[labnetwork] troubleshooting an e-beam source

[Yakimov, Michael]

Hard to point a finger at test points without knowing your exact setup. Since you have filament current going to 0, not flickering, I would look at control circuitry upstream.

Generic diagram of evaporator high voltage source is attached. Transformer T1 is usually a big heavy block near/under the chamber; solid state relay/triac T2 can be in the same block or in a main electronic unit.  R1 is your filament.


Items to check from upstream to downstream:

1. 0-5 (0-10) V from the controller (Inficon or whatever  you use).

2. This voltage can pass through some emission stabilizing circuitry or something similar before coming to the triac/SSR; (I actually had to bypass that stabilizer in our machine in Thermionics HV set because of a similar issue)

3. voltage after the SSR on the primary windings of transformer - WHATCH FOR HV!!!

4. voltage at transformer output (chamber input) STRICTLY WITH HIGH VOLTAGE CABLE DISCONNECTED AT THE SOURCE!!


Thanks


Mike






________________________________
From: labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Nathanael Sieb <sieb at 4dlabs.ca>
Sent: Thursday, July 8, 2021 1:07 PM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] troubleshooting an e-beam source


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://www.dropbox.com/s/7n42e38qviju7ga/Both_emission_and_filament_spiking_and_turning_off.mov?dl=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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