The US Electron Ion Collider Accelerator Designs

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

Technique to produce coherent x-ray radiation via laser pumping of a relativistic ion beam

The level population of a beam of relativistic positive ions with Z greater than or equal to 2 having a single bound electron may be inverted by the application of a ''..pi.. pulse'' of laser radiation tuned to the Doppler shifted 1s-2p transition. When the laser beam and ion beam move in opposite directions the required laser frequency is reduced by a factor 2..gamma... Subsequently applied short wavelength resonant radiation moving in the same direction as the ion beam (with an inverted population) will be amplified via stimulated emission, the wavelength in the lab frame now being shorter than the original laser wavelength by a factor (2..gamma..)/sup 2/. 7 refs

Recirculating Linear Accelerators for Future Muon Facilities

Neutrino Factories (NF) and Muon Colliders (MC) require rapid acceleration of short-lived muons to multi-GeV and TeV energies. A Recirculating Linear Accelerator (RLA) that uses superconducting RF structures can provide exceptionally fast and economical acceleration to the extent that the focusing range of the RLA quadrupoles allows each muon to pass several times through each high-gradient cavity. A new concept of rapidly changing the strength of the RLA focusing quadrupoles as the muons gain energy is being developed to increase the number of passes that each muon will make in the RF cavities, leading to greater cost effectiveness

Correction of the Chromaticity up to Second Order for MEIC

The proposed electron collider lattice exhibits low β- functions at the Interaction Point (IP) (βx∗100mm − βy∗ 20 mm) and rather large equilibrium momentum spread of the collider ring (δp/p = 0.00158). Both features make the chromatic corrections of paramount importance. Here the chromatic effects of the final focus quadruples are cor- rected both locally and globally. Local correction features symmetric sextupole families around the IP, the betatron phase advances from the IP to the sextupoles are chosen to eliminate the second order chromatic aberration. Global interleaved families of sextupoles are placed in the figure-8 arc sections, and non-interleaved families at straight sec- tion making use of the freely propagated dispersion wave from the arcs. This strategy minimizes the required sex- tupole strength and eventually leads to larger dynamic aper- ture of the collider. The resulting spherical aberrations induced by the sextupoles are mitigated by design; the straight and arc sections optics features an inverse identity transformation between sextupoles in each pair

Spin Rotator Optics for MEIC

A unique de­sign fea­ture of a po­lar­ized Medi­um En­er­gy Elec­tron-Ion Col­lid­er (MEIC) based on CEBAF is its 'Fig­ure-8' stor­age rings for both elec­trons and ions, which sig­nif­i­cant­ly sim­pli­fies beam po­lar­iza­tion main­te­nance and ma­nip­u­la­tion. While elec­tron (positron) po­lar­iza­tion is main­tained ver­ti­cal in arcs of the ring, a sta­ble lon­gi­tu­di­nal spin at four col­li­sion points is achieved through solenoid based spin ro­ta­tors and hor­i­zon­tal orbit bends. The pro­posed MEIC lat­tice was de­vel­oped in order to pre­serve a very high po­lar­iza­tion (more than 70%) of the elec­tron beams in­ject­ed from the CEBAF ma­chine. The oth­er­wise cou­pled beam tra­jec­to­ry due to solenoids used in the spin ro­ta­tors was de­cou­pled by de­sign. Aspin match­ing tech­nique needs to be im­ple­ment­ed in order to en­hance quan­tum self-po­lar­iza­tion and min­i­mize de­po­lar­iza­tion ef­fects

Linear Fixed-Field Multi-Pass Arcs for Recirculating Linear Accelerators

Recirculating Linear Accelerators (RLA's) provide a compact and efficient way of accelerating particle beams to medium and high energies by reusing the same linac for multiple passes. In the conventional scheme, after each pass, the different energy beams coming out of the linac are separated and directed into appropriate arcs for recirculation, with each pass requiring a separate fixed-energy arc. In this paper we present a concept of an RLA return arc based on linear combined-function magnets, in which two and potentially more consecutive passes with very different energies are transported through the same string of magnets. By adjusting the dipole and quadrupole components of the constituting linear combined-function magnets, the arc is designed to be achromatic and to have zero initial and final reference orbit offsets for all transported beam energies. We demonstrate the concept by developing a design for a droplet-shaped return arc for a dog-bone RLA capable of transporting two beam passes with momenta different by a factor of two. We present the results of tracking simulations of the two passes and lay out the path to end-to-end design and simulation of a complete dog-bone RLA

LHeC ERL Design and Beam-dynamics Issues

We discuss machine and beam parameter choices for a Linac-Ring option of the Large Hadron electron Collider (LHeC) based on the LHC. With the total wall-plug power limited to 100 MW and a target current of about 6 mA the desired luminosity of 1033 cm-2 s-1 can be reached, providing one exploits unique features of the Energy Recovery Linac (ERL). Here, we describe the overall layout of such ERL complex located on the LHC site. We present an optimized multi-pass linac optics enabling operation of the proposed 3-pass Recirculating Linear Accelerator (RLA) in the Energy Recovery mode. We also describe emittance preserving return arc optics architecture; including layout and optics of the arc switch-yard. Furthermore, we discuss importance of collective effects such as: beam breakup in the RLA, as well as ion accumulation, with design-integrated mitigation measures, and the electron-beam disruption in collision. Finally, a few open questions are highlighted

Betatron motion with coupling of horizontal and vertical degrees of freedom

Presently, there are two most frequently used parameterizations of linear x-y coupled motion used in the accelerator physics. They are the Edwards-Teng and Mais-Ripken parameterizations. The article is devoted to an analysis of close relationship between the two representations, thus adding a clarity to their physical meaning. It also discusses the relationship between the eigen-vectors, the beta-functions, second order moments and the bilinear form representing the particle ellipsoid in the 4D phase space. Then, it consideres a further development of Mais-Ripken parameteresation where the particle motion is described by 10 parameters: four beta-functions, four alpha-functions and two betatron phase advances. In comparison with Edwards-Teng parameterization the chosen parametrization has an advantage that it works equally well for analysis of coupled betatron motion in circular accelerators and in transfer lines. Considered relationship between second order moments, eigen-vectors and beta-functions can be useful in interpreting tracking results and experimental data. As an example, the developed formalizm is applied to the FNAL electron cooler and Derbenev's vertex-to-plane adapter