Cosmic Hot Interstellar Plasma Spectrometer Research Articles

EUV Spectra of the Full Solar Disk: Analysis and Results of the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)

We analyze EUV spectra of the full solar disk from the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) spanning a period of two years. The observations were obtained via a fortuitous off-axis light path in the 140 -- 270 Angstrom passband. The general appearance of the spectra remained relatively stable over the two-year time period, but did show significant variations of up to 25% between two sets of Fe lines that show peak emission at 1 MK and 2 MK. The variations occur at a measured period of 27.2 days and are caused by regions of hotter and cooler plasma rotating into, and out of, the field of view. The CHIANTI spectral code is employed to determine plasma temperatures, densities, and emission measures. A set of five isothermal plasmas fit the full disk spectra well. A 1 -- 2 MK plasma of Fe contributes 85% of the total emission in the CHIPS passband. The standard Differential Emission Measures (DEMs) supplied with the CHIANTI package do not fit the CHIPS spectra well as they over-predict emission at temperatures below log(T) = 6.0 and above log(T) = 6.3. The results are important for cross-calibrating TIMED, SORCE, SOHO/EIT, and CDS/GIS, as well as the recently launched Solar Dynamics Observatory.

Iron emission lines in solar and laboratory plasmas

We present a spectrum of the Sun taken by the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) covering 150 to 275 Å. This spectrum is dominated in the 200 Å region by emission lines from intermediate charge states of iron (Fe VIII - FeXVI). We also made laboratory measurements of iron emission at temperatures relevent to solar emission on the EBIT-II electron beam ion trap and the Large Helical Device stellerator. We used our laboratory measurements to identify lines and check the CHIANTI database and then used CHIANTI to validate line identifications in the CHIPS spectrum.

A Search for Extreme‐Ultraviolet Emission from Comets with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)

We have obtained EUV spectra between 90 and 255 8 of the comets C/2002 T7 (LINEAR), C/2001 Q4 (NEAT), and C/2004 Q2 (Machholz) near their perihelion passages in 2004 with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS). We obtained contemporaneous data on NEAT with the Chandra ACIS instrument, marking the firstsimultaneousEUVandX-rayspectralobservationsofacomet.ThetotalCHIPS/EUVobservingtimeswere337ks for NEAT, 234 ks for LINEAR, and 483 ks for Machholz, and for both CHIPS and Chandra we calculate we have capturedall the comet flux in the instrumentfield of view. We set upper limits on solar wind charge-exchange emission lines of O, C, N, Ne, and Fe occurring in the spectral bandpass of CHIPS. The spectrum of NEAT obtained with ChandracanbereproducedbymodelingemissionlinesofC,N,O,Mg,Fe,Si,S,andNesolarwindions.Themeasured X-rayemission-lineintensitiesareconsistentwithourpredictionsfromasolarwindcharge-exchangemodel.Themodel predictions for the EUVemission-line intensities are determined from the intensity ratios of the cascading X-ray and EUVphotonsarisinginthecharge-exchangeprocesses.Theyarecompatiblewiththemeasuredlimitsontheintensities of the EUV lines. For NEAT, we measured a total X-ray flux of 3:7 ; 10 � 12 ergs cm � 2 s � 1 and derive from model predictions a total EUV flux of 1:5 ; 10 � 12 ergs cm � 2 s� 1. The CHIPS observations occurred predominantly while the satellite was on the dayside of Earth. For much of the observing time, CHIPS performed observations at smaller solar angles than it was designed for, and EUVemission from the Sun scattered into the instrument limited the sensitivity of the EUV measurements. Subject headingg comets: general — comets: individual (C/2002 T7 (LINEAR), C/2001 Q4 (NEAT), C/2004 Q2 (Machholz)) — ultraviolet: solar system

Observations of Diffuse Extreme-Ultraviolet Emission with theCosmic Hot Interstellar Plasma Spectrometer(CHIPS)

The Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) was designed to study diffuse emission from hot gas in the local interstellar cavity in the wavelength range 90-265 A. Between launch in 2003 January and early 2004, the instrument was operated in narrow-slit mode, achieving a peak spectral resolution of about 1.4 A FWHM. Observations were carried out preferentially at high Galactic latitudes; weighted by observing time, the mean absolute value of the Galactic latitude for all narrow-slit observations combined is about 45°. The total integration time is about 13.2 Ms (74% day, 26% night). In the context of a standard collisional ionization equilibrium plasma model, the CHIPS data set tight constraints on the emission measure at temperatures between 105.55 and 106.4 K. At 106.0 K, the 95% upper limit on the emission measure is about 0.0004 cm-6 pc for solar-abundance plasma with a foreground neutral hydrogen column of 2 × 1018 cm-2. This constraint, derived primarily from limits on the extreme ultraviolet emission lines of highly ionized iron, is well below the range for the local hot bubble estimated previously from soft X-ray studies. If the pattern of elemental depletion in the hot gas follows that observed in much denser interstellar clouds, the gas-phase abundance of iron, relative to other heavy elements that contribute more to the soft X-ray emission, might be much lower than solar. However, to support the emission measures inferred previously from X-ray data would require depletions much higher than the moderate values reported previously for hot gas. Excluding the He II Lyman lines, which are known to be primarily terrestrial in origin, the brightest feature we find in the integrated spectrum is an Fe IX line at 171.1 A. The sky-averaged flux of the feature is about 6 photons cm-2 s-1 sr-1, a flux that exceeds the 1 σ shot noise significantly but is comparable to the systematic uncertainty. We find bright 171.1 A emission (flux greater than 10 photons cm-2 s-1 sr-1 and S/N >2) in about 10% of the observing time. However, these bright observations overwhelmingly select for daytime (96% of 1.3 Ms). Thus, a local rather than interstellar origin for much of the 171.1 A emission seems likely.

Osmium atomic-oxygen protection by an iridium overcoat for increased extreme-ultraviolet grating efficiency.

The deposition of a 30-A-thick layer of iridium upon a 250-A-thick osmium reflective layer for use as a diffraction grating in the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) satellite observatory has provided sufficient protection from an expected maximum orbital atomic-oxygen fluence of 1 x 10(16) atoms/cm2. The grating parameters of groove constant and depth, efficiencies of zeroth-order, first and second inside orders, and first inside-order efficiency positional uniformity as well as stray light near the first inside order of the Ir-Os-coated grating were measured within a CHIPS spectral bandpass of 90-260 A. Stray-light measurements were also made near the first inside spectral order at 304, 584, and 1216 A. The results make the Ir-Os coat an acceptable grating reflectivity layer for CHIPS and other spaceborne extreme-ultraviolet spectrometers that employ grazing-incidence reflection optics.

Development of a spring ring for microchannel plate stack fastening in the cosmic hot interstellar plasma spectrometer detector

This article describes the development of the spring ring used to fasten the microchannel plate (MCP) stack of the cosmic hot interstellar plasma spectrometer (CHIPS) detector. Fastening criteria specific to the CHIPS detector is developed, although the method is applicable to any MCP detector design with cylindrical symmetry. The basic equations from spring disk theory are presented along with appropriate simplifying approximations. Design criteria and test data of the final CHIPS flight version is reviewed, including comparison to results obtained with different materials and processing steps.

Extreme-ultraviolet calibration of thin-film Zr filters for the cosmic hot interstellar plasma spectrometer.

The design and calibration of thin-film Zr transmission filters for the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) spaceborne astronomical telescope is presented. The transmission of a 1,000-A-thick Zr filter is measured for wavelengths from 45 to 1,304 A as well as its variability with respect to expected space-flight enviromental extremes of temperature, vibration, and atomic O bombardment. For the CHIPS spectral band of 90-260 A, the transmission of the Zr fiter is deemed useful between 90 and 200 A and is stable with respect to expected temperature and vibrational changes. The maximum atomic O bombardment decreases the filter transmission between 90 and 130 A by approximately 20% and does not appreciably affect the rest of the CHIPS bandpass. These results make Zr an acceptable filter candidate for CHIPS.

Cosmic Hot Interstellar Plasma Spectrometer external stop delay board: An alternative to bulky and massive coax for long (>100 ns) time delays

The Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) utilizes a typical microchannel plate detector with a cross delay line event readout anode. A CHIPS delay line was predicted to approach a time delay of 80 ns. Therefore an added time delay of 100 ns was required for the stop channels. Implementation of such a delay using conventional coax cable was deemed too bulky and massive. After exploring other alternatives, which failed to meet specific requirements, a stripline delay printed circuit board was developed. This approach eventually proved to be a superior alternative to coax cable for the CHIPS detector. This article outlines and details the development of the CHIPS external stop delay board from basic microwave circuit theory to design and testing. Discussion of the mathematical and computer models used for design are contained in the Appendices.