Studies of Thermal Diffusion in Planar Absorber Designs for the Micro-X Rocket

We have studied a potential design for a transition-edge sensor (TES) microcalorimeter array for the Micro-X High Resolution Microcalorimeter X-ray Imaging Rocket. Diffusion simulations of a design that places a small TES in the center of the pixel with a large in-plane absorber around the TES demonstrate that with high-quality gold films (RRR >6) 2 eV resolution is attainable in a 700 μm pixel, meeting the Micro-X requirement. X-ray hits directly on the TES, however, create a non-gaussian high energy tail to the device response. This high energy tail contains 5% of incident photons and cannot be removed by lowering the optimal filter bandwidth.      

Phonon-Mediated Distributed Transition-Edge-Sensor X-Ray Detector with Deep Trenches

We continue our development of a phonon-mediated distributed-TES X-ray detector. X-rays are absorbed in a large silicon or germanium crystal, and the energy is read out by four distributed TESs. This design takes advantage of existing TES technology while overcoming the difficulties of designing spatially large arrays. In this paper, we discuss three detector designs. First, a silicon detector with 220 μm deep trenches through a 350 μm crystal. Second, a germanium detector with 275 μm deep trenches through a 550 μm crystal. Finally another silicon detector with 330 μm deep trenches through a 350 μm crystal. We discuss energy loss mechanisms in the detector and propose a reason for the energy resolution that we observe.      

Vibration Isolation Design for the Micro-X Rocket Payload

Micro-X is a NASA-funded, sounding rocket-borne X-ray imaging spectrometer that will allow high precision measurements of velocity structure, ionization state and elemental composition of extended astrophysical systems. One of the biggest challenges in payload design is to maintain the temperature of the detectors during launch. There are several vibration damping stages to prevent energy transmission from the rocket skin to the detector stage, which causes heating during launch. Each stage should be more rigid than the outer stages to achieve vibrational isolation. We describe a major design effort to tune the resonance frequencies of these vibration isolation stages to reduce heating problems prior to the projected launch in the summer of 2014.     

Microcalorimeter Instruments for the Spectrum-R(X)G and NeXT Missions

X-ray spectrometers utilizing a microcalorimeter array are presently under study for the Russian Spectrum R-G (or Spectrum-X-Gamma) mission, which is to be launched in 2011, and for the Japanese NeXT (New X-ray Telescope or Non-thermal energy eXploration Telescope) mission, whose launch is expected to be in 2012 to 2015. The primary instrument of Spectrum R-G is eROSITA, which will make an all sky survey in the 0.1–10 keV range using an array of seven telescopes and X-ray CCD cameras. The mission also carries smaller instruments, a wide-field monitor (Lobster) and a hard X-ray telescope (ART). We are proposing SXC—the Spectrum-X Calorimeter—to obtain spatially-resolved precision spectra of a number of nearby massive clusters of galaxies during an initial 6-month pointed phase, and to obtain a detailed spectral map of the soft X-ray diffuse background during the 4-year survey phase. The NeXT mission is a combination of wide band X-ray spectroscopy provided by multi-layer coating, focusing X-ray mirrors and pixel detectors, and high resolution soft X-ray spectroscopy by microcalorimeter instrument, SXS—the Soft X-ray Spectrometer. The effective area of the SXS is about 20 times larger than that of SXC at the iron K line energy (6.7 keV) while the solid angle of the field of view is by a factor of 15 smaller. One of the major scientific objectives of SXS is to determine turbulent and/or macroscopic velocities in the hot gas of distant clusters of galaxies. Both of the instruments will use 6×6 microcalorimeter array similar to the one launched on Suzaku, while both will adopt a ³He Joule Thomson cooler and two-stage Stirling cycle in the cryogenic systems. The ³He Joule Thomson cooler provides a thermal guard to liquid He but it can also work as a 1.8 K heat bath for the adiabatic demagnetization refrigerator.      

