Harp GUI

The picture below describes most of the functionality of the harp/radiator GUI. The most used buttons are the radiator target buttons and the SCAN button. The target buttons move the appropriate radiators into the beam. The SCAN button will move the wire through beam while data logging the beamline scalers. Offline analysis of this data results in a measure of the beam width and halo.

Device Description

The radiator/harp consists of a "tuning fork" device that is inserted in and out of the beam via a ball screw and stepper motor. Attached to the tuning fork are 4 targets and 2 wires. The purpose of the targets is to produce the bremstahling photon beam and the purpose of the wires is to allow for a determination of the beam profile. The tuning fork looks like:

The distance between targets is 0.594 inches, and the diameter of the targets is 1cm. The wire is 50micron of tungsten. The ball screw has 10 threads per inch, and the stepper motor has 2000 steps/rev. This results in: 11880 steps between targets. The software location of the four targets was done using the beam line laser. The number of steps from the high limit switch for the four targets was determined to be:

         target           number of steps        radiation lengths
            A              -55500              100*10^-6
            B              -68350               50*10^-6
            C              -79350                5*10^-6
            D              -90731                blank

The fact that the gap between targets was not found to be 11880 steps suggests that the laser is good to about 1mm in terms of repeatability. This can be improved upon with better procedures.

Creation Date: Mon Feb 24 09:54:21 EST 1997

AUTHOR: ARNE FREYBERGER