Make a New Image. I've use 300 x 300.
1) With the Elliptical Marquee Tool set style to Fexed Size Im suppossing you are ussing 300 x 300, set Width 275 px and Height 275 px.
2) Press X and D to reset your colors. Check "Reverse". Watch the image and Gradient like it:

You should have something like that:

Don't deselect yet.
3) Then go to Select -> Modify -> Contract -> 4px
4) Now go to Edit -> Transform -> 180°
Do the same like Step 3 to 4.
DONT DESELECT YET!!!! Copy And Paste and press Ctrl + U... make sure you check Colorize.

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