Author Topic: zero count rate  (Read 99 times)

neko

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zero count rate
« on: April 23, 2018, 10:14:34 am »
We recently purchased a used X-Flash detector (10mm^2) and it worked wonderfully for about a week, and then after bringing it out of standby mode on the 8th day, the countrate is exactly zero, except for a tiny noise peak.

It was installed by me into an old PGT-2000 Cameca made EDS front port flange adapter with the 3 aperture turret on SX100 #825. I have only connected up the detector part of the assembly, I've made no attempt to connect the imaging and WDS integration as of yet (assuming it can work with a SX100 and mine isn't too old or has the wrong parts, but the only really important part was the spectrum acquisition functionality). One cable from detector to the box, and megalink cable to the IO-scan card. All the cables were labelled appropriately, and as I mentioned, everything worked initially (and so, so much better than the old SiLi system).

The cooling component of the detector reports that it is functioning correctly, and reports -25˚C operating temperature.

I haven't modified any of the settings other than to change the detector angle to match the front port angle which is presumably the 40˚ that everything else was set to.

When first coming out of standby, the ratemeter jumps slightly to ~6kcps or so once or twice, then immediately resumes to zero. The spectrum auto-scales to as highly zoomed in as possible with the noise peak just off the left side of the screen.

Vacuum is all nominal. WDS is functioning just fine and nothing else seems amiss. I have, of course, rebooted everything except the SX100 itself (doesn't seem to be a need for that as there's no current integration).

It worked fine all day long the previous day, and was set into standby when the researchers left. I was the only other person to use it this week other than the researchers the day prior to malfunction, and they're professors emeriti who don't going screwing around with stuff they don't need to. I don't remember whether or not it was on and collecting counts during the hour I ran some xray maps at 100nA, but it worked fine for a day after that.

I am going to contact support (because of course everything blows up on a Friday) and see what they have to say, but figured I'd drop a line to the community of experts and see if they had any similar experiences and known solution... which I'm really, really, really hoping isn't "your detector is hosed" but at least then I'd know where to start.

Probeman

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Re: zero count rate
« Reply #1 on: April 23, 2018, 10:54:42 am »
Hi Nick,
Is it possible that the EDS aperture turret has moved somehow and the EDS aperture is no longer aligned with the detector window?  Try moving the turret handle to different positions and see if the count rate changes as the handle position changes (in between the detents).
john
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neko

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Re: zero count rate
« Reply #2 on: April 25, 2018, 12:06:58 pm »
No luck with moving the turret, but I was reminded that on our system it can cause a vacuum leak when you move it around. Since vacuum just went out, I vented the chamber and pulled the turret out for a visual inspection and to make sure nothing else had magically appeared from nowhere to block the path, but everything looks good. I just removed the aperture piece while I was in there to make doubly sure it couldn't possibly be affecting anything. While it was de-mounted I put the camera back in place and turned on the light to make sure I could get a visual on the light hitting the sample through to where the detector would be mounted (I could).

I'm going to give the excellent folks at Bruker a call after lunch.