an internal gas target. The capture of an electron and the subsequent population of a 2p or 3p state will lead to a decay by either Lyman or Balmer X-ray emission. Although measurements of the 1 s Lamb shift in U with Ge ionization detectors accurate to ∼3% have provided a test of QED for the high Z domain, the experimental errors (±13 eV) are about one order of magnitude larger than the accuracy theoreticians presently claim (±1 eV). We present the results from initial broad band experiments using NTD Ge microcalorimeters to measure the 2 s Lamb Shift in Au and U at the ESR. The broad band coverage of the microcalorimeter makes it possible to reduce the systematic uncertainties in the Doppler corrections while the high-energy resolution reduces the statistical error in the absolute energy calibration.

A high resolution, broad band X-ray microcalorimeter has been used for the first time to investigate the radiative deexcitation of highly charged 7 keV/q Ar 17+ ions as they interact with a beryllium surface at normal incidence. The 20 eV energy resolution of this instrument made it possible to clearly distinguish the argon K α and K β, γ complex simultaneously. The intensity ratio of the K β, γ to K α emission is 31%, compared to the 8% found in the neutral argon atom. There is strong evidence that the relative intensities of the KL n ( n = 1–8) transitions do not agree with those obtained with crystal spectrometers.

A large area microcalorimeter with 95% quantum efficiency at 6 keV has been developed. When fully illuminated, it produces X-ray spectra between 0.5 and 7 keV with an energy resolution of 23 eV. On a smaller, but similar detector, we measure 18 eV. The resolution is obtained at input count rates of 10–50 Hz in real-time with analog pulse processing and thermal pile-up rejection. The detector is incorporated into a compact and portable cryogenic refrigerator system that is ready for use as a tool for analytical spectroscopy.

We are developing a cryogenic dielectric microcalorimeter for X‐ray spectroscopy. This type of detector takes advantage of the temperature dependence of the dielectric permittivity in ferroelectric and pyroelectric materials. It should have many advantages over traditional resistive devices, for example, minimal self heating and the reduction of Johnson noise. Several properties of dielectrics are important to their operation as a microcalorimeter. Here we present the measurements of the dielectric permittivity, ϵ = (δD/δE)T/ ϵ0 and the spontaneous polarization, Ps , for the mixed‐crystal quantum ferroelectric KTa1−xNbxO3 (KTN) with a doping of x = 0.012, as a function of temperature and electric field across the device. Prototype dielectric microcalorimeters have been developed and operated between 4.2 K and 1.3 K. We also show the signal response from infrared LED radiation and a spectrum from an α‐particle source.

The Extreme Physics Explorer (EPE) is a concept timing/spectroscopy mission that would use micro-channel plate optics (MCPO) to provide 4 square meters effective area focused to ~1 arc-min onto an X-ray calorimeter. We describe science drivers for such a mission, possible designs for the large area MCPO needed for EPE, and the challenges of the large area MCPO design., Comment: 12 pages, 9 figures, to appear in proceedings of SPIE V8147, "Optics for EUV, X-ray, and Gamma-Ray Astronomy V"

Superconducting tunnel junction devices are being developed for use as high-resolution, high-efficiency X-ray spectrometers. A device with niobium X-ray absorbing layers coupled to two aluminum layers on either side of the tunneling barrier which serve as quasi-particle traps has been tested. These devices were fabricated photolithographically using a modified niobium/aluminum/niobium trilayer fabrication process. The first devices have a very thin barrier with specific normal state resistance of 1.5*10/sup -6/ Omega -cm/sup 2/, and also exhibit very low leakage current ( >

In response to the Comment written by Zhang et al. [Phys. Rev. A 82, 036701 (2010)] we show that the main ideas and results (about the physics and method) reported in our paper [Phys. Rev. A 79, 062715 (2009)] still appear to be correct. Although none of the conjectures given in the Comment about the potential problems in our code are correct, there was a small error in our code, so the part of our paper with numerical data, presented to support our method, appears to be incorrect. The wealth of resonance features in the x-ray line $3D$ demonstrated in our paper still appears to be real and is reconfirmed by a revised calculation with the error fixed.

