On 11/2/2017 8:38 PM, krw@notreal.com wrote:> On Thu, 2 Nov 2017 20:04:40 -0500, amdx <nojunk@knology.net> wrote: > >> On 11/2/2017 7:32 PM, krw@notreal.com wrote: >>> On Thu, 2 Nov 2017 09:09:59 -0500, amdx <nojunk@knology.net> wrote: >>> >>>> On 11/1/2017 8:44 PM, rickman wrote: >>>>> amdx wrote on 11/1/2017 8:42 PM: >>>>>> Well not a exactly a vacuum, they fill it with helium. >>>>>> "...NASA’s Ames Research Center is going back to the future with its new >>>>>> vacuum transistor — a nanometer-scale vacuum tube that, in early testing, >>>>>> has reached speeds of up to 460GHz." >>>>>>> https://www.extremetech.com/extreme/185027-the-vacuum-tube-strikes-back-nasas-tiny-460ghz-vacuum-transistor-that-could-one-day-replace-silicon-fets >>>>>>> >>>>>>> >>>>>> >>>>>> And for the audiophools, > There’s no word on whether these >>>>>> vacuum-channel >>>>>> transistors will allow for the creation of small, modern audio amplifiers >>>>>> that sound like original tube amps — but maybe! >>>>> >>>>> Why would anyone care if they sound like tube amps? We can get all the >>>>> tube amps we want. >>>>> >>>>> I thought they had recreated the sound of tubes digitally, no? >>>>> >>>> That was a bit of a joke. As I understand, in blind tests golden hears >>>> do no better than chance on A/B listening tests. The difference becomes >>>> noticeable only when over driven then the tube amps have a preferred >>>> sound over transistors. >>> >>> So you add 10dB to the transistor amp and don't do that (clip). >> >> But that tube amp distortion is an attribute, and I'm so sorry I added >> that throw away line about "sound like original tube amps". > > For guitars, sure. For "music", no way. >Yes, I should have qualified that, glad you did. Mikek
460GHz Vacuum Transistor
Started by ●November 1, 2017
Reply by ●November 3, 20172017-11-03
Reply by ●November 3, 20172017-11-03
"Jan Panteltje" <pNaOnStPeAlMtje@yahoo.com> wrote in message news:othalp$s3e$1@news.datemas.de...> Well it is a prototype radiaton detector, look up GM tube. > Last thing you want in space. >Well, you only need operating current greater than the average ionization leakage. And it's probably less sensitive to radiation upsets because of the lower density of the operating medium. Substrate would matter, but substrate can be insulating, which helps greatly (e.g., SOI).> And why 460 GHz? what is next? light? > I have an UV LED flashlight to veryfy US dollars are false, > how many GHz is that?About 500,000. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
Reply by ●November 3, 20172017-11-03
On Fri, 03 Nov 2017 06:24:47 GMT, Steve Wilson <no@spam.com> wrote:>John Larkin <jjlarkin@highlandtechnology.com> wrote: > >> On Thu, 02 Nov 2017 04:04:41 GMT, Steve Wilson <no@spam.com> wrote: > >>>John Larkin <jjlarkin@highlandtechnology.com> wrote: > >>>> The problem with field emission is that it destroys the tips. The >>>> e-field gradients have to be so high to rip electrons that it rips >>>> molecules too. > >>>An extensive search of field emission showed no mention of molecules >>>ripped from the cathode. However, numerous articles discussed cathode >>>damage from residual ionized gasses. These bombard the cathode and >>>destroy the single atom tips. > >> At high fields, atoms are ripped from a tip. I wasted a lot of time on >> tomographic atom probing, which does exactly that. > >Atom probes use pulsed voltages around 2kV.Like this: https://www.dropbox.com/s/cus0eoleswyi444/T222_2KV_Pulse.JPG?dl=0 That's -2 KV peak, which rides on a DC bias in the 8KV ballpark. I managed to get the state of the art up from 10 Hz pulse rate up to 100 KHz, with a water-cooled DSRD pulse generator. What you are talking about is>completely different from the IEEE article. > >https://en.wikipedia.org/wiki/Atom_probe >What all these things have in common is that the emitting tip erodes. In the atom probe, that's a feature. In the other cases, it's a fatality.