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Response of a delta-doped charge-coupled device to low energy protons and nitrogen ions
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View: Figures


Image of FIG. 1.
FIG. 1.

(Color) This panel shows solar wind charge states of Fe as a function of day of year (DOY) observed in 1998 using the ACE SWICS instrument. The shading represents the relative abundance of the charge states (summing to one for each time step). Fe charge states approximately nine to ten are expected in quiet solar wind. Charge states , especially those , are indicative of hot material associated with ICMEs. The period above marked by the dashed lines marks the observation of high charge states of Fe during an ICME passage at the ACE spacecraft at L1. The ability to resolve charge and mass of ions in the solar wind allows us to learn about the conditions close to the Sun during a CME eruption.

Image of FIG. 2.
FIG. 2.

Schematic of measurement technique used in the SWICS instrument on ACE. Adapted from Gloeckler et al. (Ref. 10). The quantity , the deflection voltage, is set to select ions with certain energy per charge, . Instruments such as this are key to solar wind observations but are currently inhibited by SSDs with low energy thresholds .

Image of FIG. 3.
FIG. 3.

Solid-state detector efficiency curves for SWICS on the Ulysses spacecraft. The curves were fitted to laboratory calibration data. The efficiency depends strongly on mass (Ref. 19).

Image of FIG. 4.
FIG. 4.

Solid-state detector efficiencies for for the ACE and Ulysses spacecraft. Improved technology for the ACE mission allows to be detected at lower energies compared to the Ulysses SSD. However, ions below still elude detection.

Image of FIG. 5.
FIG. 5.

Schematic of delta-doped CCD structure (not to scale) showing boron atoms below the silicon epilayer surface and protected by an oxide overlayer. Delta-doped CCDs are back-illuminated devices, meaning that particles are incident on the back surface. [Adapted from Nikzad et al. (Ref. 13).]

Image of FIG. 6.
FIG. 6.

Experimental setup (not to scale).

Image of FIG. 7.
FIG. 7.

Mean transmitted energy as a function of incident energy of 1000 ions incident on a hypothetical dead layer. The solid lines represent the results from the thin, dead layer, while the dashed lines represent the results from the thicker, dead layer. Both and lose more energy in the thicker dead layer; however, loses much more in the thicker layer and is no longer detectable at or below . In the thicker dead layer, loses half of its incident energy.

Image of FIG. 8.
FIG. 8.

Energy straggling as a function of transmitted energy. The solid lines represent the thinner dead layer, while the dashed lines represent the results for the thicker dead layer. Both the and exhibit much larger energy straggling in the thicker dead layer. The energy straggling for in the thin dead layer is nearly negligible.

Image of FIG. 9.
FIG. 9.

The response of the delta-doped CCD to beam. The squares represent the data obtained by JPL in 1999 using the CCD in imaging mode to detect individual protons (Ref. 13). The diamonds represent our data obtained in this study using the CCD in current mode.

Image of FIG. 10.
FIG. 10.

The response of the CCD to and beams. The results from Fig. 9 are plotted on this figure as diamonds. Our results are plotted as squares. The response to the beam is lower than for the beam, as expected from the simulations.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Response of a delta-doped charge-coupled device to low energy protons and nitrogen ions