ANL, Lemont, Illinois, USA
An on-axis vertical injection scheme was adopted for the Advanced Photon Source upgrade multi-bend achromat lattice. As the design of the injection scheme has become more detailed, the booster to storage ring transport line (BTS) has advanced, including effects such as the septum field map and stray fields of storage ring magnets. Various error effects are simulated for setting specifications and predicting expected performance. The beam diagnostic scheme, including emittance measurement, is incorporated into the beamline design.
ANL, Lemont, Illinois, USA
The Advanced Photon Source (APS) particle accumulator ring (PAR) was designed to accumulate linac pulses into a single bunch with a fundamental rf system, and longitudinally compress the beam with a harmonic rf system prior to injection into the booster. For APS Upgrade, the injectors will need to supply full-current bunch replacement with high single-bunch charge for swap-out in the new storage ring. Significant bunch lengthening, energy spread, and synchrotron sidebands are observed in PAR at high charge. Lower-charge dynamics are dominated by potential well distortion, while higher-charge dynamics appear to be dominated by microwave instability. Before a numerical impedance model was available, a simple circuit model was developed by fitting the measured bunch distributions to the Haissinski equation. Energy scaling was then used to predict the beam energy sufficient to raise the instability threshold to 18-20 nC. With the beam in a linear or nearly linear regime, higher harmonic radio frequency (rf) gap voltage can be used to reduce the bunch length at high charge and better match the booster acceptance.
ANL, Lemont, Illinois, USA
JLab, Newport News, Virginia, USA
A recent assessment of the scientific merit for a future Electron Ion Collider (EIC) in the US, by the National Academy of Sciences, found that such a facility would be unique in the world and would answer science questions that are compelling, fundamental, and timely. This assessment confirmed the recommendations of the 2015 Nuclear Science Advisory Committee for an EIC with highly polarized beams of electrons and ions, sufficiently high luminosity and variable center-of-mass (CM) energy. The baseline design of Jefferson Lab Electron-Ion Collider (JLEIC) has been updated to 100 GeV CM energy, corresponding to 200 GeV proton energy. We here present a high-energy design for the JLEIC ion complex. It consists of a 135 MeV injector linac, a 6-GeV non figure-8 pre-booster ring and a 40-GeV large ion booster, which could also serve as electron storage ring (e-ring). The energy choice in the accelerator chain is beneficial for a future upgrade to 140 GeV CM energy. The large booster is designed with the same shape and size of the original e-ring allowing for the option of building separate electron and ion rings by stacking them in the same tunnel along with the ion collider ring.
SLAC, Menlo Park, California, USA
Accelerator operation history data are used to train neural networks in an attempt to understand the underly-ing causes of performance drifts. In the study, injection efficiency of SPEAR3 [1] over two runs is modelled with a neural network (NN) to map the relationship of the injection efficiency with the injected beam trajectory and environment variables. The NN model can accurately predict the injection performance for the test data. With the model, we discovered that an environment parameter, the ground temperature, has a big impact to the injection performance. The ideal trajectory as a function of the ground temperature can be extracted from the model. The method has the potential for even larger scale application for the discovery of deep connections between machine performance and environment parameters.
ANL, Lemont, Illinois, USA
Illinois Institute of Technology, Chicago, Illinois, USA
As part of the alternative design approach for the Jeffer-son Laboratory Electron-Ion Collider (JLEIC) ion com-plex, the electron storage ring (e-ring) is consolidated to also serve as a large booster for the ions. The goal of reaching 16 GeV/u or higher for all ions using only room-temperature magnets forces the re-design of the e-ring because of magnetic field and lattice limitations. The new design is challenging due to several imposed constraints: (1) use of room-temperature magnets, (2) avoiding transi-tion crossing, and (3) maintaining the size and shape of the original e-ring design as much as possible. A design study is presented for a 16 GeV/u large ion booster after analyzing different alternatives that use: (1) combined-function magnets, (2) large quadrupoles or (3) quadrupole doublets in the lattice design. This design boosts the injection energy to the collider ring from 8 GeV (proton-equivalent) in the original baseline design to 16 GeV/u for all ions which is beneficial for the high-energy option of JLEIC of 200 GeV or higher. A scheme for adapting the new large ion booster design to also serve as electron storage ring is presented.
