This is a known issue and we battled with for years. The explanation that seems to make most sense is that the high energy X-rays from the tube cause the formation of ozone that attacks the mirror surface. Moisture will speed this up (probably why you noticed it after the summer) but having dry conditions doesn't stop it completely. The older generation W/Si mirrors could be cleaned and regain most of the intensity but the newer Ni/C ones don't clean up so well. We now run with a sealed mirror unit that is more often used with rotating anode sources that should stop the problem. The other way people have got around this is to continually flush the mirror housing with nitrogen or some other gas but that involves drilling a hole in rather an expensive mirror housing. If a mirror is going to be in constant use I would definitely opt for a sealed unit - although not being able to see the mirror surface makes alignment slightly trickier. Pam
________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Mon 22/01/2007 10:24 AM To: Rietveld_l@ill.fr Subject: Hello Hi, my name is Tom Gegan and I work for BASF Catalysts which used to be Engelhard Corporation. For the present my Engelhard email address is still valid as is my BASF email address below. Engelhard is still in the process of being integrated into BASF. Does anyone on the list server use an X-ray mirror in combination with a standard Cu source? My optical path consists of the X-ray tube, a single parabolic X-ray mirror, pinhole slit, collimator snout, the sample, and then an area detector. Patterns collected from NIST SRM 1976 indicate a large loss of intensity this past summer. The intensity loss is permanent and the field service engineer indicated that the mirror is the source of the problem. The face of the mirror had a "stain" or "burn mark" which the service engineer was able to remove, however, the intensity is still down to 1/3 of what it once was. The possibility that the tube is the source of the problem has been ruled out. Has anybody else had similar problems with their X-ray mirrors and do you know why they lose intensity or fail completely? Any information will be greatly appreciated. Thanks. Tom Thomas Gegan Research Chemist, Strategic Technologies Tel: (732) 205-5111 Fax: (732) 205-5300 E-mail: [EMAIL PROTECTED] BASF Catalysts LLC 101 Wood Ave. Iselin, NJ 08830 USA BASF - The Chemical Company
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