Ground motion in LEP and LHC

Vos, L.

doi:10.1109/pac.1995.505884

Cited by 6 publications

(7 citation statements)

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“…The spectral density of the ground motion measured at 10 Hz in the LEP tunnel is S gm = 5 × 10 −15 mm 2 /Hz while the logarithmic slope with frequency at low frequencies is about -2.5. Assuming that this fall-off rate continues at high frequencies, we can then expect the spectral density of the ground motion in the vicinity of the betatron tune to be about S gm = 10 −20 mm 2 /Hz [1]. It should be pointed out that ground motion measurements at various accelerators show that above approximately 400Hz, the motion is indistinguishable from electronic noise, even with the most sensitive piezo-electric accelerometers available.…”

Section: Ground Motion and Closed Orbit Spectrummentioning

confidence: 98%

“…We assume that the coupling between the transverse planes is negligible so that the linear map from 1 The length of the LHC cell is about l = 90 m and the "average" velocity of the ground waves in the LEP tunnel is about 4000 m/s. The correlation between two probes at distance l drops to zero for a frequency such that this distance is a quarter of wavelength fm = v/(4l).…”

Section: Dynamical Systemmentioning

confidence: 99%

“…It is known that ground vibration at frequencies higher than f m = 11 Hz will cause uncorrelated quadrupole motion in the LHC ring 1 [1,2]. Random quadrupole oscillations create distortions of the beam orbit and random beam-beam offset at the interaction point.…”

Section: Introductionmentioning

confidence: 99%

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Emittance growth for the LHC beams due to head-on beam-beam interaction and ground motion

Sen¹

2000

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The influence of ground motion on the LHC beam is estimated applying the existing theories of particle diffusion due to a weak-strong beam-beam collision with random offset at the interaction point. Noise at odd harmonics of the betatron frequency contributes significantly to particle diffusion. The spectrum of the random offset, as obtained from the ground motion spectrum at the LHC site, shows a fast fall-off with frequency and the amplitude is very small even at the first harmonic. We find that the head-on beam-beam force in the weak-strong approximation and ground motion by themselves do not induce significant diffusion over the lifetime of the beam.

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Section: Ground Motion and Closed Orbit Spectrummentioning

confidence: 98%

Section: Dynamical Systemmentioning

confidence: 99%

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Emittance growth for the LHC beams due to head-on beam-beam interaction and ground motion

Sen¹

2000

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“…The orbit oscillations induced by the modulated quadrupoles are detected by two sensitive pickups, installed to the left and right of LEP interaction point (IP) 1 [7]. The sensitivity of the pickups must be adequate to detect the oscillations in the orbit induced by the quadrupole modulation.…”

Section: Detection Of the Closed Orbit Oscillationsmentioning

confidence: 99%

Beam based alignment at LEP

Dehning¹,

Matheson²,

Mugnai³

et al. 2004

Nuclear Instruments and Methods in Physics Research Section A:

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We describe a beam-based method for finding the relative offset between beam position monitors (BPMs) and the magnetic centres of the adjacent quadrupole magnets. The strength of a given quadrupole is modulated and the induced closed orbit oscillation measured for different beam positions, reaching a minimum when the beam is centred in the quadrupole. The BPM reading at this point is a measure of its offset, which may be determined at LEP with an accuracy of ~ 40 µm.

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“…It is composed on one hand by the ratio of the maximum injection error and the BPM resolution (55 dB SPS and 60 dB LHC) and on the other hand by the gain ratio between the lowest and highest feedback frequency (35 dB SPS and 45 dB LHC). The data in Table 8 [25,26] Only the LHC is concerned. The tune spread in collision is expected to be 0.015 [27].…”

Section: Emittance Conservation During Injection Coast and Accelerationmentioning

confidence: 99%

Damping of coherent oscillations

Vos

1997

Nuclear Instruments and Methods in Physics Research Section A:

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Damping of coherent oscillations by feedback is straightforward in principle. It has been a vital ingredient for the safe operation of accelerators since a long time [1,2]. The increasing dimensions and beam intensities of the new generation of hadron colliders impose unprecedented demands on the performance of future systems. The arguments leading to the specification of a transverse feedback system for the CERN SPS in its role as LHC injector and the LHC collider itself are developed to illustrate this. The preservation of the transverse emittance is the guiding principle during this exercise keeping in mind the hostile environment which comprises: transverse impedance bent on developing coupled bunch instabilities, injection errors, unwanted transverse excitation, unavoidable tune spreads and noise in the damping loop.

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Ground motion in LEP and LHC

Cited by 6 publications

References 0 publications

Emittance growth for the LHC beams due to head-on beam-beam interaction and ground motion

Emittance growth for the LHC beams due to head-on beam-beam interaction and ground motion

Beam based alignment at LEP

Damping of coherent oscillations

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