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International audience; In the framework of the European Strategy Update on Particle Physics, the working group appointed to review the Muon Colliders has become the de facto seed of an on-going international effort. A muon collider, if demonstrated to be feasible, is a unique discovery machine and the best tool to fully study the Higgs potential, since it can offer collisions of point-like particles at very high energies, significantly surpassing the energy reach of other lepton colliders. It can even match the discovery potential of a proton collider with much higher energy, since the muon collision energy is fully available at the constituent level unlike for protons. The need for high luminosity faces technical challenges which arise from the short muon lifetime at rest and the difficulty of producing large numbers of muons in bunches with small emittance. Addressing these challenges requires the development of innovative concepts and demanding technologies, exploiting synergies with other new accelerator projects. A plan to launch the studies for a vigorous and conclusive R&D programme has been presented and is under discussion. A well-focused international community will be required to exploit existing key competencies and to develop such a novel and promising project for the future of High Energy Physics.

A muon collider would be both a precision and a powerful discovery machine, because it can offer collisions of point-like particles at very high energies, strongly exceeding the energy reach of other lepton colliders. It can even match the discovery of a proton collider with much higher energy, since the muon collision energy is fully available at constituent level unlike for the protons. However, the need for high luminosity faces technical challenges which arise from the short muon lifetime at rest and the difficulty of producing large numbers of muons in bunches with small emittance. Addressing these challenges requires the development of innovative concepts and demanding technologies. In view of the potential importance of muon colliders for the future of high-energy physics it is timely to start an R&D; programme now. A high-energy muon collider is receiving renewed attention as a possible frontier-exploration machine. Daniel Schulte, Nadia Pastrone and Ken Long describe the possible paths ahead.

Novosibirsk FEL facility is based on the first in the world multi-turn energy recovery linac (ERL). It comprises three FELs (stages). FELs on the first and the second tracks were commissioned in 2004 and 2009 respectively and operate for users now. The third stage FEL is installed on the fourth track of the ERL. It includes three undulator sections and 40-meters-long optical cavity. The design tuning range of this FEL is from 5 to 20 microns and the design average power at bunch repetition rate 3.74 MHz is about 1 kW. Recent results of the third stage FEL commissioning are reported.

The Novosibirsk free electron laser is the first multi-turn energy-recovery linear accelerator with three separate laser systems (the terahertz, far-infrared and mid-infrared ones). The facility is well equipped with optical elements and instrumentation available to Russian and foreign users. In this paper, we describe in brief the workstations of the facility and survey selected recent experiments using intense monochromatic terahertz laser radiation, which can be tuned from 90 to 240 μm.

The design and operational characteristics of the Novosibirsk free electron laser facility are described. Selected experiments in the terahertz range carried out recently at the user stations are surveyed in brief.

Novosibirsk free electron laser (FEL) facility contains three FELs operating in the wavelength range 8–240 micron at average power up to 0.5 kW and peak power about 1 MW. Radiation users works at 6 user stations performing biological, chemical, physical and medical research.

The scheme of final cooling for muon beams, based on using current-carrying liquid-lithium rods, is discussed. The dynamics of particles in the course of cooling taking into account the non-paraxial motion has been studied with the help of computer simulation. It is suggested to minimize the effective increase of the longitudinal emittance caused by fluctuations of ionization losses and large angular spread, by the rotation of the longitudinal phase-space portrait for arranging self-action. We have considered the non-dissipative multiple successive full emittance redistribution from the longitudinal dimension to transverse one, necessary for cooling of all degrees of freedom. This redistribution is based on special rotations of the particle six-dimensional phase space by the beam division in several streams and their consequent merging with the minimum increment of full emittance and minimal beam losses taking into account their local phase-space density. Some of the basic technical parameters of the cooling system elements have been estimated.

An overview of electron–positron colliders and experiments on them currently performed and prepared at the Budker Institute of Nuclear Physics is presented. They include a new collider VEPP-2000 (an upgrade of the VEPP-2M collider) with CMD-3 and SND experiments, the VEPP-4M collider with the KEDR detector and the electron/positron injection complex.

