[labnetwork] troubleshooting an e-beam source

Fri Jul 9 11:59:34 EDT 2021

I think what you see in the video, when the Emissions current spikes to
~130mA, is an electrical arc - the HV suddenly arcs to ground or
somewhere.  Looks for burn marks around insulators etc. to see if you can
locate the arcing region.
I agree to check the ceramic insulators- miniscule fractures or metal
coating could cause such arcs.

On our Ion-beam dep, we've found that hard to see cracks in the many
ceramic insulators around wiring will enable similar arcing, causing
Currents to spike like in your video – the power supply then faults
temporarily (for a split second), shutting it off and then attempts to
recover back to the setpoint.
-- Demis

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On Fri, Jul 9, 2021 at 8:41 AM Khanna, Rohit <r.khanna at ucl.ac.uk> wrote:

> Hi,
>      Based on the video that was shared, I suspect there is an issue with
> the filament current.
> To begin with I am not sure how thick the filament is and 26 Amp seems on
> the high side.
> Check the manual if the filament is rated to work at such high currents.
> Secondly check the
> the power supply that runs the filament as in the video there was a dip in
> the filament current
> before the emission current dipped. The emission current is highly
> dependent on the filament temperature
> which depends on the filament current. For 26-30 amp filament current the
> cable should be fairly thick and
> any issue with the vacuum feed thru or connector (corroded or oxidized
> will lead to localized heating or melting).
> Check the cable connector and filament power supply before sensing the
> unit back.
>
>
> Warm Regards
> Rohit Khanna
> Electronic Test & Measurement Engineer
> London Centre for NANO Technology, UCL
> Ph:+44-020-76799984
> Int Ext: 39984
>
> ------------------------------
> *From:* labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Stephen
> Howe <info at fabsurplus.com>
> *Sent:* 09 July 2021 09:13
> *To:* Nathanael Sieb <sieb at 4dlabs.ca>; labnetwork at mtl.mit.edu <
> labnetwork at mtl.mit.edu>
> *Subject:* Re: [labnetwork] troubleshooting an e-beam source
>
> In my opinion, you need to study the problem more methodically using the
> data you have to find the cause of the problem.
> For starters I would plot graphs of how all the parameters you are
> measuring change during the incident, which should allow you to see what is
> causing the problem.
> I would guess it looks like a high voltage breakdown.
> That can be often due to bad insulation or a vacuum problem .
> A part of a high voltage circuit that often fails is the driver part for
> the signals which end up sitting at high voltage.
> As the control signals go from the part of the circuits at low voltage to
> the part of the circuits at high voltage, they have to pass through some
> kind of transformer, which can suffer from problems of large back emfs ,
> which can blow the drivers.
>
> Yours sincerely,
>
> SDI Fabsurplus Group
> Stephen Howe
> Company Owner
> email: info at fabsurplus.com
> Mobile (USA) : +1 830-388-1071
> Mobile (Italy) : +39 335-710-7756
> WWW.FABSURPLUS.COM
> Your Marketplace for Used Semiconductor Equipment
>
>
> On Thu, 2021-07-08 at 10:07 -0700, Nathanael Sieb wrote:
>
> Hi all,
>
> We are trying to trouble-shoot a PVD e-beam source and can't seem to
> figure out the problem.  Early in the year we sent the assembly out for
> repair and refurbishment. (we burned a hole in the internal bellows tubing,
> long story)  When we got it back we connected it back to the system and
> started it up.  However, we haven't been able to get a stable emission
> current.  The HV stays on but the filament current, and hence emission
> current, occasionally cuts out.  It comes back a second later, over-shoots
> the target current, and then restabilizes.  It happens at low emission
> currents and some higher ones.  The timing is random.  Sometimes it happens
> frequently, sometimes you can run 15 min without a problem.  There are no
> errors from the power supply.
>
> We took a video of the issue and it happens at around the 1min mark here
> <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.dropbox.com%2Fs%2F7n42e38qviju7ga%2FBoth_emission_and_filament_spiking_and_turning_off.mov%3Fdl%3D0&data=04%7C01%7C%7Cdd69e26f9c4142a0830808d942cdfb99%7C1faf88fea9984c5b93c9210a11d9a5c2%7C0%7C0%7C637614276381113135%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=w6o5i64gVrOTPzuYA%2FOFN3nmy0wb2Ufv1Zn9aULhVLY%3D&reserved=0>.
> The advice from vendors was to look for a loose connection.  We have
> checked all the external connections and tried to look at the internal ones
> too.  Last week we removed the filament and reinstalled it.  We didn't see
> any problems and we still have the same issue.
>
> We're running out of ideas other than sending it back to the vendor to
> examine the entire assembly again.  Has anyone else encountered this type
> of problem?  Any suggestions?
>
> Thanks,
> Nathanael
>
> *Nathanael Sieb *
> Director of Operations and Administration  |  4D LABS
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