Magnetic-rigidity settings are set via Barney. This program can be run by clicking in the corresponding icon of the u6pc5 desktop. The rigidities for the different segments are introduced from the A900 Barney page. The values can also be displayed in the S800 Barney page, which can be accessed by clicking the button S3 in the A1900 Barney page.
The magnetic rigidity (“Brho”) of segments 6 and 7 (analysis beam line) of the S800 Barney page displayed below will be set during the secondary-beam tuning (SDT) in cooperation with the A1900 group. The energy loss in all detector systems (object scintillator, object PIN, tracking PPACs) operating in the analysis beam line has to be considered for the Brho setting. This requires the knowledge of the beam Brho at the exit of the A1900, which is typically calculated with the program LISE++ (follow this instructions and/or ask the A1900 group for assistance). In the course of secondary-beam tuning, a scintillating target (“viewer”) and camera setup at the target position of the S800 might be requested by the A1900 group.
The Brho of segment 8 (spectrograph) of the S800 Barney page (see figure below) has to be chosen by the experimenter according to the objectives of the experiment. The segment 8 Brho can roughly be estimated by assuming the segment 7 Brho (analysis beam line) and correcting for the energy loss of the desired fragment/particle in the reaction target. The “physical calculator” of the program LISE++ is well suited for this purpose. The final Brho of segment 8 will later be fine-tuned to achieve the desired setting in the S800 focal plane (fragment of interest centered, for example). Please coordinate all required Brho changes of the spectrograph beam line (segment 8) with the A1900 group as early as possible.
We strongly recommend Barney printouts after every change of the spectrograph. This not only provides a paper copy of all magnet settings from segment 0 to segment 8 but also saves this information in ascii format on disk (accessible via the A1900 web site under Beam Line Savesets). If an inverse map is desired for the tracking of the particles in the spectrograph, segment 8 Brho and the magnet currents of the dipoles and quadrupoles are needed to determine important input parameters for the calculation.