Hello, It looks very much like coming from the plastic cap and the pin (of the CryoCap). I am basing this on the fact that you mention the CryoCap is opposite to beamstop. If you look closely at the shadow you can see the profile of the plastic (hemi-circle) with lighter shade where the pin would go (small cylinder right in the middle of the hemi circle).
Beside the other helpful suggestions you have received, you may consider reducing the collimator size, so that beam arriving at the crystal is very compact. Since you say it is mar345, I am assuming the distance between the end of the collimator and beginning of the goniometer is fixed. If not you may consider bringing the crystal closer to the collimator there by reducing the scatter. > -----Original Message----- > From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On > Behalf Of Alejandro Buschiazzo > Sent: Thursday, May 03, 2007 6:52 PM > To: CCP4BB@JISCMAIL.AC.UK > Subject: [ccp4bb] image plate shadow > > Dear ccp4bb users, > > I have a question that concerns a problem with data > collection (not directly related to CCP4). It might be a > really stupid mistake I'm making... > > I'm attaching a diffraction frame where, as you can easily > see, there is an annoying shadow (on purpose the contrast on > the image has been forced to highlight the problem). The > shadow doesn't correspond to the cryo nozzle, since the > nozzle is set coming in from the same direction as the > attachment of the beamstop, i.e. right opposite to the shadow. > The detector is an image plate (Mar345), and this problem > appears when collecting at high-ish resolution (say better than 1.8). > > I wonder if someone has encountered a similar problem...I've > been playing around for a while now, unfortunately not > finding a way out. > could it be associated to the metallic pin of the cryo-loop > on which the xtal is actually mounted? I thought if the loop > is rather short, at high diffraction angles this could > actually be a shadow generated by the tip of the metallic > rod....they're pretty much conventional pins though, and I > didn't step into this type of problem before. In any case how > could I handle this, if it were the actual cause of this anomaly? > I tried to adjust the collimator end, or even change it > trying other sizes as well, with no success. > > I'll certainly appreciate any help / suggestions! > > Best regards, > > -- > Alejandro Buschiazzo, PhD > Research Scientist > Laboratory of Structural Biology > Pasteur Institute of Montevideo > Mataojo 2020 > Montevideo 11400 > URUGUAY > > Phone: +5982 5220910 int. 120 > Fax: +5982 5220910 int. 111 > >