Fermilab, Batavia, Illinois, USA
ANL, Lemont, Illinois, USA
One of the challenges of the injector for the Advanced Photon Source Upgrade (APS-U) is the measurement and monitoring of the required high charge electron beam at 6 GeV between the Booster synchrotron and the storage ring in the transport line (BTS. In APS-U charges of up to 17 nC per micropulse are specified with a beam geometrical horizontal emittance of 60 nm rad. Vertical beam sizes at the imaging station of ~80 µm (σ) are expected so system resolutions of <30 µm are warranted. A phased approach to enhance the imaging station performance has been initiated. Recently, the 20-year-old Chromox screen oriented at 45 degrees to the beam was replaced by a 100-micron thick YAG:Ce screen which gave an improved screen resolution of <10 micron(σ. However, the optical magnification of the system still needs to be increased. In addition, the high areal charge densities are expected to exceed the scintillator mechanism’s saturation threshold so an optical transition radiation (OTR) screen will be added to the station for high-charge studies. A final phase would be the use of optical diffraction radiation (ODR) as a non-intercepting, beam-size monitor during top-up injections.
SLAC, Menlo Park, California, USA
SINAP, Shanghai, People’s Republic of China
I-Tech, Solkan, Slovenia
We are upgrading the BPM processors in the SPEAR3 accelerator complex as several of the existing systems have reached end of life. To reduce the resources required for maintenance we have evaluated and installed several commercial BPM processors from the SPARK series of Libera/Instrumentation Technologies. In SPEAR3 we evaluated the SPARK-ERXR turn-by-turn BPM processor as a replacement to the in-house developed/commercially built Echotek processors that are used for a range of accelerator physics studies. We show measurements of the orbit dynamics with another SPARK-ERXR in the booster synchrotron from beam injection up to ejection. We have further evaluated a Spark-EL in the transport lines to replace the in-house built uTCA-based single-pass BPM processors. In this paper we show measurements and discuss our experience with the Libera SPARK series of BPM processors and comment on the software integration.
Fermilab, Batavia, Illinois, USA
At the Fermilab Booster, and many other proton facilities, an intense proton beam is accumulated by injection an H− beam through a stripping foil. The circulating beam scatters off the injection beam and large-angle Coulomb scattering leads to uncontrolled losses concentrated in the first betatron period. We measure the foil scattering rate in the Booster as a function of linac current, number of injection-turns, and time on injection foil. We find that current Booster operations has a 1% foil scattering loss rate and we make projections for the Proton Improvement Plan II (PIP-II) injector upgrade. We find that accurate modeling of the foil scattering loss must account for beam emittance in conjunction with the scattering rate and ring acceptance. Estimate of beam emittance at injection are discussed.
LBNL, Berkeley, California, USA
SLAC, Menlo Park, California, USA
The LCLS-II beam injector system consists of a 186 MHz normal-conducting RF gun, a two-cell 1.3 GHz normal-conducting buncher cavity, two transverse focusing solenoids, and eight 1.3 GHz 9-cell Tesla-like super-conducting booster cavities. With a coordinated effort between LBNL and SLAC, we have developed a simulation workflow combining the electromagnetic field solvers from ACE3P with the beam dynamics modeling code IMPACT. This workflow will be used to improve performance and minimize beam emittance for given accelerator structures through iterative optimization. In our current study, we use this workflow to compare beam quality parameters between using 2D axisymmetric field profiles and fully 3D non-axisymmetric fields caused by geometrical asymmetries (e.g. RF coupler ports).
Fermilab, Batavia, Illinois, USA
We report on the prototype High Temperature Superconductor (HTS) based accelerator magnet capable to operate at 12 T/s B-field ramping rate with a very low supporting cryogenic cooling power thus indicating a feasibility of its application in large accelerator requiring high repetition rate and high average beam power. The magnet is designed to simultaneously accelerate two particle beams in the separate beam gaps energized by a single conductor. The design, construction and the power test arrangement of a prototype of this fast-cycling HTS based accelerator magnet are presented. As example, the cryogenic power loss limit measured in the magnet power test is discussed in terms of feasibility of application of such a magnet for the construction of an 8 GeV dual-beam proton booster accelerator.
Fermilab, Batavia, Illinois, USA
To mitigate 8 GeV beam losses at extraction in the Fermilab Booster synchrotron, a LASER notcher system for multi-turn injection that produces notches at 720 keV is used. These notches synchronize with the revolution period of the beam [ref. HB2018, page 416] at injection in the Booster. Recently, a dedicated notching pattern that keeps a single 201 MHz LINAC bunch untouched in the middle of a notch is developed to measure the beam energy spread by studying the time evolution of this bunch in the Booster. A complementary to this method, recently, it has been realized that one can also measure energy spread of the LINAC beam by injecting <2 Booster turn beam and studying the time evolution of the multiple 201 MHz LINAC bunches. In this paper we present the general principle of the method and results from our measurements.
