COOL 2007 - Classification:Electron Cooling/

Electron Cooling

Paper	Title	Page
MOM2I03	Progress of High-energy Electron Cooling for RHIC	11
	A. V. Fedotov BNL, Upton, Long Island, New York
	Funding: Work supported by the U. S. Department of Energy. 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.
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MOM2I04	Cooling Simulations with the BETACOOL Code	16
	A. O. Sidorin JINR, Dubna, Moscow Region
	BETACOOL program developed by JINR electron cooling group is a kit of algorithms based on common format of input and output files. General goal of the program is to simulate long term processes (in comparison with the ion revolution period) leading to variation of the ion distribution function in 6 dimensional phase space. The BETACOOL program includes three algorithms for beam dynamics simulation and takes into account the following processes: electron cooling, intrabeam scattering, ion scattering on residual gas atoms, interaction of the ion beam with internal target and some others.
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MOA2C05	Calculations on High-energy Electron Cooling in the HESR	44
	D. Reistad, B. Gålnander, K. Rathsman TSL, Uppsala A. O. Sidorin JINR, Dubna, Moscow Region
	Funding: This work is supported by Uppsala University through The Svedberg Laboratory and by the European Community under Contract Number 515873, DIRACsecondary-Beams 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.
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MOA2I06	Electron Cooling Status and Characterization at Fermilab’s Recycler	49
	L. R. Prost, A. V. Burov, K. Carlson, A. V. Shemyakin, M. Sutherland, A. Warner Fermilab, Batavia, Illinois
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy 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.
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TUM1I01	Cooling Results from LEIR	55
	G. Tranquille CERN, Geneva
	The LEIR electron cooler has been successfully commissioned for the cooling and stacking of Pb⁵⁴⁺ ions in LEIR during 2006. The emphasis of the three short commissioning runs was to produce the so-called “early” beam needed for the first LHC ion run. In addition some time was spent investigating the difficulties that one might encounter in producing the nominal LHC ion beam. Cooling studies were also made whenever the machine operational mode made it possible, and we report on the preliminary results of the different measurements (cooling-down time, lifetime etc.) performed on the LEIR cooler. Our investigations also included a study of the influence of variable electron density distributions on the cooling performance.
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TUM1I02	Commissioning of Electron Cooling in CSRm	59
	X. D. Yang, D. Q. Gao, Y. He, G. H. Li, J. Li, Y. Liu, L. J. Mao, R. S. Mao, M. T. Song, J. W. Xia, G. Q. Xiao, J. C. Yang, X. T. Yang, Y. J. Yuan, W.-L. Zhan, W. Zhang, H. W. Zhao, T. C. Zhao, J. H. Zheng, Z. Z. Zhou IMP, Lanzhou V. V. Parkhomchuk BINP SB RAS, Novosibirsk
	A new generation cooler was commissioned in CSRm, ¹²C⁶⁺ beam with energy 7MeV/u was delivered by a small cyclotron SFC, then injected into CSRm by stripping mode, the average pulse particle number is about 6.8×10⁸ in one injection, with the help of electron cooling of partial hollow electron beam, 3×10⁹ particle were accumulated in the ring after 10 times injection in 10 seconds, and 2×10⁹ particle were accelerated to final energy 1GeV/u, the momentum spread and the lifetime of ion beam were measured roughly. The work point of ring was monitored during the process of acceleration. The close-orbit correction was done initially. The momentum cooling time was about 0.3sec. About 1.6×10¹⁰ particle was stored in the ring after longer time accumulation.
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TUM1I03	Comparison of Hollow Electron Devices and Electron Heating	64
	V. V. Parkhomchuk BINP SB RAS, Novosibirsk
	The first results of the electron cooling with hollow electron beam are present. The electron coolers with varable electron beam profiles was commissioned at CERN and IMP (China). Accumulation of the ion beam was demonstrated.
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WEM1C01	Status of the LEPTA Project	113
	A. G. Kobets, E. V. Ahmanova, V. Bykovsky, I. I. Korotaev, V. I. Lokhmatov, V. N. Malakhov, I. N. Meshkov, V. Pavlov, R. Pivin, A. Yu. Rudakov, A. O. Sidorin, A. V. Smirnov, G. V. Trubnikov, S. Yakovenko JINR, Dubna, Moscow Region
	The Low Energy Positron Toroidal Accumulator (LEPTA) is under commissioning at JINR. The LEPTA facility is a small positron storage ring equipped with the electron cooling system. The project positron energy is of 4-10 keV. The main goal of the facility is to generate an intense flow of positronium atoms–the bound state of electron and positron. The focusing system of the LEPTA ring after solenoidal magnetic field remeasurement and correction has been tested with pulsed electron beam by elements. Some resonant effects of beam focusing have been observed. The experiments aiming to increase the life time of the circulating electron beam and test the electron cooling elector beam are in progress. Construction of the pulsed injector of the low energy positrons is close to the completion (CPS). The injector is based on ²²Na radioactive isotope and consists of the cryogenic positron source, the positron trap and the acceleration section. In the CPS positrons from the ²²Na tablet are moderated in the solid neon and transported into the trap, where they are accumulated during about 80 seconds. Then accumulated positrons are extracted by the pulsed electric field and accelerated in electrostatic field up to required energy (the injector as a whole is suspended at a positive potential that corresponds to required positron energy in the range of 4-10 keV). In injection pulse duration is about 300 nsec. The CPS has been tested at the low activity of isotope ²²Na tablet (100 MBq). The continuous positron beam with average energy of 1.2 eV and spectrum width of 1 eV has been obtained. The achieved moderation efficiency is about 1 %, that exceeds the level known from literature. The accumulation process in the positron trap was studied with electron flux. The life time of the electrons in the trap is 80 s and capture efficiency is about 0.4. The maximum number of the accumulated particles is 2·10⁺⁸ at the initial flux of 5·10⁺⁶ electrons per second.
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WEM1C03	Analysis of Resonances Induced by the SIS-18 Electron Cooler	121
	S. Sorge, O. Boine-Frankenheim, G. Franchetti GSI, Darmstadt
	Due to the requirements concerning the quality of the particle beams in the FAIR project, i.e. a small momentum uncertainty together with high currents and, in the case of the storage rings, particle target interaction, there will be a strong need of electron cooling. On the other hand, an electron cooler acts as a non-linear optical element besides electron cooling. This may lead to the excitation of resonances possibly resulting in an increase of the emittance. The aim of this work is the calculation of resonances driven by the electron cooler in the Schwerionensynchrotron (SIS) 18 being a present device at GSI Darmstadt having an electron cooler. So, we get the opportunity to prove our results experimentally. For our calculations, we used a model system consisting of a rotation matrix representing the lattice and giving the according phase advance, and a non-linear transverse momentum kick representing the electron cooler in thin lens approximation. Proceeding in this way, we got only the resonances driven by the cooler. Furthermore, we used the MAD-X code to perform our calculations.
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WEM2C04	Status of VORPAL Friction Force Simulations for the RHIC II Cooler
	D. L. Bruhwiler, G. I. Bell, A. V. Sobol Tech-X, Boulder, Colorado I. Ben-Zvi, A. V. Fedotov, V. Litvinenko BNL, Upton, Long Island, New York
	Funding: This work is supported by the US DOE Office of Science, Office of Nuclear Physics. Novel electron-hadron collider concepts are a high priority for the long-term plans of the international nuclear physics community. Orders of magnitude higher luminosity will be required for the relativistic ion beams in such particle accelerators. Electron cooling of highly relativistic ions is under consideration for the proposed RHIC II luminosity upgrade. The parallel VORPAL code is being used for molecular dynamics simulations of the friction force on individual ions, given expected parameters of the RHIC II cooling system, including the effects of an idealized helical undulator magnet and of estimated magnetic field errors. The well-known analytical formula for the field-free case is the basis for physical intuition regarding dynamical friction, but this is derived under the assumption of very long interaction times and symmetric ion/electron collisions. For RHIC II parameters, the interaction time is short compared to the electron plasma frequency, so there is essentially no shielding of the ion charge and one must consider finite time effects and asymmetric collisions. We present the current status of this work.
