[labnetwork] troubleshooting an e-beam source

Fri Jul 9 08:51:10 EDT 2021

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<mailto:info at fabsurplus.com>
Mobile (USA) : +1 830-388-1071
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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
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