Desktop SEM

General Questions:
I see that the CDC has re-posted this solicitation. I would like to point out a few things and have a question or two.
The users did a nice job of writing the specs to be a bit more generic but there are a few items that might possibly be in error.

A) Have the users verified that the Phenom XL SEM (which the specifications appear to be written for and favor) will do this type of work and have actually witnessed a test for "nano-scale" samples? I ask because with a resolution of 20nm, it is not possible to get good quality images for particles/fibers smaller than 5 to 10X the resolution or 100-200nm. This is true for any SEM.

A resolution of 20nm is the minimum requirement for our applications to analyze nanoscale aerosol particles/fibers (20-200nm) collected on filters. Any resolution better than 20nm is acceptable. We will evaluate the resolution specifications during technical review.

B) Will the SEM be used for sizing particles and looking at chemistry also in an automated fashion? Or is it for simple manual examination? The Phenom XL can collect images automatically but the EDS chemistry has to be done manually one particle at a time or with a map which is very low resolution. There are standards for this type testing such as ASTM E2090 and D6059 and ISO 14966 to which the Phenom XL is not compliant. We do offer an SEM / EDS system that is compliant with these standards but it is not Desktop configuration although it takes about the same floor space.

The main purpose of this instrument is to perform quick screening of multiple filter samples prior to high resolution imaging and quantitative elemental analysis on a FESEM or TEM. This instrument must have automatic imaging functions to collect images of multiple samples to determine the particle loading level and overall distribution on the filters. The EDS system is used to identify any unknown particles on field blank samples to assess the potential contamination problem that can arise from the sampling environment. The chemistry of contaminant particles will be analyzed manually by EDS.

Specific questions are related to the following lines in the posting:

1) A large chamber to accommodate at least 5 standard MCE filters (each measuring 37mm in diameter) or 16 standard Polycarbonate filters (each measuring 25mm in diameter)
Q1: The Phenom XL has stage size of 100x100mm which is adequate for a holder for 5 of the 37mm filters (although Phenom does not show offering that as standard). However, it would be impossible for a stage that size to holder 16 filters on 25mm in a 4x4 grid as there needs to be some space between the filters. Phenom themselves offer a holder for nine (9) filters at this 100x100mm stage size as shown on their website.

We usually receive field samples in a batch of 20-50 samples on MCE or PC filters. Ideally, we would like to have a desktop model to house more than 20 MCE or PC filters.

Q2: Is it truly necessary to have a holder of this size or is this specified as that is what Phenom offers? Phenom is currently the only supplier offering a Desktop SEM with a stage this large so this one specification rules out all other suppliers and you will not receive competitive bids compliant with all of the specifications. If it is needed, can that be explained as to why a smaller number would not be adequate?

Any size of stage that can accommodate 5 of the 37mm MCE filters or 16 of the 25mm PC filters is acceptable. Due to the limited space in the lab and requirement for the quick screening of multiple samples simultaneously, a stage has to be large enough to house at least 5 of the 37 mm-MCE filter samples.

3) Reduced total pump down time (less than 1 minute)
Q: One again, this is a Phenom only capability. It is also counter-intuitive to #1 requiring multiple samples. If loading multiple samples, the pump-down time is negligible to the total analysis time and should not matter. If testing one sample at a time, it could be seen as important but then #1 is not applicable.

The total pump down time required is less than 1 minute. For daily in-house analysis, it is important to reduce the total screening time before the filters to be processed for the TEM analysis. When this instrument is used for the field study, the samples needs to be quickly analyzed to determine the sample loading, distribution and potential contamination from ambient air.

5) In-chamber optical camera for easy navigation and reposition of samples to the location of interest.
Q: An in-chamber camera is typically only used for adjusting the Z (height) or Tilt angle. The Phenom XL SEM with a stage to hold filters can NOT Tilt. The Phenom XL also has not means of adjusting Z height externally so this requirement while nice, does not offer any practical value. We offer a SEM with a chamber camera but that SEM has a 5-axis XYZRT stage that requires it. Instead of "in chamber" - does the user not instead mean have a sample stage camera or what is generically known as a "Nav Cam" that takes a static image of the sample layout and is later used to navigate from one sample to another. This would be more practical for both any SEM using a multiple sample holder (#1) and the Phenom as well as other Desktop SEM offer this.

The "in-chamber optical camera" refers to the integrated camera to take optical images of the desired location of a sample. It is used to navigate and reposition the sample to the desired location. Stage tilt function is not required for analyzing our filter samples.

7) Compact and vibration insensitive design to allow easy transportation and installation in versatile environment as a mobile SEM.
Q: Why is mobility needed? Phenom may claim that their SEM is insensitive to vibration. Can they present data to prove that? It simply isn't true and we can point you to numerous users of the Phenom XL that have had to acquire vibration isolation platforms for static installations, much less mobile.

This desktop SEM will be installed in a lab where vibration may exist. It may also be transported to a remote location for a field study requiring on-site analysis. We require an SEM with compact and vibration insensitive design to allow installation at different locations.

Second set of specifications:
2) High brightness long-life electron source with at least 1500 hours of lifetime.
Q: This is a Phenom lock-out specification as they are presently the only Desktop SEM supplier offering this (but this will change around Oct/Nov). There is simply no reason why a Tungsten based system with user-replaceable electron source would not be adequate for this application. Tungsten also offers the advantage of being 50% lower cost to operate and allows user source changes rather than being required to pay Phenom to service the SEM which costs more and is inconvenient.

We need to screen a large number of field samples with minimal time to be devoted to maintaining an SEM. Therefore, we require an electron source that doesn't need regular replacement and maintenance to minimize the impact on the turnaround time.

Question: Nowwhere in your solicitation can I find the meaning of the acronym SEM. In your synopsis, you are careful to spell out arconyms like CDC, NIOSH, DART, and FAR. What is SEM?

Answer:

SEM (Scanning Electron Microscope).

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