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An electron target is proposed for high precision experimental measurement at the SRing (Spectrometry Ring) of HIAF (High Intensity heavy ion Accelerator Facility). It provides low temperature electron beam with a few meV for DR (Dielectronic Recombination) experiments at the energy of 1-��I{80}{keV}. For such a low temperature, the conventional method is adopted by magnetic adiabatic expansion with a factor of 30 after acceleration within 1.2T longitudinal magnetic field at gun section. In this paper, the design optimization of the electron target is introduced., Proceedings of the 13th International Workshop on Beam Cooling and Related Topics, COOL2021, Novosibirsk, Russia

Electron cooling continues to be an invaluable technique to reduce and maintain the emittance in hadron storage rings such as the EIC and EICC where stochastic cooling is inefficient and radiative cooling is negligible. Extending the energy range of electron coolers beyond what is feasible with the conventional, electrostatic approach necessitates the use of RF fields for acceleration and, thus, a bunched electron beam. To experimentally investigate how the relative time structure of the two beams affects the cooling properties, we have set up a pulsed-beam cooling device by adding a synchronized pulsing circuit to the conventional electron source of the CSRm cooler at Institute of Modern Physics. Using both constant and modulated synchronization between electron pulses and ion bunches, we have measured the effects of the electron bunch length and longitudinal ion focusing strength on the temporal evolution of the longitudinal and transverse ion beam profile and demonstrated the detrimental effect of timing jitter as predicted by space-charge theory and simulations. Our experiment suggests a need for further investigations of specific aspects of bunched cooling such as synchro-betatron coupling and phase dithering effects when using short electron bunches to cool longer ion bunches. However, given the comparatively long IBS lifetime of higher-energy proton storage rings like the EIC, slow dithering could potentially provide an option to save cost on the electron cooler linac., Proceedings of the 13th International Workshop on Beam Cooling and Related Topics, COOL2021, Novosibirsk, Russia

The High Intensity heavy-ion Accelerator Facility (HIAF) is under constructed at IMP in China. The HIAF main feature is rapid acceleration of ions in the booster synchrotron ring (BRing) with the ramping rate up to 12 T/s. The challenges are related to the systems RF cavities, dipole power supplies, vacuum etc. Works on key prototypes of the HIAF machine are ongoing at IMP. In this paper, the test results of the power supplies, RF cavities and vacuum chambers are presented. As the construction of the HIAF facility has started, an overview of the hardware developments will also be reported., Proceedings of the 27th Russian Particle Accelerator Conference, RuPAC2021, Alushta, Russia

The hadron beam cooling plays an important role in the future e-i collider machines to achieve various physical goals. In EicC, two-stage beam cooling scheme is proposed to maintain the luminosity during the long time collision. First, a traditional electron cooler will be used to pre-cool the low energy proton beam in the BRing. Then, an ERL-based electron cooler will be applied at the pRing to cool the proton beam at high energy. The main purpose of cooling is to counteract the emittance growth due to the IBS. In this paper, we focus on the high energy beam cooling and present some simulation studies on how the cooling rate will be affected by the electron bunch size, magnetic field, and ring parameters in the cooling section, which would be helpful for the cooler design., Proceedings of the 13th International Workshop on Beam Cooling and Related Topics, COOL2021, Novosibirsk, Russia

Cooling of hadron beams is critically important in the next generation of hadron storage rings for delivery of unprecedented performance. One such application is the electron-ion collider presently under development in the US. The desire to develop electron coolers for operation at much higher energies than previously achieved necessitates the use of radio-frequency (RF) fields for acceleration as opposed to the conventional, electrostatic approach. While electron cooling is a mature technology at low energy utilizing a DC beam, RF acceleration requires the cooling beam to be bunched, thus extending the parameter space to an unexplored territory. It is important to experimentally demonstrate the feasibility of cooling with electron bunches and further investigate how the relative time structure of the two beams affects the cooling properties; thus, a set of four pulsed-beam cooling experiments was carried out by a collaboration of Jefferson Lab and Institute of Modern Physics (IMP). The experiments have successfully demonstrated cooling with a beam of electron bunches in both the longitudinal and transverse directions for the first time. We have measured the effect of the electron bunch length and longitudinal ion focusing strength on the temporal evolution of the longitudinal and transverse ion beam profile and demonstrate that if the synchronization can be accurately maintained, the dynamics are not adversely affected by the change in time structure., Comment: 13 pages, 19 figures. Submitted to Physical Review Accelerators and Beams

