This article presents results of wideband seismic measurements at the Fermilab site, namely, in the tunnel of the Tevatron and on the surface nearby, as well as in two deep tunnels in the Illinois dolomite, thought to be a possible geological environment of the Fermilab future accelerators.[S1098-4402 (98)

No abstract

No abstract

No abstract

This article presents results of wide-band seismic measurements at the Fermilab site, namely, in the tunnel of the Tevatron and on the surface nearby, and in two deep tunnels in the Illinois dolomite, thought to be a possible geological environment of the Fermilab future accelerators. MEASUREMENTSThere are several future collider projects under consideration at Fermilab, including muon collider, linear collider and Very Large Hadron Collider(VLHC). Ground motion is of concern for all of the projects, although due to different effects [1]. That was major reason for seismic studies at the Fermilab site and in the Illinois dolomite tunnels which we carried out in 1997. Our seismic instrumentation included eight modified geophone of SM3-KV type (frequency range from 0.07 to 120 Hz) two tri-axial STS-2 seismometers (0.005-15 Hz), and two Wiloxon-731A piezoaccelerometers (10-400 Hz).Measurements at Fermilab Vibration measurements in the Tevatron tunnel have been done at Sector F11 (not far from the Tevatron RF station and the E4R building) and Sector F21 some 300 m apart. The computer was located on the surface in the F0 building. Seven SM3-KV probes (four vertical and three horizontal) and two vertical piezoaccelerometers were used. Two seismic stations were placed at a distance 296 m apart. Station 1 digitized the signals from one vertical and one horizontal SM3-KV probes on the floor of the tunnel at F21, and from vertically oriented piezoaccelerometer and vertical and horizontal SM3-KV geophones on the Tevatron quadrupole magnet. Station 2 digitized the signals from four SM3-KV geophones (vertical and horizontal on the quadrupole magnet at F11 and vertical and horizontal on the tunnel floor nearby), one piezoaccelerometer placed on the same magnet, and additionally from a beam position monitor (BPM) and a beam loss monitor (BLM). Recording vibration signals in the Tevatron tunnel over several days, we observed little day-night variation of the maximum tunnel floor motion amplitude. Cultural noise dominates in vibrations of the magnet and the tunnel floor. At frequencies above 1 Hz it is due to the technical equipment (water and helium pipes, power cables, magnets themselves, etc.) At frequencies around 1 Hz and lower the main contribution is possibly due to strong mechanical distortions of the magnets during the Main Ring acceleration cycle (about 3 s) and the Tevatron acceleration cycle (about 60 s in fixed target operation).The closed orbit distortions are caused by the displacements of all magnetic elements along the circumference of Tevatron. We detected strong coherence between the magnet and beam vibrations. It means that there is a common source of vibration along the whole accelerator ring. For example, several remarkable peaks in the orbit-magnet coherence occur at 4.6 Hz, 9.2 Hz, 13.8 Hz, etc., at the Fermilab site specific frequencies caused by Central Helium Liquefier plant operation.