Re: X-ray crystalography

[tdc@ehssun.lbl.gov (Ted M. de Castro)]

>>Until recently it been my experience that the newer the machine, the more
>>in-built safety features it had.  The Philips range of XRF/XRD units are a
>>very good example if this progression away from reliance on the operator's
>>experience and caution towards engineered safety features.

Look closely!!!

Except for the Siemans D500 unit I have found that the newer machines are 
often not as safe as they may look on first blush.

First off the interlocks are usually NOT redundant.

Second - the enclosures don't make allowances for the necessary cables and 
hoses the unit needs.

Third - (in order to accomodate 2 above) the user is provided with a simple 
override plug which ends up always inserted.

The WORSE new machine I have ever seen was some off brand that ran ALL 
interlock signals through a microprocessor for the micro to turn the unit on 
or off.  Totally unsafe!!


>>Apparently, some of this make come with a safety housing, but this one
>>doesnt because of the size of the image receptor.  We have had to devise
>>barriers and sample loading/unloading procedures to reduce the possibility
>>of inadvertent exposure to the main beam (Cu k-alpha, abt 8 keV).

In once case where the installation needed to be ultimately flexible and 
some apparatus was large - we simple made the room the interlocked enclosure 
and located the controls outside!  That installation is working well with no 
user dissatisfaction.

>>I would recommend to any RSO/HP: discuss the purchase of new XRD equipment
>>with researchers well before they buy and make sure the manufacturer can
>>supply equipment which complies with appropriate standards.

ABSOLUTELY!!!  This IS ultimately the cheapest way to get well protected 
equipment and when enough customers demand this ... it will become the norm.