Development of an Advanced Space Weather Warning System: The PreSTIM Laboratory Prototype, 15-R9557

Principal Investigators
Frédéric Allegrini
Mihir I. Desai
Arik Posner
Dave McComas
Stefano Livi

Collaborators
Nick Paschalidis, George Ho
Applied Physics Laboratory, Johns Hopkins University

Inclusive Dates:  07/01/05 – Current

Background - Explosions – coronal mass ejections and flares – on the surface of the sun can release large amounts of energy and mass into the interplanetary medium. A fraction of these perturbations will inevitably impact directly on the Earth’s magnetosphere. Geospace, the region surrounding our planet with a magnetosphere, is a protective environment that shields the upper atmosphere and low-Earth orbit against the solar wind and energetic particles. Under solar storm conditions, when transient solar activity impacts and transforms the magnetic bubble, the reaction of the Earth's environment is, at times, violent and dangerous. Changing magnetic fields induce currents, and this is also true for the ionosphere (the uppermost layer of the Earth's atmosphere). These currents can interfere with human technology on the Earth's surface and in space. The positions of the radiation belts, carefully avoided by human space mission planners, become uncertain and often suddenly interfere with human presence in space. Severe radiation damage to humans and their support systems can result and needs to be avoided. Such severe space weather conditions can now be forecast well in advance, with the Pre-Shock Suprathermal Ion Monitor (PreSTIM) placed on upcoming space weather monitoring missions. The objective of this project is to bring PreSTIM from the concept level to a fully functional laboratory prototype. PreSTIM is being developed in collaboration with the Applied Physics Laboratory at Johns Hopkins University.

The traditional way to derive kinetic energy (E), mass (m) and charge (q) is to determine the mass-per-charge by selecting a certain E/q, the time of flight (TOF) of the particle over a known distance, and the total kinetic energy with a solid-state detector. The PreSTIM concept of measuring suprathermal ions is entirely new. The stopping power of two carbon foils in combination with a newly designed ion optics aperture is used to separate ion species and determine individual fluxes. The sophisticated ion optics configuration separates ions in energy-per-charge so that they are ordered when they enter the TOF section with nearly parallel paths. The kinetic energy, the mass, and the charge of the particle can be derived if the energy loss of the particle in the carbon foils is known.

Approach - The project was divided into four objectives.

• Modeling and optimization of the instrument. For this task electro-optics simulations will be performed using the powerful software Simion®. The model of the instrument will include carbon foil effects (energy straggling and angular scattering of the particles). Time-of-flight measurements will also be simulated to estimate the mass resolution of this instrument.
• Design and fabrication of laboratory prototype. Based on the results of the first objective, a laboratory prototype will be designed and built.
• Integration of detectors and electronics and tests with ion beam. The detectors will be integrated into the laboratory prototype in a clean area, and the tests with ion beam will be carried out in a high vacuum chamber.
• Extend research on suprathermal ions.

Accomplishments - The project team created a three-dimensional electro-optics model for the laboratory prototype. This model consists of two parts: the energy disperser and the TOF section. Both were optimized to improve the energy per charge resolution and the mass resolution. The model was used to test different design options to determine the optimum configuration within our parameter space. The model showed promising results.

Based on the results from the optimization of the electro-optics, a laboratory prototype was designed and built. The energy disperser was first tested separately in a vacuum chamber with ion beams, and subsequently tested with the TOF section. The mass resolution exceeded expectations, which were based on the model. The testing thus far showed very promising results.

As a result of this project, SwRI was awarded a Supporting Research and Technology (SR&T) grant from NASA to further develop the concept over a period of three years. The development of PreSTIM will continue with assembly and testing of a collimator. The full prototype will be tested at the Johns Hopkins University Applied Physics Laboratory over a higher energy range and with an improved detector.

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