We discuss how by using the wake fields generating in a corrugating plate we may increase the resolution of a transverse diagnostic cavity while producing an extremely short X-ray pulse at LCLS.

With the completion of the National Academies of Sciences Assessment of a US Electron-Ion Collider, the prospects for construction of such a facility have taken a step forward. This paper provides an overview of the two site-specific EIC designs: JLEIC (Jefferson Lab) and eRHIC (BNL) as well as brief overview of ongoing EIC R&D.

The international Future Circular Collider (FCC) study aims at a design of $pp$, $e^+e^-$, $ep$ colliders to be built in a new 100 km tunnel in the Geneva region. The $e^+e^-$ collider (FCC-ee) has a centre of mass energy range between 90 (Z-pole) and 375 GeV (tt_bar). To reach such unprecedented energies and luminosities, the design of the interaction region is crucial. The crab-waist collision scheme has been chosen for the design and it will be compatible with all beam energies. In this paper we will describe the machine detector interface layout including the solenoid compensation scheme. We will describe how this layout fulfills all the requirements set by the parameters table and by the physical constraints. We will summarize the studies of the impact of the synchrotron radiation, the analysis of trapped modes and of the backgrounds induced by single beam and luminosity effects giving an estimate of the losses in the interaction region and in the detector.

We discuss the nature of the electromagnetic fields excited by the beams in the beam pipe of an interaction region. In trying to find an optimum geometry for this region with a minimum of electromagnetic wave excitation, we have discovered one mode, which remains even in a very smooth geometry. This mode has a longitudinal electrical component and can be easily excited by the beam. By analyzing the structure of this mode we have found a way to absorb this mode. The work was done in connection with a proposal for a future electron-positron collider.

K. Oide∗a, M. Aibab, S. Aumonc, M. Benediktc, A. Blondele, A. Bogomyagkovd , M. Boscolo f , H. Burkhardtc, Y. Caih, A. Doblhammerc, B. Haererc, B. Holzerc, J.M. Jowettc, I. Koopd , M. Koratzinose, E. Levichevd , L. Medinac, K. Ohmia, Y. Papaphilippouc, P. Piminovd , D. Shatilovd , S. Sinyatkin, M. Sullivanh, J. Wenningerc, U. Wienandsg, D. Zhoua and F. Zimmermannc E-mail:Katsunobu.Oide@kek.jp aKEK, Oho, Tsukuba, Ibaraki 305-0801, Japan bPSI 5232, Villigen PSI, Switzerland cCERN, CH-1211 Geneva 23, Switzerland dBINP SB RAS, Novosibirsk 630090, Russia eDPNC/Geneva University, CH-1211 Geneva 4, Switzerland f INFN/LNF, 00044 Frascati, Rome, Italy gANL, Argonne, Illinois 60439, U. S. A hSLAC, Menlo Park, California 94025, U. S. A.

The interaction region layout for the e(+)e(-) future circular collider FCC-ee is presented together with a preliminary estimate of synchrotron radiation that affects this region. We describe in this paper the main guidelines of this design and the estimate of synchrotron radiation coming from the last bending magnets and from the final focus quadrupoles, with the software tools developed for this purpose. The design follows the asymmetric optics layout as far as incoming bend radiation is concerned with the maximum foreseen beam energy of 175 GeV and we present a feasible initial layout with an indication of tolerable synchrotron radiation.

The introduction of magnetic charge into Maxwell's equations has led to an extensive search for magnetically charged particles (magnetic monopoles). A particle model developed by one of us (DF) adds an additional feature to Maxwell's symmetric equations in that the stable magnetic monopole should have the same charge strength as the electron. We have not found any experiments in high-energy physics that have explicitly ruled out this possibility. However, the few experiments at colliders that had no magnetic field might have observed a signal for these 1e strength magnetic monopoles as an unexpected enhancement in the mu+mu- production rate. The absence of any such observation leads us to set a tentative lower mass limit for these unit charge magnetic monopoles at 4.5-5 GeV/c2. Using a MC generator for magnetic charge and tracking these events through a simplified model of the BELLE II detector, we have found that the central drift chamber of BELLE II has a remarkably high efficiency for triggering on magnetically charged tracks. We suggest that the BELLE II collaboration perform a specific search for stable magnetically charged particles having a field strength of 1e when they run for the first time with colliding beams in 2018. This would be the first time anyone has specifically looked for such a particle.

Received 28 March 2017DOI:https://doi.org/10.1103/PhysRevAccelBeams.20.049901Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.© 2017 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeam dynamicsBeam opticsNonlinear beam dynamicsSingle-particle dynamicsPhysical SystemsAccelerators & storage ringsHigh-energy accelerators & collidersParticle acceleratorsTechniquesLepton collidersAccelerators & Beams

The Jefferson Lab Electron-Ion Collider (JLEIC) will accelerate protons and ions from 8 GeV to 100 GeV. A very low beta function at the Interaction Point (IP) is needed to achieve the required luminosity. One consequence of the low beta optics is that the beta function in the final focusing (FF) quadrupoles is extremely high. This leads to a large beam size in these magnets as well as strong sensitivity to errors which limits the dynamic aperture. These effects are stronger at injection energy where the beam size is maximum, and therefore very large aperture FF magnets are required to allow a large dynamic aperture. A standard solution is a relaxed injection optics with IP beta function large enough to provide a reasonable FF aperture. This also reduces the effects of FF errors resulting in a larger dynamic aperture at injection. We describe the ion ring injection optics design as well as a beta-squeeze transition from the injection to collision optics.

