Article: ATF2 Summary and Status[Show abstract] [Hide abstract] ABSTRACT: The Accelerator Test Facility (ATF)  at KEK was originally constructed as a Damping Ring (DR) demonstration facility for the next generation of electron linear colliders. It consists of a 1.3 GeV s-band linac and a 136m circumference damping ring which can routinely generate 1.6 nC electron bunches with very small vertical emittances (
- [Show abstract] [Hide abstract] ABSTRACT: ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U.S. scientists. The present status and first results are described.
- [Show abstract] [Hide abstract] ABSTRACT: Since 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.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: Since several years, the vertical beam emittance mea- red in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, that will transport the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus beam line, is signiﬁcantly larger than the emittance measured in the DR itself, and there are indications that it grows rapidly with increasing beam intensity. This long- standing problem has motivated studies of possible sources of this anomalous emittance growth. One possible contri- bution is non-linear magnetic ﬁelds in the extraction region experimented by the beam while passing off-axis through magnets of the DR during the extraction process. In this pa- per, simulations of the emittance growth are presented and compared to observations. These simulations include the effects of predicted non-linear ﬁeld errors in the shared DR magnets and orbit displacements from the reference orbit in the extraction region. Results of recent measurements using closed orbit bumps to probe the relation between the extraction trajectory and the anomalous emittance growth are also presented.
Technical Report: Results of the EUROTeV Post Collision Line Design (PCDL) Task[Show abstract] [Hide abstract] ABSTRACT: This paper is the deliverable of the EUROTeV Post Collision Line Design (PCDL) task and gives an overview of the published results.
- [Show abstract] [Hide abstract] ABSTRACT: 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<sup>+</sup>e<sup>-</sup> and e<sup>-</sup>e<sup>-</sup> modes of operation. The beam-beam effects in the e<sup>-</sup>e<sup>-</sup> collisions make both the luminosity and the deflections more sensitive to offsets at the interaction point (IP) than in the case of the e<sup>+</sup>e<sup>-</sup> collisions. This reduces the performance of the feedback system in comparison to the standard e<sup>+</sup>e<sup>-</sup> collisions, and may require a different beam parameter optimization.
- [Show abstract] [Hide abstract] ABSTRACT: An interaction region (IR) with head-on collisions is considered as an alternative to the baseline configuration of the International Linear Collider (ILC) which includes two IRs with finite crossing-angles (2 and 20 mrad). Although more challenging for the beam extraction, the head-on scheme is favoured by the experiments because it allows a more convenient detector configuration, particularly in the forward region. The optics of the head-on extraction is revisited by separating the e+ and e- beams horizontally, first by electrostatic separators operated at their LEP nominal field and then using a defocusing quadrupole of the final focus beam line. In this way the septum magnet is protected from the beamstrahlung power. Newly optimized final focus and extraction optics are presented, including a first look at post-collision diagnostics. The influence of parasitic collisions is shown to lead to a region of stable collision parameters. Disrupted beam and beamstrahlung photon losses are calculated along the extraction elements.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: Contribution to the Tenth European Particle Accelerator Conference "EPAC'06'', Edinburgh, United-Kingdom, 26-30 June 2006 - Groupe ILC
- [Show abstract] [Hide abstract] ABSTRACT: 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.
Article: ATF2 Proposal, Vol. 2.
Article: ATF2 Proposal: v. 2[Show abstract] [Hide abstract] ABSTRACT: For achieving the high luminosity required at the International Linear Collider (ILC), it is critical to focus the beams to nanometer size with the ILC Beam Delivery System (BDS), and to maintain the beam collision with a nanometer-scale stability. To establish the technologies associated with this ultra-high precision beam handling, it has been proposed to implement an ILC-like final focus optics in an extension of the existing extraction beamline of ATF at KEK. The ATF is considered to be the best platform for this exercise, since it provides an adequate ultra-low emittance electron beam in a manner dedicated to the development of ILC. The two major goals for this facility, called ATF2, are : (A) Achievement of a 37 nm beam size, and (B) control of beam position down to 2 nm level. The scientific justification for the ATF2 project and its technical design have been described in Volume 1 of the ATF2 Proposal . We present here Volume 2 of the ATF2 Proposal, in which we present specifics of the construction plans and the group organization to execute the research programs at ATF2. The sections in this report have been authored by relevant ATF2 subgroups within the International ATF Collaboration. The time line of the project is described in Section 2. Section 3 discuss the structure of the international collaboration. Sections 4 and 5 discuss budget considerations, which are presented as well as the design and construction tasks to be shared by the internationalcollaboration at ATF2. Concluding remarks have been contributed by Dr. Ewan Paterson, Chair of the International Collaboration Board of the ATF collaboration.