NetNotes


repair? We would need the W wire — can it be replaced? Easy? Is it W? We have an Edwards PRE10K (D02428000) — and we asked Edwards and they told us that this Pirani is not available anymore. Does anybody have one for sale? Does anybody know another type which would fi t into the Scancoat Six? Reinhard Rachel reinhard.rachel@biologie. uni-regensburg.de Tue Nov 15 To my knowledge, aſt er Edwards dropped this kind of equipment from their portfolio, the Indian company HHV continued to market these instruments and sell spare parts for them. I once heard rumors that HHV may have been where this Edwards equipment was built. If this were true, then contacting HHV would be the best approach for you. T ere webpage states: “We hold an exclusive license from Edwards to manufacture and supply the well-known ScanCoat Six, Auto306, Auto500 and forensic deposition systems under the HHV brand and have added our own range of systems to our product line-up.” ( http://www.hhvltd. com/ ). Marco Möller mmoller@cicbiomagune.es Tue Nov 15 If you can dismantle the gauge and get to the fi lament you can try sonicating in mild HCl solution. I do this routinely with my Penning gauge on my FESEM when it gets coated with carbon. Michael Delannoy mdelann1@jhmi.edu Tue Nov 15


Pirani can be repaired if you really wanted to do it, you can DIY


aſt er reading some of books and papers on vacuum instrumentation and techniques, or contact some of the places that routinely repair vacuum instrumentation. Examples would be Duniway Stockroom (duniway. com), or VGM Inc. (vgminc.net), or Scientifi c Instrument Services (sisweb.com) - I am sure there are also plenty of places capable of repairing Pirani in Europe as well, Google is your friend. Replacement PRE10K also available elsewhere: there are four of these gauges listed on E*Bay, also check Labsource (labsoruce.come) and PLC Center (plccenter.com). Valery Ray vray@partbeamsystech.com Tue Nov 15 I might suggest checking with Duniway Stockroom Co. T ey sell and service all kinds of vacuum gauges, and may be able to help you. ( www. duniway.com ) Wilbur C. Bigelow bigelow@umich.edu Tue Nov 15


TEM: grid orientation When a grid with a protein polymer is placed in the scope, should it


be placed fi lament side up, or fi lament side down for the sharpest digital pictures? T e samples are small biopolymers in diff erent conformations. T ey are negatively stained with ethanolic 2% uranyl acetate. Vickie Kimler vakimler@oakland.edu Mon Nov 28


I was taught, a long time ago, that the sample should be “placed


fi lament side up”. Did you consider using carbon fi lm grids for your samples? Negative staining on thin carbon support fi lm should result in better signal-to-noise ratio (“sharpest digital picture”). Oldřich Benada benada@biomed.cas.cz Tue Nov 29


TEM: imaging magnetite particles


Is it safe for a TEM microscope to image a holey C fi lm dispersed with thousands of Fe 3 O 4 magnetite particles (100 nm)? T e specimen is prepared in the usual way as many other nanoparticles specimens. Will the particles fly to the pole pieces? The user said the particles are iron oxide and are superparamagnetic (and have no permanent magnetization). I don’t quite understand these terms, but by diff raction I identifi ed magnetite Fe 3 O 4 . If it’s not safe, what solutions are there to get the job done? I would be very grateful if you can share with me your experience and comments. Z Zhou z.zhou@lboro.ac.uk Wed Nov 30 I know it’s alarming, but yes, it is in general safe. I have looked at magnetite nanoparticles at both HP and at OSU in a JEOL 2500 and Titan TEM respectively without serious issues. T ey key is they need to be nanoparticles. I believe Steve Chapman and Protrain wrote


66


a nice reply to a similar question 4 or 5 years ago. In that reply Steve mentioned that the Van der Waals force is so large on a nanoparticle they really stick well to the carbon fi lm! I agree, I have seldom seen one fl y up. However, as a precaution, I blow a duster can or dry nitrogen gas over my grids before putting any nanoparticles in the TEM (suggestion from Debby Sherman of Purdue). T is works very well to dislodge any nanoparticles that are not well adhered. T en as you magnify up on the nanoparticles, halt the analysis if they begin to move! Pete Eschbach peter.eschbach@oregonstate.edu Wed Nov 30


Adding to the nice comments that Peter made, you are able to reduce the level of magnetic interference with any “uncomfortable” material, by simply extending the objective lens focal length through adjusting your eucentric stage to its lowest position. Cranking the z’ so that you are turning your focus controls anticlockwise will reduce the active objective lens current. T e magnifi cation will drop, as will the level of resolution achievable. For those who want a little more resolution the trick is to take the z’ the other way, shortening the focal length, with the increase in the operating lens current serving to reduce the aberrations and increase resolving power. Steve Chapman protrain@emcourses.com T u Dec 1


SEM:


Position changes when change sample height I have a problem about using an FEI SEM. Aſt er I focused and linked Z, the sample position will always change a lot when I raise or drop the sample. Basically the area in the image will go to the opposite direction with the sample. Why would this happen? I don’t have much knowledge about SEM theory so, any advice is appreciated. Jason 13qw9@queensu.ca Sun Dec 11


It does sounds like there is quite a bit of movement in the image. If so, it may be that the stage Z axis isn’t parallel to the beam axis. First determine in which direction the image is shiſt ing. On most of the FEI scopes I’ve worked with, the stage Y axis is vertical and X axis is horizontal on the screen. If the image shiſt is along the vertical ( Y ) axis, adjust your sample tilt several degrees plus and minus. One direction should increase the shiſt and the other decrease it. If the shiſt is along the X axis, visually examine the stage from the side and see if you can see anything that is cocked. I would recommend discretion when fi ddling with the stage since the bearings and other components are matched for submicron precision. T is may be worth a service call. Henk Colijn colijn.1@osu.edu Mon Dec 12


When you say change or drop the specimen I assume you mean


a Z position adjustment? T e “problem” that you see with a change in Z is quite normal. The vertical motion of the stage is through a thread and the take up of any slack in that thread results in specimen movement in X and Y directions. With an electrically driven stage, manufacturers have the option of providing anti-backlash adjustments to make X and Y movements more positive. I do not know a manufac- turer that has anti-backlash compensation in the Z direction. Steve Chapman protrain@emcourses.com Tue Dec 13


SEM: Peltier cooling stage


We are trying to purchase a Peltier cooling stage for SEM samples that need to be frozen like: milk, ice cream, fruits and similar food industry items. T e stage that has been off ered to us achieves -50ºC to +70ºC. I was wondering, for our applications, if this temperature range is enough? Or should we go for other cooling stages with -180ºC? Sun researchers4u@gmail.com Fri Dec 23


As you consider the cooling stage, you should think about the vapor pressure of what you are inserting into your chamber. I assume that you have a high-vacuum SEM and that the primary vapor you are concerned with is water. The tables of water vapor pressure as a function of temperature should be readily available online. You want


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