The Universe is rich with X-ray sources which can now be observed with unprecedented resolution using instruments on Chandra and XMM-Newton. In order to interpret their spectral signatures and derive reliable information regarding the physical characteristics and the dynamics of these objects and their environments, detailed spectral models have been developed which require vast amounts of highly accurate data on atomic collisional and radiative properties for ions in a broad range of ionization states. These data are usually obtained from theoretical calculations through which a large parameter space of physical conditions such as temperature and density can be explored. Critical to the reliability of these models is the careful benchmarking of the theoretically generated data through high-precision laboratory measurements. To provide a picture of the astrophysics, the goal is to develop a set of key spectroscopic diagnostics with an accuracy ( ∼ 5–10%) that is commensurate with the uncertainties in the highest quality astrophysical spectra. Using a broad band, high resolution X-ray microcalorimeter coupled to an EBIT, we are studying the behavior of highly charged plasma ions. Our goals for accuracy and reliability are now achievable and some of our results are presented here. A new technique for improving the measurement accuracy is also described.

The Stellar X-ray Polarimeter (SXRP) is a focal plane instrument which will be flown on the SPECTRUM-X-Gamma mission in 1993. The polarimeter is composed of two separate instruments: the first exploits the dependence on the polarization of the Bragg reflection from a graphite crystal, and of the Thomson scattering from a metallic lithium target. The second instrument makes use of the recently discovered polarization dependence of X-ray photoemission from CsI. The SXRP will permit sensitive measurements of several classes of galactic X-ray sources, such as X-ray pulsars, black-hole candidates and supernova remnants. Moreover, and for the first time, SXRP will be able to perform highly sensitive measurements of the brightest extragalactic sources.

We have developed a method within the Dirac $R$-matrix theory to calculate x-ray line polarization resulting from electron-impact excitation to excited-state magnetic sublevels of complex ions. We apply this method to the excitation of two well-known x-ray lines of Fe XVII, $3C$ $(\ensuremath{\lambda}=15.015\text{ }\text{\AA{}})$ and $3D$ $(\ensuremath{\lambda}=15.262\text{ }\text{\AA{}})$. We find strong resonance effects which contribute to complicated energy dependence in the polarization. Our results show large differences, up to 30% or more, from earlier theoretical work, and thus provide a stimulus for direct experimental measurement of the $3C$ and $3D$ line polarizations and further theoretical studies.

Superconducting absorbers for thermal X-ray microcalorimeters should convert into thermalized phonons and transfer to the thermal sensor most of the energy deposited by single photons, on a time scale as short as a few tens of microseconds. Since deposition of X-ray energy in a superconductor produces quasiparticles by breaking up of Cooper pairs, the thermalization efficiency depends on the time scale on which they survive within the absorber volume, trapping part of the absorbed energy. According to the predicted values of their microscopic parameters, in many standard type-I superconducting metals the quasiparticle life time at very low temperatures results too long to allow for recombination on the relatively short time scale of the thermal sensors. In type-II superconductors the existence of a mixed state with Abrikosov vortices could speed up the recombination process and increase the efficiency of thermalization. We discuss this topic by presenting experimental results of laboratory tests conducted on tantalum and lead-bismuth absorbers in a comparison with an absorber made of gold, where no trapping is expected.

A new mode of operation for ionization detectors is described. The amount of ionization produced in a detector is determined by measuring the amount of heat generated during the carrier collection process. Very high detection sensitivities, including single carrier detection, may be achieved at cryogenic temperatures. Results from an experimental device operated at T = 0.3 K are presented.

The X‐ray telescopes and spectrometers flown on Chandra and XMM‐Newton are returning exciting new data from a wide variety of cosmic sources such as stellar coronae, supernova remnants, galaxies, clusters of galaxies, active galactic nuclei and X‐ray binaries. To achieve the best scientific interpretation of the data from these and future spectroscopic missions and related ground‐based observations, theoretical calculations and plasma models must be verified or modified by the results obtained from measurements in the laboratory. Such measurements are the focus of several laboratory astrophysics programs that use an electron beam ion trap (EBIT) to simulate astrophysical plasma conditions. Here we describe our recent spectroscopic measurements of neon‐like iron and nickel using a microcalorimeter on the EBIT at the National Institute of Standards (NIST). We obtain values for the intensity ratios of the well‐known lines emitted by these ions and compare the results with new large scale electron‐ion scattering calculations. Additional details about our laboratory astrophysics work can be found in some earlier papers.

