electrospinning +15kV and -4kV = 19kV

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 Electrospinning is an interesting technique for making
 nanofibers.  We used +15kV on the needle of a motorized
 syringe pump and -4kV on a collection mat = 19kV total.
 The electric field pulls off a thin stream of molecules,
 which landed into a random mat of nanocarbon filaments.
 My RIS-769 instrument could be adjusted up to 25kV, but
 less seemed to work better.  Here's its first result.
https://www.dropbox.com/s/i8a3znvfdcvaryc/2017_Jiang_Transition-Metals.pdf?dl=1

 I had lots of fun fighting off corona discharge, etc.
 Now I'm making s/n 2, improved with its own PCB, etc.,
 this time for use with different compounds, to provide
 touchless support web for surface-tension experiments.
 A safety interlock, adjustable HV voltages, and meter
 readout of both voltages and the negative mat current.


--  
 Thanks,
    - Win

Re: electrospinning +15kV and -4kV = 19kV
wrote:

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Fun. I helped Tom Kelly start Imago, the tomographic atom probe outfit
which was eventually acquired by Cameca. It was fun, I got named on a
patent, and spent a lot of money on airline tickets.


Re: electrospinning +15kV and -4kV = 19kV
snipped-for-privacy@highlandsniptechnology.com wrote...
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 As an engineer, it's fun to get involved with atomic-
 molecular-nano stuff.  And, if it also requires high
 voltages, so much the better!


--  
 Thanks,
    - Win

Re: electrospinning +15kV and -4kV = 19kV
On Sun, 15 Sep 2019 14:39:04 -0700, Winfield Hill wrote:

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How are you generating them? C-W (or variant) style multipliers?



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Re: electrospinning +15kV and -4kV = 19kV
Cursitor Doom wrote...
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 Standard high-voltage dc-dc converter modules.  Most
 are proportional types, which means you add a control
 system for their supply voltages.


--  
 Thanks,
    - Win

Re: electrospinning +15kV and -4kV = 19kV
On 9/15/2019 7:30 PM, Winfield Hill wrote:
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How much output current or power is required?



Re: electrospinning +15kV and -4kV = 19kV
Depends on the carrier solvent, polymer concentration, forced or gravity flow, type of polymer, a ton of things. However a typical single jet in the lab is a few hundred nanoamps.


Steve


Re: electrospinning +15kV and -4kV = 19kV

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  Is the ripple any issue?

  With x-ray I know that the cleaner the HVDC supply, the cleaner the  
flux, and thus the better the contrast ratio of the imagery.

  If the supply is overtly noisey, the flux carries so much of it  
that the image is very grainy and 'snow-filtrated'.

  Seems all you need though are the 'degrees of separation' that 19kV  
provides and noise is not an issue as the stream 'spins' out based on  
the attraction, not something directly related to the HV excitation  
as far as time goes.

Re: electrospinning +15kV and -4kV = 19kV
snipped-for-privacy@decadence.org wrote in

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  So, I am a troll, and everyone comes in and calls me one and says I  
do not discuss electronics.

  It seems, however, that whenever I do, I get crickets.

  My question is relevant.

  I didn't think that win was another of these filtertards.

Re: electrospinning +15kV and -4kV = 19kV
snipped-for-privacy@decadence.org wrote...
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 No, but I usually don't say anythng unless I have something
 to say.  You pretty well spelled out the scene, and if I was
 forced to guess, I'd imagine that ripple has little effect.
 In fact, I haven't measured the ripple on my HV modules.
 While I do have a stock of high-V caps, setting up the 20kV
 measurement is painful to contemplate, so I'll probably just
 take a pass.  I am setting up a feedback-loop response test
 today, using Ohmite SM108 500M 1% HV resistors.  They're
 2.1-inches long and rated at 20kV.  I promise to be careful.


