Seismometers for High Energy Physics

07 Jan

Gaiacode has delivered several broadband seismometers to Chinese high energy physicists. The 5 digital sensors (model Alpha-TAD120) will be monitoring the ground motion on the tunnel slab of High Energy Photon Source (HEPS). The HEPS is an ultralow-emittance, kilometer-scale storage ring light source to be built in western outskirts of Beijing. The facility is operated by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences. As the fourth-generation synchrotron radiation light source, the vibrations of the foundation are the main factor affecting the beam stability.

Ground motion affects a Particle Beam

What does a seismometer have to do with such high end particle physics? At first glance there does not seem to be any connection. There is, however, a pivotal function for Gaiacode's sensitive instruments. The particle beams are guided by magnets, which are mounted on foundations fixed solidly on the ground. Although highly stabilized, these foundations are subject to the tiniest vibrations of the Earth. When the ground moves ever so slightly, be it from elastic waves generated by earthquakes or from cultural noise like motions caused by a heavy truck or a train driving by, the magnet move as well. In turn, this movement makes the particle beams wiggle. Even though these wiggles are tiny, they can defocus the beam.

 High Energy Photon Source

 Artist rendering of the High Energy Photon Source to be built in the western outskirts of Beijing (Photo: IHEP)

Measuring Movement of Nanometers

The Alpha seismometers are so sensitive, that they can measure ground motion as small as dozens of nanometers or about 1/100 of the diameter of a human hair. Scientist working at the accelerator use these extremely precise measurements of the ground motion to study the relationship between vibration and beam motions. The vibration source could be traced and damped accordingly and thereby make the beam more stable to produce high luminosity light for experiment scientists.

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