Optical/UV and X-Ray Microwave Kinetic Inductance Strip Detectors

Microwave Kinetic Inductance Detectors (MKIDs) are superconducting detectors that sense the change in the surface impedance of a thin superconducting film when Cooper Pairs are broken by using a high quality factor resonant circuit. We are developing strip detectors that have aluminum MKID sensors on both ends of a rectangular tantalum strip. These devices can provide one dimensional spatial imaging with high quantum efficiency, energy resolution, and microsecond time resolution for single photons from the IR to the X-ray. We have demonstrated X-ray strip detectors with an energy resolution of 62 eV at 6 keV, and hope to improve this substantially. We will also report on our progress towards optical arrays for a planned camera for the Palomar 200″ telescope.     

Modular high frame rate detector for synchrotron applications

The development of detectors often lags the development in X-ray sources. However, advanced detectors are critical for fully utilizing and exploiting the capabilities of the new bright sources. We report on the development of a modular high frame rate detector for synchrotron applications such as small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS). The detector consists of four modules, each providing an imaging area of 5×5 cm(2) and capable of frame rates of 200 frames per second (fps) with full resolution, and 650 fps with smaller region of interest (ROI). Details of the detector design and experiments at synchrotron beamlines are discussed in the paper.     

Nanoscopic study of chemical species during uranium electrodeposition for alpha spectrometry sources

High resolution alpha spectrometry (AS) is commonly applied for the determination of actinides and other alpha-emitting nuclides in many applications. Electrodeposition is the standard procedure for preparing α-particle sources usually made of a thin and uniform radioactive deposit onto a metallic substrate. Natural U sources prepared by the Hallstadius method are known to contain co-deposited Pt from the anode. In this sense, the main aim of this work is to conclusively review the behaviour of Pt and U in the electrodeposition process and their distribution in the resulting deposit, factors that are responsible for the thickness and uniformity of the sources. In addition to new scanning electron microscopy/energy dispersive spectroscopy (SEM–EDX) and X-ray absorption fine structure (XAFS) data, the electrodeposited surface has been analyzed using both atomic force microscopy (AFM) and synchrotron radiation Grazing Incidence X-ray diffraction (GI-XRD). The results concerning morphology of the deposit, surface roughness, topography and surface structure obtained from sources prepared at different electrodeposition times agree with the AS results concerning electrodeposition yield and spectral resolution.     

Absorber Materials for Transition-Edge Sensor X-ray Microcalorimeters

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. A.-D. Brown’s and S. Smith’s research was supported in part by appointments to the NASA Postdoctoral Program at NASA Goddard Space Flight Center administered by Oak Ridge Associated Universities through a contract with NASA.     

High-Resolution and Low-Voltage FE-SEM Imaging and Microanalysis in Materials Characterization

Nanometer-resolution imaging in field-emission SEM (FE-SEM) instruments is now widely used in materials characterization. The use of a high-brightness field-emission gun and a high-resolution lens system makes it possible to acquire nanometer-resolution surface images at low voltages (<5kV). The advantages of low-voltage FE-SEM include enhanced surface sensitivity, reduced sample charging for nonconducting materials, reduced damage of delicate samples, and significantly reduced electron range and interaction volume in bulk samples. For microanalysis using characteristic X-ray signals, the spatial resolution is significantly improved and the surface sensitivity is enhanced because of the fall of electron range at low voltages. With further development of high energy resolution X-ray detectors and probe-forming lenses, low-voltage imaging and microanalysis in FE-SEM instruments will be competitive both in spatial resolution and in chemical sensitivity to those now achievable in analytical TEM instruments. Applications of low-voltage SE imaging and microanalysis techniques to the study of various types of bulk materials are discussed.     

X-ray Microcalorimeter Research for Solar Physics at LMSAL and NIST: An Update

LMSAL and NIST are developing position-sensitive X-ray strip detectors based on TES microcalorimeter arrays for solar physics. An important application of these devices will be the study of high temperature (>10 MK) X-ray lines, e.g. Fe XXV, at high spectral (E/ΔE≥1000) and temporal (sub-ms) resolution. Diagnostics from these lines will provide significant new insights into the physics of microflares and the early stages of flares. In this paper, we will describe the current status of our laboratory test program and applicability of our research to future space missions      

Performance of Micro-fabricated Magnetic Calorimeters Arrays for X-Ray Spectroscopy

