Theta-2Theta Scans

These are the command formats for $\theta{}-2\theta$ scans:

ONLINE> scan/t2t
ONLINE> scan/om_tt
ONLINE> scan/tt_om
ONLINE> scan/t2t=motor_tt motor_omega

The first three commands can be used, if diffractometer angles have been defined. The qualifiers /t2t and /om_tt select the same scan type. Let's take a closer look at /om_tt scans: The $\omega$ motor is scanned and the $2\theta$ motors follows. The position of $2\theta$ is calculated according to $2\theta_{new} = (\omega_{new} - \omega_{start}) * 2 + 2\theta_{start}$. With $\omega_{start}$ and $2\theta_{start}$ being stored when the scan is started. $\omega$ runs from START to STOP and $\omega_{new}$is the current scan position. This way it is ensured that $\theta - 2\theta$ scans can be performed with arbitrary offsets.

/tt_om scans are performed similarly, except that this time $2\theta$ is scanned and $\omega$ follows. This scan type is chosen, if $2\theta$ should be the x-axis of the data.

The command scan/t2t=motor_tt motor_omega specifies the motors for $2\theta$ and $\omega$ explicitly. It is used at those experiments which have no diffractometer angles defined.

The symbol position_cm holds the position of the second motor, the symbol scan_device_cm the name of the second motor.

Mind that it is also possible to make combined scans with two motors which are related by an arbitrary factor ().