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Magnetic Measurements
Sources & accelerators Contents > Accelerators > Magnetic Measurements
DIPOLES Measurements
Last Update : September 2005
38 dipoles (32 for the Storage Ring) have been manufactured by TESLA.
The measurements were performed by SOLEIL.

The prototype and several dipoles have been measured with the Hall probes bench BCH15 to produce some Cartesian field mapping in order to characterize the trnasverse field homogeneity and the fringe field.

The measurements of the series have used the stretched wire bench BCD (see figure on the right) to perform the integrated field comparison between each dipole and the reference one, and then define the magnetic identity of the dipoles.

Results:
- Effective magnetic length=1.0555m
- Homogeneity around real trajectory:
Δ∫Bdl / ∫Bdl<5 10-4 at x=±20mm.
- Identity from magnet to magnet:
Standard deviation = 6 10-4
- Sorting has been performed in order to define the optimized location of each dipole in the ring.
 The BCD bench
 
QUADRUPOLES Measurements
Last Update : September 2005
Figure 1: The quadrupoles stored at the 706 building

 

164 quadrupoles (see figure 1 on the left) have been manufactured by DANFYSIK.
The measurements were performed by SOLEIL with the rotating coil bench BMS (see figure 2) optimized for a very precise magnetic axis centering within tolerances: ± 25µm in x and z, and ± 0.1 mrad in θs. A very rigid sensor (figures 3 and 4) has been developed to avoid sagitta effect.

Reference radius for harmonic analysis = 30mm


Results :
- Magnetic axis centering, performed at nominal current, satisfies tolerances. Mean values are close to 0 and standard deviations are 10 µm in x and z, and 40 µrad in angle.

- Chamfer widths have been optimized on the two prototypes during magnetic measurements in order to cancel the 12-poles term. The width are 4.0 mm and 3.6 mm for short and long quadrupoles respectively.

- Gradient identity from one quadrupole to the other (same at all current levels): 1 10-3 and 7 10-4 for short and long quadrupoles respectively.
 
 Figure 2: A quadrupole installed on the BMS bench Figure 3: The rigid sensor
 
 
Figure 4: The sensor structure 
Harmonic Content

An=an/b2 Bn=bn/2, given in unit of 10-4 at R=30 mm for I=200 A

Harmonics Short Quadrupoles Long quadrupoles
Mean value RMS value Mean value RMS value
A3 0.4 3.2 -0.2 3.8
B3 -1.0 2.9 3.1 1.3
B4 -2.9 3.7 -8.2 1.8
B6 1.9 0.5 0.6 0.5
B10 0.7 (1.4)* 0.1 1.9 (1.8)* 0.1
B14 0.9 (0.7)* 0.1 1.0 (1.7)* 0.1
()*: Design value

An unexpected strong component B4 is measured in all the long quadrupoles. It is a "Banana" effect due to the weight.



SEXTUPOLES Measurements
Last Update : September 2005
124 sextupoles have been manufactured by SIGMAPHI.
Measurements were performed by SIGMAPHI with a rotating coil bench (See figures 1 and 2).
Reference radius for harmonic analysis = 32 mm
Tolerances for magnetic centering:± 30 µm in x and z
± 0.2 mrad in θs

Results:

- Shimming: A special procedure has been applied to compensate for non-expected large harmonics B1, observed during preliminary measurements. When it was necessary, some additional shims have been fixed on chamfers as shown on figure 3. Then, it has been measured that the B9 systematic component depends on the number of shims: -8.6 10-4 for 0 shims, -5.0 10-4 for 4 shims and -1.0 10-4 for 8 shims.

- Sorting has been performed in order to minimize the effect on beam dynamics of the residual B5 component. The allocation of the 120 sextupoles around the ring is now defined.

- Magnetic axis centering at 300A satisfies tolerances. The standard deviation is 15 µm in x and z, and 100 µrad in angle.

- Strength identity from one sextupole to the other at 300A is 3 10-3.

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