The first stage of Novosibirsk high-power free electron laser (FEL) was commissioned in 2003. It is based on the normal conducting CW energy recovery linac (ERL). Now the FEL provides electromagnetic radiation in the wavelength range 120–230 μm. The maximum average power is 400 W. The minimum measured linewidth is 0.3%, which is close to the Fourier-transform limit. Four user stations are in operation now. Manufacturing of the second stage of the FEL (based on the four-turn ERL) is in progress.

Relativistic beams produced by the VEPP-5 injection complex (Budker Institute of Nuclear Physics, Siberian Division, Russian Academy of Sciences) can be used to generate plasma waves with a longitudinal electric field of 1 GV/m. A part of the electron (or positron) driver bunch is accelerated by this field over a distance of up to 1 m. The main advantage of the proposed design over the previous wakefield acceleration experiments is the beam preparation system capable of compressing bunches to a length of σz = 0.1 mm in the longitudinal direction and producing an optimal longitudinal profile of the beam density. The main parameters of the planned device are as follows: the electron energy at the entrance to the plasma is 510 MeV, the number of particles in the bunch is 2 × 1010, the plasma density is up to 1016 cm−3, the number of accelerated particles is up to 3 × 109, and their energy spread is less than 10%. The physical project of the experiment is presented, and the results of computer simulations of the beam-plasma interaction are described.

The first lasing near wavelength 140 μm was achieved in April 2003 on a high-power free electron laser (FEL) constructed at the Siberian Center for Photochemical Research. In this paper, we briefly describe the design of FEL driven by an accelerator–recuperator. Characteristics of the electron beam and terahertz laser radiation, obtained at the first experiments, are also presented in the paper.

Activities of the Budker Institute of Nuclear Physics in the field of high-energy physics are reviewed. The most interesting results as well as plans for future are discussed.

A high-power infrared free electron laser is under construction in Novosibirsk. As the full-scale machine seems to be complicated and quite expensive, the project was divided into two stages so that the first-stage machine can be assembled and commissioned as soon as possible. Main features of the project and the current status are described.

The new approach for the fourth generation X-ray source—Multiturn Accelerator–Recuperator Source (MARS)—was proposed recently. The installation consists of the radiofrequency (RF) multiturn accelerator (similar to the race-track microtron) and long undulator(s). After passing through the undulator(s) the electron beam is decelerated in the same RF accelerating structure. Such energy recovery reduces dramatically the radiation hazard and decreases the required RF power. In this paper we present a more detail explanation of this scheme, and specify further the parameter limitations and requirements for the accelerator.

Limitation of the luminosity caused by the beam–beam interaction is one of the major obstacles in future colliders. In order to suppress this interaction, there was proposed to intercept the colliding beams with a plasma at the interaction region. In this paper, the theory of plasma compensation of beams’ electric and magnetic fields is developed for arbitrary densities of beams and the plasma. Because of nonlinear effects, the compensation is shown to depend on the charge of beam particles. The optimum plasma thickness ensuring maximum suppression of the beam–beam effects is found. An analytical expression for the compensation degree in the linear approximation in the case of a finite-thickness plasma is derived, and the criterion of applicability of the linear model is obtained.

Radiative decays of the φ meson have been studied using a data sample of about 20 million φ decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From selected e + e − → π + π − γ events the φ → π + π − γ decay has been observed for the first time. Under the assumption that the intermediate f 0 (980) γ state dominates in the φ → π + π − γ decay, the corresponding branching ratio is Br ( φ → f 0 (980) γ )=(1.93±0.46±0.50)×10 −4 . Selected e + e − → μ + μ − γ events were used to obtain Br ( φ → μ + μ − γ )=(1.43±0.45±0.14)×10 −5 for E γ >20 MeV. Using the same data sample, upper limits at 90% CL have been obtained for the C-violating decay of the φ : Br ( φ → ργ ) −5 ; and for the P- and CP-violating decay of the η : Br ( η → π + π − ) −4 .

The proton accelerator complex for neutron production in lithium target discussed, which can operate in two modes. The first provides a neutron beam kinematically collimated with good forward direction in 25° and average energy of 30 keV, directly applicable for neutron-capture therapy with high efficiency of proton beam use. The proton energy in this mode is 1.883–1.890 MeV that is near the threshold of the 7 Li ( p , n ) 7 Be reaction. In the second mode, at proton energy of 2.5 MeV, the complex-produced neutron beam with maximum energy board of 790 keV which can be used directly for fast neutron therapy and for neutron-capture therapy after moderation. The project of such a neutron source is based on the 2.5 MeV original electrostatic accelerator tandem with vacuum insulation developed at BINP which is supplied with a high-voltage rectifier. The rectifier is produced in BINP as a part of ELV-type industrial accelerator. Design features of the tandem determining its high reliability in operation with a high-current (up to 40 mA) H − ion beam are discussed. They are: the absence of ceramic accelerator columns around the beam passage region, good conditions for pumping out of charge-exchange gaseous target region, strong focusing optics and high acceleration rate minimizing the space charge effects. The possibility of stabilization of protons energy with an accuracy level of 0.1% necessary for operation in the near threshold region is considered. The design description of H − continuous ion source with a current of 40 mA is also performed. To operate with a 100 kW proton beam it is proposed to use liquid-lithium targets. A thin lithium layer on the surface of a tungsten disk cooled intensively by a liquid metal heat carrier is proposed for use in case of the vertical beam, and a flat liquid lithium jet flowing through the narrow nozzle – for the horizontal beam.

Requirements of high-energy physics impose some restrictions on parameters of future plasma-based accelerators; these restrictions are analyzed for the accelerator driven by particle beams. With two-dimensional simulations of driver dynamics it is shown that properly prepared 10 GeV electron driver can accelerate up to 5×109 particles with energy gain of about 10 GeV in 10 m long plasma section and with energy spread less than 5%. On the basis of these simulations, the draft concept of high-gradient linear collider of TeV-range energy is briefly considered. To prove the possibility of precise driver handling and to test simulation results, the experiment is under preparation at Budker Institute, Novosibirsk. The modulated electron beam (0.8 GeV) is expected to excite the electric field up to 0.5 GeV/m at the distance of about 1 m.

In this paper, we report first lasing results in the near-UV and visible spectral ranges with the OK-4/Duke storage ring – the first storage ring FEL operating in the United States. The OK-4/Duke FEL was commissioned in November 1996 and demonstrated lasing in the 345–413 nm range with extracted power of 0.15 W. In addition to lasing, the OK-4/Duke FEL generated a nearly monochromatic (1% FWHM) γ-ray beams. In this paper, we describe initial performance of the OK-4/Duke storage ring FEL and γ-ray source in this demonstration experiment. We briefly discuss the present status of the project and its future user program.

The first stage of the Novosibirsk high-power free-electron laser (FEL) was commissioned in 2003. It is driven by a CW energy recovery linac. The next step will be the full-scale machine, a four-track accelerator-recuperator based on the same RF accelerating structure. This upgrade will permit to get shorter wavelengths in the infrared region and increase the average power of the FEL by several times. The scheme and some technical details of the project are set out. The installation will be a prototype for future multiturn accelerator-recuperators.

The decay φ → η ′ γ has been observed by the CMD-2 detector at the e + e − collider VEPP-2M at Novosibirsk. Of 5.5 million produced φ 's, six events of the φ → η ′ γ decay were selected with the expected background less than one event. The corresponding branching ratio is B( φ → η ′ γ )=1.2 +0.7 −0.5 ·10 −4 . It is the first observation of this radiative decay.

A search for φ radiative decays has been performed using a data sample of about 2.0 million φ decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From the selected e + e − → π + π − γ events the following results were obtained: B( φ → f 0 (980) γ ) −4 for destructive and B( φ → f 0 (980) γ ) −4 for constructive interference with the Bremsstrahlung process respectively, B( φ → γ → π + π − γ ) −5 for E γ >20 MeV, B( φ → ργ ) −4 . From the selected e + e − → μ + μ − γ events B( φ → μ + μ − γ )=(2.3±1.0)×10 −5 has been obtained for E γ >20 MeV. The upper limit on the P,CP-violating decay η → π + π − has also been placed: B( η → π + π − ) −4 . All upper limits are at 90% C.L.

A nearly monochromatic beam of 100% linearly polarized g rays has been produced via Compton backscattering inside a free electron laser optical cavity. The beam of 12.2 MeV g rays was obtained by backscattering 379.4 nm free-electron laser photons from 500 MeV electrons circulating in a storage ring. A detailed description of the g-ray beam and the outlook for future improvements are presented. [S0031-9007(97)03322-X]

The scheme of antihydrogen generation using storage rings proposed recently [1] permits one to obtain intense and fine directed fluxes of antihydrogen and orthopositronium atoms. Experimental studies of such objects demand a specific experiment set-up. The possibility to generate extremely slow atoms is of special interest. Further development of the proposed scheme and possible experimental studies of generated atoms are discussed in this report.

In this paper, the current status and the upgrading plans for the near future of the electron-positron colliders VEPP-2M and VEPP-4 are briefly described. The ongoing program for the design and construction of the electron-positron factory complex VEPP-5 is presented.

The scheme of antihydrogen beam generation is proposed. Two storage rings should be used for effective generation of antihydrogen - an antiproton ring and a small additional one for storing and cooling of positrons. This scheme has advantages compared with those discussed earlier due to the use of a longitudinal magnetic field as the focusing system of the positron ring with the positron source immersed in this field. The electron cooling of positrons is an essential part of the project. The Low Energy Antiproton Ring (LEAR) at CERN is chosen as the basic machine for idea demonstration and all the numerical applications are made for it. The rate of antihydrogen generation is limited in the case discussed here by the positron source intensity. The simplest version of this scheme permits one to achieve a rate of about 3 × 10 4 fast (50 MeV) atoms/s and 30 slow (0.5 MeV) ones. Simultaneously such a scheme is a generator of orthopositronium with a productivity of about 2 × 10 4 and 35 “atoms”/s, correspondingly. The particle dynamics in the positron storage ring are considered.

The high power infrared free electron laser is under construction at the Novosibirsk Scientific Centre. The goal of this project is to provide a user facility for Siberian Centre of Photochemical Researches. The features of the installation and its status are described.

In the last decade the Siberian SR Centre has implemented a wide program of SR and FEL research in cooperation with various research centres and institutions in Russia and abroad. The report illustrates this program, including joint experiments with the use of SR and FEL sources available at the Budker Institute of Nuclear Physics, the implementation of new joint projects in Novosibirsk and in the other centres, as well as the delivery of equipment to foreign countries, designed and manufactured at the Budker INP or in collaboration with Russian industry. Some technical information on the storage rings-SR sources, wigglers, undulators and free electron lasers which are being constructed, used or developed at the Budker INP, is given.

High power THz applications on the Novosibirsk terahertz free electron laser are described.

Creation of a fully spatial coherent 4th generation SR source is possible in case of a shift from the electron storage rings to accelerators with energy recovery. However, in practice, all the projects assume the use of a single‐turn version (ERL) compared to our first proposal of 1997 to use a multi‐turn accelerator‐recuperator (MARS). The purpose of this report is presentation of the modern conception of MARS and comparison of the ERL and MARS based radiation sources from the viewpoint of their realization in practice.

The main aim of the next-generation synchrotron radiation sources is to provide diffraction-limited undulator radiation in the 0.1–4 nm range with an average power of 10–1000 W and monochromaticity of 10−3–10−4. A review of new accelerator technologies that could be used for the construction of such types of synchrotron radiation sources is given.

HIRFL-CSR, a new ion accelerator complex, is under construction at IMP, Lanzhou, China. It is equipped with two electron cooling devices. This article describes the commissioning of cooler at electron energy 300 keV. The cooler is one of the new coolers with some unique manufactured in BINP, Russia. It has a new electron gun producing a hollow electron beam, electrostatic bending and a new structure of solenoid coils at the cooling section. The test results of cooler obtained in Novosibirsk and Lanzhou are reported.

The subject of the report is the problem of the technical feasibility of fast electron cooling in the energy range between 0.8 and 14.5 GeV. It is very useful for one of the major objectives of the GSI and COSY future plans. For the realization of the cooler device BINP team proposes the design that is like the conventional and elaborated for the low energy cooling (up to 300 keV). The main features of this design are the accelerating tube immersed in the magnetic field along the whole length and the strong magnetic field in the cooling section. The physics of electron cooling is based on the idea of the fast magnetized cooling. The cooling force at strong magnet field was measured at many experiments and can be surely estimated. The magnetized cooling rate enables to obtain the required beam parameters, eliminate the beam heating due to intrabeam scattering, fluctuations of ionization energy losses and multiple scattering in the internal target.

