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We have measured the collisional excitation cross sections for the 3d→4f and 3d→5f excitations in Au ions near the Ni-like charge state by using beam plasmas created in the Livermore electron beam ion trap EBIT-I. The cross sections have been experimentally determined at approximately 1, 2 and 3 keV above the threshold energy, ET, for the 3d→4f excitations (ET ∼ 2.5 keV) and at approximately 0.1, 1 and 2 keV above the threshold energy for the 3d→5f excitations (ET ∼ 3.3 keV). The cross section measurements were made possible by using the GSFC x-ray microcalorimeter at the Livermore EBIT facility. The absolute cross sections are determined from the ratio of the intensity of the collisionally excited bound-bound transitions to the intensity of the radiative recombination lines produced in EBIT-I plasmas. The effects of polarization and Auger decay channels are accounted for in the cross section determination. Measured cross sections are compared with those from HULLAC, DWS and FAC calculations. The measurem...

Charge exchange recombination, the transfer of one or more electrons from an atomic or molecular system to a positive ion, is a common phenomenon affecting laboratory and astrophysical plasmas. Controlled studies of this process in electron beam ion traps during the past one and a half decades have produced multiple observations that are difficult to explain with available spectral models. Some of the most recent observations are so puzzling that they bring in doubt the existence of a coherent predictive capability for line formation by charge exchange, making investigations of charge exchange a fertile ground for continued measurements and theoretical development.

The Micro‐X Imaging X‐ray Spectrometer is a sounding rocket payload slated for launch in 2011. An array of Transition Edge Sensors, which is operated at a bath temperature of 50 mK, will be used to obtain a high resolution spectrum of the Puppis‐A supernova remnant. An Adiabatic Demagnetization Refrigerator (ADR) with a 75 gram Ferric Ammonium Alum (FAA) salt pill in the bore of a 4 T superconducting magnet provides a stable heat sink for the detector array only a few seconds after burnout of the rocket motors. This requires a cold stage design with very short thermal time constants. A suspension made from Kevlar strings holds the 255 gram cold stage in place. It is capable of withstanding loads in excess of 200 g. Stable operation of the TES array in proximity to the ADR magnet is ensured by a three‐stage magnetic shielding system which consists of a superconducting can, a high‐permeability shield and a bucking coil. The development and testing of the Micro‐X payload is well underway.

A decade has elapsed since the design, development and realization of a SQUID‐based time‐division multiplexer at NIST. During this time the system has been used extensively for low‐temperature‐detector‐array measurements. Concurrently, there have been substantial advancements both in detector array and commercial electronic component technology. The relevance and applicability of the technology has blossomed as well, often accompanied by more demanding measurement requirements. These factors have motivated a complete redesign of the NIST room‐temperature read‐out electronics. The redesign has leveraged advancements in component technology to achieve new capabilities better suited to the SQUID multiplexers and detector arrays being realized today. As examples of specific performance enhancements, the overall system bandwidth has been increased by a factor of four (a row switching rate of 6.24 MHz), the compactness has been increased by over a factor of two (a higher number of detector columns and rows per circuit board), and there are two high speed outputs per column (allowing fast switching of SQUID offsets in addition to digital feedback). The system architecture, design implementations, and performance advantages of the new system will be discussed. As an application example, the science chain flight electronics for the Micro‐X High Resolution Microcalorimeter X‐ray Imaging Rocket will be described as both a motivation for, and a direct implementation of the new system.

We present experimental results and designs of large‐absorber transition‐edge‐sensor (TES) X‐ray microcalorimeters. Much of our effort has focused on developing close‐packed arrays of 250–300 μm‐sized pixels suitable for the X‐ray Microcalorimeter Spectrometer (XMS) on the International X‐ray Observatory. These efforts have produced devices with the requisite energy resolution of ≳2.5 eV (FWHM) at 6 keV. There are several upcoming applications, however, that require arrays composed of significantly larger pixels. In this contribution we present experimental results from 490 μm‐sized pixels that have attained 3.5 eV energy resolution at 6 keV. These devices are precursors to the pixels that are being developed for the XMS extended array. In addition, we briefly describe detector designs for the Micro‐X sounding rocket experiment, which also requires an array of large‐area TES microcalorimeters.

X‐ray observations of solar wind charge exchange (SWCX) emission, a nuisance to astrophysicists, will dramatically enhance our ability to determine the structure and variability of the Earth’s magnetosheath. Such observations could be made from the lunar surface or an Earth‐orbiting spacecraft and will resolve key controversies about magnetopause physics as well as better characterize SWCX emission with the aim of avoiding or removing it from astrophysical observations.

The XRS microcalorimeter will be launched in 2005 as part of the Astro‐E2 mission. It will cover the energy band from 0.3 to 10 keV with a nearly constant energy resolution of 6.0 eV and a peak effective area of 200 cm2 at 1.5 keV. The XRS will provide unprecedented throughput and resolving power, particularly at high energies. Detailed spectral features in the Fe K region will be resolved for the first time, providing access to spectroscopic diagnostics for a wide range of astrophysical objects. In this presentation we will describe the XRS instrument, details of its spectral performance, and how it compares to the current high‐resolution instruments on the Chandra and XMM‐Newton observatories.

