Radiation Shielding Method Of Energetic Particles For Ultraviolet Photomultiplier Of The Tiny Ionospheric Photometer

The satellites and space stations are mainly operated in the Earth's thermosphere and ionosphere. Studying on parameters of thermosphere and ionosphere would be used to provide the spacecrafts the safety, elongate their lifetime and to promote the measurement precision of remote sensors. The electron's irregular variation in ionosphere has effects on communication and measurement&control. And ionosphere's stochastic rapidly variation,especially in the lower latitude that causes ionosphere's flaring, could suspends communication of satellites in some serious condition.The newly employed technologies has enlarged the space of exploration of the ionosphere, the time interval for measurements also gets smaller.So that the investigation on physics of ionosphere and propagating of iono-wave are more important than before. The microluminometer onboard the satellite which could conduct measurements of parameters in ionosphere is an optical sensor measuring the radition magnitude of airglow's ultraviolet in vaccum, the total abundance of electron in ionosphere would be extracted by refutations. Due to its higher sensibility, smaller power and size, this sensor is paid attention by society of space physics.Probes are exposed in galatic radiation, solar ion eruption and radiactive sphere formed by trapped particles during satellite's operating. Therefore the energtic particles can penetrate the satellite. Furthermore, the second radiation caused by galatic rays interacting with the materials of satellite's container could deteriorate the condition in which the optical electrial amplifier works. In extremely condition, equipents could not work at all. The energtic particals effects on vacuum ultraviolet PMT are mainly two aspects as follow: 1.spacecrafts total dose effects of vacuum ultraviolet PMT by energtic particals. This effects contributing by energtic particals orginated from trapped protons electrons and solar ions in Van Allen radition belt. Total dose effects could decline the electronics of sensors. Once the total dose reaches the threshold, the electric components will fade rapidly until not functioning at all. 2. Energric particals could penetrate the PMT window, directly bombard the photocathode and first and second multiple cathode to generates counts, lead to lower sensitive of the probe.By using the calculation program MULASSIS (multi-layered shielding simulation software, MULASSIS) which developed under the cooperation between QinetiQ, BIRA and ESA, Energetic particles environment of the sun synchronous orbit and Monte-Carlo simulation calculation are used in simulating PMT's high-energy particles shielding material combination's model. The simulations have determined an optimized shield constituted by an Aluminum/Tungsten/Aluminum tri-layer. For each thickness is 2mm/0.5mm/2mm and in a sun-synchronous environment, the dose received by PMT will be decreased from 9.98×106rad to 8.41×102rad, this optimized multilayer structure could meet our performance requirements. The result has important practical engineering guidance.