The Warm Iron Geometry of the ?Average? RHIC Dipole Page: 1 of 7
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The Warm Iron Geometry of the
"Average" RHIC Dipole
S. Peggs, S. Tepikian, D. Trbojevic, J. Wei
The code RAPIDEAL , maintained by RAP, is used by the surveyors to
place RHIC arc dipoles (and other magnets) into exactly the right location in the
tunnel, prior to their connection to neighboring magnets. Although RAPIDEAL
accounts for the individual idiosyncrasies of particular dipoles, it nonetheless
incorporates a model iron geometry of a nominal dipole. Until recently, the
model of a "theoretical" dipole was assumed. This note describes the derivation
and parameters of an "average" dipole model, based purely on data available
from as many as 159 DRG magnets. Now that RAPIDEAL uses this new model,
the systematic error in the offset of beam tubes (and other piping) is greatly
reduced, from about 100 mils to about 20 mils.
Having established the iron geometry of the average RHIC dipole, this note
goes on to advocate an intentional 50 mil radial offset of the dipoles (and tubes
and pipes). With this intentional offset, injected beam is closer to the magnetic
center of the dipole, optimizing the field quality seen by the beam.
Fitting the average sagitta data
The eight data points in Figure 1 are derived from measurements taken
on every dipole at Northrop-Grumman, information stored in the "magbase"
Sybase database. Error bars correspond to the standard deviation for the dis-
tribution of 159 dipoles, for which data were available in late June, 1995. The
end data points (at approximately 5 and 375 inches) are not quite at the ex-
treme ends of the iron, and so the "total iron sagitta", shown as a single data
point on the vertical axis, is slightly larger than the mid-arc maximum.
The solid line shows the best fit possible when a constant radius arc is
constrained to go through the outer data points. Note that the adjacent data
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S., Peggs; Tepikian, S.; Trbojevic, D. & Wei, J. The Warm Iron Geometry of the ?Average? RHIC Dipole, report, July 1, 1995; United States. (https://digital.library.unt.edu/ark:/67531/metadc868164/m1/1/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.