Following the discovery of the Higgs boson at LHC, new large colliders are being studied by the international high-energy community to explore Higgs physics in detail and new physics beyond the Standard Model. In China, a two-stage circular collider project CEPC-SPPC is proposed, with the first stage CEPC (Circular Electron Positron Collier, a so-called Higgs factory) focused on Higgs physics, and the second stage SPPC (Super Proton-Proton Collider) focused on new physics beyond the Standard Model. This paper discusses this second stage., 34 pages, 8 figures, 5 tables

Intrabeam scattering is the main reason of degradation of the beam brightness and shortening of brightness lifetime in the collider, light source and storage ring. The intrabeam scattering presents dissimilar influence in the different facilities. Electron cooling was chose to suppress the effect of intrabeam scattering, another unexpected effect happened during the cooling. The distribution of ion beam quickly deviates from the initial Gaussian type, form a denser core and long tail. The ions standing in the tail of beam will loss soon due to large amplitude. This solution will focus on the investigation on the suppression of intrabeam scattering in the high intensity heavy ion beam in the storage ring with the help of longitudinally modulated electron beam. The stronger cooling was expected in the tail of ion beam and the weaker cooling was performed in the tail of ion beam. The particle in the outside will experience stronger cooling and will be driven back into the centre of ion beam. The ion loss will be decreased and the lifetime will be increased. The intensity of ion beam in the storage ring will be kept and maintain for long time., Proceedings of the 11th Workshop on Beam Cooling and Related Topics, COOL2017, Bonn, Germany

Two electron coolers are designed for the new project HIAF, one cooler with the highest energy 50keV is for the booster ring (BRing) to decreasing the transverse emittance of injected beams and another one with the highest energy 450keV is for the high precision Spec-trometer Ring (SRing). In this paper the results of the gun and collector simulation for these two electron coolers are presented. After optimization, the gun can produce 2A profile variable electron beam. The one time collecting efficiency is higher than 99.99%. The results of electron motions in toroid calculated by a numerical method are also summarized in this paper., Proceedings of the 11th Workshop on Beam Cooling and Related Topics, COOL2017, Bonn, Germany

A combination of electron cooling and RF system is an effective method to compress the beam bunch length in storage rings. A simulation code based on multi-particle tracking was developed to calculate the bunched ion beam cooling process, in which the electron cooling, Intra-Beam Scattering (IBS), ion beam space charge field, transverse and synchrotron motion are considered. Meanwhile, bunched ion beam cooling experiments have been carried out in the main cooling storage ring (CSRm) of the Heavy Ion Research Facility in Lanzhou (HIRFL), to investigate the minimum bunch length obtained by the cooling method, and study the dependence of the minimum bunch length on beam and machine parameters. It is observed that the IBS effect is dominant for low intensity beams, and the space charge effect is much more important for high intensity beams. The experimental results in CSRm shown a good agreement with the analytical model in the IBS dominated regime. The simulation work offers us comparable results to those from the analytical model both in IBS dominated and space charge dominated regimes., Proceedings of the 13th Symposium on Accelerator Physics, SAP2017, Jishou, China

Electron cooling at high energy is presently considered for several ion colliders, in order to achieve high luminosities by enabling a significant reduction of emittance of hadron beams. Electron beam at cooling channel in a few to tens MeV can be accelerated by a RF/SRF linac, and thus using bunched electrons to cool bunched ions. To study such cooling process, the DC electron gun of EC35 cooler was modified by pulsing the grid voltage, by which a 0.5-3.5 us of electron bunch length with a repetition frequency of less than 250 kHz was obtained. The first experiment demonstrated cooling coasting and bunched ion beam by a bunched electron beam was carried out at the storage ring CSRm at IMP. A preliminary data analysis has indicted the bunch length shrinkage and the momentum spread reduction of bunched 12C+6 ion beam. A longitudinal grouping effect of coasting ion beam by the electron bunch has also observed. In this paper, we will present the experiment result and its preliminary comparison to the simulation modeling., Proceedings of the 11th Workshop on Beam Cooling and Related Topics, COOL2017, Bonn, Germany

