NetNotes
but some are permanent. Te risk I mentioned by opening the camera head is that microlenses on the image sensors are very oſten soſt and smooth, such that any mechanical attempts to remove dust particles will likely cause damage. However, a dust particle can easily generate a non-usable cluster of a few pixels. Gerhard Holst
gerhard.holst@pco.de
Since our original message about the Andor condensa-
tion issue we have barely used our Andor Zyla. Roy’s email is quite interesting since it seems possible, although a bit risky, to breathe some new life into our Andor Zyla without spend- ing tons of money. If we end up trying his procedure, I’ll fol- low up with information on how things turned out. I would like to add two extra notes. First, I have received emails from 5–10 researchers (not via the listserv) who indicated the same prob- lem. Surely there are others who don’t read the list. So, I have gathered that this is a pretty common issue for cameras that are aging a bit but probably have their electronics still functioning very well. Second, we do regularly use the cheap ZWO cam- eras that I mentioned but we noticed that they have a different problem. Tese cameras, while amazing for the price, don’t have much in the way of a seal, just some desiccant bags near the sensor. It seems that these desiccant bags eventually create a bit of debris on the sensor. Aſter 6–9 months, we ended up open- ing up the camera, cleaning the sensor, re-drying the desiccant similar to what Roy has described, and reassembling. Mostly this has worked well for us. Joshua Vaughan
jcv2@uw.edu
Great information from Roy Bainer. We also had conden-
sation on one of our two Andor Zyla 4.2 sCMOS cameras on an Andor Diskovery spinning disk confocal system (Spectral Applied Research). At that time (October 2018), there were two issues: Andor and Coherent Scientific (Australia; who supplies products from Andor, Nikon, Coherent, TMC, etc.) took a long time to discuss maintenance agreements for the Diskovery sys- tem (Andor will repair the Diskovery but will not do a contract that covers parts), and the condensation on the Zyla. Te pic- tures in this link show the condensation:
https://imgur.com/a/ yF0Jbem. Note that when switching between objectives, the size of the actual structures change, but not that of the drop- lets. Initially, we did what others here have done: we leſt the camera on as the condensation would disappear aſter the cam- era reached a certain temperature. However, one can only do this for so long as eventually the sensor will fail. Rumelo Amor
r.amor@
uq.edu.au
Moisture and Vacuum Leaks when Inserting the Talos 626 Holder 3DEM Listserver Dear all, I am using a Gatan 626 holder on a side entry
TALOS microscope. I have problems with very frequent crystal- line ice formation on the grids. Sometimes I get a mix of vit- reous water and crystalline ice but most of the time I only get crystalline ice. I have been extra careful during sample prepara- tion, transferring the grid on to the holder, and I have done a 48-hour holder bake out before insertion. However, I still get ice on the grid. I also monitor the temperature of the holder during the insertion process, including 3 minutes for the airlock pump.
76
During those 3 minutes the temperature increases to -152.2°C. Can this be the reason for the unwanted ice formation? How high can the temperature of the holder be to ensure vitreous water? I also have vacuum problems while inserting the holder. Aſter the 3-minute airlock pump (I cannot use a longer time because of the aforementioned temperature issue) as soon as I open the column port the vacuum either increases or completely crashes the column vacuum. Tis has happened with two different hold- ers either cooled with liquid nitrogen or at room temperature. So, my question: is this insertion process always that sensitive or is there something wrong with the holders/airlock pump? Ariel Talavera Perez
ariel.talavera@ulb.be
Is that a Talos 120? New users find it difficult to insert even
the room temperature holder, and although I’m fine with the room temperature holder, I’ve almost never managed to insert the 626 without a vacuum break. So, we rarely use this micro- scope for cryo for this reason. As for how you do it, I would consider trying a shorter pumping time (try 60 or 90 sec.) and just accept that the vacuum will crash. Once the holder is in you can refill it and then it won’t warm up that much. Another thing that may help is to pretilt the stage when you’re insert- ing the holder, in case you aren’t already doing this. If none of this helps, you may have a problem with the shutter of the 626. Lars-Anders Carlson
lars-anders.carlson@
umu.se
Te vacuum breaks could be an o-ring issue. Make sure the
o-ring is completely clean—no hairs etc.—and is VERY lightly greased. Try replacing it with a new one. We have had horrible problems with vacuum breaks due to garbage on the o-rings. Don’t let people into the room with sweaters, for instance. Te crystalline ice could also mean that you need to replace the clip ring. If it is not clamping the grid tightly, you will have ice. Also, there is a spring that lines the depression where the grid sits. Tat also occasionally needs to be replaced. Finally, it is worth finding out if your controller is functioning properly during bake-out. Is your holder heating up? Is the vacuum in the pumping station sufficient? Sharon G Wolf sharon.wolf@
weizmann.ac.il
To add to Krishna’s comments the airlock may also need
to be cleaned. I recently had frequent vacuum crashes on our CM200 and a careful cleaning of the airlock tube removed a lot of particulates that were the cause of the problem. I would rec- ommend your field service engineer clean it as there are some sensitive components that you don’t want to damage. Christos Savva
gwcsl@leicester.ac.uk
You are pumping your cold 626 for 3 mins before insert-
ing? Most people (including us) only use 20–30 seconds (!) to pump and then insert it. Tis way the sample does not warm up so much. It is more risky that the column vacuum will crash, but in reality this oſten happens. Also cleaning/exchanging the o-ring of the 626 helps to maintain a good vacuum. Te o-rings are reasonably cheap, and we exchange them every two months as a preventive measure. Of course, the o-ring must be greased properly (not too much, not too little) and must be undamaged with no dust or fibers. Also make sure that the o-ring is not cold when inserting the 626 or it will not seal properly. Also do the “trick” of rotating the stage to -60o
so that you can insert
the 626 with its dewar pointing to the right (or leſt) instead of
www.microscopy-today.com • 2020 May
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