[3dem] glow discharge "fireball"

[Guillaume Gaullier]

Hello Jason,

Last October there was a discussion on this same list about glow
discharge difficulty, see the summary here:
https://mail.ncmir.ucsd.edu/pipermail/3dem/2025-October/012172.html 

One thing that was mentioned was that dust or other things in the
chamber can cause flickering and sparks. Could it be what you are observing?
Batch to batch variability of grids was also mentioned, and some people
apparently still find it necessary to clean their grids with organic
solvents (I remember doing it around 2017, but haven't needed to in a
long time).

Not sure this is related to your problem, but I hope this helps!
Cheers,

Guillaume

On 04/02/2026 22.20, Jason Kaelber via 3dem wrote:
> Dear 3DEM,
> When glow discharging with our Pelco easiGlow (e.g. at 15 mA, 0.39 mBar
> room air for 25 seconds) on the aircraft aluminum grid blocks, sometimes
> a ball of plasma will be observed above one grid, or one ball each among
> several randomly-placed grids in the block. The ball is light pink and
> may manifest at any time during the discharge, typically enduring until
> the end of the cycle but perhaps flickering in and out of existence.
> Below I enclose a photograph of the phenomenon:
> Have any of you observed this? Do you know the cause or solution? It
> doesn't happen when we glow discharge on glass slides—but on the other
> hand, we we using the aluminum blocks for a couple years without issue
> before ever seeing this, and ordering a brand-new block doesn't help.
>
> Thank you in advance for your helpful replies,
> Jason Kaelber
>
> --
> J T Kaelber, PhD
> Director, Rutgers CryoEM & Nanoimaging Facility <https://urldefense.com/ 
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