Optimization of the e-e- option for the ILC

The e-e- running mode is one of the interesting physics options at the International Linear Collider (ILC). The luminosity for e-e- collisions is reduced by the beam-beam effects. The resulting beamstrahlung energy loss and beam-beam deflection angles as function of the vertical transverse offset are different compared to the e+e- collisions. In this paper, the dependence of these observables with the offset for different beam sizes has been analyzed to optimize performances for the e-e- mode, taking into account the requirements of the beam-beam deflection based intra-train feedback system. A first study of the implications for the final focus and extraction line optics is also presented for the cases of the 20 mrad and 2 mrad ILC base line crossing angle geometries

Luminosity, beamstrahlung energy loss and beam-beam deflections for e+e−e^+e^- collisions at the ILC with 500 GeV and varying transverse beam sizes

At the interaction point of the International Linear Collider, beam-beam effects due to the strong electromagnetic fields that the bunches experience during collisions cause a mutual focusing called pinch effect, which enhances the luminosity in the case of $e^+e^-$ collisions. The opposite is true for $e^+e^-$ collisions. In this case the luminosity is reduced by mutual defocusing, or anti-pinching. The resulting beamstrahlung energy loss and beam-beam deflection angles as function of the vertical transverse offset are also different for both modes of operation. The dependence of these quantities with transverse beam sizes are presented for the case of $e^+e^-$ collisions

Luminosity, beamstrahlung energy loss and beam-beam deflections for e+e- and e-e- collisions at the ILC with 500 GeV and varying transverse beam sizes

At the interaction point of the International Linear Collider, beam-beam effects due to the strong electromagnetic fields that the bunches experience during collisions cause a mutual focusing called pinch effect, which enhances the luminosity in the case of $e^+e^-$ collisions. The opposite is true for $e^+e^-$ collisions. In this case the luminosity is reduced by mutual defocusing, or anti-pinching. The resulting beamstrahlung energy loss and beam-beam deflection angles as function of the vertical transverse offset are also different for both modes of operation. The dependence of these quantities with transverse beam sizes are presented for the case of $e^+e^-$ collisions

Comparison of ILC Fast Beam-Beam Feedback Performance in the e−e−e^- e^- and e+e−e^+ e^- Modes of Operation

Several feedback loops are required in the Beam Delivery System (BDS) of the International Linear Collider (ILC) to preserve the luminosity in the presence of dynamic imperfections. Realistic simulations have been carried out to study the performance of the beam-beam deflection based fast feedback system, for both e+e- and e-e- modes of operation. The beam-beam effects in the e-e- collisions make both the luminosity and the deflections more sensitive to offsets at the interaction point (IP) than in the case of the e+e-collisions. This reduces the performance of the feedback system in comparison to the standard e+e- collisions, and may require a different beam parameter optimization

Modeling of the shared magnets of the ATF Extraction Line

After extraction from the ATF Damping Ring, the linear beam optics is matched before injection into a section dedicated to beam diagnostics. Experimentally, vertical emittances in this section have since several years been observed to be larger than expected, byfactors of two to three, with a seemingly strong dependence on intensity. This has motivated studies of the possible sources of emittance growth. One of these is thought to be the non-linearity experienced by the beam during the extraction, as it is transported off-axis through several magnets which are shared with the Damping Ring. Such non-linearity can generate a sensitivity of the emittance to the orbit parameters in the extraction, which would be very undesirable in the newly built ATF2 final focus system, where the same extraction line is used. In this report, a detailed calculation of the modeling of these shared magnets is presented, in order to quantify the magnitudes of both the linear and non-linear fields to be used in the evaluation of the optics and in tracking simulations of the performance of the extraction line

Tracking simulation studies of the vertical emittance growth in the ATF extraction line

Since several years, the vertical emittance of the beam measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK has been significantly larger than that measured in the Damping Ring (DR) itself. This long-standing problem has motivated studies of possible sources of anomalous emittance growth. One possible contribution is the non-linearity in the magnetic fields that the beam experiences while passing off-axis through the magnets shared between the DR and thge EXT line. In order to quantify this effect, these magnets have been carefully modeled in terms of multipole expansions, to enable tracking simulations. Results indicate that there is significant emittance growth when the extracted beam passes with a vertical offset with respect to its reference position

Effect of the non-linear magnetic fields on the emittance growth in the ATF extraction line

WE6PFP075International audienceSince several years, the vertical beam emittance measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, has been significantly larger than that measured in the damping ring (DR) itself. The EXT line that transports the beam to the ATF2 Final Focus beam line has been rebuilt, but the extraction itself remains in most part unchanged, with the extracted beam transported off- axis horizontally in two of the quadrupoles, beyond the linear region for one of them. A few other nearby magnets have also modelled or measured non-linearity. In case of a residual vertical beam displacement, this can result in increased vertical emittance through coupling between the two transverse planes. Tracking studies as well as measurements have been carried out to study this effect and the induced sensitivity of beam optical parameters to the trajectory at injection, in view of deriving tolerances for reproducible and stable operation

GUINEA-PIG++ : an upgraded version of the linear collider beam-beam interaction simulation code GUINEA-PIG

http://cern.ch/AccelConf/p07/PAPERS/THPMN010.PDFInternational audienceGUINEA-PIG++ is a newly developed object-oriented version of the Linear Collider beam-beam simulation program GUINEA-PIG. The main goals of this project are to provide an reliable, modular, documented and versatile framework enabling convenient implementation of new features and functionalities

Experimental studies and analysis of the vertical emittance growth in the ATF extraction line in 2007-2008

The Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK will transport the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus beam line. Since several years, the vertical beam emittance measured in the EXT line is significantly larger than that measured in the DR itself, and there are observations that the growth increases with beam intensity. A possible contribution is the non-linearity in the magnetic fields experienced by the beam when passing off-axis through several magnets shared by the DR and the EXT beam line in the initial part of the extraction process. Tracking simulations including non-linear field errors in these magnets predict significant emittance growth when the beam is displaced vertically with respect to the nominal trajectory. An experimental program has been carried out during 2007-2008 to study the relation between the extraction trajectory and the anomalous emittance growth. This note reports on the results of this program

IR2 aperture measurements at 3.5 TeV

Aperture measurements in the ALICE interaction region were carried out to determine a safe configuration of β ∗ and crossing angle for the 2011 heavy ion run. Proton beams were used at the end of the proton run, after the commissioning of the squeeze to β ∗ = 1 m in IR2. In this paper, the results of aperture measurements are summarised and the final collision configuration is presented. Results of parasitic measurements of the effect of non-linear triplet fields with large orbit bumps in the IRs are also summarised.peer-reviewe