A. J. F. den Boggende

The Reflection Grating Spectrometer on board XMM-Newton

The ESA X-ray Multi Mirror mission, XMM-Newton, carries two identical Reflection Grating Spectrometers (RGS) behind two of its three nested sets of Wolter I type mirrors. The instrument allows high- resolution (E=E = 100 to 500) measurements in the soft X-ray range (6 to 38 A or 2.1 to 0.3 keV) with a maximum eective area of about 140 cm 2 at 15 A. Its design is optimized for the detection of the K-shell tran- sitions of carbon, nitrogen, oxygen, neon, magnesium, and silicon, as well as the L shell transitions of iron. The present paper gives a full description of the design of the RGS and its operational modes. We also review details of the calibrations and in-orbit performance including the line spread function, the wavelength calibration, the eective area, and the instrumental background.

High resolution X-ray spectroscopy of zeta Puppis with the XMM-Newton reflection grating spectrometer

We present the rst high resolution X-ray spectrum of the bright O4Ief supergiant star Puppis, obtained with the Reflection Grating Spectrometer on-board XMM-Newton. The spectrum exhibits bright emission lines of hydrogen-like and helium-like ions of nitrogen, oxygen, neon, magnesium, and silicon, as well as neon-like ions of iron. The lines are all signicantly resolved, with characteristic velocity widths of order 1000{1500 km s 1 . The nitrogen lines are especially strong, and indicate that the shocked gas in the wind is mixed with CNO-burned material, as has been previously inferred for the atmosphere of this star from ultraviolet spectra. We nd that the forbidden to intercombination line ratios within the helium-like triplets are anomalously low for N VI, O VII, and Ne IX. While this is sometimes indicative of high electron density, we show that in this case, it is instead caused by the intense ultraviolet radiation eld of the star. We use this interpretation to derive constraints on the location of the X-ray emitting shocks within the wind that are consistent with current theoretical models for this system.

First light measurements with the XMM-Newton reflection grating spectrometers: Evidence for an inverse first ionisation potential effect and anomalous Ne abundance in the Coronae of HR 1099

The RS CVn binary system HR 1099 was extensively observed by the XMM-Newton observatory in February 2000 as its first-light target. A total of 570 ks of exposure time was accumulated with the Reflection Grating Spectrometers (RGS). The integrated X-ray spectrum between 5-38A is of unprecedented quality and shows numerous features attributed to transitions of the elements C, N, O, Ne, Mg, Si, S, Fe. Ni, and probably others. We perform an in-depth study of the elemental composition of the average corona of this system, and find that the elemental abundances strongly depend on the first ionisation potential (FIP) of the elements. But different from the solar coronal case, we find an inverse FIP effect, i.e., the abundances (relative to oxygen) increase with increasing FIP. Possible scenarios, e.g., selective enrichment due to Ne-rich flare-like events, are discussed.

The interstellar oxygen-K absorption edge as observed by XMM-Newton - Separation of instrumental and interstellar components

High resolution X-ray spectra of the Reflection Grating Spectrometer (RGS) on board the XMM satellite are used to resolve the oxygen K absorption edge. By combining spectra of low and high extinction sources, the observed absorption edge can be split in the true interstellar (ISM) extinction and the instrumental absorption. The detailed ISM edge structure closely follows the edge structure of neutral oxygen as derived by theoretical R-matrix calculations. However, the position of the theoretical edge requires a wavelength shift. In addition the detailed instrumental RGS absorption edge structure is presented. All results are verified by comparing to a subset of Chandra LETG-HRC observations.

Back-illuminated CCDs made by gas immersion laser doping

Abstract Back-illuminated CCDs with high quantum efficiency in the soft X-ray range have been developed by EEV in collaboration with the Space Research Organisation Netherlands. By using Gas Immersion Laser Doping (GILD) for producing the backside accumulation layer very shallow doping profiles can easily be achieved. Additionally the GILD process does not affect the silicon behind the p+ layer in contrast to the commonly used ion implantation process. This implies that only the electrons generated in, or reaching the very small accumulation layer will have a probability to recombine at the surface or in the accumulation layer itself. Therefore only a small fraction of the electron clouds produced by the absorbed soft X-rays will suffer charge loss, resulting in a high quantum efficiency. X-ray measurements of back-illuminated CCDs with doping profiles of 50 and 100 nm depth are presented and shown to be consistent with calculations based on minority carrier transport.