We have been developing array technology for fabricating magnetic calorimeters for X-ray astronomy. The magnetization change in each pixel of the paramagnetic sensor material due to the heat input of an absorbed X-ray is sensed by a meander shaped coil. With this geometry it is possible to obtain excellent energy sensitivity, low magnetic cross-talk and large format arrays fabricated on wafers that are separate from the SQUID read-out. A magnetic bias field for each pixel is generated by the use of a persistent current that is stored. We report on the results from our prototype arrays, which are coupled to low noise DC-SQUIDs. The first test results are presented and the sensitivity is compared with calculations.     

以科学发展观规范地源热泵系统建设

分析我国当前地源热泵系统工程建设与发展的特点,地源热泵系统的基本原理、优缺点与适用条件,并对“浅层地热能”的资源观点与评价方法作相应的剖析。在此基础上,回顾近10年国内地源热泵系统工程的设计与建设,概括在科学认识与科学宣传、科学规划与科学建设、科学运行与严格管理3个方面所存在的问题,提出对地源热泵系统建设推行与实施强制性监测、监管的建议。最后,希望暖通空调与水文地质2个专业、2个行业的专业人员能够在监测、监管的实践基础上统一认识,不断地相互沟通、相互学习、相互补充,共同努力,以科学发展观来规范与指导地源热泵系统的建设。     

A 5 in. Si(Li)/Pb sampling calorimeter telescope for observation of cosmic gamma rays in the GeV region

A 5 in. diameter Si(Li)/Pb sampling calorimeter with a depth of 28 radiation lengths (30 unit cells × 0.93 radiation lengths) has been constructed. The energy and angular resolutions of the calorimeter have been investigated using CERN SPS positron beams with energies of 10 to 147.8 GeV. The calorimeter shows good linearity over this energy region and the energy resolution is expressed well by σ_E (rms)/E = (16.9 ± 0.9)%/ √E[GeV], where E represents the incident beam energy. The angular resolution of the calorimeter for a single event is 0.3° (rms) at 80 GeV/c. The agreement between these results and Monte Carlo simulations is good.

We are showing a new design of the Si(Li)/Pb sampling calorimeter telescope (SSCT) with an angular resolution (point source localization capability) of about 0.04° (rms) for bright galactic gamma-ray sources. We believe that this telescope is a suitable detector for future observations of cosmic gamma rays in the GeV region, especially when used to search for point sources.     

基于CZT探测器的双能X线骨密度测量技术

提出了一种应用碲锌镉(CdZnTe或CZT)晶体探测器的骨矿密度测量方法。该方法通过对被测对象的定位,X射线扫描,应用CZT晶阵对被骨组织吸收、衰减后的双能X射线进行测量。测量信号经分级处理后,实现了骨矿密度定量测量和成像。实验结果表明,CZT探测器具有良好的工作性能,系统测量具有快速,高精度,高空间分辨率等特点。     

The X-ray Quantum Calorimeter Sounding Rocket Experiment: Improvements for the Next Flight

We have developed a new calorimeter array to increase our collecting area by a factor of four. The 6×6 pixel device has a total area of 144 mm², making it one of the largest X-ray microcalorimeter arrays yet constructed. A relatively thin high-z absorber consisting of a 0.7 μm HgTe layer supported on 15 μm high-purity silicon provides good efficiency up to photon energies of 1.5 keV. The heat capacity of this composite is low enough to obtain an energy resolution of ∼6 eV FWHM on the 2 mm×2 mm pixels when operated at a base temperature of 50 mK. The infrared blocking filters have also been improved. Room temperature radiation must be attenuated by about 9 orders of magnitude between 2 μm and 2 cm to avoid having photon shot noise dominate the detectornoise. Accomplishing this while maintaining a high transmission for very soft X-rays that can penetrate only a few μg cm⁻² is a problem common to all soft X-ray calorimeters that observe external targets. We are constructing monolithic silicon two-layer support meshes with a 350 μm pitch front layer on a 5 mm pitch backing layer. These are 98% open and have >95% effective transmission over a 60° field of view, while providing robust support for 38 mm diameter filters consisting of 20 nm of aluminum on 50 nm of polyimide. Five of these filters in series provide the necessary infrared attenuation. Integral deicing heaters are ion implanted in the fine mesh to remove contamination when necessary.      

