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11.2 Dipole fields from measurement

11.2.1 Coordinates conventions

The measurements data take as convention for the $x$ axis, the fact that the edge of the pole tip is at -5 inches. The trapezoidal dipoles measuring 8 inches along the $x$ axis(figure 11.3), the origin does not correspond to the center of the dipole. I chose to change this convention to use the one drawn on figure 11.2, so that the origin point is the barycenter of the dipole.

Figure 11.2: Definitions of the dipole origins

Figure 11.3: Dipoles dimensions at A0

11.2.2 Organization of measurement data

Three sets of measurements data were provided, the latest being the data taken by Marcellus Parker while studying fringe fields interactions between the dipoles at A0[36]

• Exp1 : Files provided by Philippe Piot, concerning the trapezoidal dipole TDA006, and the parallelogram TDA004.
• Exp2 : Files provided by Helen Edwards, concerning the trapezoidal dipole TDA011, and the parallelogram TDA003.
• Exp3 : Fields provided by Marcellus Parker , concerning only the dipole TDA011, but for a wider range of points.
• ... : At this time, no measurement has been done to study the evolution of the field along the $y$ axis, or to study TDA011 with a wider range of points, but it should be done pretty soon.

After concatenations of original experimental files into bundles, we post-treated them for them to be comparable: same coordinates and same structure. These files are stored in the folder /fields/dipoles and are named dip-paral-expX.dat and dip-trapez-expX.dat for the parallel and trapezoidal dipoles of each experiments. Their structure is as presented in table 11.1. ''$B_n$`` corresponds to the transverse magnetic field measured for a current $I=4.5$A and normalized at 1, so that $B_n=B_y/$max$(B_y)$. $X$ $Y$ $Z$ are expressed in meters with respect to the origin point $(0,0,0)$ at the barycenter of the dipole(cf figure 11.2).

Table 11.1: Structure of the experimental dipoles data files

$X$ [m]

$Y$ [m]

$Z$ [m]

$I$ [A]

$B_n$[T]

11.2.3 Field map from measurement

It appeared that the three sets of measurements that were given to me, provide all the same results(see the following figure 11.6). Nevertheless, the one from Marcellus (exp3) are the most interesting as they provide more points. On figure 11.4, the fields measured for the trapezoidal dipole during exp3 and for the parallelogram dipole during exp1 are presented.

Figure 11.4: Field map from the experimental measurement for the dipoles of A0. (a) trapezoidal dipole - (b) : Parallelogram dipole. The field plotted here is of course $B_y$, but normalised so that it's maximum value is one. On black solid line, the hard edges are plotted. The dashed line are at the distance 1.5$g$ fromn the hard edges, where $g$ is the dipole gap.

(a) (b)

Emmanuel Branlard
http://emmanuel.branlard.free.fr/