Re: 7904 excessive shadow/flare


Albert Otten
 

Hi John,

If there is effect of the beam current on the bouncing back electrons then the effect would increase when intensity (so beam current and the B field) is cranked up. I didn't notice this.
I also played with Trace Rotation. Trace rotation did nothing special; the primary spot and image stay in line. Probably the field of the trace rotation coil is to weak in the region where bounced back electrons fly.

[I can't attribute to the discussion until after the weekend.]
Albert

On Thu, Jul 4, 2019 at 04:42 PM, John Griessen wrote:


There is going to be some magnetic field action. We have a strong current of
e- going straight down the tube perpendicular to the phosphor. When an e- does
a bounce, it is going in a partly outward direction, but the
rest of the e- beam is going straight, and making a current surrounding
magnetic field that is unaffected by the
odd bouncing electrons.

The strong main B field is circles around the impact spot since it is caused
by the e- beam, and the direction
will be counterclockwise looking at the phosphor surface from inside the tube.

If an electron is bouncing back off perpendicular, its outward velocity will
interact with the B field and it will feel a force. the force will be
perpendicular to velocity X B, (thumb of right hand rule), so while bouncing
outward and upward, (v X B) points down and out, and as that makes it go more
outward the effect is more downward, but getting weaker with distance. The
weakening with distance could mean that as e- falls it is just
mostly newton mechanics trajectory, and it is curve more only close in.

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