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THM2I06	Electron Beams as Stochastic 3D Kickers	154
	V. B. Reva, A. V. Ivanov, V. V. Parkhomchuk BINP SB RAS, Novosibirsk
	This article describes an idea combining electron and stochastic cooling in one device. The amplified signal about displacements of the ion from pick-up electrode applied to the control electrode of an electron gun. Thus, a wave of the space charge in the electron beam is induced. This wave propagates with the electron beam to the cooling section. The space charge of the electron beam acts on the ion beam producing a kick. The effectiveness of the amplification can be improved with using a structure similar to a traveling-wave tube.
THAP01	Electron Cooling Simulation for Arbitrary Distribution of Electrons	159
	A. O. Sidorin, A. V. Smirnov JINR, Dubna, Moscow Region I. Ben-Zvi, A. V. Fedotov, D. Kayran BNL, Upton, Long Island, New York
	Typically, several approximations are being used in simulation of electron cooling process, for example, density distribution of electrons is calculated using an analytical expression and distribution in the velocity space is assumed to be Maxwellian in all degrees of freedom. However, in many applications, accurate description of the cooling process based on realistic distribution of electrons is very useful. This is especially true for a high-energy electron cooling system which requires bunched electron beam produced by an Energy Recovery Linac (ERL). Such systems are proposed, for instance, for RHIC and electron – ion collider. To address unique features of the RHIC-II cooler, new algorithms were introduced in BETACOOL code which allow us to take into account local properties of electron distribution as well as calculate friction force for an arbitrary velocity distribution. Here, we describe these new numerical models. Results based on these numerical models are compared with typical approximations using electron distribution produced by simulations of electron bunch through ERL of RHIC-II cooler.
THAP04	Optimization of the Magnet System for Low Energy Coolers	167
	A. V. Bubley, V. M. Panasyuk, V. V. Parkhomchuk, V. B. Reva BINP SB RAS, Novosibirsk
	Aspects of magnet design and field measurements are discussed in the view of low energy coolers construction. The paper describes some engineering solutions for the magnetic field improvement which provides appropriate conditions for the cooling process as well as electron and ion beams motion.
THAP06	Cooling in a Compound Bucket	171
	A. V. Shemyakin, C. M. Bhat, D. R. Broemmelsiek, A. V. Burov, M. Hu Fermilab, Batavia, Illinois
	Funding: FNAL is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. 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.
THAP08	Electron Cooling in the Recycler Cooler	175
	A. V. Shemyakin, L. R. Prost Fermilab, Batavia, Illinois A. V. Fedotov BNL, Upton, Long Island, New York A. O. Sidorin JINR, Dubna, Moscow Region
	Funding: FNAL is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. 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.
THAP09	Beam-based Field Alignment of the Cooling Solenoids for Fermilab’s Electron Cooler	179
	L. R. Prost, A. V. Shemyakin Fermilab, Batavia, Illinois
	Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy 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.
THAP10	Status of Design Work Towards an Electron Cooler for HESR	182
	B. Gålnander, T. Bergmark, O. Byström, S. Johnson, T. Johnson, T. Lofnes, G. Norman, T. Peterson, K. Rathsman, D. Reistad TSL, Uppsala H. Danared MSL, Stockholm
	Funding: Work supported by Uppsala University and by the European Union under FP6, Contract number 515873 - DIRAC Secondary Beams. The HESR-ring of the future FAIR-facility at GSI will include both electron cooling and stochastic cooling in order to achieve the demanding beam parameters required by the PANDA experiment. The high-energy electron cooler will cool antiprotons in the energy range 0.8 GeV to 8 GeV. The design is based on an electrostatic accelerator and shall not exclude a further upgrade to the full energy of HESR, 14.1 GeV. The beam is transported in a longitudinal magnetic field of 0.2 T and the requirement on the straightness of the magnetic field is as demanding as 10^-5 radians rms at the interaction section. Furthermore, care must be taken in order to achieve an electron beam with sufficiently small coherent cyclotron motion and envelope scalloping. This puts demanding requirements on the electron beam diagnostics as well as the magnetic field measuring equipment. Prototype tests of certain components for these tasks are being performed. The paper will discuss these tests and recent development in the design including the high-voltage tank, electron gun and collector, magnet system, electron beam diagnostics and the magnetic field measuring system.
