Accelerator Magnet Technology Division

Booster magnets

The booster synchrotron was constructed almost thirteen to fourteen years back (1992 check!!) and the magnets for this machine were among the first magnets to be built at the centre. Since then the magnets (dipoles and quadrupoles) are in routine operation. The booster synchrotron is ramped from 20 MeV beam energy to 700 MeV beam energy. The dipole fields corresponding to these energy levels are 0.037 T & 1.3 T respectively. The maximum strength of the quadrupole magnet is 9.32 T/m (integrated strength of 2.33 T).

New magnets for Booster

The ageing effect weakened the bonding of the core laminations of the dipole magnets at the entry/exit sides, causing changes in the magnetic lengths during excitations. Higher the excitation, larger is the separation between the laminations (at the entry/exit sides). The magnet to magnet fabrication (geometrical) errors are also quite high in existing booster magnets. The effective magnetic length of the dipole magnet at the injection energy has been found higher than the ideal length. With the advancement in technology, it is now possible to fabricate much better magnets with tight tolerances as required for an accelerator than those built fourteen years ago. Therefore it is proposed to replace the existing booster dipole magnets with new magnets. Besides this, at present there are no sextupole magnets in the booster synchrotron ring to correct the chromatic aberration of the beam. To correct the chromaticity, a new design of quadrupole magnets, incorporating auxiliary coils to generate the desired sextupole strength has to be carried out.  Therefore it is proposed to design and fabricate new sets of main magnets (6 dipole and 12 quadrupole magnets having auxiliary coils to generate required sextupole strength) for the booster synchrotron. Design specifications for the quadrupole magnet and sextupole magnet are given in table-1 and table- 2 respectively.

Table 1: Quadrupole  Specifications

Quadrupoles

Strength (m-2)

Integrated gradient (T)
GL = (dB/ dx)L

20 MeV

700 MeV

Qf

4

0.067

2.33

Qd

4

0.067

2.33

Table 2: Sextupole   Specifications

Sextupoles

Integrated gradient (T/m) : G'L = (d2B/ dx2)L 

20 MeV

700 MeV

Sf

0.039

3.2

Sd

0.051

4.3

The booster synchrotron machine will be operated with an increased repetition rate of 1.5 Hz (from present 1 Hz) to increase the injection rate thereby to reduce the filling time of Indus-1 & Indus-2. The design and magnetic characterization of the magnets is done taking into consider the repetition rate of 1.5 Hz. Figure 1 shows the flux line plot of quadrupole magnet core along with coils.

Figure 1: Flux line plot of quadrupole magnet core and coils

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