>>>An intriguing possibility is very close electrode spacing that allows >>>operation in atmospheric pressure. I have come across a number of >>>articles describing this, but cannot find any references in a brief >>>search. > >> Field emitters, and field emitting triodes, have been played with for >> decades. A sharp tip would be an ideal point source of electrons for >> an electron microscope, operating in ultra-high vacuum, but the tips >> don't last. The compromise is to heat the tip, which really makes it a >> low-temperature thermionic cathode where the high field helps >> emission. > >Did you read the article? They use 10 volts and think they can reduce it to >around 1-2 volts. They also can operate at atmospheric pressure using >helium. The voltage is too low to ionize the gas, so there is no risk of >damage from ion bombardment. See > >http://tinyurl.com/y9sjzl6aLet me know when it's in stock at Digikey. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●November 3, 20172017-11-03
On Thursday, November 2, 2017 at 10:36:13 PM UTC-6, bitrex wrote:> On 11/02/2017 03:29 PM, DemonicTubes wrote: > > >> And we can't digitally emulate overdrive distortion of tubes? > >> > >> -- > >> > >> Rick C > >> > >> Viewed the eclipse at Wintercrest Farms, > >> on the centerline of totality since 1998 > > > > It seems like we should be able to, in theory, however, if there is a solid state guitar amp that does this well I am unaware of it. I am open to suggestions, if anybody has any, as my life would be simpler if I didn't need to maintain and lug around tube amps. > > > > There are probably like 500 different amps, effects pedals, rackmounts, > and sequencer plug-ins that do that. Line 6 being probably the most well > known company: > > <http://line6.com/>Thanks for the suggestion. I am aware of the various Line 6 attempts, they just don't do it for me. I am willing to accept that I can't set them up correctly, my ears are broke, or I am just crazy, but I just can't make myself happy with the sound and dynamics at high gain.
Reply by ●November 3, 20172017-11-03
John Larkin <jjlarkin@highlandtechnology.com> wrote:> What all these things have in common is that the emitting tip erodes. > In the atom probe, that's a feature. In the other cases, it's a > fatality.What causes erosion in a device running at 10 volts when there is no ionization impact? I'm assuming it runs at low enough current to avoid melting the collector and to avoid electromigration.>>Did you read the article? They use 10 volts and think they can reduce it >>to around 1-2 volts. They also can operate at atmospheric pressure using >>helium. The voltage is too low to ionize the gas, so there is no risk of >>damage from ion bombardment. See>>http://tinyurl.com/y9sjzl6a
Reply by ●November 3, 20172017-11-03
On Fri, 03 Nov 2017 15:30:54 GMT, Steve Wilson <no@spam.com> wrote:>John Larkin <jjlarkin@highlandtechnology.com> wrote: > >> What all these things have in common is that the emitting tip erodes. >> In the atom probe, that's a feature. In the other cases, it's a >> fatality. > >What causes erosion in a device running at 10 volts when there is no >ionization impact?The same thing that has ruined every other field-effect emitter for the last 40 years or so? This is just press-release nonsense. You could post a hundred such breakthroughs a day here. Review the last thousand or so and see how many became real. What use is a 2 volt, nanoampere fet? I'll get some from Digikey and try them.> >I'm assuming it runs at low enough current to avoid melting the collector and >to avoid electromigration.Another uselessness factor. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●November 3, 20172017-11-03
John Larkin <jjlarkin@highlandtechnology.com> wrote:> On Fri, 03 Nov 2017 15:30:54 GMT, Steve Wilson <no@spam.com> wrote:>>John Larkin <jjlarkin@highlandtechnology.com> wrote:>>> What all these things have in common is that the emitting tip erodes. >>> In the atom probe, that's a feature. In the other cases, it's a >>> fatality.>>What causes erosion in a device running at 10 volts when there is no >>ionization impact?> The same thing that has ruined every other field-effect emitter for > the last 40 years or so?What causes the erosion? Is it the high voltage used? I'm not trying to prove you wrong. I'm trying to understand what the mechanism is in case it has any bearing on some of my other projects. As I stated earlier, I could find no reference to tip erosion except that caused by ion impact damage or operation at high voltage. There was nothing on tip erosion at low voltages.