We present detailed collisional-radiative modeling for a benchmark x-ray spectrum of highly charged tungsten ions in the range between 3 and $10\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ produced in an electron beam ion trap (EBIT) with a beam energy of $4.08\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$. Remarkably good agreement between calculated and measured spectra was obtained without adjustable parameters, highlighting the well-controlled experimental conditions and the sophistication of the kinetic simulation of the non-Maxwellian tungsten plasma. This agreement permitted the identification of spectral lines from Cu-like ${\mathrm{W}}^{45+}$ and Ni-like ${\mathrm{W}}^{46+}$ ions, led to the reinterpretation of a previously known line in Ni-like ion as an overlap of electric-quadrupole and magnetic-octupole lines, and revealed subtle features in the x-ray spectrum arising from the dominance of forbidden transitions between excited states. The importance of level population mechanisms specific to the EBIT plasma is discussed as well.

We have identified an inexpensive, readily available, mechanically stable, extremely smooth, elastic, and mechanically uniform plastic suitable for thin film X-ray optics. Polyethylene terephthalate (PET) is easily deformed without losing its elastic properties or surface smoothness. Most important, PET can be coated with mono- or multilayers that reflect X-rays at grazing incidence. We have used these properties to produce X-ray optics made either as a concentric nest of cylinders or as a spiral. We have produced accurately formed shells in precisely machined vacuum mandresl or used a pin and wheel structure to form a continuously wound spiral. The wide range of medical, industrial and scientific applications for our technology includes: a monochromatic X-ray collimater for medical diagnostics, a relay optic to transport an X-ray beam from the target in a scanning electron microscop0e to a lithium-drifted silicon and microcalorimeter detectors and a satellite mounted telescope to collect celestial X-rays. A wide variety of mono- and multilayer coatings allow X-rays up to ~100 keV to be reflected. Our paper presents data from a variety of diagnostic measurements on the properties of the PET foil and imaging results form single- and multi-shell lenses.

A single stage Adiabatic Demagnetization Refrigerator (ADR), has been set-up at the X-ray Astronomy Calibration and Testing (XACT) facility of INAF - Osservatorio Astronomico di Palermo G.S. Vaiana, for the development and testing of cryogenic X-ray detectors for laboratory and astrophysical applications. The ADR allows to cool detectors at temperatures below 40 mK and to maintain them at constant operating temperature for many hours. We describe the design and construction of the ADR and present test results and performances.

A hot, magnetized plasma such as the solar corona has the property that much of the physics governing its activity takes place on remarkably small spatial and temporal scales, while the response to this activity occurs on large scales. Observations from SMM, TRACE, SOHO and Yohkoh have shown that typical solar active regions have loops ranging in temperature from 0.5 to 10 MK, and flares up to 40MK. The spatial and temporal domains involved have been heretofore inaccessible to direct observations from Earth, so that theory has relied heavily on extrapolations from more accessible regimes, and on speculation. The RAM Solar-Terrestrial Probe consists of a set of carefully selected imaging and spectroscopic instruments that enable definitive studies of the dynamics and energetics of the solar corona.

Using multilayer coated mirrors to provide high reflectivity at large graze angles, we have proposed to launch a small telescope that is capable of measuring the linear polarization of the soft x-ray fluxes from many astronomical sources. Three identical mirror-detectoer assemblies are designed for maximum efficiency at 0.25 keV, where the photon spectra of many celestial targets peak. In observations lasting 1-3 days using this low risk instrument with proven heritage, we can detect polarizations of 5-10% at 5σ due to Compton scattering or synchrotron processes in the relativistic jets of BL Lac objects, accretion disks or jets in active galactic nuclei and atmospheres of isolated pulsars. Pulsar data can be binned by pulse phase to measure the orientation of the neutron star rotation and magnetic field axes and constrain the mass to radius ratio. This project has been selected for technology development funding by the NASA Explorer Program.