Efficiency Of X-Ray Reflection Gratings

A series of prototype blazed reflection gratings, designed for incorporation in a satellite-borne, high efficiency, moderate resolution, astronomical x-ray spectrometer, have been tested for x-ray reflectivity in the relevant spectral orders. Both mechanically-ruled and ion-etched holographic master and replica grat-ings produced by various manufacturers, have been measured at 8.34 A, 13.34 A, and 44.7 A. We find near theoretical performance from a particular ion-etched sample and from one of the mechanically ruled samples. The other mechanically ruled samples exhibit lower efficiency, which can in part be ascribed to imperfections in the groove profile. A comparision between scalar diffraction theory and the rigorous electromagnetic calculations of grating efficiency for these samples is also presented.

Degradation of back-illuminated CCD's due to low energy protons

To investigate the behavior of a back illuminated CCD as an X-ray detector in a space environment some devices have been irradiated by protons. These CCDs have a depleted layer of about 30 micron. The proton irradiations have been carried out with unshielded CCDs in a calibrated monoenergetic proton beam with energy in the range between 0.75 to 1.6 MeV from an R.J. Van de Graaff Generator of the Utrecht University. These protons are stopped in the depleted part of the CCD so it can be expected that they will have a strong influence on the Charge Transfer Efficiency (CTE). Calculations with TRIM showed that protons of about 1.4 MeV are stopped just in the buried channel in which the charge transfer takes place. The proton irradiations were performed in bunches of about 10/sup 8/ protons/cm/sup 2/. Before and after each irradiation the CTE was determined with X-rays from a MgF/sub 2/ anode producing 0.667 and 1.25 keV radiation. Afterwards the CTE was determined with AlK radiation (1.486 keV) as function of operating temperature between -70 and -130/spl deg/C. It is shown clearly that protons with energies in the range from 1.25 to 1.45 MeV produce the largest degradation. For higher energies the effects diminish again.To investigate the behavior of a back illuminated CCD as an X-ray detector in a space environment some devices have been irradiated by protons. These CCDs have a depleted layer of about 30 micron. The proton irradiations have been carried out with unshielded CCDs in a calibrated monoenergetic proton beam with energy in the range between 0.75 to 1.6 MeV from an R.J. Van de Graaff Generator of the Utrecht University. These protons are stopped in the depleted part of the CCD so it can be expected that they will have a strong influence on the Charge Transfer Efficiency (CTE). Calculations with TRIM showed that protons of about 1.4 MeV are stopped just in the buried channel in which the charge transfer takes place. The proton irradiations were performed in bunches of about 10/sup 8/ protons/cm/sup 2/. Before and after each irradiation the CTE was determined with X-rays from a MgF/sub 2/ anode producing 0.667 and 1.25 keV radiation. Afterwards the CTE was determined with AlK radiation (1.486 keV) as function of operating temperature between -70 and -130/spl deg/C. It is shown clearly that protons with energies in the range from 1.25 to 1.45 MeV produce the largest degradation. For higher energies the effects diminish again.

The X-Ray Efficiency Of Replicas Of A Master Blazed Reflection Grating

The influence of replication on the X-ray diffraction efficiency of blazed reflection gratings is studied by measurements at 0.834 and 1.334 nm. Full electromagnetic calculations show that the differences in the diffraction efficiency of the first generation replicas can be explained by rounding off of the tops of the grooves as measured by stylus measurements of the groove profiles. The efficiency degradation of the second generation replica can not easily be attributed to a different groove shape. The cause of this degradation is as yet unclear. The apex angle of a blazed X-ray grating is not a critical parameter for its efficiency.