Fermilab, Batavia, Illinois
I will present the current operational status of the Fermilab Recycler Ring. Using a mix of stochastic and electron cooling, we prepare antiproton beams for the Fermilab Tevatron Collider program.
CERN, Geneva
BNL, Upton, Long Island, New York
The fundamental questions about QCD which can be directly answered at Relativistic Heavy Ion Collider (RHIC) call for large integrated luminosities. The major goal of RHIC-II upgrade is to achieve 10 fold increase in luminosity of Au ions at the top energy of 100 GeV/n. A significant increase in luminosity for polarized protons is also expected, as well as for other ion species and for various collision energies. Such a boost in luminosity for RHIC-II is achievable with implementation of high-energy electron cooling. The design of the higher-energy cooler for RHIC recently adopted a non-magnetized approach which requires a low temperature electron beam. Such high-intensity high-brightness electron beams will be produced with superconducting Energy Recovery Linac (ERL). Detailed simulations of the electron cooling process and numerical simulations of the electron beam transport including the cooling section were performed. An intensive R&D of various elements of the design is presently underway. Here, we summarize progress in these electron cooling efforts.
JINR, Dubna, Moscow Region
FZJ, Jülich
CNS, Saitama
CERN, Geneva
Fermilab, Batavia, Illinois
In the course of Tevatron Run II (2001-2007) improvements of antiproton production have been one of major contributors into the collider luminosity growth. Commissioning of Recycler ring in 2004 and making electron cooling operational in 2005 freed Antiproton source from a necessity to keep large stack in Accumulator and allowed us to boost antiproton production. That resulted in doubling average antiproton production during last two years. The paper discusses improvements and upgrades of the Antiproton source during last two years and future developments aimed on further stacking improvements.
TSL, Uppsala
JINR, Dubna, Moscow Region
The HESR will work in a high-resolution mode with 1·1010 stored antiprotons and a high-luminosity mode with 1·1011 stored antiprotons. It will be equipped with both stochastic cooling and electron cooling systems. The main purpose of the electron-cooling system is to provide relative momentum spread in the antiproton beam of a few 1·10-5 (90 %) during experiments with an internal hydrogen pellet target and with luminosity 2·1031 – 2·1032 cm-2s-1. The hydrogen pellet target is expected to produce a stream of frozen hydrogen pellets with diameter 30 μm, which move with 60 m/s and at a rate of 20,000 s-1. The pellet stream is expected to have a diameter of 2–3 mm. Therefore, in order to avoid excessive fluctuations in the count rate, the antiproton beam size at the target must not be too small. This is solved by slightly tilting the electron beam with respect to the antiproton beam, thus making use of a so-called Hopf bifurcation. In order to get a high duty factor on another time scale, while not sacrificing momentum acceptance, a barrier-bucket rf. system will be employed. The electron-cooling system will initially be built for an antiproton energy range from 800 MeV to 9 GeV, but will be built so that its energy can be extended to the full energy of the HESR (14 GeV) at a later stage. The paper discusses the choice of parameters for the electron cooling system and presents simulations.
Fermilab, Batavia, Illinois
FNAL’s electron cooler (4.3 MV, 0.1 A DC) has been integrated to the collider operation for almost two years, improving the storage and cooling capability of the Recycler ring (8 GeV antiprotons). In parallel, efforts are carried out to characterize the cooler and its cooling performance. This paper discusses various aspects of the cooler performance and operational functionality: high voltage stability of the accelerator (Pelletron), quality of the electron beam generated, operational procedures (off-axis cooling, electron beam energy measurements and calibration) and cooling properties (in the longitudinal and transverse directions). In particular, we show measurements of the friction force and cooling rates, which we compare to a non-magnetized model and conclude that the effective electron beam radius is smaller than expected.
BINP SB RAS, Novosibirsk
Muons, Inc, Batavia
All three components of a particle’s momentum are reduced as a particle passes through and ionizes some energy absorbing material. If the longitudinal momentum is regenerated by RF cavities, the angular divergence of the particle is reduced. This is the basic concept of ionization cooling. What can be done for a muon beam with this simple idea is almost amazing, especially considering that the muon lifetime is only 2.2 μs in its rest frame. In this lecture we will discuss the evolution and present status of this idea, where we are now ready to design muon colliders, neutrino factories, and intense muon beams with very effective cooling in all six phase space dimensions. The discussion will include the heating effects and absorber Z-dependence of multiple scattering, numerical simulation programs, the accuracy of scattering models, emittance exchange, helical cooling channels, parametric-resonance ionization cooling, reverse emittance exchange, and the ionization cooling demonstration experiments, MICE and MANX.
