Propeller P8X32A Radiation hardness?
Dr. Mario
Posts: 331
After thinking about probably making myself my own storage (event-recording) geiger counter that's intelligent, and has organic LED display to show the radiation strength / counts per minutes, I am truly wondering how much Sievrets per seconds (since P8X32A runs much faster, I went with uSv/Sec - Sv/Sec as I need to emphasize on rapidly-changing events, which this geiger counter would be for, recording what's going on, onto the X-ray - proofed SD card, if the claims is to be believed, though) before P8X32A gets hit with Single-Event Upset (SEU), a transistor-level phenomenal which will cause the CPU to freeze or go loopy.
I am curious, if anybody have done radiation torture on P8X32A, I would be interested to know the results for numbers of hits, and how much milligrays was imposed on P8X32A before it go nuts.
I am curious, if anybody have done radiation torture on P8X32A, I would be interested to know the results for numbers of hits, and how much milligrays was imposed on P8X32A before it go nuts.
Comments
The reason I asked if the P8X32A would be able to withstand specific amount of Gamma-rays before it go crazy was because I may want to build my own storage geiger counter to keep track of emissive energy over time, like from few seconds to few days. Apparently, there is no solid answer as of now, so I kinda decided that I will have to find out on my own, and probably post the result for the others...
I have heard that some SD are designed to be Radiation-Hardened (as the airport X-rays machine really do great job at bulk-erasing some types of SD cards), I am not sure, but if it can be confirmed, alright then I will use it in this geiger counter.
And for dirty method of testing the thickness of Lead for required energy absorption, you can use cheap MOSFET, such as IRF510, and then observe its behavior as you hit it with X-rays or Gamma-rays, if it ain't latching, then thickness is good enough, although I would tend to derate that by 10% to buy me some space in the risk assessment.
I think you could determine the rad-hardness of the Prop based on the "process" from which it was made.
There are probably lots of chips made with the same process, all with about the same level of hardness.
My guess is that this process is not specially rad hard.
There are SOI processes that are more rad hard used for space applications...
I asked about something similar some time ago, so you might look at this;
http://forums.parallax.com/showthread.php?130448-Is-a-DIY-radiation-detector-possible-using-memory-devices-such-as-EEPROMs-SD-cards&p=985655&viewfull=1#post985655
Especially the comments of localroger might throw some light on this.
-phar
Rayman, it may be true, depending on purity of elemental Uranium. However, as mentioned here, http://en.wikipedia.org/wiki/Depleted_uranium military and medical equipments have been using it for a while to curb all of those nasty radiation, possibly several hundreds times the LD50 fatal dosage of human model, or way higher. I will still go with Lead as it's much cheaper and lighter (and also more malleable - DU will have to be melted and poured into ceramic mold).
Do a google image search for "DU babies" to see what I mean.
I thimk your project is a worthwile one. I think you will have to do constant memory testing of hub ram and cog ram. Does anyone know if there is internal parity memory in the prop? I haven't heard of it mentioned, so I doubt it.
Doug
Therefore, DU is only used as a last resort if thick Lead shield won't work - CT X-ray tube don't use this kind of material, they're packaged in thick Lead alloy material - DU also heat up much when it starts to absorb 800W X-ray energy, and it's a crappy heatsink material, so Lead + Copper (probably with trace of Tungsten) alloy is used instead for this kind of X-ray equipment.
Also concerning battery type as mentioned here http://forums.parallax.com/showthread.php?132961-Propeller-Power-Consumed-Based-on-Code , my geiger counter would be powered off by a Lithium-ion battery so it would last my measurement long enough (for safety reason, what's good of a geiger counter with expired Alkaline batteries) - P8X32A consumes lesser power so it's a nice asset.
How will I have it detect radiation? There are two ways to do it: Geiger-Muller tube and / or PIN photodiode. Geiger-Muller tube, either sealed or axial flowing type, detects radiation (X-rays, Gamma-rays, Alpha [Proton], and Beta [Electron]) by ionizing noble gas (Neon, Argon or Xenon, depending on type of counter) distilled in Iodine vapor, and once radiation hits the noble gas atoms, they start to conduct electricity upon the path of radiation and would be quenched by Iodine, bringing it back to non-conducting state to be repeated - the way Geiger Counter works.
PIN Photodiode works similarly to GM tubes, only they are safer to touch than the tubes (in most case, though. Some go up to 200V) - they're shielded by thin Aluminum foil (like the one used to be wrapped around the food) to keep long-wavelength lights (Microwave to Extreme UV) out to prevent false reading, allowing only X-rays and Gamma-rays to pass through and latch the photodiode. One such example - http://www.maxim-ic.com/app-notes/index.mvp/id/2236 - as mentioned in the application note, you will have better chance if the photodiode has large light-sensitive area (more larger PIN light-absorber the better chance you will have at detecting very short light wavelength - and it will work better if it's packaged in plastic package.) An example of plastic-packaged large-area PIN photodiode - http://www.mouser.com/ProductDetail/Vishay-Semiconductors/BPW34/?qs=sGAEpiMZZMtWNtIk7yMEsVnpcClC5AWfAIjz0gFScyY%3d - I know it's Mouser, but it was just an example. And, wavelength sensitivity is not going to matter much anymore after passing 20nm, as it got plentiful of energy, thus having higher chance of knocking off two-electron pairs. Your digital camera(s) are also sensitive to X-rays (in certain brightness - a very powerful X-ray tube, such as the one used in NDT equipment will cause it to snow much - blinding it completely).
I would probably go with solid-state option - Geiger Muller tube may need to be included too, just in case, and I may need to ground Lead shielding as it would be one outrageously sensitive RF receiver, not what I would want seeing on the OLED screen - a very bad thing. They also will need to be calibrated by firmware after booting up. SMPS will do fine here as long as you do generous filtering on its resultant DC rail and Aluminum Oxide polymer capacitor would do great job at acting like a battery upon SMPS' off-state.
Also, you guys think it's good idea to put in SMD fuse holder holding a 1.25A Instant-blow fuse (http://www.mouser.com/ProductDetail/Schurter/3422001011/?qs=YybYKR%2fZNJEk9Jbe8NJHig%3d%3d) in line to Lithium-ion battery's anode connection to the intelligent Li-Ion protector chip, just in case? I thought it would probably be a good idea to fuse the battery anyways, as the total failure of Li-ion battery protector do happen, although very rarely.
And, of course, generous filtering on SMPS will have to be required (any switching noise is unacceptable, but I need to make a gamble here, though - battery life is very important.... And I dunno if most ICs will be happy with less than 3.3 Volts DC power...) and many digital chips or even RF-class chips will need to have low-ESR 100nF MLCC [multi-layer Ceramic capacitors] to be able to keep the RF-induced current from causing some weird issue.
I would also hook up a pin from P8X32A to the output of amplifier to count the "events", that it counts the time the heavily biased photodiode or geiger-muller tube, thus allowing the P8X32A to truly count it out and print the events onto the display or write the timestamp events onto the SD card the moment it "collect" the values. It also simplify the counter calibration, the moment it's turned on (compared with stored calibration reference values on the firmware ROM).