Documentation > SXT Observation Notes > this page

Shadowing by SXT Analysis Filter Support Mesh

Image name: Filter_mesh_effects.png (click image to enlarge)
Image size: 390.858 KB (1024x512)
Date submitted: 11-Nov-1994

LWA 4/11/94

The SXT analysis filters (except for Be) are supported by stainless
steel mesh with a square pattern and approximately 80% transmission.
The mesh wires are about 35.6 micrometers wide and the pitch (repeat
interval) of the mesh is approximately 360.7 micrometers.

The x-ray image of a point source at the position of the filter is an
annulus of roughly 11 mm diameter and width 17 micrometers, broken by
the shadows of the "spider" of the entrance windows at 12 locations.
For different positions in the SXT field of view this annulus will fall
on the x-ray filter at different locations and be partially blocked by
the wires of the mesh. It is this modulation, which Barry LaBonte
calculates to be approximately 2%, which produces the square shadow
pattern in the portions of the image illuminated by x-rays. This is
illustrated by the highly processed sub image (in the upper inset) of a
portion of the image above the SE limb where x-rays dominate straylight.

Superposed upon the square x-ray grid shadow is a pattern of lines which
are the one-dimensional shadows of the mesh wires cast by visible light
which is transmitted by the thin aluminum filter at about a 1e-7 level.
This solar image comes in through the failed entrance filter. The
visible image is better focussed in one direction than the other because
the entrance aperture of the x-ray mirror is only 350 microns radially
whereas a 30 degree sector of the entrance filter provides about a 5 cm
aperture in the circumferential direction. The 1-d shadow is
illustrated in the bottom inset--is taken from the south coronal hole
region where the x-ray signal is very small.

To the YLA Guide front page with side-frame
To contact us: