[en] All next-generation linear collider designs rely heavily on beam-based alignment and emittance tuning techniques. This paper describes the different techniques proposed for the linear collider linacs and discusses some of the operational experience with the different approaches

[en] To increase the luminosity or improve the stability of the US Cold LC design, it would be advantageous to decrease the bunch length below the specified 300 mu m. It is unlikely that further compression would be possible with the single stage compressor proposed in TESLA design and thus in this note we scale the two-stage NLC bunch compressor design to the US Cold LC design. The primary difficulties with this scaling are related to the much larger (factor of 3.6 times larger) longitudinal emittance in the US Cold LC design

[en] The next generation linear colliders require damping rings to generate beam with very small transverse emittances to attain the desired luminosity. The required emittances are smaller than that of most operating synchrotron radiation sources. In this paper, the alignment tolerances needed to attain these small emittances are compared with those of the operating synchrotron radiation facilities and a prototype damping ring, the ATF at KEK. The concept of this study originated at the Nanobeams Workshop during a discussion in the Storage Rings Working Group although the results were not discussed at that meeting

[en] Coherent Synchrotron Radiation (CSR) can play an important role by not only increasing the energy spread and emittance of a beam, but also leading to a potential instability. Previous studies of the CSR induced longitudinal instability were carried out for the CSR impedance due to dipole magnets. In this paper, the instability due to the CSR impedance from a wiggler is studied assuming a large wiggler parameter K. The primary consideration is a low frequency microwave-like instability in the damping rings of several linear collider projects. The threshold is determined by the instability with the longest possible wavelength

[en] The concept of a high-gradient plasma wakefield accelerator is considered as an upgrade path for the International Linear Collider, a future linear collider. Basic parameters are presented based on those developed for the SLC ''Afterburner.'' Basic layout considerations are described and the primary concerns related to the collider operation are discussed

[en] The future generation of electron storage rings for synchrotron light sources or damping rings for linear colliders will require very low impedance vacuum systems, the design of which relies heavily on the impedance modeling. This workshop will have three goals: first, examine the accuracy of the impedance models by comparing calculations, bench measurements, and beam measurements from recently commissioned rings; second, discuss techniques of quantifying the impedance models that are relevant for estimating the instability thresholds but are still useful to compare to bench and beam measurements; finally, consider instability mechanisms and components of the impedance that may limit the performance of future storage rings as the vacuum chamber impedance is further reduced

[en] The present JLC/NLC parameters are chosen to provide luminosities between 0.5 ∼ 0.75 x 10³⁴ s^-1 cm^-2 at a cms energy of 500 GeV; the parameters are listed in Table 1 for both the 500 GeV and 1 TeV cases. In all cases, these luminosities assume extensive margins and emittance dilutions to ensure that they are attainable. In this note, they consider the feasibility of substantially higher luminosities which might be attained by operating with smaller emittance dilutins and higher beam currents. The parameters they describe are listed in Table 2 where these high luminosity sets (ILC-IHa and ILC-IHb) are compared with the base JLC/NLC set (ILC-Ib) and with the high luminosity TESLA parameter set. In the next sections, they will discuss the limitations and assumptions leading to these higher luminosity parameter sets. The details in their discussion will be based on the NLC design described in the Zeroth-order Design Report (ZDR) but the same arguments, with slightly different values, could be applied to the JLC reference design

[en] In this note, we describe the proposed working parameter set for the KEK-SLAC ILC linear collider and discuss the reasons leading to the values listed; more extensive discussion of the optimization process will be found in subsequent notes. The parameter set is listed in Table 1 and is compared with the JLC 3-97 parameters and the NLC ZDR parameters in Table 2. The new parameter set has an operating plane which ranges from low IP emittances and high luminosity (cases A) to large IP emittances and smaller luminosity (cases C). Over this range, the bunch charge, bunch length, and IP beta functions are varied, however, the parameters have been chosen so that the tolerances on the accelerating structures are roughly constant. The collider must be designed to operate over the entire parameter range. In all cases, the parameters were optimized for 120 Hz operation. The scaling to 150 Hz is straightforward--either the beam parameters are held constant and the luminosity and ac power are increased or there are small reductions in the bunch charge and an ensuing loosening of the tolerances. Similarly, scaling to 100 Hz operation is also possible, although, if one wants to maintain the luminosity in this case, the bunch charge must be increased and the beamstrahlung energy loss increases to as much as 15%. In arriving at the parameters, most of the emphasis has been on cost reduction. Thus, at times, we have sacrificed the rf and ac efficiency to obtain a situation that requires fewer rf power sources or significantly looser tolerances; this will be discussed further below. The other issues considered in the parameter determination include: the bunch spacing and beam pulse length limits, the rf structure length, the iris radii (α/λ), and the upgrade path from 500 GeV to 1 TeV cms; each of these issues will be discussed further subsequently

[en] Ion induced beam instability is one critical issue for the electron damping ring of the International Linear Collider (ILC) due to its ultra small emittance of 2pm. Bunch train filling pattern is proposed to mitigate the instability and bunch-by-bunch feedback is applied to suppress it. Multibunch train fill pattern is introduced in the electron beam to reduce the number of trapped ions. Our study shows that the ion effects can be significantly mitigated by using multiple gaps. However, the beam can still suffer from the beam-ion instability driven by the accumulated ions that cannot escape from the beam during the gaps. The effects of beam fill pattern, emittance, vacuum and various damping mechanism are studied using self-consistent program, which includes the optics of the ring

[en] Future linear colliders will likely use sophisticated beam-based alignment and/or steering algorithms to control the growth of the beam emittance in the linac. In this paper, a mathematical framework is presented which simplifies the evaluation of the effectiveness of these algorithms. As an application, a quad alignment that uses beam data taken with the nominal linac optics, and with a scaled optics, is evaluated in terms of the dispersive emittance growth remaining after alignment