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NetNotes


Considering that is more than 100 times the thickness you normally put down, that is an issue. I tried using evaporation to put down a thick layer of antimony on glass before. First, when I calculated the mass of Sb to put down a micron at a certain distance, I found I had to fi ll my tungsten basket to the full and maybe even run a couple of times. T en I think I found the thermal stresses Henk described. T e layer curled up off the glass. Why do they want such a thickness? Warren Straszheim wesaia@iastate.edu Mon Feb 19


Specimen Preparation critical point dryer


I am considering replacing an older critical point dryer for a multi-user microscopy lab that serves faculty and undergraduate student users for research projects, and trains undergraduates via courses. Aſt er training, users carry out their own specimen preps. Two models I have come across are the Leica EMCPD300 and the Tousimis Autosamdri- 931. I would appreciate any comments from folks who have experience with either of these, as well as suggestions about other models I may have overlooked but should consider. Feel free to respond directly to me if you would like. Jan Factor jan.factor@purchase.edu Sun Feb 18 Tousimis is good, I’ve used those a lot. Not the Autosamdri, but the previous model. Have you considered the Polaron “bomb”? T e larger sample chamber (in the regular size) is very handy. SPI sells this as a rebranded product. I use it in a multi-user facility that teaches undergrads and grad students. Phil Oshel oshel1pe@cmich.edu Mon Feb 19 We have a CPD300 here that users have access to. One of our users is only trained on our bench top SEM and she uses it regularly, independently. Top tips for things that might catch out students: 1. As per the manual, the fi llers should be on top of the holders. If you have them the other way around, the chamber doesn’t fi ll up correctly 2. Do not overfi ll the chamber. Should be OK as long as the level is below the outlet hole at the top, otherwise you might have some liquid leſt at the end. It is easy to use with a simple user interface; it has been easy to train people on it. We use it quite a lot and it gives nice results. Matt Russell matt.russell@crick.ac.uk Mon Feb 19


EM fl oor vibration & cutting the slab


I know this is a subject on which reasonable people can disagree, but I wanted to ask what has been your experience with cutting the slab to reduce low frequency vibrations? T e fl oor appears to be moving in the horizontal plane at 1.6Hz (4.4 reduction factor needed) and in the vertical direction at 5HZ (3.1 reduction factor needed). Bryan Tracy btracy@eag.com Fri Feb 16


3-4X attenuation of ambient vibrations is very diffi cult. Finding another location would be the preferred solution. A. John Mardinly john.mardinly@asu.edu Fri Feb 16


Do you know if the vibration is resulting from sources inside the building or from the general area outside? EAG is in between a number of freeways there in Sunnyvale and the 101 is not far away, so if it is the underlying ground below slab, you might make it worse cutting the slab. I am sure some of the experts on here have experience doing this and will advise. You might also check with Vibration Engineering Consultants - www.vibeng.com - in Pacifi ca, CA. T is is their specialty. I would also be remiss if I did not suggest that you consider a Vibration Isolation Base Platform. T e active type we off er suppresses vibration starting at 0.7 Hz and has 90% suppression by 2 Hz. I would avoid a passive type isolator as most of them have a resonant frequency right around 2 to 4 Hz, which would make things even worse for the vibrations you have. Likewise, if you decide to cut the slab, careful if you use an elastomeric sealant and check its resonant frequency. Have a look here at our line of Vibration Isolation Platforms for SEM/TEM/ FIB:


http://www.elementpi.com/active-vibration-isolation-platform- products/ Mike Toalson miketoalson@gmail.com Fri Feb 16


58


T ose are very low frequencies. T ey should be in a range that an active compensation system should be able to handle it. Another thing to consider is the resonant frequency of the slab (even though it is damped by the ground). T e more mass in the slab, the lower its resonant frequency. T e install guides for our microscopes show that the microscope is much more sensitive at very low frequencies. T e allowable vibration at 10 Hz is approximately 10× lower than at 20 Hz. Since too much mass can push the slab resonance down into the range where the microscope is more sensitive you may want to estimate the resonant frequency of your current slab and then consider whether to slice it or not. It would also be useful to measure the ground vibration away from the instrument to get an idea of the driving frequencies. Henk Colijn colijn.1@osu.edu Sun Feb 18


Cutting the slab is dangerous can may compromise the building. It is better to install active vibration isolation. I have a number of SEMs in T ousand Oaks, CA. One LaB 6 system is on the second fl oor. We use Herzan to reach vendor spec resolution with gold on carbon. Gianpiero Torraca gtorraca@amgen.com Mon Feb 19 One thing I do not think has been mentioned is that the soil under


many slab fl oors has settled, and the slab is “fl oating” above without being supported. I have heard of holes being drilled and a foam material being injected under the slab to support and dampen vibrations. T is is done sometimes, in addition to other vibration isolation measures. Darrell Miles milesd@us.ibm.com Mon Feb 19 20


TEM beam always on


I’m using a Philips CM12 and I’ve been noticing recently I still have a beam and image with the fi lament supposedly desaturated. I have to turn the high voltage off to get the beam completely gone. I do not remember this scope doing this before. T erefore, I suspect something is not right but before I request a service call (we are a fugal company), I would like to confi rm that the scope is acting abnormally. I am also fi shing for ideas on what is wrong. Frank Karl frank_karl@ardl.com Wed Feb 7 I have had a similar issue with our FEI Morgagni 267D (for most purposes similar to the CM12). I would bet the Wehnelt assembly is almost identical. For us it was almost certainly a fi lament break in such a way that it was shorting across the Wehnelt. I say “almost certainly” because in our case this happened at almost the same time that a bunch of electronics issues occurred and so we had mixed symptoms. However, replacing the fi lament (which we had only just replaced as part of our diagnosis of elimination), did the trick for us. At least it is a simple check. Duane Harland duane.harland@agresearch.co.nz Wed Feb 7 T is is called dark current. It comes from the evaporation of fi lament material onto the insulator base creating a pathway for electrons to leak to ground, and therefore, creating a current in the fi lament that causes it to glow with only the kV on. It’s not a problem but indicates that your fi lament is old. Kenneth JT Livi klivi@jhu.edu Wed Feb 7


SEM


tungsten fi laments We use tungsten fi laments in our Hitachi S3400N VPSEM. Does anyone have any suggestions for extending fi lament life? We try to operate slightly under saturated except for EBSD or EDS mapping. I have heard of “seasoning” the fi lament but have never seen an actual protocol or talked with anybody who’s actually done it. Any suggestions would be appreciated! Bil Schneider wschneider@wisc.edu Fri Feb 9 With seasoning a tungsten fi lament, you perhaps (might) think of slow and carefully controlled “heating” of a new fi lament (as I have done that with every new fi lament aſt er mounting in a TEM, a ZEISS109 with diff erential pumping system=rotary pump -for RV as well as an Ion Getter Pump for HV). IMHO ‘slow heating’ of the cathode fi lament


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