13 ms·

Post-mortem: MRI disables every iOS device in facility

66 points by onuralp 8y ago

kiesel 8y ago
So, what could it be that makes iPhones "react" with helium? Helium is an inert gas and shouldn't really chemically react with anything in there. Any clues why such an environment doesn't make Android phones behave in such a way?
- chopin 8y ago
  The same thread explains it here: https://old.reddit.com/r/sysadmin/comments/9si6r9/postmortem_mri_disables_every_ios_device_in/e8pkhzd/ https://old.reddit.com/r/sysadmin/comments/9si6r9/postmortem.... Sounds plausible to me. If it wasn't dangerous one could try the same with hydrogen. If the post is correct it should have a similar effect (if the device doesn't explode during the test).
- hatsunearu 8y ago
  Basically electronic oscillators rely on a very small piece of quartz crystal that is cut in just the right shape. Quartz has a phenomena called piezoelectricity, where if you apply an electric field, it deflects slightly. Conversely, if you deflect it, it creates a small electric potential. A properly shaped quartz, when exposed to some circuitry (oscillator circuitry; positive feedback), it will resonant at its natural frequency, not unlike how a tuning fork resonates at its natural frequency. Since the crystal is literally vibrating inside the metal can it's packaged in, the atmosphere around the crystal influences the natural frequency. Helium will make it vibrate it faster, since it presents less air resistance to the crystal.
  - alxlaz 8y ago
    Note, however, that MEMS oscillators (which modern iPhones use) and quartz oscillators are not the same thing. SiTime's MEMS oscillator is made of silicon, not quartz.
  - berbec 8y ago
    Would an iPhone lock up in a vacuum?
- tyingq 8y ago
  "Any clues why such an environment doesn't make Android phones behave in such a way?" A bit of googling seems to indicate most smart phones have a crystal oscillator. But, Android would have the advantage of manufacturer diversity...so lots of different types of crystal oscillators, perhaps some that are sealed better than the iphone ones, or quartz vs silicon, etc. This does sort of illustrate an issue with the iphone tech monoculture. Lots of devices with similar components, and similar versions of software. Find something that adversely affects them, and you can disrupt a lot of people. It's probably hard to find something similar for Android since the hardware and even software varies a lot.
  - alxlaz 8y ago
    Most crystals have better sealing :-). SiTime explicitly(-ish) acknowledges that their older-generation packaging was less efficient on their website: "How effective is the hermetic seal of MEMS oscillators?? One of the key elements enabling extremely stable MEMS resonators is SiTime’s EpiSeal™ process which hermetically seals the resonators during wafer processing, eliminating any need for hermetically sealed ceramic packaging. SiTime’s EpiSeal resonator is impervious to the highest concentration elements in the atmosphere, nitrogen and oxygen, and therefore acts as a perfect seal. Previous generations of EpiSeal resonators may have been impacted by large concentrations of small-molecule gas. Newer EpiSeal resonators are impervious to all small-molecule gases. Please contact SiTime in case you are planning to use a SiTime device in large concentrations of small-molecule gas, so that we can recommend an appropriate, immune part." https://www.sitime.com/support/faqs https://www.sitime.com/support/faqs
    - NormM 8y ago
      Apple uses these oscillators. They are substantially more expensive than crystal oscillators, but are much smaller and use less power. This may explain why the Android phones, which are more price sensitive, didn't use them. It does seem that the current generation of SiTime oscillators don't have a problem with Helium, so perhaps current generation iPhones don't either.
Cogito 8y ago
Description of the issue from the original thread [0]: The processor in a modern, high volume device typically has its main clock driven by what's known as a MEMS oscillator. These are barely visible mechanical systems that resonate at some designed frequency, and include packaging to convert this resonance into a useful electrical clock signal. These devices are extraordinarily cheap ways to produce a steady clock, but they have a number of drawbacks. Most relevant, in order for these types of devices to function properly, the mechanical resonator must be inside a tiny hermetically sealed chamber with either a controlled gas inside or a vacuum, as the gas composition in the chamber can affect the output frequency. For both cost and physics reasons, these hermetic seals are not perfect, and are somewhat commonly permeable to small atomic gasses such as helium. ... For this specific case, Apple devices probably share a common family of MEMS resonator to reduce manufacturing costs. This clock likely leaks in helium rich atmospheres, pushing the output frequency outside of the bounds that the main processors are designed to handle, rendering them non-functional. If left idle long enough, the devices may begin to function again, but depending on the concentration of helium which leaked in, this could take anywhere from weeks to years to occur in natural atmosphere and temperatures. [0] https://www.reddit.com/r/sysadmin/comments/9mk2o7/mri_disabled_every_ios_device_in_facility/e7g5rcw/ https://www.reddit.com/r/sysadmin/comments/9mk2o7/mri_disabl...
- SilasX 8y ago
  >For this specific case, Apple devices probably share a common family of MEMS resonator to reduce manufacturing costs. At risk of provoking a standard flame war... They had mentioned that Android phones are unaffected, but don't those generally use even more "economical" manufacturing?
  - Cogito 8y ago
    It’s not economical in the sense of cheap parts, rather it’s economical in that Apple uses the same part in all devices. This can simplify supply chain and engineering efforts, so makes sense when possible. The comment is looking to explain why all the Apple devices failed; they were all affected by the same sensitivity to helium. Android devices tend to use a multitude of different parts to each other, so while some may have been affected you wouldn’t expect them all to fail in sync like the Apple devices did.
hatsunearu 8y ago
Wow, that's a really insane and cool phenomena. I should keep this in my memory in case I encounter it in my career. Also, if there was enough helium to contaminate the entire atmosphere, was there not a pretty significant chance of an asphyxiation hazard?
- alxlaz 8y ago
  I don't think there was. It's not like people figured out today that bad quantities of helium can be bad, and that big tanks have big quantities of helium, so MRI rooms are routinely equipped with oxygen sensors (see e.g. https://www.pureairemonitoring.com/oxygen-o2-monitor-for-mri-rooms-pureaire-sells-a-hassle-free-10-year-oxygen-monitor/ https://www.pureairemonitoring.com/oxygen-o2-monitor-for-mri... -- not affiliated, it's just the first result on Google). If the spill had been significant, these would have definitely caught it. Besides, an MRI's liquid helium tanks are big, but not that big to cause trouble if they leak over a period of a couple of hours in a ventilated room.
- deleted 8y ago
  [deleted]
- loco5niner 8y ago
  "Hey Bob, you ok? You're talking kinda funny".
anowlcalledjosh 8y ago
See also: https://news.ycombinator.com/item?id=18340693 https://news.ycombinator.com/item?id=18340693

