BNL, Upton, Long Island, New York, USA
High luminosity and high polarization in RHIC require good control and measurement of emittance in its injector, the Brookhaven AGS. In the past, the AGS emittance has been measured by using an ion collecting IPM during the whole cycle. The beam profiles from this IPM are distorted by space charge forces at higher energy, which makes the emittance determination very hard. The effect has been measured with IPM measurement at different energies with RF off to mitigate the space charge effect. In addition, helical snake magnets and near integer vertical tune for polarized proton operation distort the lattice in the AGS and introduce large beta beating. For more precise measurements of the emittance, we need turn-by-turn (TBT) measurements near injection and beta function measurements at the IPM. The AGS has also been modeled to get the beta functions at the locations of IPM. A new type of electron collecting IPM has been installed and tested in the AGS with proton beam. The vertical beta functions at the IPM locations have been measured with a local corrector near the IPM. This paper summarizes our current understanding of AGS emittances and plans for the further improvements.
BNL, Upton, Long Island, New York, USA
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
UMAN, Manchester, United Kingdom
The CBETA project[*] is a prototype electron accelerator for the proposed eRHIC project[**]. The electron accelerator is based on the Energy Recovery Linac (ERL) and the Fixed Field Alternating Gradient (FFAG) principles. The FFAG arcs and the straight section of the accelerator are comprised of one focusing and one defocusing quadrupoles which are designed as Halbach-type permanent dipole magnets with quadrupoles component[***]. We will present the beam optics of the FFAG cell which is based on 3D field maps derived with the use of the OPERA computer code[****]. We will also present the electromagnetic design of the corrector magnets of the cell.
* http://arxiv.org/abs/1504.00588
** http://arxiv.org/ftp/arxiv/papers/1409/1409.1633.pdf
*** K. Halbach, Nucl. Instrum. Meth. 169 (1980) pp. 1-10
**** http://www.scientificcomputing.com
BNL, Upton, Long Island, New York, USA
UMAN, Manchester, United Kingdom
The Cornell-BNL Electron Test Accelerator CBETA is based on a 36 MeV superconducting linac and on a single 4-pass up/4-pass down linear FFAG return loop, for beam acceleration from 6 to 150 MeV and energy recovery. Numerical beam dynamics simulations have accompanied and eventually validated the quadrupole-doublet FFAG cell technology and parameters, and following that the complete return loop, all along the ERL lattice design process. They are key to assessing and validating the ERL optics and beam behavior over the whole acceleration/ER cycle, and in preparing future machine operation. This paper presents various of these beam dynamics studies, including start-to-end simulations.
BNL, Upton, Long Island, New York, USA
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
JLab, Newport News, Virginia, USA
Cornell University, Ithaca, New York, USA
Cornell's Lab of Accelerator-based Sciences and Education (CLASSE) and the Collider Accelerator Department (BNL-CAD) are developing the first SRF multi-turn energy recovery linac with Non-Scaling Fixed Field Alternating Gradient (NS-FFAG) racetrack. The existing injector and superconducting linac at Cornell University are installed together with a single NS-FFAG arcs and straight section at the opposite side of the the linac to form an Electron Energy Recovery (ERL) system. Electron beam from the 6 MeV injector is injected into the 36 MeV superconducting linac, and accelerated by four successive passes: from 42 MeV up to 150 MeV using the same NS-FFAG structure made of permanent magnets. After the maximum energy of 150 MeV is reached, the electron beam is brought back to the linac with opposite Radio Frequency (RF) phase. Energy is recovered and reduced to the initial value of 6 MeV with 4 additional passes. There are many novelties: a single NS-FFAG structure, made of permanent magnets, brings electrons with four different energies back to the linac. A new adiabatic NS-FFAG arc-to-straight section merges 4 separated orbits into a single orbit in the straight section.
BNL, Upton, Long Island, New York, USA
Recent analyses of RHIC run12 to run15 proton-carbon polarimeter measurements have shown significant tilt of the polarization vector from vertical, at high energy essentially. This is confirmed by extensive measurements performed in the present Run 17. Possible origins of such large tilt may reside in snake spin rotation angle or orbit defects, to mention just two. Dedicated simulations have been undertaken to investigate possible causes, they are presented and discussed, they include the computation and use of 3-D field maps of RHIC siberian snakes.
BNL, Upton, Long Island, New York, USA
The 2017 operation of the Relativistic Heavy Ion Collider (RHIC) involved the running of only a single experiment at STAR with PHENIX offline in the process of the upgrade to sPHENIX. For this run there were several notable changes to machine operations. These included, transverse polarization, luminosity leveling, a new approach to machine protection and the development of new store and ramped lattices. The new 255 GeV store lattice was designed to both accommodate the necessary phase advance between the e-lens and IP8 for testing and to maximize dynamic aperture. The new lattices on the ramp were designed to maximize polarization transmission during the three strong intrinsic spin resonances crossings. Finally we are also commissioning new 9 MHz RF cavities during this run.
BNL, Upton, Long Island, New York, USA
Imperfection and vertical intrinsic depolarizing resonances have been overcome by the two partial Siberian snakes in the Alternating Gradient Synchrotron (AGS). The relatively weak but numerous horizontal resonances are overcome by a pair of horizontal tune jump quads. 70% proton polarization has been achieved for 2·1011 intensity. Further gain can come from maintaining smaller transverse emittance with same beam intensity. The main efforts now are to reduce the transverse emittance in the AGS and Booster, as well as robust jump quads timing generation scheme. This paper summarizes the operation results in the injectors.
BNL, Upton, Long Island, New York, USA
The ring-ring electron-ion collider eRHIC aims at an electron-ion luminosity in the range from 1032 to 1033cm-2sec-1 over a center-of-mass energy range from 20 to 140GeV. To minimize the technical risk the design is based on existing technologies and beam parameters that have already been achieved routinely in hadron-hadron collisions at RHIC, and in electron-positron collisions elsewhere. This design has evolved considerably over the last two years, and a high level of maturity has been achieved. We will present the latest design status and give an overview of studies towards evaluating the feasibility.
UMAN, Manchester, United Kingdom
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
BNL, Upton, Long Island, New York, USA
The Cornell-BNL Electron Test Accelerator CBETA is a 4 pass up, 4 pass down energy recovery linac using Fixed-Field Alternating-Gradient (FFAG) recirculation arcs with a top energy of 150 MeV. We present lattice implemented in the tracking code pyZgoubi, with both hard edge and field map magnet versions. We also describe the recent developments in pyZgoubi such as importing lattice tables from other tracking codes.
BNL, Upton, Long Island, New York, USA
Muons, Inc, Illinois, USA
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
We present an algorithm to calculate the off-plane components of the magnetic field from the on-plane components of the magnetic field which are measured on a grid of the plane. The algorithm, which is a general one and it is not restricted on a mid-plane symmetry, is based on the Taylor series expansion of the magnetic field components in terms of the normal to the plane location. The coefficients of the Taylor series expansion are expressed in terms of the on-plane derivatives of the field components which are generated by the measured magnetic field components on the grid of the plane. The algorithm is use in the RATRACE computer code[*] and has been used[**] on a dipole magnet with median plane symmetry.
* S.B. Kowalski and H.A. Enge The Ion-Optical Program Raytrace NIM A258 (1987) 407
** N. Tsoupas et. al. Effects of Dipole Magnet Inhomogeneity on the Beam Ellipsoid NIM A258 (1987) 421-425