--  
 Thanks,
    - Win

Re: electrospinning +15kV and -4kV = 19kV
Winfield Hill wrote...
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 My 20kV supply module, an H20, made by ELDEC, seems to
 have a very tightly regulated voltage, judging from my
 measurements yesterday.  So I suppose it might also  
 have low ripple.  The last time we did this, we started
 with +15kV and -4kV, or 19kV total, which worked well, so
 we didn't make any changes.  But I've heard that higher
 voltages may be better to maximize the random lay-down of
 a mat of nano-fibers, so we might turn it up towards our
 25kV limit.  Haha, maybe we should add ripple?


--  
 Thanks,
    - Win

Re: electrospinning +15kV and -4kV = 19kV
With all due respect, Xrays are not focused by aluminum lenses. They are fi
ltered by shaped aluminum disks or sheets, to prevent the PT from being exp
osed to the huge amount of low energy X-rays that comes off a typical tube  
anode, usually made of Tungsten with a touch of Iridium for toughening.  Th
ese low energy X-rays do make it through the PT to the detector. Thus they  
just result in extra cumulative dose to the patient if not filtered out.  

 Aluminum, Nylon, and Beryllium are typical filters used in CT or real Time
 Imaging  X-ray systems.  

 The Filters are also shaped to avoid hot spots at the detector array from  
scattering in the frame or from the tube's inherent beam profile.   With 64
 or 256 detectors in an CT machine array, normalizing the beam is important
.  

I'll give you an example based on one I worked on.

Modern medical CT machines use dual, split,  supplies aka  programmable PSU
s that can source 80 to 120 Kvp at 10 to 900 mA adjustable. This supply is  
actually modulated as it spins round the patient with the detectors on the  
opposite side of the Rotor.  440 VAC slip rings around the patient supply t
he power.  Modulating the supply is used to reduce dose, and it can change  
tube current  very fast during a rotation based on a "prescan" of the PT or
 real time on the fly calculations.  

The supply also provides an auxiliary voltage to drive a deflection plate n
ext to the cathode to slightly move the X-ray beam to enhance resolution by
 shifting the beam around one detector width along the patient axis. That p
ulses like crazy  

A high tube current such as 800 mA would be used in an emergency "once in a
 lifetime" scan to quickly find a bleed or injury in the ER. Normal doses a
re much lower, say 350 mA.  

I spent a year as a CT Electronics Trainer...

Steve  


      

Re: electrospinning +15kV and -4kV = 19kV
Correction:

"These low energy X-rays do NOT  
make it through the PT to the detector"

I should know better then to type when I have a professor talking to me.

Steve  

Re: electrospinning +15kV and -4kV = 19kV
snipped-for-privacy@gmail.com wrote in

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  'than to type'.

  It makes a completely different sentence.

  You make it sound like you actually feel as though you should wait  
until you know better, then type while your professor is talking.

  Have you done this waiting then typing thing before?  :-)

Re: electrospinning +15kV and -4kV = 19kV
snipped-for-privacy@gmail.com wrote in news:2ab209fe-b287-4a5c-af8e-
snipped-for-privacy@googlegroups.com:

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  With all due respect, x-rays are indeed focussed by using Aluminum  
lenses and grazing incidence 'mirrors'.  Just not all machine designs  
incorporate it in that way.

  Aluminum is *almost* transparent to x-rays.  There is your key.

  Your CT experience uses coils, IIRC.

  Sounds like you are 'brand specific' or 'type specific' and that is  
how *that* machine works.  You cannot possibly think that all x-ray  
generation uses the nmethod you describe.

  I have seen them as small as 4kV, and Los Alamos had us build a  
50kV supply for them.  A single ended design.  The 180kV ECG  
contracted supply we made was for the machines the airports were  
using *at that time* and is was a dual 90kV monster supply using a  
huge tube with a Palladium target anode.

