Nice question(s) dear Satu....

Don't have the exact structural design /plan of the JEOL-1400 but I guess that your Anti-Contamination-Chamber is similar to a "dewar" or dewar-like "appendix" (e. g., an insulated thermosjug/-flask) mounted alongside your TEM-column. Filled with LN2 at (minus) -196°degr.C, at least most of that low temperature [usually] will be transferred into the 'specimen-in place'- containing evacuated chamber by means of highly-thermo-conductive material (like a flexible or static 2-3 cm thick meshwork made from 0.2mm diameter copper-wires).

Anticontamination and liquid nitrogen: producing a "really cold" surface in the evacuated (=highly evacuated!) portion of the objective pole piece (and - perhaps- the whole space the grid is in place for being "penetrated" by the e-beam - as this was implemented also in the "old" ZEISS 109 EM I worked with years ago) any contaminant (i.e. residual organic molecules, residual atmospheric and gaseous molecules, eventually - if using oil-diffusion pump - also remnants of oily vapour) as well as contaminants arising from the specimen itself when perpetrated by the high-energy e-beam [support-film like Formvar, Butvar or Pioloform, resin, tissular material, etc. ] (at least this is anticipated!) will adsorb to that supercold surface.

The aim is to keep the specimens "microenvironment" free from disturbing molecule-cracking and thus "contaminating", induced by the high-energy electrons...

Preventing "drifting" of the sections/your specimen would allow also easier and sustainable, correct imaging of your specs, since an improved stability of the probe and imaging system in former times due to "really long" exposition time (usually 'analog' image formation to a negative film) for sure was essential to cope with high magnification and high resolution without blurring.

Naturally it is possible to view/examine the specimen WITHOUT the anticontamination-device/without cooling by LN2....risking disturbances of conventient viewing by heating of the specimen-section/or analytic probe on the filmed grid, resulting primarily as unwanted 'drifting' of the sections viewed under the beam. Parts of or even the hole specimen could 'vanish' by sudden evaporation....

So - if you forget to refill the isolated LN2-tank(small, usually 1.5 to 2 L LN2-receiving dewar) nothing happens....neither to the TEM nor to you.

[But CAVE: contrary to that: If you use analytic hardware for e.g. crystallography or X-ray analysis of spectra, etc.- the detectors (and detecting windows) have to be (super-)cooled all the time....so then you really would have a "deadly" problem with "late" refilling!) .

Heating of the "chamber" or inner parts of the TEM's column AFTER prolonged viewing and examining your specs has been implemented ("consumer-friendly today") to set free all those contaminant molecules adsorbed to the supercool surface(s) "more less AT ONCE, leading to effective pumping of those molecules in one or two pre-VAc and High-vac-pumps used in your TEM...

Hope not to have left out/forgotten one of your questions so far...(I am wondering about what the manufacturer's manuals are telling about the special matter....

.... More information you should be able to generate by doing a Google search with keywords: | Anticontamination analysis TEM | or similar search phrases....

Best regards and good luck

PS: not only the use of LN2 to be done with caution ....also: don't lick the anticontamination device by your tongue or press your wet fingers unto the copper wire or surface of the Anticontamination chamber/device...!(:-))

WOW!! Thank you very much for this in-depth explanation, Wolfgang! Up until now, I was under the impression that I'll somehow contaminate and destroy the whole microscope if I don't keep the anti-contamination chamber filled. And yes, it's just like you guessed - an insulated container alongside the column. I'll also try to remember to not lick it, no matter how tempting that may seem! :D

Dear Satu, you're welcome! : D

PS:

1) always try to fully use the time when you insert the specimen with the "grid holder" (hoping that there is a similar system of entering the probe as I am ... WAS familiar with the ZEISS 109........(but I guess at the JEOL-1400 it might be implemented a bit different...

2) always try to let adapt the cooling effect [i.e. filling the anti-contaminant-dewar] at least some minutes before inserting the first specimen grid for viewing...and imaging....

3) GROSS VENTING the Specimen chamber (only if your system would allow such action) or the column parts which are in fact part of the super-cooled inner surface(s), e.g. by opening flanges for inspection or any other reason WHEN the anti-contamination system is ON (= filled and cooling) should be prevented. if such an action would be necessary: Wait until the system has warmed up and a good vacuum has been achieved again...

OK: NEWLY - just now I found out that when writing more text into the existing form-rectangle the RG-system kicks out not only one word but whole sentences, and paragraphs, etc. Not really friendly, my fellow ResearchGate-ad- and supervisors! (this is the third edited version and I hope that this time my comment will be accepted as a whole....

An additional insight from Jeol TEM user: ACD indeed (also) freeze the evaporating molecules on cold-finger, acting similar as sort of additional cryo-pump. Thus you'll also minimise those nasty carbon rings during observation (see attached image for an example of carbon pile-up after EDS spot analysis).

The VAC sistem with ACD on Jeol will thus go like this: add LN2, observe, stop, switch to rough pumping + evaporate LN2. Why in this order: while degassing all those frozen molecules by heating, you'll be in rough pumping regime, in order to preserve your ion-pump.

So the ACD is just a cool trap for gas molecules that are absorbed. When you press ACD heat then two things happen at once: the cool trap is heated so the dirt condensed on it desorbs, and the pumping is rerouted so this dirt can be pumped out (ion pump offturbo pump

So the ACD is just a cool trap for gas molecules that are absorbed. When you press ACD heat then two things happen at once: the cool trap is heated so the dirt condensed on it desorbs, and the pumping is rerouted so this dirt can be pumped out (ion pump off and turno pump on). If you forget this, all the dirt that comes off will re- deposit on ipn pump and sample.

Hi

I just wish to ask whether in case of negatively stained samples only then ACD is required, this is what manual of JEOL 1400 says.

But in some cases as an operational incharge I have seen that samples are usually not dried properly and while imaging I could easily see that particular area when focused gets a burning mark.

In that case also do we need ACD? OR with pumping only it can be easily resolved.

Request you to please clear my thoughts on it.

Thanks

Akshey kaushal

Cryo EM scientist

IIT DELHI

Hi; I don't work with biological samples but if you have partially wet samples then any vacuum system will have a pretty hard time to pump water vapour, and an ACD may help. However, it will accumulate a lot of ice, and you need to follow the ACD heat procedure by your EM manufacturer to ensure the ion pumps stay off during that cycle. Thomas

I like this machine (JEM 1400) and know at least four microscopes including one JEM 1400 Plus (the classic one is better, they really have spoiled a good machine with the glitchy and unnecessary electronics). Three of them were working with biological (slices and lots of negative staining) samples for many years without LN2 in the ACD, nothing happened, all good. The last one - JEM 1400 Plus in the Cryo-EM facility is used a lot, about 50/50 - with LN2 in the ACD and without. Honestly speaking, I didn't see any differences.