Celestial objects are often home to complex, dynamic, intriguing environments. High‐resolution x‐ray spectra from these sources measured by satellites such as the Chandra, XMM‐Newton, the Solar Maximum Mission, and the soon‐to‐be‐launched Astro‐E2 provide a means for understanding the physics governing these sources. Especially rich is the x‐ray emission from L‐shell transitions in highly charged iron ions. This emission is the source of a variety of diagnostics whose utility lies in the accuracy of the atomic data employed to model the x‐ray spectra. The atomic data used to describe these diagnostics are generally provided by large theoretical calculations and benchmarked by laboratory data. In this paper we discuss laboratory measurements of Fe L‐shell x‐ray emission including wavelengths, relative and absolute excitation cross sections, and line ratios that provide diagnostics of temperature and density.

The mixing of atomic and macroscopic processes taking place in non‐terrestrial objects creates complex, dynamic, and intriguing environments. High resolution x‐ray spectra from these sources measured by satellites such as Chandra, XMM‐Newton, and the Solar Maximum Mission provide a means for understanding the physics governing these sources. Laboratory measurements of the atomic processes have proved crucial to the interpretation of these spectra. For example using the LLNL electron beam ion traps EBIT‐I & EBIT‐II a detailed study of the x‐ray spectrum of Fe XVII has been conducted addressing the large ratio predicted by theory compared to observations of considerably smaller values of the relative intensity of the 2p‐3d 1P1 resonant to the 3D1 intercombination line. The difference was often attributed to opacity effects. However, laboratory measurements in the optically thin limit agree with observations demonstrating that the prediction is too large and opacity need not be invoked. The laboratory result...

Charge state distributions (CSDs) have been determined in low density (≈1012 cm−3) gold plasmas having either a monoenergetic beam (EBeam = 2.66, 3.53 and 4.54 keV) or experimentally simulated thermal electron distributions (Te = 2.0, 2.5 and 3.0 keV). These plasmas were created in the Livermore electron beam ion traps EBIT‐I and EBIT‐II. Line emission and radiative recombination features of Ni to Kr‐like gold ions were recorded in the x‐ray region with a crystal spectrometer and a photometrically calibrated microcalorimeter. The CSDs in the experimentally simulated thermal plasmas were inferred by fitting the observed 4f→3d and 5f→3d lines with synthetic spectra from the Hebrew University Lawrence Livermore Atomic Code (HULLAC). Additionally, the CSDs in the beam plasmas were inferred both from fitting the line emission and fitting the radiative recombination emission to calculations from the General Relativistic Atomic Structure Program (GRASP). Despite the relatively simple atomic physics in the low de...

Recent measurements of the K‐shell and L‐shell x‐ray spectra of highly charged helium‐like and neonlike ions are presented that were performed on the Livermore electron beam ion traps and the Princeton tokamaks. These measurements provide new insights into collisional and indirect line formation processes, identifications of forbidden lines, and a new plasma line diagnostic of magnetic field strength.

Using a microcalorimeter detector on a sounding rocket experiment creates difficulties in the data analysis that are not normally encountered on the ground or on satellite-based experiments. In analyzing the data obtained from two recent sounding rocket flights that employed microcalorimeter detectors, we have developed procedures for reducing the raw data to a data set suitable for astrophysical analysis. The data acquired from the instrument include fully sampled digitized waveforms for each X-ray event plus “quick-look” X-ray pulse heights from an on-board analog pulse shaping circuit, and large quantities of housekeeping information. In the post-flight data analysis we first characterize the events, then the X-ray waveforms from each pixel are digitally filtered, gain-drift corrected, and an energy scale is applied before combining the events into a single spectrum. Our final product is a set of events that are with high probability produced by cosmic X-ray photons and are well-characterized and free ...

In the past year a spare NASA/GSFC Astro-E microcalorimeter has been installed, tested, and run successfully on the electron beam ions traps EBIT-I and EBIT-II at the Lawrence Livermore National Laboratory. The microcalorimeter complements crystal and grating spectrometers already part of the LLNL ebit program making it possible to measure a broad bandwidth (∼0.3–10 keV) with moderate resolution while simultaneously measuring a narrow bandwidth (∼0.7–1.3 keV) with high resolution. An overview of recent work is presented including measurements by the microcalorimeter of absolute excitation cross sections. These results continue our effort to provide atomic data of high quality to be used as benchmarks for theoretical calculations and to be included in atomic data bases employed by spectral fitting packages used to interpret spectra obtained by XMM-Newton and the Chandra X-Ray Observatory.

We have recently deployed an XRS (the X-ray Spectrometer on the Astro-E mission) engineering model microcalorimeter at the electron beam ion traps (EBIT I/II) at Lawrence Livermore National Laboratory. The EBIT I/II can produce well defined astrophysically interesting plasmas for a wide range of plasma conditions. The XRS engineering model was mated with a 32 element XRS 6×6 microcalorimeter array and integrated into a laboratory cryostat. The system was then transported to the EBIT I/II and operated over the last year. The microcalorimeter array has a composite resolution of 8 eV at 1 keV and 11 eV at 6 keV. During the campaign, we performed a number of high resolution, broad band observations including: K and L shell Fe with single ionization energies from 1–8 keV, Maxwellian distributions of Fe with 〈kT〉=0.5–3 keV, non-equilibrium states of Fe with very fine time resolution for η=109−1012 s cm−3. The total observation time for the campaign was over 10 Ms and the analysis is ongoing. We will present her...