Reply by ●November 3, 20172017-11-03
Steve Wilson <no@spam.com> wrote:> John Larkin <jjlarkin@highlandtechnology.com> wrote:>> On Fri, 03 Nov 2017 15:30:54 GMT, Steve Wilson <no@spam.com> wrote:>>>John Larkin <jjlarkin@highlandtechnology.com> wrote:>>>> What all these things have in common is that the emitting tip erodes. >>>> In the atom probe, that's a feature. In the other cases, it's a >>>> fatality.>>>What causes erosion in a device running at 10 volts when there is no >>>ionization impact?>> The same thing that has ruined every other field-effect emitter for >> the last 40 years or so?> What causes the erosion? Is it the high voltage used?> I'm not trying to prove you wrong. I'm trying to understand what the > mechanism is in case it has any bearing on some of my other projects.> As I stated earlier, I could find no reference to tip erosion except > that caused by ion impact damage or operation at high voltage. There was > nothing on tip erosion at low voltages.For background information, I have a project that uses 40 nm emitters in normal atmosphere with large swings in temperature and relative humidity. I have been concerned about ozone generation and tip erosion from the beginning, which would require replacement of the electrodes and some way to destroy the ozone. The IEEE article gives some hope that a lower voltage would still emit the electrons I need, but greatly reduce tip erosion and ozone. The obvious solution is to try it, but this would require redesigning the structure to take advantage of a different mechanism than I envisioned at the beginning. I will probably do this anyway. If you can give a mechanism for tip erosion at low voltage, it would be very helpful for this project.
Reply by ●November 3, 20172017-11-03
"Steve Wilson" <no@spam.com> wrote in message news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23...> What causes the erosion? Is it the high voltage used? > > I'm not trying to prove you wrong. I'm trying to understand what the > mechanism is in case it has any bearing on some of my other projects. > > As I stated earlier, I could find no reference to tip erosion except that > caused by ion impact damage or operation at high voltage. There was > nothing > on tip erosion at low voltages. >What's the physics at work, anyway? One would suppose the required voltage is proportional to the binding energy and/or work function of the material, and so tungsten would be the best. But those are infinite and ideal properties. One needs to take into account the boundary conditions, which are quite significant in an atomic-scale point. The band structure will be very different in that region (annular confinement modes, where the band splits into discrete levels spaced according to the dimensions of the tip?), and maybe that leads to weakening of the material (a zone of low electron density acting as a stress raiser?). One would then suppose, there exists an ideal tip shape which maximizes its minimum binding energy, while minimizing the work function or electron tunneling probability. Maybe it's a surface of rotation, with a funny curved profile; maybe it's not round, but polygonal; maybe it's a stepped cylinder, or pyramid or cone; maybe it's even hollow, or filled with other elements! Would be interesting to see some analysis of this ... but wouldn't be so interested as to dare attempt it myself. :-x Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: https://www.seventransistorlabs.com/
Reply by ●November 3, 20172017-11-03
"Tim Williams" <tmoranwms@gmail.com> wrote:> "Steve Wilson" <no@spam.com> wrote in message > news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23... >> What causes the erosion? Is it the high voltage used?>> I'm not trying to prove you wrong. I'm trying to understand what the >> mechanism is in case it has any bearing on some of my other projects.>> As I stated earlier, I could find no reference to tip erosion except >> that caused by ion impact damage or operation at high voltage. There >> was nothing on tip erosion at low voltages.> What's the physics at work, anyway?> One would suppose the required voltage is proportional to the binding > energy and/or work function of the material, and so tungsten would be > the best. But those are infinite and ideal properties.> One needs to take into account the boundary conditions, which are quite > significant in an atomic-scale point. The band structure will be very > different in that region (annular confinement modes, where the band > splits into discrete levels spaced according to the dimensions of the > tip?), and maybe that leads to weakening of the material (a zone of low > electron density acting as a stress raiser?). One would then suppose, > there exists an ideal tip shape which maximizes its minimum binding > energy, while minimizing the work function or electron tunneling > probability. Maybe it's a surface of rotation, with a funny curved > profile; maybe it's not round, but polygonal; maybe it's a stepped > cylinder, or pyramid or cone; maybe it's even hollow, or filled with > other elements!> Would be interesting to see some analysis of this ... but wouldn't be so > interested as to dare attempt it myself. :-x> TimWikipedia has a long article on field emission: https://en.wikipedia.org/wiki/Field_electron_emission It does not discuss tip erosion. A few articles I found say the electric field exceeds the binding energy of the atom, so it separates from the tip. This means that high voltage and a sharp tip are needed. This has been my biggest problem from the beginning, since I thought I needed high voltage for electron emission, but I worried it would cause tip erosion and ozone generation. However, if I can get sufficient electron emission at low voltage as described in the IEEE article, that should reduce tip erosion and ozone generation. I'm going to give it a try.