Random speckle modulation technique for laser interferometry

In spite of its obvious advantages over conventional contact and immersion techniques, laser interferometry has not yet become a practical tool in ultrasonic nondestructive evaluation since its sensitivity is insufficient in most practical applications. Part of the problem is that the maximum signal-to-noise ratio often cited in scientific publications and manufacturers' specifications cannot be maintained on ordinary diffusely reflecting surfaces. Although these surfaces reflect a fair amount (5–50%) of the incident laser light, this energy is randomly distributed among a large number of bright speckles. Unless the detector happens to see one of these bright speckles, the interferometer's signal-to-noise ratio will be much lower than the optimum. This adverse effect is almost completely eliminated by the suggested random speckle modulation technique. The conventional interferometric technique was modified to assure random occurrence of a few very bright speckles and to move the whole speckle pattern around at an appropriate speed. Random but frequent bright flashes detected from the surface of the specimen resulted. The bright periods are 0.1 ms or longer, sufficient to trigger the ultrasonic pulser and detect the transmitted signals before the flash subsides. As much as 5–10 times improvement of the optical sensitivity was achieved by this novel approach and close to maximum signal-to-noise ratio was maintained everywhere on the surface of a diffuse object.     

Emerging X-ray imaging technologies for energy materials

With the growing need for sustainable energy technologies, advanced characterization methods become more and more critical for optimizing energy materials and understanding their operation mechanisms. In this review, we focus on the synchrotron-based X-ray imaging technologies and the associated applications in gaining fundamental insights into the physical/chemical properties and reaction mechanisms of energy materials. We will discuss a few major X-ray imaging technologies, including X-ray projection imaging, transmission X-ray microscopy, scanning transmission X-ray microscopy, tender and soft X-ray imaging, and coherent diffraction imaging. Researchers can choose from various X-ray imaging techniques with different working principles based on research goals and sample specifications. With the X-ray imaging techniques, we can obtain the morphology, phase, lattice and strain information of energy materials in both 2D and 3D in an intuitive way. In addition, with the high-penetration X-rays and the high-brilliance synchrotron sources, operando/in-situ experiments can be designed to track the qualitative and quantitative changes of the samples during operation. We expect this review can broaden readers’ view on X-ray imaging techniques and inspire new ideas and possibilities in energy materials research.     

Metallic magnetic calorimeters (MMC): detectors for high-resolution X-ray spectroscopy

X-ray detectors based on the concept of magnetic calorimetry are well suited for high-resolution spectroscopy. Metallic magnetic calorimeters (MMC) make use of a metallic paramagnetic temperature sensor, which is in tight thermal contact with a metallic X-ray absorber. The paramagnetic sensor is placed in a small magnetic field. Its magnetization is used to monitor the temperature, which in turn is related to the internal energy of the calorimeter. High-energy resolution can be obtained by using a low-noise, high-bandwidth DC SQUID to measure the small change in magnetization upon the absorption of an X-ray. With recent prototype detectors an energy resolution of ΔE_FWHM=3.4 eV for X-ray energies up to 6.5 keV has been achieved. We discuss general design considerations, the thermodynamic properties of such calorimeters, the energy resolution, and the various sources of noise, which are observed in MMCs.     

Coexistence of university-industry relations and academic research: Barrier to or incentive for scientific productivity

In this article we analyse whether university-industry relations (UIR) are penalising research activity and inhibiting university researchers’ scientific productivity and, if so, to what extent. The analysis is based on a case study of two Spanish universities. We find that UIR exercise a positive effect on university scientific productivity only when they are based on the development of R&D contracts, and when the funds obtained through these activities do not exceed 15% of the researcher’s total budget. We also find that researchers who combine research and UIR activities obtain higher funding from competitive public sources than that engage only in research. In addition, their average scientific productivity is higher and they achieve higher status within their institutions than those members of faculty who concentrate only on research.