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- Path: sparky!uunet!sun-barr!ames!agate!overload.lbl.gov!lll-winken!hpuplca!jeff
- From: jeff@hpuplca.nsr.hp.com ( Jeff Gruszynski)
- Newsgroups: sci.electronics
- Subject: Re: Airport X-Rays
- Message-ID: <10400010@hpuplca.nsr.hp.com>
- Date: 29 Jul 92 01:07:46 GMT
- References: <1992Jul13.020123.3132@mccc.edu>
- Organization: Hewlett-Packard Neely Golden Gate Area (Northern Calif.)
- Lines: 25
-
- > In sci.electronics, polish@cs.columbia.edu (Nathaniel Polish) writes:
- >
- > I think we should clarify the model for how an airport x-ray damages
- > a magnetic medium. Certainly large fields will degauss a floppy but this
- > is unlikely except as noted from the motors. The real problem with x-rays
- > is that they are high-energy radiation. They can cause small ionizations
- > on the surface of the disk. If the ionizations are small relative to the
- > size of the magnetic domains, then there is no visable problem. As the
- > media get denser, the domains get smaller and the problems appear. However,
- > modern airport x-ray equipment is very sensative and they use very weak
- > sources -- mostly to protect the workers.
-
- You'd probably need mega or giga Rad X-ray levels before you'd affect the
- magnetic media. In a previous life I worked with radiation testing hardened
- memories including both semiconductor and magnetic types. In the latter
- the magnetic memory cells were never the issue, but rather getting the
- semiconductor support circuitry to keep up with what the magnetics could
- take. The cell sizes of these magnetic memories (bubble and
- magnetoresistive) were smaller than the domain size of most floppies.
-
- Probably a bigger threat to floppies, tapes, etc. would be the HV
- supplies and fields generated by the E-beam in the X-Ray tube, **if even
- this**.
-
- Jeff
-
