Hi Alex, I can now access the website finally, interesting! About the Weston book, You are right. It is too general and low level, there is no way how to calculate actual sputtering rates using information provided there. Also as You mentioned, they deal with low pressure mostly. But there are some interesting information such as the experiment with one shape of anode grid and different pressures. They found that the rate of deposition of the metal on the glass at 20torr was much lower than at 50torr, there is a relation between the shape (size) of the hole in anode grid and pressure inside the tube.
I think it is better to spend a few hours setting up the real experiment than bothering with theoretical calculations in this case. There is too many variables - metal composition, anode cage shape, purity of the gas and so.. I am definitely interested in your experiment as it is far the closest to our needs! Dalibor 2013/11/22 AlexTsekenis <alextseke...@gmail.com>: > Hi Dalibor, > > I just got confirmation from Eastern Europe that they can access the page. > Can I ask who is your ISP/host in Czech Republic so I can check with our > host. Thanks in advance. The same goes for anyone else that might be having > issues. Glad you have temporary access! > > It seems our timing is good ;-) Certainly, Weston's book is idea for > bed-time reading.The chapter on sputtering (ch 4) is informative of the > state of research in those days, but it falls short if you are reading it to > find out when the tube has reached its end of life. Here is why. > > The theoretical models presented (section 4.3) are too low level. The > researchers tried to create models almost from first principles. The > sputtering process is very complex, so they inevitably resorted in number of > assumptions and simplifications. As you go through the chapter you will see > that the results agree under some conditions, but disagree on others.I think > Weston mentions this somewhere. > > In terms of experimental work most setups were at too low pressures to > sustain a glow discharge (fractions of a torr). Consequently the > back-diffusion of cathode material that is present in commercial nixie tubes > was not present (as stated in top of page 138 and section 4.2.2) in those > experiments. Additionally the ion beam setups look nothing like a nixie tube > (mercury pool, charged collection target etc). > > As I described in SHINE, the most relevant experiments were those from > Stocker (reference in SHINE page, page 140 in Weston's book). Stocker used a > cylindrical tube with a wire cathode and a cylindrical anode (much like an > IN-13 tube!). However he used a filament light source inside the tube, > whereas we are using the emission from the glow itself as the light source. > We are not using internal light sources as anything carrying current or > being at a potential will distort the fields inside the tube. Stocker ends > up with the empirical equation 4.18 in Weston's book or 2 in SHINE page > which you one can use. But the equation only gives the sputtering rate, not > the loss of brightness. To put the final nail in the coffin, none of the > above experiments or theories incorporates anti-darkening measures such as a > mesh anode like the IN-13 uses! > > We decided to measure brightness directly as at the end of the day that's > what causes one to throw the tube away. Doing so automatically accounts for > whatever processes might be taking place at an atomic level and any measures > taken by the manufacturer to increase the lifetime. Using this method I > cannot do a calculation and tell you how long a tube you made will last if > you run it at 5 or 10mA. But I can measure it and then tell you with great > confidence :-) hope this clarifies the distinction. > > As long as chapter 4 (and other literature on sputtering) is concerned, my > personal feeling is that technology declined before the leaders at the time > had time to develop a unified model. What do you think? > > Alex > > > > On Friday, November 22, 2013 5:25:29 PM UTC, Dalibor wrote: >> >> Hi Alex, >> >> I think it will actually be something with settings of the firewall on >> your server. The server doesnt respond to ping, from my IP and even >> not from my server that is in a big czech telehouse. >> >> however, I checked your site from the proxy and there is plenty good >> information! >> >> I was just reading about sputtering two days ago, (Weston, 1968), >> there were mentioned some experiments for measuring the deposit >> thickness, have You already read it? >> >> Bye! >> >> Dalibor >> >> 2013/11/22 AlexTsekenis <alexts...@gmail.com>: >> > Hi Dalibor, >> > >> > Thanks. I'm surprised you cannot access the site, no issues here from >> > multiple computers. Maybe try from the home page >> > http://www.saltechips.com/ >> > and clearing your cache. Please let us know if you are still having >> > issues, >> > there is a wealth of information on the site including equations, plots >> > etc. >> > >> > We have data for the first 7k minutes (6810 to be exact), but I would >> > like >> > to collect more before drawing any conclusions. The plan is to do curve >> > fitting on the collected data points, thus suppressing noise and other >> > artefacts. If you follow our theoretical working you will see that the >> > light >> > emitted is falling exponentially, so we expect the data points to fit >> > such a >> > curve: >> > http://www.ibm.com/developerworks/rational/library/mar06/cantor/fig7.gif >> > The >> > sampling rate of the data published is currently slow (1 point per >> > week). >> > This Sunday is time for the second measurement. I will need to judge >> > whether >> > to increase or decrease the sample rate then. >> > >> > Yes, you are right on current affecting sputtering rate. Also the gas >> > pressure and composition as well as the electrode material may I add. >> > This >> > is mentioned in the description and an empirical equation is given. >> > However >> > the method we are using is independant from these factors - we are just >> > interested in the rate that the glass becomes darker. So the experiment >> > can >> > be repeated for different currents and tube constructions to optimise >> > the >> > tube and operating point. >> > >> > We are running it at about 4mA with a constant current sink. This makes >> > the >> > glow reach about 3/4 of the tube's length. In other words the tube is in >> > the >> > normal glow region and we are 1/4 away from abnormal glow. In the normal >> > glow region increasing the current increases the area of cathode being >> > covered by the glow. These conditions were selected to best replicate >> > typical usage of this particular tube, thus giving the most accurate >> > lifespan figure possible. >> > >> > How is website access now? >> > >> > Alex >> > >> > >> > On Friday, November 22, 2013 2:16:00 PM UTC, Dalibor wrote: >> >> >> >> Hi Alex, >> >> >> >> this is pretty interesting! I cant access the website, it is probably >> >> unavailable now, but the stream is clear! Do You have any graph how >> >> the absorbance rise during that those 7000 minutes? >> >> >> >> Are You running it on specs current or on higher to make the process >> >> faster? The sputtering is not directly proportional to current, so it >> >> would be nice to have data for currents from datasheet.. >> >> >> >> Thanks! >> >> >> >> Dalibor >> >> >> >> 2013/11/22 AlexTsekenis <alexts...@gmail.com>: >> >> > It is my great pleasure to announce that the SHINE (SALTechips IN-13 >> >> > Endurance) experiment is now online. >> >> > >> >> > For the first time since the Cold War era we are able to rigorously >> >> > measure >> >> > the end of life of a nixie tube due to darkening of its glass >> >> > envelope. >> >> > We are super nixited as we can now accurately answer the frequent >> >> > question >> >> > of the lifespan of a given nixie. >> >> > >> >> > The experimental method relies upon a theoretical basis and custom >> >> > precision >> >> > instrumentation developed by SALTechips specifically for this >> >> > purpose. >> >> > In summary, we are monitoring the optical absorbance demonstrated by >> >> > the >> >> > envelope of the tube as cathode material is being deposited by >> >> > sputtering. >> >> > The absorbance increases with time, thereby causing the tube to >> >> > become >> >> > dimmer. At some time a brightness threshold is reached which we treat >> >> > as >> >> > the >> >> > end of life of the tube. >> >> > The method and experimental setup are described in detail here: >> >> > http://www.saltechips.com/lab/ >> >> > This time we are measuring the IN-13 bargraph tube that is of >> >> > immediate >> >> > interest to us, although the tools and techniques can be used on most >> >> > glow >> >> > discharge tubes. >> >> > >> >> > We anticipate the experiment that is currently in progress to take a >> >> > while.Data is plotted live as it is collected and we also have a live >> >> > stream >> >> > of the instrumentation screens available 24/7(follow link above or >> >> > directly >> >> > here: http://www.ustream.tv/channel/from-the-salte-lab). These are >> >> > the >> >> > same >> >> > screens we use to record data! Nearly 7000 minutes into the >> >> > experiment >> >> > and >> >> > we are already collecting valuable data. >> >> > >> >> > The future of this method is bright as it is applied to measure and >> >> > compare >> >> > other nixie tubes! >> >> > >> >> > >> >> > Alex >> >> > >> >> > >> >> > >> >> > -- >> >> > You received this message because you are subscribed to the Google >> >> > Groups >> >> > "neonixie-l" group. >> >> > To unsubscribe from this group and stop receiving emails from it, >> >> > send >> >> > an >> >> > email to neonixie-l+...@googlegroups.com. >> >> > To post to this group, send an email to neoni...@googlegroups.com. >> >> > To view this discussion on the web, visit >> >> > >> >> > >> >> > https://groups.google.com/d/msgid/neonixie-l/b16aa111-40c9-49f9-b6c5-f0a5b4a788a0%40googlegroups.com. >> >> > For more options, visit https://groups.google.com/groups/opt_out. >> >> >> >> >> >> >> >> -- >> >> Dalibor Farny >> >> http://dalibor.farny.cz >> > >> > -- >> > You received this message because you are subscribed to the Google >> > Groups >> > "neonixie-l" group. >> > To unsubscribe from this group and stop receiving emails from it, send >> > an >> > email to neonixie-l+...@googlegroups.com. >> > To post to this group, send an email to neoni...@googlegroups.com. >> > To view this discussion on the web, visit >> > >> > https://groups.google.com/d/msgid/neonixie-l/732ecf75-a44a-4ffb-b877-9f3bfad6072b%40googlegroups.com. >> > >> > For more options, visit https://groups.google.com/groups/opt_out. >> >> >> >> -- >> Dalibor Farny >> http://dalibor.farny.cz > > -- > You received this message because you are subscribed to the Google Groups > "neonixie-l" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to neonixie-l+unsubscr...@googlegroups.com. > To post to this group, send an email to neonixie-l@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/5b1ece2d-1b69-47a7-8980-66787cda3dcd%40googlegroups.com. > > For more options, visit https://groups.google.com/groups/opt_out. -- Dalibor Farny http://dalibor.farny.cz -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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