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To assure accuracy in the scanning procedure, the detector must be placed correctly on the scanning table and its position must be measured accurately.

The scanning table contains a box of aluminum beams onto which the detector's stand is installed. The detector needs to be lifted carefully and placed so that the Green and Blue crystals face to the west. (In this configuration, the Red and White crystals will face the ISAC II experiment hall.)

Once the detector has been secured and bolted to the beams on the table, it is important to calibrate the scanning table so that x=0 and y=0 are at the centre of the detector. To do that, the online interface on midtig03 can be used to move the scanning platform and a caliper needs to be used to measure the distances between the edge of the table and the legs of the detector stand. The procedure for that is as follows:

[edit] Procedures

The position of the detector on the scanning table

1. After connecting to midtig03.triumf.ca:8081 and selecting tigscan, go to ODB-->Equipment-->Motors-->settings.
2. That page will allow you to move the scanning platform. Select the destination ([1] and [2]) to 300 each in order to move the platform to the bottom right extreme of the table. The platform will stop when it reaches its maximum. In order to move the platform, change both 'n' values in the move rows to 'y'. Remember that X goes N-->S while Y goes E-->W.
3. Once the platform is finished moving, use the calipers to measure the distance between the edge of the platform and the legs of the detector stand in both X and Y directions. The X and Y values will be called Xoffset and Yoffset for this point (A). It is important to keep all the data in order so a diagram of the platform will help. Finally in order to calibrate the table, the previous position values can be read at ODB-->Equipment-->Motors-->Variables-->Position. This needs to be recorded for points A and C. We'll call this Xposition and Yposition.
   
   

   

   Measuring the Y offset at point A
4. Moving the platform to -300, 300 will place it in position B and the measurement procedure can be repeated again. Note the Xoffset and Yoffset for B in the notebok near the corresponding edge of the square. Moving the platform to -300, -300 will reach point C, where measurements can be repeated. At point C, it's important to record the Positions as mentioned in part 3.
5. Finally moving the platform to 300, -300 will get to point D, and the offset measurements can be repeated.
6. After the measurements, 2 values for +/-X and +/- Y will be obtained (8 in total). The average of these values in each direction needs to be taken for improved accuracy.
7. In order to calculate the positions of the detector stand, it is required to add (or subtract in the -X, -Y directions) the corresponding offset values to the corresponding Position values. This means for example, subtracting the average of Xoffset of C and B from the Xpos value at C. Once 2 X values and 2 Y numbers are obtained for the detector stand, their absolute values need to be added up and the sum divided by 2. This will determine the position at which the centre of the detector stand is.
8. Once the table is moved to the position obtained from 7, it can be set to 0,0 by power cycling (turning off and on) the motor control box at the top of the rack.

The leaad castle encasing the source

Procedure for calculating the origin (0,0)