Re: eiger2 vacuum sequencing power status

[Maren Purves via Tech-talk <tech-talk at aps.anl.gov>]

Agree.

If you want to make sure it is really off you need something like a networked power switch and do this by hand.

Maren Purves
retired from East Asian Observatory / JCMT

On Wed, Feb 11, 2026 at 11:45 AM Guruswamy, Tejas via Tech-talk <tech-talk at aps.anl.gov> wrote:

Hi Keith,

I assume you are turning the entire detector power supply on/off and not just the high voltage bias.

If that's the case I would not rely on the IOC to confirm detector power off for equipment protection purposes; the opposite is true, if it reads 'ready/idle' the detector is definitely powered on, but there are other ways to end up with Status=error with the detector still powered. (Error during initialization, communications error, ...)

Logically I do not believe you can use any reporting from the DCU computer to reliably tell you detector power is off. Trivial example: what if the detector is simply disconnected from the DCU, but still powered on?

Best,

Tejas Guruswamy

APS, XSD-DET

Argonne National Laboratory

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From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Keith Surrena via Tech-talk <tech-talk at aps.anl.gov>
Sent: Wednesday, February 11, 2026 3:28 PM
To: Jemian, Peter R <jemian at anl.gov>; tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: RE: eiger2 vacuum sequencing power status

 

Thanks, Pete. We'll have a vacuum gauge with relay contacts and the IoT relay connected to the eiger power supply will be controlled from the PLC, so our setup won't be too dissimilar from your mono. What I'm looking for is a level of verification from the eiger that is indeed unpowered before we begin the pumpdown or vent sequencing. The IOC seemed like a useful tool for feedback but I can understand how it could fall prey to unexpected output.

KMS

-----Original Message-----
From: Jemian, Peter R <jemian at anl.gov>
Sent: Wednesday, February 11, 2026 4:10 PM
To: tech-talk at aps.anl.gov; Keith Surrena <ks2339 at cornell.edu>
Subject: Re: eiger2 vacuum sequencing power status

[You don't often get email from jemian at anl.gov. Learn why this is important at https://gcc02.safelinks.protection.outlook.com/?url="">  ]

You need this protection to be available, even if EPICS is not working.  Don't rely on EPICS for machine protection work.

________________________________________
From: Jemian, Peter R <jemian at anl.gov>
Sent: Wednesday, February 11, 2026 3:08 PM
To: tech-talk at aps.anl.gov; Keith Surrena
Subject: Re: eiger2 vacuum sequencing power status

To avoid arcing high-voltage ion gauges in the intermediate vacuum region (of a double-crystal monochromator), I used a thermocouple vacuum gauge.  The gauge controller has setpoints for this range.  Each setpoint was connected to a relay contact.  The PLC (outside the vacuum chamber) sensed those contacts and operated a relay to energize when conditions allow.  Being the brutal sort, that relay switched on/off the mains power for the device being protected.

Pete


________________________________________
From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Keith Surrena via Tech-talk <tech-talk at aps.anl.gov>
Sent: Wednesday, February 11, 2026 2:38 PM
To: tech-talk at aps.anl.gov
Subject: eiger2 vacuum sequencing power status

We're working on some PLC control for protecting our eiger2 4M that will live in vacuum and I'm looking for some feedback. Dectris specifies that it must be unpowered while chamber pressure is between 1bar and .01 mbar, so we're interested in using an IoT relay to disable the power supply remotely. To verify that the detector is off, I was thinking about querying detector state with the State_RBV record. I noticed that so long as the read status rate is set reasonably, this should return "Error" as the state, instead of "Idle". I could create logic based around these states but I'm worried that I could be missing a different interpretation of the "Error" state that could lead to believing the detector is unpowered when it isn't. Are there any other records that would be useful for verification?


Keith Surrena
Research Support Specialist
Cornell High Energy Synchrotron Source