Development of a 3Pi Ion Spectrometer, 15-R9468

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Principal Investigators
Philip W. Valek
Frédéric Allegrini
Jerry Goldstein
David J. McComas
Oleg Vaisberg

Inclusive Dates:  04/01/04 – 04/03/06

Background - Space science studies the flow of mass and energy of plasmas throughout our solar system. NASA conducts spacecraft missions to directly measure the plasmas responsible for this flow. The current state of the art in space plasma instrumentation used in these missions has a limited field of view. To make a complete measurement of the ions arriving from all possible incident directions requires that the instrumentation be either physically scanned over space or to use multiple sensors to cover the full field of view. Either of these approaches adds complexity and additional resources. In this internal research project, we have developed a sensor that can instantaneously view three quarters (3 Pi sterradians) of all look directions. This view will allow future missions to perform measurements of space plasmas with few resources and with a higher time resolution.

Approach - Our instrument uses a series of electrostatic mirrors to focus the incident ions onto an imaging plane. The mirrors generate an electric field inside the sensor to control the path of the ions. Numerical methods were used to calculate the electric fields of each mirror design. After the electric fields are calculated, Monte Carlo techniques were used to fly millions of virtual particles though the sensor. The transmission properties of the ions were used as we iterated the design for and optimized mirror design. To verify the results of the modeling, key components of the mirrors were built and tested with ions in our calibration facility.

Accomplishments - We have designed a sensor that can measure ions incident from over three quarters (3 Pi Sterradians) of the sky. We have multiple configurations of this design, which allows us to apply this technique to different mission requirements. For example, one configuration that directs the ions through a series of thin apertures would be used in missions that have a high background of ultraviolet light. The series of thin apertures make it less likely for light to scatter into the detector, giving a source of noise.

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