or Technician. Toss in a few years of Field Service and Factory Training E ngineer work away from the University. There are weeks that I am totally shocked by the cool gear I get to work on, or design, or modify.
h when I worked in private industry.
The problem with American physicists - I didn't see it in the UK - seems to be that they think that electronics is merely applied physics, and don't t ake it as seriously as they might.
Sensible people understand that if you immerse yourself in a particular sub ject you tend to be better at it than people who dabble.
Ernest Rutherford is claimed to have said that "All science is either physi cs or stamp collecting" which probably reflected the idea that physics was about teasing out fundamental principles, and the flip side of that is the idea that if you understand the fundamental principles you can work out the details - the fact that it can take forever, and some of the details are n ot all that obvious isn't always appreciated.
ior Technician. Toss in a few years of Field Service and Factory Training Engineer work away from the University. There are weeks that I am totally shocked by the cool gear I get to work on, or design, or modify.
ch when I worked in private industry.
A laboratory course on electronics for scientists at Harvard - thus aimed a t bright and motivated students. It got picked up as an undergraduate text at Cambridge in the UK not much later - Cambridge can be just as picky abou t the students it admits as Harvard. I got onto it when new engineers at Ca mbridge Instruments had a copy on their desks.
Part of the way I got in to electronics involved David Dewhurst
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who was professor of physiology at Melbourne at the time and had a half sha re in the PDP-8 I used. He notoriously found it easier to teach electronic engineers physiology than physiologists electronics, and the stuff he was m easuring needed fancy electronics.
The fact that so many people confirmed the excess energy does make it unlik ely that it was bad instrumentation. The nuclear reaction that might have p rovided that energy probably wasn't cold fusion, but perhaps rather palladi um transmutation to another isotope of palladium by deutron capture, which isn't quite as improbable as cold fusion.
Good lord, that's a coincidence. David was a fairly close friend of my father's, and meeting him inspired me to attempt to qualify in first Physiology and then in Electrical Engineering, at a time well before all the modern fad for various forms of combining those as bio-engineering was the sort of thing people had yet thought of.
When I realised it would involve seven or eight years of study to get two undergraduate degrees, ans would leave me with no commercial career options, I thought better of it, and settled on computer science (with some EE units spliced in) instead.
The first scientific paper I ever saw was David's paper on diagnosing injury of the knee joint by looking at phase plots of the knee jerk reflex recorded from an accelerometer attacked to the ankle.
My UK physics course included electronics right from the start. How to use an oscilloscope was one of the first things taught since many of the practicals depended on using one. Opamps, FETs and bipolar transistors were used as concrete examples at various stages.
It also included a course of computing for scientists and electronics for physicists which went from basic soldering technique as a far as Karnaugh maps and finite state machines. The final practical was to design and then make a digital dice. It put those of us with a hobby electronics background at something of an advantage.
Certainly some of us were better at it than others. My supervision partner is now a grey beard at Argonne who keeps their synchrotron running. UK physicists are quite sought after by US facilities because they are used to making things work again with string and sealing wax.
He didn't anticipate DNA sequencing or AI which now makes molecular genetics probably one of the most key areas of modern day research.
OTOH Rutherford's field of HEP has pretty much become stamp collecting.
It has been that way for quite a while too - at least in most cutting edge physics. Insanely high magnetic fields, ultra low noise amplifiers chasing ever smaller signals in a noisy environment.
It was a nice compendium of circuits that worked for scientists to use and examples of horrors that don't. I still have a copy on my shelf.
The F&P cold fusion thing was almost certainly due to bad calorimetry (which is notoriously difficult). The experimenters were experienced electrochemists but were rushed into publication by news that someone else was about to publish (genuine muon catalysed cold fusion).
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Lack of neutron emission tends to suggest it wasn't fusion. Isotopic analysis of their palladium might show if some other side reaction had occurred (I presume this has been done and drawn a black). Kit to do it was available at the time.
Compared to the number of experimenters that tried Pd/D2O the number that reported any kind of success was quite small. For months after the news broke it was almost impossible to obtain supplies of either. There are still people who keep on flogging this probably dead horse.
Similar laboratory DIY super conductor manufacture occurred when news of high temperature LN2 ceramics formulation was in the news.
AoE, at a mere 1170 pages, doesn't devote much time to Signals and Systems; there are bits here and there. Any scientist should get a separate outline of that.
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.
Seems there was similar project of artificial photosynthese wherein they cr eated the array by genetically modifying virus particles, multiply them che aply and in great numbers, and then killing them. The genetic modification was such that residual electrostatics of the virus molecules causes them to self-organize into a perfect array on the nanometer scale they couldn't ho pe to do otherwise. Then they laid the photo-material onto/into the array u sing another relatively low-tech process.
How does power supply ripple affect x-ray image quality? Xray tubes emit broadband radiation and maybe a few sharp spectral lines, with neither affected much by acceleration voltage.
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A lot of older medical and dental x-ray machines drove the tube with unrectified AC.
snipped-for-privacy@highlandsniptechnology.com wrote in news: snipped-for-privacy@4ax.com:
With respect to the generation of X-rays, we (the world) use an electron beam made via DC to strike a medium which repsonds by emitting x-rays.
Typically Palladium, typically at a 45 degree angle of incidence.
The resultant emission is referred to by the industry and scientific community as 'flux'. The 'purity' of that flux determines the resultant imagery clarity. So, "x-ray flux" would be the full, proper term for it.
The main consideration for the purity of that flux is the purity of the DC electron beam splashing into the palladium (or other) ingot.
Whenever an electron beam strikes a metal an x-ray emission occurs. Different metals respond better. So your old CRT TV screen 'wive's tale' about it causing one to go blind (or 'get cancer') because of being situated too close to the TV was true inasmuch as the mask on the CRT does emit a tiny amount of X-rays. Very tiny. Practically negligible. More likely get it from the carpets of the day.
I made a 4kV supply for a customer that was x-ray inspecting iron (IIRC) natural gas lines in Boston (IIRC) for cracks. This supply had very LOW power capacity, but an *extremely* low ripple figure by design. It came out to like 0.0006%. The same supply minus the HV filtration and EOL storage puts out several milliamps at that 4kV figure, at more realistic ripple values for off the shelf HV use and sales. This guy, however needed it very clean. Our power supplies gave him back his profits because it made his imagery so good it was easier to read and easier to gather making the business more profitable and sellable. But that x-ray supply had to be real clean. Thta is when I learned that the purity of that DC exciter determines the purity of that flux which determines the contrast ratio ond other elements of the quality of the imagery produced. Think about it. Porperly emitted and focussed beams make clean optical 'pass through' images. Noisey beams makes noisey images via random scattered x-ray flux during the exposure event. Essentially affecting contrast ratio, which in a monochromatic exposure of film is paramount.
We also made one with +90kV and -90kV (180kV) excitation that is what ECG used in the airport x-ray machines that were used for decades. Not the new ones.
That was in an 80Lb sealed 18 inch by 26 inch by 6 inch lead lined oil filled tank with a pressure regulating diaphragm. Hottest supply I ever developed. The tube alone for those is made in Germany and costs about $900 each. It is like 9 inches long and 2.5 inches in diameter.
Also made a 50kV 250W supply for LANL to peer into warhead shell casings (and containment vessels, etc.). That one also had to be
*very* clean. The 3/8" diamter (5 inch long) HV output 'tip' from the coax had to be inserted into the connection node through a insulative gel filled 'stab' tube before getting locked in with a std
50Ohm coax connector of the variety we used on CB radios. What was that RG-58 IIRC.
Why? Did you think I meant solder flux?
Oh, that's right... I get no intellectual credence from you, so you did not even really read the post at all to start with, OR the context and term meaning would have been obvious... to anyone I know claiming to be scientific.
snipped-for-privacy@highlandsniptechnology.com wrote in news: snipped-for-privacy@4ax.com:
Think of it as injected noise that shows up in the produced flux stream, that decidedly affects image quality, or the pursuit of clean HV supplies to drive them would not have evolved.
