Judith R. Fleischman

Multilayer anode with crossed serpentine delay lines for high spatial resolution readout of microchannel plate detectors

We have designed, built, and tested the first successful imaging microchannel plate (MCP) detector that uses two crossed, printed circuit, serpentine delay lines, one stacked above the other in a three‐dimensional architecture. Laser ablation machining is used to cut slots that allow delay lines in two layers parallel to the MCP to sample and read out x and y image positions. Previous readouts that use delay line timing to read out both dimensions of an image employ a wire‐wound anode. The goal of this readout is to provide as many picture elements (pixels) as possible in two dimensions, with high temporal resolution, high throughput, high dynamic range, and good spatial linearity. This detector achieves this goal with off‐the‐shelf electronics and is robust for space flight. The full width half maximum (FWHM) spatial resolution is 32 μm at the center of the detector and is typically <35 μm throughout the detector. The rms linearity is 40 μm in each readout dimension, after applying only radial correction...

Status of the stellar x-ray polarimeter for the Spectrum-X-Gamma mission

The Stellar X-Ray Polarimeter (SXRP) uses the polarization sensitivity of a graphite Bragg crystal and a lithium Thomsom scattering target to measure the polarization of X-rays from astrophysical sources. The SXRP is a focal plane detector for the Soviet-Danish SODART telescopes which will be launched on the Soviet Spectrum-X-Gamma mission. The SXRP will be the third orbiting stellar X-ray polarimeter, and should provide an order of magnitude increase in polarization sensitivity over its predecessors.

Multilayer anode with orthogonal serpentine delay lines for high-spatial-resolution readout of microchannel plate detectors

We have designed, built, and tested the first successful imaging microchannel-plate (MCP) detector that uses two orthogonal, printed circuit, serpentine delay lines in a three-dimensional architecture. Laser-ablation machining is used to cut slots that allow delay lines in two layers parallel to the MCP to sample and read out x and y image positions. Previous anodes that use delay-line timing to read out both dimensions of an image employ a wire-would anode. The goal of this readout is to provide as many picture elements (pixels) as possible in two dimensions, with high temporal resolution, high throughput, high dynamic range, and good spatial linearity. This detector achieves this goal with off-the-shelf electronics and is robust for space flight. The full width half maximum spatial resolution is 32 micrometers at the center of the detector and is typically < 35 micrometers throughout the detector. The rms linearity is 40 micrometers in each readout dimension, after applying only radial corrections for fringe field effects near the perimeter, and < 20 micrometers after applying additional simple (1- dimensional) corrections. We discuss fabrication techniques.

Wide-field-of-view 83.4-nm self-filtering camera

Photometric imaging of ionospheric/magnetospheric O II emission at 83.4 nm is a primary objective for mapping the distribution of O+ ions. However, instrumental sensitivity has been a major barrier to realizing this goal. We report an instrumental design employing a low focal ratio camera where the reflecting surfaces act as both narrowband reflection filters at 83.4 nm and wide field of view imaging system. The design includes coatings with reflectances that are relatively insensitive to the angle of incidence of light. The peak reflectance per mirror is more than 60% at 83.4 nm with the average reflectance for out-of- band wavelengths less than 5%. The net reflective transmission for the three imaging mirrors is greater than 20% with 6.8 nm bandwidth and 0.01% maximum transmittance for out-of- band wavelengths.

Vectorial photoelectric effect at 2.69 keV

Recent experiments conducted to study the vectorial photoelectric effect with CsI, Al2O3 and Si photocathodes at 2.69 keV indicate null results. Detailed analysis shows that previously measured modulation can be well explained by geometrical misalignment and a combination of the asymmetric shape of the incident X-ray beam and a small detection area of the photoelectron detector. After the elimination of the sources of spurious modulation, we observed a modulation factor of less than 3 percent for a grazing incidence angle as small as 5 deg. There is no observable difference in the pulse height distribution between s and p states.