Friday, November 20, 2009

Estimation of sensitivity to radiation damage by sacrificing a crystal

The goal of this new development is to enable the estimation of radiation damage by sacrificing a crystal. The proposal of Sasha Popov and Ricardo Leal is to this it in four steps:

1. Collect one or several reference images from the crystal to be sacrificed.

2. Use EDNA characterisation and a new version of BEST (3.3) to calculate a strategy that both "fries" the crystal and collects some reference frames at regular intervals. The proposal is that this strategy consists of 10 data collection sets, where each data set consists of:

- A couple of reference frames collected at e.g. 5 % transmission

- A data set for burning the crystal with 100 % transmission, the idea is to give a certain dose to the crystal. The images of this data set are not needed in the analysis.

3. Collect this strategy using the BCM (e.g. mxCuBE)

4. Analyse the reference frames with new EDNA plugins. What I understand being the most important parameter to monitor is the increase of B-factor with dose/exposure time. The angle of the slope of this line is a measure of the crystal life time on the beamline.

I will work together with Ricardo Leal to implement step 2. The work in EDNA for step 2 should be straightforward:

- Modification of the MXv1 and BESTv1_1 data model, add "strategyOption" [XSDataString] to XSDataDiffractionPlan (bug #379).

- Update the BEST plugin to version 1.2 in order to use the strategyOption attribute for running BEST with the correct command line option (bug #384).

This new attribute obsoletes the current attribute "anomalousData" [XSDataBoolean] since the anomalousData could be passed as a string to "strategyOption". I suggest though to keep "anomalousData" in the data models in order to not break any existing plugins.

Step 4 will be developed later...

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