A low-power, successive-approximation, analog-to-digital converter (ADC) for low-rate, low-cost, battery-powered applications is described. The ADC is based on a commercial 50-mW successive-approximation CMOS device (CS5102). An on-chip self-calibration circuit reduces the inherent differential nonlinearity to 7%. A further reduction of the differential nonlinearity to 0.5% is attained with a four-bit Gatti function. The Gatti function is distributed to minimize battery power consumption. All analog functions reside with the ADC, while the noisy digital functions reside in the personal-computer-based histogramming memory. Fiber-optic cables carry all digital information between the ADC and this memory. >

We present new results from a program to develop large area X-ray telescopes that are made from thin plastic shells. We use multi-shell cylindrical lenses in a point-to-point configuration to form full aperture images of the small focal spot in a an X-ray tube on a microchannel plate detector. The image data are analyzed to yield radial profiles and encircled energy curves. The derived parameters can be extrapolated to the case of a telescope that is a conical approximation to Wolter 1 optics. The plastic shells can be coated with suitable mono- or multilayers that allow for a wideband coverage of X-ray energies. Our current program is focused on the development of a large area, hard X-ray telescope for a balloon payload (see the paper 4851 -107 by E. Silver, et al at this conference).

We describe a cryostat and 2-stage ADR specifically designed for making measurements at the NIST EBIT (Electron Beam Ion Trap) facility. The design is compact and consists of a single helium bath with two vapor-cooled shields. The 2-stage ADR has two separate magnets and two heat switches. The interface between the EBIT and microcalorimeter array will also be described.

In response to the Italian Space Agency announcement "New Ideas for Space Missions", we have proposed an observatory "CALorimetri per Osservazioni Solari" (CALOS) that will perform spatially resolved (Deltatheta similar to 2) X-ray spectroscopy of the solar corona over the 0.1 - 10 keV band using an array of NTD germanium microcalorimeters. The observatory will also include an X-ray polarimeter of radically new design that will study the hard X-ray solar emission and its polarization and will serve as a flare alarm.

The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA’s scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe Kα region (1100 cm2). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin2. A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations.

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Composite microcalorimeters using neutron transmutation-doped germanium (NTD) thermistors have been tested at hard x-ray energies. We present a broad band spectrum showing the energy resolution at 60 keV to be approximately 50 eV. The application of these microcalorimeters to the field of nuclear line astrophysics is discussed.

A temperature control system was constructed for an adiabatic demagnetization refrigerator operating between 50 mK and 4 K. The control algorithm is discussed and the system performance is presented. A temperature stability of 2 μK RMS at 100 mK has been maintained for more than 8 h. To improve the thermodynamic efficiency, the magnetic field is used as the control parameter, rather than resistive heating.

COnstellation-X is a cluster of identical observatories that together constitute a promising concept for a next- generation, high-throughput, high-resolution, astrophysical x-ray spectroscopy mission. The heart of the Constellation-X mission concept is a high-quantum-efficiency imaging spectrometer with 2 eV resolution at 6 keV. Collectively across the cluster, this imaging spectrometer will have twenty times the collecting efficiency of XRS on Astro-E and better than 0.25 arc minute imaging resolution. The spectrometer on each satellite will be able to handle count rates of up to 1000 counts per second per imaging pixel for a point source and 30 counts per second per pixel for an extended source filling the array. Focal plane coverage of at least 2.5 arc minutes X arc minutes, comparable to XRS but with a factor of thirty more pixels, is required. This paper will present the technologies that have the potential to meet al these requirements. It will identify the ones chosen for development for Constellation-X and explain why those were considered closer to realization, and it will summarize the results of the development work thus far.

New design concepts and materials can be used to produce very lightweight, thin foil approximations, to Wolter I and other x-ray optics. Structures are designed around a central hub and spacers that connect one spoked wheels. Figure defining, thin pins span the distance between the wheels. Thin, metal coated or multilayered, plastic foils can be formed into cones, cylinders or spirals for x-ray telescopes or lenses. Imaging and spectroscopic data obtained with x- ray lenses are presented and they indicate that a 60 cm diameter, 4.65 m focal length x-ray telescope can have a half power diameter of < 2 arcmin.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The Stellar X-Ray Polarimeter (SXRP) will be more than an order of magnitude more sensitive than any previous x-ray polarimeter in the 2-15 keV energy band. The SXRP is a focal plane detector for a Danish-Russian SODART telescope, which will be launched on the Russian Spectrum-X-Gamma (SXG) mission. The SXRP exploits the polarization dependence of Bragg reflection from a graphite crystal, and of Thomson scattering from a target of metallic lithium. The SXRP flight model (FM) was calibrated at a facility at Lawrence Livermore National Laboratory (LLNL) equipped with polarized and unpolarized x-ray sources producing x-rays in the band pass for the graphite and the lithium scatterers. By adjusting the orientation of the SXRP with respect to the incident x-ray beam, it was possible to simulate the converging beam from a SODART telescope and to measure the SXRP response to telescope pointing errors. In this paper we describe the SXRP-FM calibration and present results for the graphite polarimeter.

