Damping links, which are damping devices to attenuate the vibrations of the ESRF machine girders, have been implemented in half of the storage ring. The installation on the other half of the storage ring will be accomplished during the winter 2000 and March 2001 shutdowns.

The damping links are installed between the two extremities of each girder and the floor as shown in Figure 130 for a G20 assembly. Enormous efforts have been made for the installation since the available space for the installation is very limited. Cooling pipes and some cable trays had to be moved.

Figure 130
Fig. 130: Girder equipped with damping links. 

Vibration tests were performed on the quadrupoles both before and after the damping link installation. Results in terms of Q-value (peak value in the transfer function at the fundamental resonant frequency) are shown in Figure 131. The Q-value of the quadrupole is about 50 before installation of the damping links, and is reduced to about 10 after installation. It should be noted that in cell 26, damping plates were installed between the jacks and the floor in 1997. The jacks were bolted to the floor. Damping plates were partially shunted, but there is still some damping effects.

Figure 131
Fig. 131: Vibration tests.

Periodic measurements on two quadrupoles,

  • QD4 in cell 8 without damping links : C8QD4noDL
  • QF7 in cell 16 with damping links : C16QF7DL


have been being made in real working conditions. RMS displacements versus time (Figure 132) show higher vibration levels during weekdays, and lower vibration levels during nights and week-ends. Vibrations of the quadrupole with damping links (C16QF7DL) are reduced by a factor larger than 2 compared to the quadrupole without damping links (C8QD4noDL). In the working frequency range of the damping links (4-12 Hz), the attenuation factor reaches 5.

Figure 132
Fig. 132: RMS displacement of quadrupoles.

These tests performed both before and after damping link installation as well as the periodic measurements performed under real working conditions, have clearly demonstrated the beneficial effects of the damping links. An even greater effect is expected once all storage-ring girders are equipped.