But they do so in a pseudo-linear fashion as it splashes off the target ingot and that flux stream is affected by the DC electron beam that hits it. That stream then enters an Aluminum lens and becomes what gets used to pass through the target under test and create the resultant image. It has nothing to do with the spectral element. We only need what is able to make it through the item we are trying to image the internals of. It has to do with the moment by mement splash of the e-beam into the flux ingot. The polish on the face of the ingot also matters as it is the first surface involved with the creation of a nice, pure, clean, mostly linear flux.
Overall flux output varies kind of spongey with tens or hundreds of volts of change. But the noise in that excitation voltage makes it through and screws up the image quality.
Again... not about the spectrum.
with
A dental shot is essentially inches from the emitter and the film is imediately behind the target. Exposure time is a factor and image quality for certian x-ray results only needed what was needed for the job. Modern x-ray machines are far more sophisticated.
The corresponding Swiss army knife of computing for scientists, numerical analysis and basic signal processing is "Numerical Recipes" by Press, Flannery, Teukolsky and Vettering which isn't a bad practical introduction (although some of their code doesn't quite work and some algorithms are obfuscated by FORTRAN array starts at 1 indexing). The bibliography is fine though specialist newer texts are better.
Anything more than that and you are into university signal processing texts like Digital Signal Processing by Prokalis & Manolakis (sp?) etc.
Linear systems and control theory was a specific final year module aimed at the best students in my physics course. It covered all the usual stuff for PID, loop stability up to and including Routh stability test. It was much more mathematical than the corresponding engineering course.
It's still line-of-sight xray photons. No focussing optics, no chromatic effects, just pure geometry. Acceleration voltage has almost no effect on image quality.
Just hundreds of google hits for xray unrectified ac
Maybe you can find one that relates voltage ripple to image resolution.
The good thing about my engineering courses in S+S is that we started with visual, graphical, intuitive concepts of impulse response, filtering, modulation, convolution. That's what an engineer needs to design. Being "much more mathematical" is not necessarily a virtue, especially nowadays when computers can do the grunt work.
snipped-for-privacy@highlandsniptechnology.com wrote in news: snipped-for-privacy@4ax.com:
With direct feedback from major customers, I am decidedly certain that it is related. Sorry to burst your hate me bubble. You can continue to attempt to come up with something to discredit my knowledge on this, but I am not going out and hunting up electronic facts for you.
Otherwise extremely noisey HVPSes would be used and they simply are not. The reason? Image quality. Customers used us because we were able to make quiet, repeatable performing supplies, which they had trouble getting elsewhere. A truly good HVPS is a science and art, and very application specific as to the level of "cleanliness" required to perform the task.
On miniature HVPS, one notices that ripple also has an effect on overall performance efficiency.
Noise has (power) costs depending on where it gets generated at. It has performance costs if the requisite is a pure DC output as well. Clean is clean. Parts is parts. HV is HV. Noisey HV is worse than some simple noisey USB dongle that your phone dislikes and won't go into fast charge mode over, while other phones do fine. Noisey HVDC is BAD.
Take a dynode for a PMT for example. Even picoamps of leakage causes problems. So too can noise in the supply. Not as big an issue there though.
There are applications where it is optimal. We made supplies that went up on NOAA weather balloons. We even made a few that NASA bought in which the test survivor candidate went up on the Shuttle Mission, while one was literally destroyed in test and the second survivor candidate perfomred in some minutely lesser way, such that they chose the one they sent on the mission. NOAA does the same thing. Lots of waste in redundancy, but mission assurance costs. That was a nice supply. Fully potted in CONAP rendering them 100% non- serviceable. Space Ready, however.
We had others where noise did not matter at all... like a getter for a lamp ignition circuit, where the coiled HV wire was outside the glass envelope of the lamp, and only the attractive force was needed.
And as far as your unrectified AC claim, I would only ask... "You do know what a vacuum tube is, right? X-ray tubes are specifically labelled "ANODE" and "CATHODE". Guess what they get energized by... it is NOT AC."
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