DPNC, Genève
BNL, Upton, Long Island, New York
Fermilab, Batavia, Illinois
Muons, Inc, Batavia
UMiss, University, Mississippi
Hiroshima University, Higashi-Hiroshima
HU/AdSM, Higashi-Hiroshima
LBNL, Berkeley, California
Liouville's theorem implies that the six-dimensional phase-space volume occupied by a charged-particle beam is an approximate invariant unless the beam is subjected to dissipative interactions (such as in cooling). Symplectic conditions, in a Hamiltonian system (once again, no dissipation), put constraints upon emittance transfer between the various degrees of freedom. [1] We can, however, even in non-dissipative Hamiltonian systems arrange for partial emittance transfers. This process results in phase space correlations and change in the emittance projections on to various phase planes; namely, the projected emittances in three degrees of freedom are controllable while the direction and amount of a possible emittance flow are not very flexible because of the symplectic nature of Hamiltonian system. In some applications, it is clearly advantageous to optimize the ratios of projected emittances despite the effect of correlations. Since the three emittances are not always equally important, we may consider reducing the emittance of one direction at the sacrifice of the other emittance(s). As a possible scheme to achieve such emittance control, we study a compact storage ring operating near resonance. The basic features of linear and nonlinear emittance flow are briefly discussed with numerical examples. A general discussion touching on some of these matters has been previously presented. [2]
[1] E. D. Courant, Perspectives in Modern Physics, edit R. E. Marshak (1966).[2] H. Okamoto, K. Kaneta and A. M. Sessler, to be published in J. Phys. Soc. Jpn.
Fermilab, Batavia, Illinois
GSI, Darmstadt
BNL, Upton, Long Island, New York
With the experimental success of longitudinal, bunched beam stochastic cooling in RHIC it is natural to ask whether the system works as well as it might and whether upgrades or new systems are warranted. A computer code, very similar to those used for multi-particle coherent instability simulations, has been written and is being used to address these questions.
JINR, Dubna, Moscow Region
BNL, Upton, Long Island, New York
Fermilab, Batavia, Illinois
Presently antiprotons in Fermilab’s Recycler ring are stored between rectangular RF barriers and are cooled both by a stochastic cooling system in full duty-cycle mode and by a DC electron beam. Electron cooling creates correlation between longitudinal and transverse tails of the antiproton distribution because particles with large transverse actions are cooled much more slowly than the core ones. Introducing additional RF barriers of lower amplitude allows separating spatially (along the bunch) the core and the tail. In this scenario, stochastic cooling can be “gated” to the tail, i.e. applied with a high gain to the low-density region and turned off for the core portion of the beam. This significantly increases the cooling rate of the tail particles, while the temperature of the core is preserved by electron cooling. In this paper, we will describe the procedure and first experimental results in detail.
Fermilab, Batavia, Illinois
BNL, Upton, Long Island, New York
JINR, Dubna, Moscow Region
A 0.1-0.5 A, 4.3 MeV DC electron beam provides cooling of 8 GeV antiprotons in Fermilab's Recycler storage ring. Properties of electron cooling have been characterized in measurements of the drag force, cooling rates, and equilibrium distributions. The paper will report experimental results and compare them with modeling by BETACOOL code.
Fermilab, Batavia, Illinois
The cooling section of FNAL’s electron cooler is composed of ten (10) 2 m-long, 105 G solenoids. When FNAL’s electron cooler (4.3 MeV, 0.1 A DC) was first install at the Recycler ring, the magnetic field of the cooling solenoid was carefully measured and compensated to attain the field quality necessary for effective cooling [V. Tupikov et al. COOL’05]. However, the tunnel ground motion deteriorates the field quality perceived by the beam over time. We have developed a technique which uses the cooling strength as an indication of the relative field quality and allowing us to re-align the longitudinal magnetic field in the successive solenoids of the cooling section assuming that the transverse component of the field in each solenoid has not varied.
Jefferson Lab, Newport News, Virginia
An electron-ion collider (EIC) of center mass energy 90 GeV (9 GeV of electron beam x 225 GeV of proton beam) at luminosity level up to 1035/cm2s is envisioned by high energy Nuclear Physics community as a facility adequate for studying of the fundamental properties of quark-gluon structure of nucleons and strong interactions. In response to this quest, a high luminosity ring-ring EIC design (ELIC) is developed at Jefferson Laboratory utilizing 12 GeV upgrade CEBAF accelerator as a full energy injector for electron storage ring . An inevitable component of EIC is high energy electron cooling (EC) for ion beam. The EC facility concept for ELIC is based on use of 30 mA, 125 MeV energy recovery linac (ERL) and 3A circulator-cooler ring (CCR) operated at 15 and 1500 MHz bunch repetition rate, respectively. To switch electron bunches between ERL and CCR, fast kickers of a frequency bandwidth above 2 GHz are designed. The design parameters of EC facility and preliminary results of study of electron beam transports, stability and emittance maintenance in ERL and CCR, together with scenario of forming and cooling of ion beam will be presented.
GSI, Darmstadt
GSI, Darmstadt
Utsunomiya University, Utsunomiya
CERN, Geneva
BNL, Upton, Long Island, New York
Recently, a strong interest emerged in running RHIC at low energies in the range of 2.5-25 GeV/n total energy of a single beam. Providing collisions in this energy range, which in RHIC case is termed “low-energy” operation, will help to answer one of the key questions in the field of QCD about existence and location of critical point on the QCD phase diagram. Applying electron cooling directly at these low energies in RHIC would result in dramatic luminosity increase, small vertex distribution and long stores. On the other hand, even without direct cooling in RHIC at these energies, significant luminosity gain can be achieved by decreasing the longitudinal emittance of the ion beam before its injection into RHIC from the AGS. This will provide good RF capture efficiency in RHIC. Such an improvement in longitudinal emittance of the ion beam can be provided at by a simple electron cooling system at injection energy of AGS. Simulations of electron cooling both for direct cooling at low-energies in RHIC and for pre-cooling in AGS were performed, and are summarized in this report.