The pulsed electron beam can be applied to high ener-gy beam cooling and the researches of ion-electron inter-action in the future. In this paper, we studied the pulsed e-beam cooling effects on coasting and bunched ion beam by simulation code which is based on the theory of elec-tron cooling, IBS and space charge effect etc. In the simu-lation, a rectangular distribution of electron beam was applied to 7 MeV/u 12C⁶⁺ ion beam on CSRm. It is found that the coasting ion beam was bunched by the pulsed e-beam and the rising and falling region of electron beam current play an important role for the bunching effect, and similar phenomenon was found for the bunched ion beam. In addition, the analyses of these phenomena in simulation were discussed., Proceedings of the 11th Workshop on Beam Cooling and Related Topics, COOL2017, Bonn, Germany

A 13 Tm multifunction storage ring dedicated to nucleon and atomic experiment research - the SRing (Spectrometry Ring) is a significant part of the new heavy-ion research complex - HIAF (High Intensity heavy ion Accelerator Facility). In additional to an electron cooler and a gas internal target planned at the SRing, a beam of low temperature electron is also required to collide with the storage beam and to cool the decelerated ion beam at low energy. A magnetic adiabatic expansion is proposed to attain a low temperature by applying a 1.2 T longitudinal magnetic field upon the thermionic cathode at the electron gun. In this paper, preliminary design of the electron target is introduced., Proceedings of the 11th Workshop on Beam Cooling and Related Topics, COOL2017, Bonn, Germany

Cooling ion beams at high energy is presently considered for several ion colliders, in order to achieve high luminosities by enabling a significant reduction of emittance of hadron beams. Electron beam at cooling channel in a few to tens MeV can be accelerated by a RF/SRF linac, and thus using bunched electrons to cool bunched ions. To study such cooling process, the DC electron gun of EC35 cooler at the storage ring CSRm, IMP was modified by pulsing the grid voltage. A 0.07-3.5 micro-second pulse length with a repetition frequency of less than 250 kHz and synchronized with the ion revolution frequency was obtained. The first experimental demonstration of cooling of a coasting and bunched ion beam by a pulsed electron beam was carried out. Data analysis indicates the bunch length shrinkage and the momentum spread reduction of bunched 12C+6 ion beam as evidence of cooling. A longitudinal grouping effect of the coasting ion beam by the electron pulses has also been observed*. In this paper, we will present experimental results and comparison to the simulation modelling, particularly on the bunched electron cooling data after carefully analyzing the beam diagnostic signals., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

A combination of electron cooling and RF system is an effective method to compress the beam bunch length in storage rings. A simulation code based on multi-particle tracking was developed to calculate the bunched ion beam cooling process, in which the electron cooling, IntraBeam Scattering (IBS), ion beam space charge field, transverse and synchrotron motion are considered. In the paper, the cooling process was simulated for C beam in HIRFL-CSRm, and the result was compared with experiments, according to which the dependence of the minimum bunch length on beam and machine parameters was studied in the paper., Proceedings of the 13th Symposium on Accelerator Physics, SAP2017, Jishou, China

The motivation for formation of bunched electron beam at the electron cooler of CSRm is based on the three requirements. Firstly, the high energy electron cooling, especially, the ion beam with TeV energy, the bunched electron beam for cooling would be easier than the DC operating mode. Secondly, the electric field induced by the intensity modulated electron beam will be used for the suppression of instability developed in the high intensity ion beam after accumulation with the help of electron cooling, Thirdly, the electron beam was required to turn on and off in the different period of the atomic physics experiments. Some initial design and consideration were presented in this paper. And also the current situation and condition of CSRm electron cooler were described here. An off-line testbench will be established in the laboratory, and the test and the optimization will be explored in this experimentation. The validity of this system will be verified in the near future. The procedure of the modulation on the voltage of control electrode in the electron gun of the CSRm cooler was discussed. The scheme of off-line measurement was devised according to the progress., Proceedings of the Workshop on Beam Cooling and Related Topics, COOL2015, Newport News, VA, USA

In order to investigate the one-dimensional beam ordering in HIRFL-CSR, the ion beam of 58Ni19+ with the energy of 6.39 MeV/u was accumulated in the main ring of HIRFL-CSR with the help of electron cooling. The maximum accumulated ion beam intensity in the 10 seconds was measured, and the lifetime of ion beams was measured. The momentum spread of the ion beam varying with the particle number was measured during the ion beam decay, the power exponent was derived from these data, in additional, the momentum spread in the case of a constant particle number was plotted with the angle between ion and electron beams and electron beam profile. The oscillation and shift of the central frequency of the ion beam were observed during the experiments when the angle was large.

