electrospinning +15kV and -4kV = 19kV

What is PARD? (I couldn't find it with Google.)

--
 Thanks, 
    - Win

An xray tube powered by a simple 60 Hz HV transformer gets AC and self-rectifies.

(Of course they got the "current flow" backwards)

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

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

Periodic And Random Disturbances, another term for "noise."

Also means "good buddy."

snipped-for-privacy@highlandsniptechnology.com wrote in news: snipped-for-privacy@4ax.com:

sound

I never said that the lens would "be sensitive to tube voltage".

The e-beam creates the x-ray flux prior to the beam manipulation. The image noise is also there prior to steerage.

Damn, Johnny... you look even funnier when you are grasping at straws.

Winfield Hill wrote in news: snipped-for-privacy@drn.newsguy.com:

electro-phoresis is not affected by ripple either. It simply works by the attractive force of the voltage, so any ripple has zero effect. This too counts on net attraction and any noise is an order of magnitude down in the mud of that attractive force.

You increasing voltage makes the needle have a higher 'pressure' against it. EMF attraction is what "pressure" means in this case.

X-rays, OTOH, are the result of a direct collision between an accelerated electron beam, and the surface of the anode. A nice, hard collision. E-phoresis and your needle tech are far more 'mushy' and therefore not susceptible to noise in the attraction supply. Electrons hitting a metal and exhibiting x rays directly off that impingement means each electron is likely involved in that flux generation so noise can be 'seen' much more easily in the end product.

Hey, I know... maybe you should get some of that fake hair spray with the little fibers in it. Spray that on with a charge in place. You atre essentially talking about tightly controlled 'powder coating' here. Except yours is single strand instead of powder. :-)

Winfield Hill wrote in news: snipped-for-privacy@drn.newsguy.com:

Periodic and random deviation

It is an old linear supply term.

snipped-for-privacy@highlandsniptechnology.com wrote in news: snipped-for-privacy@4ax.com:

Nope. Anode is positive. Electron beam moves from negative to positive. That angled plate in the tube in that diagram is the anode... is the metal target of the e-beam. Is the positive node.

This ain't hole flow.

snipped-for-privacy@gmail.com wrote in news:2ab209fe-b287-4a5c-af8e- snipped-for-privacy@googlegroups.com:

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.

snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

'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? :-)

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

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.

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.

They could have labeled the drawing electron flow, rather than current flow.

--
 Thanks, 
    - Win

I've met techs who learned "electron flow" in the military, and then later switched to conventional current notation. It wrecked them for life.

Not in any useful way, they aren't.

I've started on Lyon's book "Understanding Digital Signal Processing" and like it. The explanations are more intuitive, less abstract math (though still a primarily mathematical subject of course).

Anyone else like this book?

Clifford Heath.

Haven't seen it. I like Signals And Systems For Dummies.

Dunno. I tend towards very mathematical treatments since I was mostly working on the borderline between applied maths and theoretical physics.

At some point you need an algorithm that can be converted into a computer program to execute it. Pictures and illustrations may help you to get a qualitative feel for what is going on but at some point you do have to knuckle down and do the mathematics.

That said libraries like NAGLIB are pretty much gold standard numerical analysis and data processing tools if you have a license to use them:

It is a lot more reliable than Numerical Recipes on the difficult edge cases when there are hidden traps lurking in the simple algorithms. An algorithm that works for 99% of cases is easy but nailing that last awkward 1% or 0.1% can be incredibly difficult. In Excel 2007 first release they ruined a perfectly good chart polynomial fit routine to make it agree with another flawed implementation in their reference tool :(

Users screamed at them pretty soon after it came out!

--
Regards, 
Martin Brown

John Larkin wrote in news: snipped-for-privacy@4ax.com:

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.