Re: electrospinning +15kV and -4kV = 19kV
On Thu, 19 Sep 2019 09:16:11 -0700 (PDT), snipped-for-privacy@gmail.com
wrote:

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There do seem to be aluminum x-ray focussing refractive lenses, and
gold things too.

https://en.wikipedia.org/wiki/X-ray_optics#Focusing_optics

But the spectrum out of an xray tube doesn't change much with voltage.
I can't see how a bit of ripple could matter.

I did a bunch of work in EUV lithography. The ca 13 nm light doesn't
refract much, so the lenses are grazing-incidence things, look sort of
like a cross between a beer barrel and a diesel engine.


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I got CT scanned three times in the Zuckerberg ER [1]. They kept not
liking the results and sending me back. I don't remember much of that.

[1] he bought the hospital for his wife.


Re: electrospinning +15kV and -4kV = 19kV

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It is not about "the spectrum".  It is about the purity of the  
stream.

  The e beam striking the emissive target.  Call it 'sputtering' if  
you need to get a grasp on what happens.  Clean, pure e-beam...  
clean pure x-ray flux...   cleaner imagery.

  Noisey e-beam...   noisey imagery.

  Known fact.  Sorry.  I cannot really explain the mechanism.  I can  
theorize what the causal element is, but it is not about your  
imagined spectrum/voltage thing.  To me, it is likely more about how  
the e-beam 'flux' emits from the cathode, on its way to the anode.
The ripple causes the electrons to dance off axis a bit.

  Whatever the actual physics are, the fact remains that a clean DC  
source makes cleaner images than a noisey one does.  I do know that.
You seem to not know that, and I guess that intimidates you as you  
have obsessively tried to bolster your feeling that it changes  
nothing.

  With an application for simple HV attraction, like as in e-
phoresis, noise would not change.

  This application is NOT simply about attractive force.  An actual,  
hard electron beam is generated, and obviously noise in the  
accelerated stream apparently makes a difference.

  I am sure that a DC battery fired unit would be even cleaner.

  So I would say that apparently the x ray imagery is affected by the  
'noise floor'.  IOW it is pretty sensitive if PS ripple makes a  
notable difference...   and it does.

Re: electrospinning +15kV and -4kV = 19kV
On Fri, 20 Sep 2019 14:30:18 +0000 (UTC),
snipped-for-privacy@decadence.org wrote:

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What does that mean?

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Do you sputter the xray tube anode? How long does it last, being
splattered onto the glass?

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Makes no sense. The image is made of random xray photons. It doesn't
matter how "pure" they are.

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Uh, right.


Re: electrospinning +15kV and -4kV = 19kV
snipped-for-privacy@highlandsniptechnology.com wrote in  

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doesn't

Maybe the difference is that of a single exposure and that of live  
imagery.

  It would not affect single exposures as they are a function of  
exposure time and dosage level.

  It would affect frame by frame live imagery because the exposure is  
so short lived that the frame data gathered is affected.  Maybe that  
is where it is.

  You tell us, crazy Mr. Spectrumboy. (thank you, Adam).

  Then there are 'quantum noise' affects with x ray realm as well.
Are you familiar with those?

  Now you will come back stating how it is not related.  I never said  
it was.

Re: electrospinning +15kV and -4kV = 19kV
On Saturday, September 21, 2019 at 12:58:22 AM UTC+10, snipped-for-privacy@highlandsniptechnology.com wrote:
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Short term variations in the intensity of the beam translate into variations in intensity from one pixel to the next. The "image" is created by array of pixels, where the information is contained in the variations in intensity from one pixel to the next.

Short term variations in the intensity of the beam as it moves from pixel to pixel show up as noise on the image.

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Quite a while. The atoms that get "sputtered" off the target condense back onto it.
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Their "purity" isn't the issue. The number of x-ray photons associated with each pixel is. The item being scanned influences the number of x-ray photons associated with each pixel.

That's your signal. The intensity of the beam at each point in the scan also influences the number of photons associated with each pixel in a way that has nothing to do with the nature of the object being imaged. That's noise.
  
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He shouldn't have needed to. It's pretty obvious.

--  
Bill Sloman, Sydney


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