HIRFL-CSR, a new heavy ion cooler-storage-ring system at IMP, had been in commissioning since the beginning of 2006. In the two years of 2006 and 2007 the CSR commissioning was finished, including the stripping injection (STI), electron-cooling with hollow electron beam, C-beam stacking with the combination of STI and e-cooling, the wide energy-range synchrotron ramping from 7 MeV/u to 1000 MeV/u by changing the RF harmonic-number at mid-energy, the multiple multi-turn injection (MMI), the beam accumulation with MMI and e-cooling for heavy-ion beams of Ar, Kr and Xe, the fast extraction from CSRm and single-turn injection to CSRe, beam stacking in CSRe and the RIBs mass-spectrometer test with the isochronous mode in CSRe by using the time-of-flight method.

The 2 MeV electron cooler was installed in the COSY ring in the spring 2013. The new system enables electron cooling in the whole energy range of COSY. The electron beam is guided by longitudinal magnetic field all the way from the electron gun to the collector. This well-proven optics scheme was chosen because of the wide electron energy range of 0.025-2 MeV. The electrostatic accelerator consists of 33 individual sections of identical design. Electrical power to each section is provided by a cascade transformer. Electron beam commissioning and first studies using proton and deuteron beams were carried out. Electron cooling of proton beam up to 1662 MeV kinetic energy was demonstrated. Maximum electron beam energy achieved so far amounted to 1.25 MeV. Voltage up to 1.4 MV was demonstrated. The cooler was operated with electron current up to 0.5 A. The paper provides insights into the recent progress in high energy electron cooling at COSY and perspectives for the HESR ring at FAIR., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

Two electron cooling devices have been used at HIRFL-CSR in order to provide high quality heavy ion beams for nuclear and atomic research. The momentum spread is one of the most important characteristics of the beam quality. At HIRFL-CSR, the momentum spread is measured directly with the aid of longitudinal Schottky spectra system. In this paper, the measurements for various ion species are presented. At relatively high intensity, longitudinal Schottky spectra is double peak due to collective phenomena and the momentum spread can be obtained by fitting the spectra. The dependence of momentum spread on stored particle number is proportional to N**a. Moreover, the heating factor was investigated after switching off the electron cooling. The residual gas scattering, the intrabeam scattering and instabilities are studied according to the measured data., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan

The 2 MeV electron cooling system for COSY-Julich was proposed to further boost the luminosity in presence of strong heating effects of high-density internal targets. The 2 MeV cooler is also well suited in the start up phase of the High Energy Storage Ring (HESR) at FAIR in Darmstadt. It can be used for beam cooling at injection energy and for testing new features of the high energy electron cooler for HESR. The COSY cooler is designed on the classic scheme of low energy coolers like cooler CSRm, CSRe, LEIR that was produced in BINP before. The electron beam is transported inside the longitudinal magnetic field along whole trajectory from an electron gun to a collector. This optic scheme is stimulated by the wide range of the working energies 0.025-2 MeV. The electrostatic accelerator consists of 33 individual unify section. Each section contains two HV power supply and power supply of the magnetic coils. The electrical power to each section is provided by a cascade transformer. This report describes the cooler design, diagnostics, control system and the result of the commissioning in BINP and FZJ at the different energies., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The HIAF is a new accelerator complex under design at IMP to provide intense primary and radioactive ion beams for nuclear physics, atomic physics, high energy density physics and other applications. As a key part of HIAF, the Booster Ring (BRing) is designed to accumulate and accelerate heavy ion beams provided by iLinac up to high intensity and energy. The high quality, well focused, strongly bunched intense Uranium beam (U³⁴⁺) with high energy and high intensity of 10¹¹ will open a new area for the HED physics research in laboratory. Based on the beam parameters of 238U³⁴⁺ proposed by the BRing, the two critical issues of producing short bunch with high beam intensity are studied. One is efficiency of adiabatic capture which can be a necessary prerequisite to ensure the beam intensity, and the other one is bunch compression in longitudinal which is an effective way of producing short pulse duration bunch. In this article, the analytical calculations and tracking simulations are described, the capture efficiency and possible bunch length under the action of planning RF system are presented, Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark