Vasiliy Morozov

Parametric-resonance ionization cooling of muon beams

Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a high-luminosity muon collider. Combining muon ionization cooling with parametric resonant dynamics should allow an order of magnitude smaller final equilibrium transverse beam emittances than conventional ionization cooling alone. In this scheme, a half-integer parametric resonance is induced in a cooling channel causing the beam to be naturally focused with the period of the channel’s free oscillations. Thin absorbers placed at the focal points then cool the beam’s angular divergence through the usual ionization cooling mechanism where each absorber is followed by RF cavities. A special continuous-field twin-helix magnetic channel with correlated behavior of the horizontal and vertical betatron motions and dispersion was developed for PIC. We present the results of modeling PIC in such a channel using GEANT4/G4beamline. We discuss the challenge of precise beam aberration control from one absorber to another over ...

Polarization Preservation and Control in a Figure-8 Ring

We present a complete scheme for managing the polarization of ion beams in Jefferson Lab’s proposed Medium-energy Electron-Ion Collider (MEIC). It provides preservation of the ion polarization during all stages of beam acceleration and polarization control in the collider’s experimental straights. We discuss characteristic features of the spin motion in accelerators with Siberian snakes and in accelerators of figure-8 shape. We propose 3D spin rotators for polarization control in the MEIC ion collider ring. We provide polarization calculations in the collider with the 3D rotator for deuteron and proton beams. The main polarization control features of the figure-8 design are summarized.

Symmetric achromatic low-beta collider interaction region design concept

We present a new symmetry-based concept for an achromatic low-beta collider interaction region design. A specially-designed symmetric Chromaticity Compensation Block (CCB) induces an angle spread in the passing beam such that it cancels the chromatic kick of the final focusing quadrupoles. Two such CCB?s placed symmetrically around an interaction point allow simultaneous compensation of the 1st-order chromaticities and chromatic beam smear at the IP without inducing significant 2nd-order aberrations. We first develop an analytic description of this approach and explicitly formulate 2nd-order aberration compensation conditions at the interaction point. The concept is next applied to develop an interaction region design for the ion collider ring of an electron-ion collider. We numerically evaluate performance of the design in terms of momentum acceptance and dynamic aperture. The advantages of the new concept are illustrated by comparing it to the conventional distributed-sextupole chromaticity compensation scheme.

Polarized Electron Beams In The MEIC Collider Ring At JLab

The nuclear physics program of the Medium-energy Electron-Ion Collider (MEIC) at the JLab requires a highly-polarized (over 70%) electron beam with longitudinal polarization at the collision points. This can be achieved by arranging the equilibrium polarization direction to be vertical in the arcs of the figure-8 shape ring and longitudinal at collision points. The rotation of the polarization is accomplished at each energy by using universal spin rotators, each of which consists of a set of solenoids and dipoles placed at the end of each arc. To reduce the spin-orbit depolarization effect due to the synchrotron radiation, spin matching to make the sections between the rotators in the long straights spin transparent has to be considered. We present the current universal spin rotator design, address various coupling compensation schemes for the solenoids, provide polarization configurations based on the spin rotators’ layout, and briefly explore the use of continuous injection of electrons from the CEBAF into the MEIC collider ring for maintaining high equilibrium polarization. This continuous injection might be less demanding than spin matching.

Polarized positrons in Jefferson lab electron ion collider (JLEIC)

The Jefferson Lab Electron Ion Collider (JLEIC) is designed to provide collisions of electron and ion beams with high luminosity and high polarization to reach new frontier in exploration of nuclear structure. The luminosity, exceeding 1033 cm−2s−1 in a broad range of the center-of-mass (CM) energy and maximum luminosity above 1034 cm−2s−1, is achieved by high-rate collisions of short small-emittance low-charge bunches with proper cooling of the ion beam and synchrotron radiation damping of the electron beam. The polarization of light ion species (p, d, 3He) and electron can be easily preserved, manipulated and maintained by taking advantage of the unique figure-8 shape rings. With a growing physics interest, polarized positron-ion collisions are considered to be carried out in the JLEIC to offer an additional probe to study the substructure of nucleons and nuclei. However, the creation of polarized positrons with sufficient intensity is particularly challenging. We propose a dedicated scheme to generate ...

Complete Beam Dynamics of the JLEIC Ion Collider Ring Including Imperfections, Corrections, and Detector Solenoid Effects

The JLEIC is proposed as a next-generation facility for the study of strong interaction (QCD). Achieving its goal luminosity of up to 1034 cm⁻²s^{−1} requires good dynamical properties and a large dynamic aperture (DA) of ~ ±10 σ of the beam size. The limit on the DA comes primarily from non-linear dynamics, element misalignments, magnet multipole components, and detector solenoid effect. This paper presents a complete simulation including all of these effects. We first describe an orbit correction scheme and determine tolerances on element misalignments. And beta beat, betatron tunes, coupling, and linear chromaticity perturbations also be corrected. We next specify the requirements on the multipole components of the interaction region magnets, which dominate the DA in the collision mode. Finally, we take special care of the detector solenoid effects. Some of the complications are an asymmetric design necessary for a full acceptance detector with a crossing angle of 50 mrad. Thus, in addition to coupling, the solenoid causes closed orbit excursion and excites dispersion. It also breaks the figure-8 spin symmetry. We present a scheme with correction of all of these effects.

Optimization of a Skew Parametric Resonance Ionization Cooling Channel Using Genetic Algorithm

Skew Parametric-resonance Ionization Cooling (Skew PIC) is designed for the final 6D cooling of a high-luminosity muon collider. Tracking of muons in such a channel has been modeled in MADX and matter-dominated simulation tool G4beanline in previous studies. In this work, we developed an optimization code based on Genetic Algorithm (GA). We optimized the cooling channel and increased the acceptance of the channel by using the GA code.

Acceleration of polarized protons and deuterons in the ion collider ring of JLEIC

The figure-8-shaped ion collider ring of Jefferson Lab Electron-Ion Collider (JLEIC) is transparent to the spin. It allows one to preserve proton and deuteron polarizations using weak stabilizing solenoids when accelerating the beam up to 100 GeV/c. When the stabilizing solenoids are introduced into the collider’s lattice, the particle spins precess about a spin field, which consists of the field induced by the stabilizing solenoids and the zero-integer spin resonance strength. During acceleration of the beam, the induced spin field is maintained constant while the resonance strength experiences significant changes in the regions of “interference peaks”. The beam polarization depends on the field ramp rate of the arc magnets. Its component along the spin field is preserved if acceleration is adiabatic. We present the results of our theoretical analysis and numerical modeling of the spin dynamics during acceleration of protons and deuterons in the JLEIC ion collider ring. We demonstrate high stability of the deuteron polarization in figure-8 accelerators. We analyze a change in the beam polarization when crossing the transition energy. PRESERVATION OF ION POLARIZATION IN FIGURE-8 ACCELERATORS A characteristic feature of JLEIC [1] is its figure-8shaped rings [2]. Such a ring topology is transparent to the spin: the combined effect of arc fields on the spin in an ideal collider lattice reduces to zero after one particle turn on the design orbit, i.e. any orientation of the particle spin at any orbital location repeats from turn to turn. To preserve the polarizations of the proton and deuteron beams during acceleration from 8 GeV/c to 100 GeV/c in the ion collider ring, it is sufficient to use a weak solenoid with a field integral of 1.2 Tm, which does not perturb the design orbit and has practically no effect on the beam’s orbital parameters [3-10]. The solenoid then stabilizes longitudinal spin polarization at its location. A solenoid with the indicated field integral allows one to induce a spin tune � of 10-2 for protons and 310-3 for deuterons, i.e., when a particle with a vertical spin makes one turn on the design orbit, its spin tilts by an angle of �� from its initial orientation. For polarization stability, one must ensure that the spin tune � induced by the solenoid significantly exceeds [3-6] the strength of the zero-integer spin resonance �: � ≫ �. The resonance strength is the average spin field �⃗ (the zero-integer Fourier harmonic of the spin perturbation without a stabilizing solenoid) determined by deviation of the trajectory from the design orbit due to machine element errors and beam emittances. In the absence of a solenoid, the spin precesses by an angle of �� about the �⃗ direction in one particle turn. The resonance strength consists of two parts: a coherent part arising due to additional transverse and longitudinal fields on a trajectory deviating from the design orbit and an incoherent part associated with the particles’ betatron and synchrotron oscillations (beam emittances) [8, 9] �⃗ = �⃗ ��h + �⃗ ��� , ���h ≫ ���� In practice, the coherent part ���h significantly exceeds the incoherent one ���� . The coherent part does not cause beam depolarization and only results in a simultaneous rotation of the polarization about the field determined by the strength and alignment errors of collider elements. In principle, the direction and size of the coherent part of the resonance strength can be measured and taken into account for polarization control. To preserve the polarization, it is then sufficient to satisfy a weaker condition: � ≫ ���� . CALCULATION OF ZERO-INTEGER SPIN RESONANCE STRENGTH IN JLEIC Figure 1 shows  functions of the JLEIC collider lattice in the acceleration mode [11] used in our spin dynamics calculations. The origin of the coordinate frame is located at the colliders IP. Figure 1 also indicates the location of the solenoid stabilizing the spin during acceleration. The difference from the collision mode [12] where functions in the IP region reach 2.5 km is that, in the acceleration mode, the functions in the detector section do not exceed 150 m. Figure 1: functions of the ion collider ring. ___________________________________________ * Authored by Jefferson Science Associates, LLC under U.S. DOE Contracts No. DE-AC05-06OR23177 and DE-AC02-06CH11357. The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes. WEPIK038 Proceedings of IPAC2017, Copenhagen, Denmark ISBN 978-3-95450-182-3 3014 Co py rig ht

Decoupling and Matching of Electron Cooling Section in the MEIC Ion Collider Ring

To get a luminosity level of 10³³ cm⁻² s⁻¹ at all design points of the MEIC, small transverse emittance is necessary in the ion collider ring, which is achieved by an electron cooling. And for the electron cooling, two solenoids are used to create a cooling environment of temperature exchange between electron beam and ion beam. However, the solenoids can also cause coupling and matching problem for the optics of the MEIC ion ring lattice. Both of them will have influences on the IP section and other areas, especially for the beam size, Twiss parameters, and nonlinear effects. A symmetric and flexible method is used to deal with these problems. With this method, the electron cooling section is merged into the ion ring lattice elegantly.

Compensation of Chromaticity in the JLEIC Electron Collider Ring

The Jefferson Lab Electron-Ion Collider (JLEIC) is being designed to achieve a high luminosity of up to 10 cms. The latter requires a small beam size at the interaction point demanding a strong final focus (FF) quadrupole system. The strong beam focusing in the FF unavoidably creates a large chromaticity which has to be corrected in order to avoid a severe degradation of momentum acceptance. This has to be done while maintaining sufficient dynamic aperture. An additional requirement in the electron ring is preservation of a low beam emittance. This paper reviews the development of a chromaticity correction scheme for the electron ring.