E. Maddox

Development and Characterization of Large La-Halide Gamma-Ray Scintillators for Future Planetary Missions

Future planetary missions such as BepiColombo are resource limited in both mass and power. Due to the proximity of the spacecraft to the Sun, the instrumentation will encounter harsh environments as far as radiation levels and thermal loads are concerned. Only radiation hard detectors that need little or no cooling will be able to successfully operate after long cruise times and over the expected mission lifetimes. The next generation of lanthanum halide scintillators promises to provide sufficient resolution in the spectral range between 1 and 10 MeV where most of the elemental gamma-ray emission lines can be detected. In order to be suitable for planetary gamma-ray spectrometers with sufficient sensitivity it had to be proven that larger crystals of size 3 can be produced and that they maintain their resolution of 3% at 662 keV. For that purpose we have produced and characterized several larger crystals and assessed their radiation hardness by exposing the crystals to radiation doses that are representative of the expected conditions in the space environment. Systematic measurements on several crystals allowed the determination of the activation potential and the performance verification from which the consequences for instrument flight performance can be derived. From these investigations we conclude that these scintillators are well suited for planetary missions, with excellent and stable performance.

Performance characterization of silicon pore optics

The characteristics of the latest generation of assembled silicon pore X-ray optics are discussed in this paper. These very light, stiff and modular high performance pore optics (HPO) have been developed [1] for the next generation of astronomical X-ray telescopes, which require large collecting areas whilst achieving angular resolutions better than 5 arcseconds. The suitability of 12 inch silicon wafers as high quality optical mirrors and the automated assembly process are discussed elsewhere in this conference. HPOs with several tens of ribbed silicon plates are assembled by bending the plates into an accurate cylindrical shape and directly bonding them on top of each other. The achievable figure accuracy is measured during assembly and in test campaigns at X-ray testing facilities like BESSY-II and PANTER. Pencil beam measurements allow gaining information on the quality achieved by the production process with high spatial resolution. In combination with full beam illumination a complete picture of the excellent performance of these optics can be derived. Experimental results are presented and discussed in detail. The results of such campaigns are used to further improve the production process in order to match the challenging XEUS requirements [2] for imaging resolution and mass.

Gamma-Ray Induced Radiation Damage in

The effect of high dose 60Co gamma irradiation on photoelectron yield, energy resolution, optical transmission, scintillation time profiles and thermoluminescence glow curves of LaBr3:5%Ce and LaCl3:10%Ce crystals has been investigated. Both materials show lower yields and deteriorated resolutions after exposure to a strong 60Co source, however their transmission, yield proportionality, scintillation decay, and thermoluminescence remain unaffected. Initial scintillation characteristics can be retrieved neither by spontaneous recovery nor upon heating in vacuum.

{\rm LaBr} _{3}{:}5\char"25{\rm Ce}

The establishment of Silicon Pore Optics (SPO) as the technology of choice for the implementation of future large X-ray space optics has opened up the road to its use in all classes of X-ray missions with varying scientific goals. This interest has given us the possibility to broaden the design parameter space which is normally considered for SPO optics. In doing so a number of classical space X-ray optics design issues (e.g., field of view, stray light, baffling, aberrations) have been tackled. In this paper we report on recent results achieved in this effort. Particular attention will be given to the issues of stray light and baffling, a topic upon which a combination of analytical, simulation, and data analysis means can be effectively brought to bear. Missions considering the use of SPO optics have requirements spanning more than two orders of magnitude in energy, and a factor 20 in focal length. The possibilities that can be considered and the trade offs that must be made when applying SPO to such a wide range of optical designs will be illustrated, and some of the possible solutions discussed.

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A new Interplanetary electron environment model based on statistical analyses of historical datasets is presented. The model reports generates confidence limits for solar electron fluences in a similar fashion to existing Solar proton models, as well as peak event fluxes and fluences. Electrons of Jovian origin are also modeled based on simplified diffusive transport equations to provide predicted fluxes for locations within the ecliptic plane.