The persistence of long living quasiparticles created in the energy thermalization process can affect the performances of a thermal X-ray microcalorimeter with superconducting absorber. Numerical simulations indicate that in an ab- sorber made of high-purity Sn, operated at temperatures lower than 100 mK, up to 60% of the deposited energy can remain trapped in the quasiparticle system for a time much longer than the time scale of the thermal sensor response, producing a reduction of the SNR of the detector. Other pure superconductors can present the same problem and therefore a microscopic analysis of the physical properties can be useful to identify suitable absorbing materials and optimize the detector performances.

The performance of the engineering prototype Stellar X-Ray Polarimeter (SXRP) has been evaluated. One hundred percent polarized monochromatic x rays at 2.6 keV and 9.7 keV were used to measure the response of the instrument in the energy bands of the graphite and lithium polarizing elements, respectively. On-line analysis showed that the respective depths of modulation are 96% ad 70% as expected. Irradiating SXRP with broadband unpolarized x rays in the energy band 2 - 17 keV demonstrated that the level of spurious modulation inherent in the instrument is less than 3%. Up-to-date results are presented and compared to the predictions of Monte Carlo simulations.

The Stellar X-Ray Polarimeter (SXRP) uses the polarization sensitivity of a graphite Bragg crystal and a lithium Thomsom scattering target to measure the polarization of X-rays from astrophysical sources. The SXRP is a focal plane detector for the Soviet-Danish SODART telescopes which will be launched on the Soviet Spectrum-X-Gamma mission. The SXRP will be the third orbiting stellar X-ray polarimeter, and should provide an order of magnitude increase in polarization sensitivity over its predecessors.

A large area thin graphite crystal and a lithium scattering block are used as the polarization sensitive elements of the Stellar X-Ray Polarimeter. We discuss the construction, selection and characterization of these two polarizing elements. In addition, we describe the plans for calibration of the completed instrument and the facility where it will be conducted.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper contains a brief introduction to the main parameters of a micro-calorimeter designed to operate at the Shanghai electron beam ion trap. This is followed by short descriptions of some aspects of the calorimeter.

New laboratory measurements using an Electron Beam Ion Trap (EBIT) and an x-ray microcalorimeter are presented for the n=3 to n=2 Fe XVII emission lines in the 15 {\AA} to 17 {\AA} range, along with new theoretical predictions for a variety of electron energy distributions. This work improves upon our earlier work on these lines by providing measurements at more electron impact energies (seven values from 846 to 1185 eV), performing an in situ determination of the x-ray window transmission, taking steps to minimize the ion impurity concentrations, correcting the electron energies for space charge shifts, and estimating the residual electron energy uncertainties. The results for the 3C/3D and 3s/3C line ratios are generally in agreement with the closest theory to within 10%, and in agreement with previous measurements from an independent group to within 20%. Better consistency between the two experimental groups is obtained at the lowest electron energies by using theory to interpolate, taking into account the significantly different electron energy distributions. Evidence for resonance collision effects in the spectra is discussed. Renormalized values for the absolute cross sections of the 3C and 3D lines are obtained by combining previously published results, and shown to be in agreement with the predictions of converged R-matrix theory. This work establishes consistency between results from independent laboratories and improves the reliability of these lines for astrophysical diagnostics. Factors that should be taken into account for accurate diagnostics are discussed, including electron energy distribution, polarization, absorption/scattering, and line blends., Comment: 29 pages, including 7 figures

We are developing a dielectric microcalorimeter for X-ray spectroscopy. We will present the results of our measurement of the dielectric permittivity, the spontaneous polarization, and the pyroelectric coefficient of the mixed-crystal quantum ferroelectric KTa(1-x)Nb(x)O3 with a doping of x = 0.012, as a function of temperature and bias voltage across the device. The effects of surface layers on the permittivity and the pyroelectric coefficient are discussed. We also show the signal results from infrared LED and alpha-particle radiation.