The upgrade of the CERN accelerator complex
has been planned in order to further increase the
LHC performances in exploring new physics frontiers.
One of the main limitations to the upgrade is represented by the collective
instabilities.
These are intensity dependent phenomena triggered by electromagnetic
fields excited by the interaction of the beam with its surrounding.
These fields are represented via wake fields in time domain
or impedances in frequency domain.
Impedances are usually studied assuming ultrarelativistic bunches while we
mainly explored low and
medium energy regimes in the LHC injector chain.
In a non-ultrarelativistic framework we carried out a complete study of the impedance
structure of the PSB which accelerates proton bunches up to 1.4 GeV.
We measured the imaginary part of the impedance which creates betatron tune shift.
We introduced a parabolic bunch model which together with dedicated measurements
allowed us to point to the resistive wall impedance as the source of one of the main PSB instability.
These results are particularly useful
for the design of efficient transverse instability dampers.
We developed a macroparticle code to study the effect of the space
charge on intensity dependent instabilities. Carrying out the analysis of the bunch
modes we proved that the damping effects caused by the space charge, which has been
modelled with semi-analytical method and using symplectic high order schemes,
can increase the bunch intensity threshold.
Numerical libraries have been also developed in order to study, via numerical simulations
of the bunches, the impedance of the whole
CERN accelerator complex.
On a different note, the experiment
CNGS at CERN, requires high-intensity beams.
We calculated the interpolating Hamiltonian of the beam
for highly non-linear lattices. These calculations provide the ground
for theoretical and numerical studies aiming to improve the CNGS beam
extraction from the PS to the SPS.
| Identifer | oai:union.ndltd.org:unibo.it/oai:amsdottorato.cib.unibo.it:3403 |
| Date | 06 June 2011 |
| Creators | Quatraro, Diego <1982> |
| Contributors | Turchetti, Giorgio |
| Publisher | Alma Mater Studiorum - Università di Bologna |
| Source Sets | Università di Bologna |
| Language | English |
| Detected Language | English |
| Type | Doctoral Thesis, PeerReviewed |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/restrictedAccess |
Page generated in 0.0017 seconds