66 points by onuralp 8y ago

So, what could it be that makes iPhones "react" with helium? Helium is an inert gas and shouldn't really chemically react with anything in there. Any clues why such an environment doesn't make Android phones behave in such a way?

chopin 8y ago
The same thread explains it here: https://old.reddit.com/r/sysadmin/comments/9si6r9/postmortem_mri_disables_every_ios_device_in/e8pkhzd/ https://old.reddit.com/r/sysadmin/comments/9si6r9/postmortem.... Sounds plausible to me. If it wasn't dangerous one could try the same with hydrogen. If the post is correct it should have a similar effect (if the device doesn't explode during the test).
hatsunearu 8y ago
Basically electronic oscillators rely on a very small piece of quartz crystal that is cut in just the right shape. Quartz has a phenomena called piezoelectricity, where if you apply an electric field, it deflects slightly. Conversely, if you deflect it, it creates a small electric potential. A properly shaped quartz, when exposed to some circuitry (oscillator circuitry; positive feedback), it will resonant at its natural frequency, not unlike how a tuning fork resonates at its natural frequency. Since the crystal is literally vibrating inside the metal can it's packaged in, the atmosphere around the crystal influences the natural frequency. Helium will make it vibrate it faster, since it presents less air resistance to the crystal.
- alxlaz 8y ago
  Note, however, that MEMS oscillators (which modern iPhones use) and quartz oscillators are not the same thing. SiTime's MEMS oscillator is made of silicon, not quartz.
- berbec 8y ago
  Would an iPhone lock up in a vacuum?
tyingq 8y ago
"Any clues why such an environment doesn't make Android phones behave in such a way?" A bit of googling seems to indicate most smart phones have a crystal oscillator. But, Android would have the advantage of manufacturer diversity...so lots of different types of crystal oscillators, perhaps some that are sealed better than the iphone ones, or quartz vs silicon, etc. This does sort of illustrate an issue with the iphone tech monoculture. Lots of devices with similar components, and similar versions of software. Find something that adversely affects them, and you can disrupt a lot of people. It's probably hard to find something similar for Android since the hardware and even software varies a lot.
- alxlaz 8y ago
  Most crystals have better sealing :-). SiTime explicitly(-ish) acknowledges that their older-generation packaging was less efficient on their website: "How effective is the hermetic seal of MEMS oscillators?? One of the key elements enabling extremely stable MEMS resonators is SiTime’s EpiSeal™ process which hermetically seals the resonators during wafer processing, eliminating any need for hermetically sealed ceramic packaging. SiTime’s EpiSeal resonator is impervious to the highest concentration elements in the atmosphere, nitrogen and oxygen, and therefore acts as a perfect seal. Previous generations of EpiSeal resonators may have been impacted by large concentrations of small-molecule gas. Newer EpiSeal resonators are impervious to all small-molecule gases. Please contact SiTime in case you are planning to use a SiTime device in large concentrations of small-molecule gas, so that we can recommend an appropriate, immune part." https://www.sitime.com/support/faqs https://www.sitime.com/support/faqs
  - NormM 8y ago
    Apple uses these oscillators. They are substantially more expensive than crystal oscillators, but are much smaller and use less power. This may explain why the Android phones, which are more price sensitive, didn't use them. It does seem that the current generation of SiTime oscillators don't have a problem with Helium, so perhaps current generation iPhones don't either.

