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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.

Photon counting x‐ray spectroscopy using microcalorimeters combines the high resolution power of a Bragg crystal with the broad bandwidth capability and high efficiency of charge sensitive detectors. To date, the developers of microcalorimeters take advantage of the strong temperature dependence of resistance in doped semiconductor crystals for converting the calorimeter temperature changes into useful voltage signals. Resistive sensors limit the ultimate sensitivity of microcalorimeters because they dissipate heat and add Johnson noise to the electronic conversion circuit. Potentially, these detrimental properties can be eliminated by exploiting the temperature dependence of the dielectric constant in ferroelectric materials. A mixed crystal quantum ferroelectric shows great promise for a dielectric thermal sensor. We present results from our most recent measurements which include the first detection of individual 6 MeV alpha particles with a dielectric calorimeter operating at 1.2 K.

Complex, transient, spatially inhomogeneous tokamak plasmas require careful diagnosis. As the reactor regime is approched, soft x rays become more important as a versatile diagnostic tool and an energy‐loss mechanism. Continuum emission provides a measure of electron temperatures and light impurity content. Impurity lines serve as a probe for ion and electron temperature, impurity behavior, and radiative cooling. The entire spectrum yields vital information on instabilities and disruptions. The importance of impurities is illustrated by the extensive efforts toward understanding impurity production, effects, and control. Minute heavy impurity concentrations can prevent reactor ignition. Si(Li)‐detector arrays give a broad overview of continuum and line x‐ray emission (.3−50 keV) with moderate energy (200 eV) and time (50 ms) resolution. Bragg crystal and grating spectrometers provide detailed informaion on impurity lines with moderate to excellent (E/ΔE=100−23,000) resolving power and 1−50 ms time resolution. Imaging detector arrays measure rapid (∼10 μs) fluctuations due to MHD instabilities and probe impurity behavior and radiative cooling. Future tokamaks require more diagnostic channels to avoid spatial scanning; higher throughput for fast, single‐shot diagnosis; increased spectral information per sample period via fast scanning or use of multi‐element detectors with dispersive elements; and radiation shielding and hardening of detectors.