mar345 Information

The main purpose of the mar345 detector is to provide backup for the Saturn 944+.  To use it, turn on the computer above the desk, take down keyboard and mouse, and switch the input on the left screen.  The password for the mar345 account, which should be used for data collection, is taped to the computer.

Technical details

Unlike the Saturn 944+, the Mar detector uses a fixed phi axis rotation.  There's neither a chi arc nor a 2-theta arm.  The detector is 345mm in diameter versus 135mm for the Saturn.  The Mar uses a phosphorescent image plate instead of a CCD chip which means it has a higher dynamic range but is not as sensitive as the CCD or as fast.  Readout times are approximately 80 seconds on the Mar versus a few seconds on the Saturn.

Instrument preparation

The cold stream is operated the same way as on the Saturn side.  The beam stop slides in and out along the beam.  Move in to collect data.  Mount your sample and align it on the goniometer by adjusting it perpendicular to the vertical axis.  The camera is viewing the crystal from below.  Once the sample is aligned, click the phi rotation wheel into its locked position.  You can feel the resistance if you rotate it round, there is a specific spot where the wheel will click into this position.

Close the doors to the enclosure and manually open the shutter by pressing the right hand “Open” button on the generator control panel.  The orange light on the button will light up as will the orange light in the rear of the deck on the table top.

Data collection

On the control PC open a terminal window and type mar345.  The Mar control software will start up.  Click "Collect" to bring the up the collection control panel.  Change your directory to one that is your own and the image root to reflect your sample.  Note that you must create a directory first to be able to use it from the software.

Once finished entering in all the data click "Go".  If it's the first image of the day click "Go/Erase first" to erase the image plate before exposing.  If you do not do this the image plate will have a large amount of background interference.  Images can be indexed in the same window.