Exact Phase Advances for a Two-Stage Collimation System

We propose a specification for a two-stage collimation insertion. We compute exact correlated phase advances between primary and secondary collimators, and determine the number of jaws needed to reach an almost ultimate performance

Optics of a two-stage collimation system

We derive the exact specification that a two-stage betatronic collimation insertion must satisfy to cut the halo of a proton beam down to its ultimate limit which is the aperture of the secondary collimators. Our result is a set of correlated phase advances between primary and secondary collimators. We then determine the number of jaws needed to reach a given level of performance. We also specify the optic of a momentum collimation insertion

Thermal and acoustic effects in CLIC beam absorbers

We study thermal and acoustic effects in the beam absorbers of CLIC. While solid dumps and water at ordinary temperature must be ruled out, we propose to make a dump of water working at 4 degrees centigrades, where the thermal elongation vanishes. This solution might solve the problem of excessive acoustic emission in the dumps which would otherwise prevent the collision of the beams

Optimisation of a Beam Transfer FODO Line

With in view the design of the CLIC long transfer lines, we develop a formal approach for the optimisation of a straight FODO line. Optimum phase advance and cell length depending on beam parameters are derived for power consumption, overall cost and sensitivity to quadrupole misalignment

Using microwave quadrupoles to shorten the CLIC beam delivery section

The chromatic correction of the final focus, based on sextupoles and dipoles, requires for CLIC at 3 TeV a section which is long with respect to the main linac and the bare de-magnification telescope. The length needed is in conflict with the tight alignment of the beam delivery elements, necessary for the control of the collisions. This scheme also implies large peaks of betatron amplitudes which generate aberrations. To circumvent these problems, we explore the potential of microwave quadrupoles. They could be used for chromatic corrections since, in the presence of a correlation z-delta between momentum and position along the bunch, they play a role similar to that of sextupoles in the presence of dispersion. The correlation is done in the linac and no special optics is required, thus strongly reducing the space needed for the correction. Furthermore, the final doublet of the telescope could be only made of microwave quadrupoles, provided sufficiently high gradients be achievable, since a judicious choice of the RF phase renders them achromatic. This would make the beam delivery at high energies even more compact and simple. We underline advantages and drawbacks of this proposal and list some items which need further study

A proposal to use microwave quadrupoles to shorten the beam delivery section of CLIC

The chromatic correction of the final focus, based on sextupoles and dipoles, requires for CLIC at 3 TeV a section which is long with respect to the main linac and the bare de-magnification telescope. The length needed is in conflict with the tight alignment of the beam delivery elements, necessary for the control of the collisions. This scheme also implies large peaks of betatron amplitudes which generate aberrations. To circumvent these problems, we explore the potential of microwave quadrupoles. They could be used for chromatic corrections since, in the presence of a correlation between momentum and position within the bunch, they play a role similar to that of sextupoles in the presence of dispersion. The correlation is done in the linac and no special optics is required, thus strongly reducing the space needed for the correction. Furthermore, the final doublet of the telescope could be only made of microwave quadrupoles, provided sufficiently high gradients be achievable, since a judicious choice of the RF phase render them achromatic. This would make the beam delivery at high energies even more compact and simple. We underline advantages and drawbacks of this proposal and list some items which need further study