1. MD #453 Effect of low frequency noise
Goal: Can low frequency noise cause emittance growth and stronger population of tails?
Motivation:
measurements show that the IT amplifies low frequency vibrations (ground motion) by up to a factor 100. These frequencies are possibly already visible in the LHC!
HL-LHC aims at β*=15 cm => βmax,IT = 20 km (compared to 6 km at β*=40 cm LHC)
possible effects:
luminosity loss (emittance growth)
higher losses at collimators (tail population + orbit deviation at collimators)
Is a more careful design of the IT cryostats necessary?
Do we need an additional local high frequency orbit feedback (0.1 Hz – 100 Hz)
Q1, vertical
M. Guinchard et al.
Courtesy
first vertical IT eigen-frequency
beam 1, vertical
preliminary!

2. MD #453 Effect of low frequency noise
possibility to merge MD #284 (Beam tail population measurements using collimator scans), however 1 train colliding with 1 bunch is highly favored over 1 bunch colliding with 1 bunch
flat top, squeezed
beam 1: 1 nominal 25 ns train
emittance measurements with BSRT and wire scanners
Scenario 1 (preferred): diamond detectors are available and working reliably:
procedure: collimator scans on beam 2 to determine tail population (losses of individual bunches can be reconstructed thanks to high sampling rate of diamond detectors)
Scenario 2: diamond detectors are not available:
beam 2: bunch 1
procedure:
collimator scan on beam 2 -> distribution without excitation
a) apply low frequency excitation/repopulation of halo (30 min)
b) collimator scan on beam 2 -> distribution with excitation
a) repopulation of halo
b) collimator scan on beam 2 -> distribution without excitation as reference
beam 2: bunch 1 = reference bunch, bunch 2 = colliding with 1 train, bunch 3 = colliding with 1 train + low frequency excitation
bunch train
excitation
single bunch 1 2 3
Beam 1
Beam 2