making temporary vacuum windows for the Tracer

[Vanessa Muros]

Hi everyone,

I'm analyzing glass samples using the Tracer SD-III and find that I am going through a lot of gridded vacuum windows during this analysis.  I've used the last one I have and while I wait for my order of new windows to arrive, I wondered if anyone had suggestions on how to make some temporary vacuum windows so that I could continue my analysis.  I have tried to use Prolene thin-film as a temporary fix, but no matter how much tape I use, cannot get a good seal.

I wondered if anyone had any tips on how to get a better seal or a better film material to use.  

thanks,

Vanessa

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Vanessa Muros

Conservation Specialist/Lecturer

UCLA/Getty Conservation Program

[Jillian Huntley]

I’ve used the Bruker Tracer on rock art in remote locations in northern Australia. I would blow about 20-30 windows per day on rock faces with the Tracer under vacuum.

I used very thin Mylar (~50 micron) and duck tape with a punch to fit the instrument aperture shape that I found in a local metal fabrication workshop – total cost of about $50 and the materials have lasted me years and probably saved me hundreds, if not thousands of dollars.

 

Good luck

 

Jillian Huntley
Archaeologist
Honorary Research Fellow, University of Queensland

http://une-au.academia.edu/JillianHuntley

[MacKenzie, Mark, DCA]

Good morning Jillian.

If it wouldn't be too much detail would you mind listing step wise how you go about making these windows?  I would like to add this technique to our store of protocols.

On site field work needs such techniques.

Thank you for sharing.

Mark MacKenzie, Chief Conservator

MNM-Conservation, 

Santa Fe, NM

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From: px...@googlegroups.com [px...@googlegroups.com] on behalf of Jillian Huntley [hunt...@tpg.com.au]
Sent: Sunday, July 05, 2015 7:05 PM
To: px...@googlegroups.com
Subject: [pxrf] Re: making temporary vacuum windows for the Tracer

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[Lee Drake]

Hi all,

I would recommend using prolene (4μm) in place of mylar - the calcium contaminants of mylar show up easily with the Tracer, at least in my experience. It is #416 on this page: http://www.chemplex.com/spectrocertifiedr-thin-film-sample-support-windows-in-continuous-rolls-pre-perforated-rolls-and-precut-circles. 

Even if the prolene rips on the windows, you can still use the vacuum grid build into them - just tape the new prolene over (and/or under) the old window. 

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B. Lee Drake

Department of Anthropology
University of New Mexico
(505) 510.1518
b.lee...@gmail.com

    

[Vanessa Muros]

Dear Jillian,

Thanks for the suggestion. Do you have a photo of what it looks like?  Do you use the punch to cut a piece out of the middle of a piece of duct tape and attach a piece of Mylar to the adhesive side, like you're recreating what the vacuum windows look like?

I'm also curious as to how good of a vacuum you've achieved  I can only get the reading on the pump to go down to 30-50 but would like achieve a better vacuum like I do with the purchased windows.  I've just been taking a piece of the Prolene film, laying it across the opening and taping around it.  I thought that I had sealed all the sides well with all the duct tape I've used but it's not as air tight as i would like it to be.

Vanessa

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[Vanessa Muros]

Dear Lee,

That's the film I've been using so I'm glad to see it's the one recommended. And thanks for mentioning the calcium contaminants in Mylar.  

I was worried that the 4 micron Prolene might be too thin which is why it keeps tearing so easily for me.  I was going to try some LDPE stretch wrap we have in the lab which is a little thicker as an alternative to see if that holds up a little better.

thanks,

Vanessa

[Jillian Huntley]

Yes, I should have mentioned, for my application the contribution of any chemistry from the Mylar is negligible because I only ever use the pXRF for relative abundances and the Mylar’s chemistry is consistent enough – I have experimental data to quantify it, easy to gather in under an hour before you head into the field.

 

I was able to get a seal on the vacuum equal to the Bruker windows – reading on the vacuum was ≥ 10 and I had a working tolerance for ≥ 20 before I replaced them.

 

I cut the Mylar into 1cm² pieces and then just took a pair of small scissors with me to cut the duck tape off. I would punch the tape, cut it off with about 2cm either side of the hole, adhere the Mylar under, place it on the Tracer, draw with a sharpie the edges of the aperture on the new duck tape widow at the snout of the instrument (so I could line up the next analyte location), then zap away until the window blew and start all over again.

 

I do have a photo somewhere, but I would have to dig it out and am a bit pushed for time just now.

 

At present I am using a Bruker Turbo S1 that I have rented for a rock art project and with depth of the aperture I didn’t replace the window at all in the two weeks I’ve just spent in the field. I still have a few more weeks of data collection and then the number crunching to do, but form the preliminary data this gear is fit for my purpose. I am missing the tripod though having been twisted up is strange yoga posses myself against the panels holding the ‘ray-gun’.