Cogito 8y ago

Description of the issue from the original thread [0]: The processor in a modern, high volume device typically has its main clock driven by what's known as a MEMS oscillator. These are barely visible mechanical systems that resonate at some designed frequency, and include packaging to convert this resonance into a useful electrical clock signal. These devices are extraordinarily cheap ways to produce a steady clock, but they have a number of drawbacks. Most relevant, in order for these types of devices to function properly, the mechanical resonator must be inside a tiny hermetically sealed chamber with either a controlled gas inside or a vacuum, as the gas composition in the chamber can affect the output frequency. For both cost and physics reasons, these hermetic seals are not perfect, and are somewhat commonly permeable to small atomic gasses such as helium. ... For this specific case, Apple devices probably share a common family of MEMS resonator to reduce manufacturing costs. This clock likely leaks in helium rich atmospheres, pushing the output frequency outside of the bounds that the main processors are designed to handle, rendering them non-functional. If left idle long enough, the devices may begin to function again, but depending on the concentration of helium which leaked in, this could take anywhere from weeks to years to occur in natural atmosphere and temperatures. [0] https://www.reddit.com/r/sysadmin/comments/9mk2o7/mri_disabled_every_ios_device_in_facility/e7g5rcw/ https://www.reddit.com/r/sysadmin/comments/9mk2o7/mri_disabl...

SilasX 8y ago
>For this specific case, Apple devices probably share a common family of MEMS resonator to reduce manufacturing costs. At risk of provoking a standard flame war... They had mentioned that Android phones are unaffected, but don't those generally use even more "economical" manufacturing?
- Cogito 8y ago
  It’s not economical in the sense of cheap parts, rather it’s economical in that Apple uses the same part in all devices. This can simplify supply chain and engineering efforts, so makes sense when possible. The comment is looking to explain why all the Apple devices failed; they were all affected by the same sensitivity to helium. Android devices tend to use a multitude of different parts to each other, so while some may have been affected you wouldn’t expect them all to fail in sync like the Apple devices did.

hatsunearu 8y ago

Wow, that's a really insane and cool phenomena. I should keep this in my memory in case I encounter it in my career. Also, if there was enough helium to contaminate the entire atmosphere, was there not a pretty significant chance of an asphyxiation hazard?

alxlaz 8y ago
I don't think there was. It's not like people figured out today that bad quantities of helium can be bad, and that big tanks have big quantities of helium, so MRI rooms are routinely equipped with oxygen sensors (see e.g. https://www.pureairemonitoring.com/oxygen-o2-monitor-for-mri-rooms-pureaire-sells-a-hassle-free-10-year-oxygen-monitor/ https://www.pureairemonitoring.com/oxygen-o2-monitor-for-mri... -- not affiliated, it's just the first result on Google). If the spill had been significant, these would have definitely caught it. Besides, an MRI's liquid helium tanks are big, but not that big to cause trouble if they leak over a period of a couple of hours in a ventilated room.
deleted 8y ago
[deleted]
loco5niner 8y ago
"Hey Bob, you ok? You're talking kinda funny".

anowlcalledjosh 8y ago

See also: https://news.ycombinator.com/item?id=18340693 https://news.ycombinator.com/item?id=18340693