When a beam travels near collimator jaws, it gets an energy loss and a transverse kick due to the back reaction of the beam field diffracted on the collimator’s jaws. The effect becomes very important for an intense short bunch when a tight collimation of the background beam halo is required. In the Linac Coherent Light Source (LCLS) at SLAC a collimation system is used to protect the undulators from radiation due to particles in the beam halo. The collimators in the LCLS must remove the halo particles before they affect and eventually degrade the very precise fields of the permanent magnet undulators [1]. The wake field effect from the collimators not only brings an additional energy jitter and change of the trajectory of the beam, but also rotates the beam on the phase plane that consequently leads to a degradation of the performance of the Free Electron Laser (FEL) at LCLS. In this paper, we describe a model of the wake field radiation in the SLAC linac collimators. We also present results of experimental measurements, which clearly confirm our model.

This White Paper presents the science case of an Electron-Ion Collider (EIC), focused on the structure and interactions of gluon-dominated matter, with the intent to articulate it to the broader nuclear science community. It was commissioned by the managements of Brookhaven National Laboratory (BNL) and Thomas Jefferson National Accelerator Facility (JLab) with the objective of presenting a summary of scientific opportunities and goals of the EIC as a follow-up to the 2007 NSAC Long Range plan. This document is a culmination of a community-wide effort in nuclear science following a series of workshops on EIC physics over the past decades and, in particular, the focused ten-week program on “Gluons and quark sea at high energies” at the Institute for Nuclear Theory in Fall 2010. It contains a brief description of a few golden physics measurements along with accelerator and detector concepts required to achieve them. It has been benefited profoundly from inputs by the users’ communities of BNL and JLab. This White Paper offers the promise to propel the QCD science program in the US, established with the CEBAF accelerator at JLab and the RHIC collider at BNL, to the next QCD frontier.

Precision polarimetry is an important component for the EIC. It aims at reaching 1% level precision. Compton Polarimetry is commonly use for electron polarimetry. It allows a non invasive measurement of the electron polarization. Accuracies up to 0.52% were achieved using the Compton Electron detection. Sub-percent precision is foreseeable for EIC though the significantly higher current and space constraints require an extensive study. This proposal is looking at the option of a semi-conductor detector in a Roman Pot chamber to detect the Compton electrons.

A beam optics scheme has been designed for the future circular collider-e(+) e(-) (FCC-ee). The main characteristics of the design are: beam energy 45 to 175 GeV, 100 km circumference with two interaction points (IPs) per ring, horizontal crossing angle of 30 mrad at the IP and the crab-waist scheme [P. Raimondi, D. Shatilov, and M. Zobov, arXiv: physics/0702033; P. Raimondi, M. Zobov, and D. Shatilov, in Proceedings of the 22nd Particle Accelerator Conference, PAC-2007, Albuquerque, NM (IEEE, New York, 2007), p. TUPAN037.] with local chromaticity correction. The crab-waist scheme is implemented within the local chromaticity correction system without additional sextupoles, by reducing the strength of one of the two sextupoles for vertical chromatic correction at each side of the IP. So-called "tapering" of the magnets is applied, which scales all fields of the magnets according to the local beam energy to compensate for the effect of synchrotron radiation (SR) loss along the ring. An asymmetric layout near the interaction region reduces the critical energy of SR photons on the incoming side of the IP to values below 100 keV, while matching the geometry to the beam line of the FCC proton collider (FCC-hh) [A. Chance et al., Proceedings of IPAC'16, 9-13 May 2016, Busan, Korea, TUPMW020 (2016).] as closely as possible. Sufficient transverse/longitudinal dynamic aperture (DA) has been obtained, including major dynamical effects, to assure an adequate beam lifetime in the presence of beamstrahlung and top-up injection. In particular, a momentum acceptance larger than +/- 2% has been obtained, which is better than the momentum acceptance of typical collider rings by about a factor of 2. The effects of the detector solenoids including their compensation elements are taken into account as well as synchrotron radiation in all magnets. The optics presented in this paper is a step toward a full conceptual design for the collider. A number of issues have been identified for further study.

When a beam travels near collimator jaws, it gets an energy loss and a transverse kick due to the back reaction of the beam field diffracted from the jaws. The effect becomes very important for an intense short bunch when a tight collimation of the background beam halo is required. In the Linac Coherent Light Source (LCLS) at SLAC a collimation system is used to protect the undulators from radiation due to particles in the beam halo. The halo is most likely formed from gun dark current or dark current in some of the accelerating sections. However, collimators are also responsible for the generation of wake fields. The wake field effect from the collimators not only brings an additional energy jitter and change in the trajectory of the beam, but also rotates the beam on the phase plane, which consequently leads to a degradation of the performance of the Free Electron Laser (FEL) at the LCLS. In this paper, we describe a model of the wake field radiation in the SLAC linac collimators. We use the results of a numerical simulation to illustrate the model. Based on the model, we derive simple formulas for the bunch energy loss and the average kick. We also present results from experimental measurements which confirm our model.