We had the opportunity to abuse some props by bombarding them with 2GeV protons using a synchrotron. The beam had a particle density of ~10^8/s*cm² and while the PICs stood their ground for ~8..15min without apparent malfuntion the propeller chip did IMMEDIATELY latchup every time we turned on the beam, I~600mA seems to be a latchup anyway. The propeller could reboot after the event, so the only apparent use in a radiation environment seems to be as a canary... Any ideas why it would do that?
You might also try disabling the brownout and operating the Prop at 1.1-1.5 volts. The Prop should still do a 20-40MHz clock, but with such a low supply voltage any parasitic thyristors might not be able to turn on? (I've only tested rise and fall times at these voltages. They're ~1.5nS versus the normal ~0.8nS)
You might also try disabling the brownout and operating the Prop at 1.1-1.5 volts. The Prop should still do a 20-40MHz clock, but with such a low supply voltage any parasitic thyristors might not be able to turn on? (I've only tested rise and fall times at these voltages. They're ~1.5nS versus the normal ~0.8nS)
Marty
This is a very good idea. We will run a new set of tests with no PLL and low voltage operation, hopefully this might have a positive effect. Unfortunately that will take a while as we won't get any beam time soon. I wonder if it would be possible to increase the thickness of the insulation layers towards the substrate. That might counteract the spilling of charge created by the photoeffect into the circuit. Anyway, we should find out what is happening here before drawing any conclusions. Anybody out there who exposed the prop to any kind of ionizing radiation?
Anybody out there who exposed the prop to any kind of ionizing radiation?
60 kV x-rays from W target had no effect on a propeller in one test I performed. In fact, there seems to be an additive to the epoxy encapsulation (lime?) that is partly radiopaque to such soft rays.
60 kV x-rays from W target had no effect on a propeller in one test I performed. In fact, there seems to be an additive to the epoxy encapsulation (lime?) that is partly radiopaque to such soft rays.
Any numbers on the total dose and flux? Nobody else who fried the prop out of curiosity?
Those 2N3055's may well have been mil grade. I used to know a guy with a warehouse at the Hunter's Point shipyard in SF. He had tons of mil parts, repairs kits and so on. I got some 2N3055's with gold plated leads and some kind of mil designation number after the part num. I used 'em for a flyback driver. The lasted much better than ordinary ones but still died eventually.
Comments
"Operation under conditions exceeding 2M eV ercos is not supported."
: ) : )
You might also try disabling the brownout and operating the Prop at 1.1-1.5 volts. The Prop should still do a 20-40MHz clock, but with such a low supply voltage any parasitic thyristors might not be able to turn on? (I've only tested rise and fall times at these voltages. They're ~1.5nS versus the normal ~0.8nS)
Marty
This is a very good idea. We will run a new set of tests with no PLL and low voltage operation, hopefully this might have a positive effect. Unfortunately that will take a while as we won't get any beam time soon. I wonder if it would be possible to increase the thickness of the insulation layers towards the substrate. That might counteract the spilling of charge created by the photoeffect into the circuit. Anyway, we should find out what is happening here before drawing any conclusions. Anybody out there who exposed the prop to any kind of ionizing radiation?
David
60 kV x-rays from W target had no effect on a propeller in one test I performed. In fact, there seems to be an additive to the epoxy encapsulation (lime?) that is partly radiopaque to such soft rays.
Any numbers on the total dose and flux? Nobody else who fried the prop out of curiosity?
Jonathan