	Poster
THAP12	Electron Cooling Design for ELIC - a High Luminosity Electron-Ion Collider *	187
	Y. S. Derbenev Jefferson Lab, Newport News, Virginia
	*Funding: Authored by Jefferson Science Associate under U. S. DoE Contract No. DE-AC05-06OR23177** 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.
FRM1C03	Electron Cooling with Photocathode Electron Beams Applied to Slow Ions at TSR and CSR	230
	D. Orlov, H. Fadil, M. Grieser, J. Hoffmann, C. Krantz, O. Novotny, S. Novotny, A. Wolf MPI-K, Heidelberg
	We report electron cooling experiments using a cold electron beam of 55 eV produced by a cryogenic GaAs photocathode. With this device the beam of singly charged ions with a mass of 31 amu, specifically the CF⁺ ion, was cooled at an energy of 3 MeV (about 90 keV/u). Transverse cooling within 2-3 seconds to a very small equilibrium beam size was observed with an electron current of 0.3 mA (electron density of 3×10⁶ cm^-3, magnetic guiding field of 0.04 T). A beam size of about 0.1 mm was deduced from imaging of recombination products. The short cooling times are mostly due to the low electron temperatures of 1 meV in transverse and 0.03 meV in longitudinal direction. An electrostatic Cryogenic Storage Ring (CSR) for slow ion beams, including protons, highly charged ions, and polyatomic molecules is under construction at the MPI-K. It will apply electron cooling at electron beam energies from 165 eV for 300 keV protons down to a few eV for polyatomic singly charged ions. Photoelectrons from the GaAs photocathode with laboratory energy spreads of about 10 meV [1] will be applied for generating such electron beams. In a storage ring of this type, even low electron-ion merging magnetic fields of toroids cause a strong coupling between the horizontal and vertical motions of the stored ions, reducing the ring acceptance to an intolerably low level. We present a new merging scheme of eV-electrons with stored ions, based on the idea of bringing electrons to the ion axis in a uniform dipole magnetic field superimposed to a straight solenoid field. The new magnetic field arrangement strongly improves the ring acceptance and allows to use guiding magnetic fields as high as required to provide high-quality electron beams of eV-energies for the cooling of ions and for merged beam studies in storage rings. [1] D. A. Orlov et al., Appl. Phys. Letters 78, 2721 (2001)
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FRM2C04	Studies of Cooling and Deceleration at CRYRING for FLAIR	234
	H. Danared, A. Källberg, A. Simonsson MSL, Stockholm
	It is planned that the CRYRING synchrotron and storage ring will be moved to the future FAIR facility at GSI. There it will be used as the Low-energy Storage Ring LSR at FLAIR (Facility for Low-energy Antiproton and Ion Research). LSR will mainly be used for deceleration of antiprotons from 30 MeV down to minimum 300 keV and for deceleration of highly charged ions in the same range of magnetic rigidities. As a preparation for the transfer of CRYRING to FAIR, studies have been made in order to evaluate the performance of CRYRING for deceleration of particles relevant to FLAIR and to set specifications for beams in and out of LSR. Deceleration of protons have been studied by first accelerating the particles to 30 MeV, then decelerating back to 300 keV again. Up to 3·10⁸ protons have been decelerated in 1.8 s without intermediate cooling, and requirements on longitudinal and transverse emittances at 30 MeV for successful deceleration have been estimated. Other studies have included investigations of the space-charge limit for protons at 300 keV and measurements of transverse cooling times for H^- ions, simulating antiprotons. Also an attempt to compare longitudinal cooling forces between protons and H^- ions has been made.
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FRM2C06	Electron Cooling Simulations for Low-energy RHIC Operation	243
	A. V. Fedotov, I. Ben-Zvi, X. Chang, D. Kayran, T. Satogata BNL, Upton, Long Island, New York
	Funding: Work supported by the U. S. Department of Energy 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.
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