The first stage of Novosibirsk high-power free-electron laser (FEL) was commissioned in 2003. It is based on a normal conducting CW energy recovery linac. Now the FEL provides electromagnetic radiation in the wavelength range of 120…180 micrometers. An average power is 400 W. The minimum measured line width is 0.3%, which is close to the Fourier-transform limit. A user-beamline assembly is in progress, parts of the full-scale machine are manufactured. The latter will operate in the near IR region and provide higher average power В 2003 году в Новосибирске заработала первая очередь мощного лазера на свободных электронах (ЛСЭ). Машина построена на базе линака-рекуператора непрерывного действия. В настоящее время ЛСЭ работает в диапазоне длин волн 120…180 мкм, его средняя мощность достигает 400 Вт. Минимальная измеренная ши- рина полосы излучения составляет 0.3%, что близко к теоретическому минимуму. В настоящее время монтируются каналы разводки излучения для пользователей, части полномасштабной машины запущены в производство. Полномасштабная машина будет работать в ближнем ИК-диапазоне и обладать большей мощностью. В 2003 році в Новосибірську заробила перша черга потужного лазера на вільних електронах (ЛВЕ). Машина побудована на базі лінака-рекуператора безперервної дії. Зараз ЛВЕ працює в діапазоні довжин хвиль 120...180 мкм, його середня потужність досягає 400 Вт. Мінімальна виміряна ширина смуги випромінювання становить 0.3%, що близько до теоретичного мінімуму. Зараз монтуються канали розведення випромінювання для користувачів, частини повномасштабної машини запущені у виробництво. Повномасштабна машина буде працювати в ближньому ІЧ-діапазоні і мати більшу потужність.

The first experience of the application of film micropore filters with regularly spaced holes of 0.4 μm in diameter for X-ray fluorescent elemental analysis of atmospheric aerosols and water suspensions is described.

To provide a user facility for the Siberian Centre of Photochemical Researches in Novosibirsk a high power free electron laser is under construction. The project status and installation are described.

We describe the status of our effort to realize a first neutrino factory and the progress made in understanding the problems associated with the collection and cooling of muons towards that end. We summarize the physics that can be done with neutrino factories as well as with intense cold beams of muons. The physics potential of muon colliders is reviewed, both as Higgs Factories and compact high energy lepton colliders. The status and timescale of our research and development effort is reviewed as well as the latest designs in cooling channels including the promise of ring coolers in achieving longitudinal and transverse cooling simultaneously. We detail the efforts being made to mount an international cooling experiment to demonstrate the ionization cooling of muons., Comment: 112 pages, Large report

A low-energy positron beam is a unique probe of materials. In high-energy electron and positron storage rings it is possible to generate intense synchrotron radiation with a photon energy of 1–3 MeV by installing a high-field (8–10 T) superconducting wiggler. High-energy photons are converted to low-energy positrons by using a suitable target–moderator system. For an 8 GeV electron storage ring at a beam current of 100 mA, final yields are estimated to be about 108–1010 slow-e+ s−1 or larger depending on the moderation efficiency, with the size of the positron source 101–102 cm2. In the present work a wiggler magnetic system of 10 T is proposed. The main parameters of the superconducting wiggler are presented.

The integrated luminosity about 4000 inverse nanobarn of around phi meson mass ( 5 millions of phi mesons) has been collected with the CMD-2 detector at the VEPP-2M collider. A latest analysis of the KS KL coupled decays based on 30 % of available data is presented in this paper. The KS KL pairs from phi meson decays were reconstructed in the drift chamber when both kaons decayed into two charged particles. From a sample of 1423 coupled decays a selection of candidates to the CP violating KL into pi+ pi- decay was performed. CP violating decays were not identified because of the domination of events with a KL regenerating at the Be beam pipe into KS and a background from KL semileptonic decays. The regeneration cross section of 110 MeV/c KL mesons was found to be 53 +- 17 mb in agreement with theoretical expectations. The angular distribution of KS mesons after regeneration and the total cross section of KL for Be have been measured., Comment: 14 pages, 8 figures

A short review of ionization cooling features, important for the preparation of muon beams for a high luminosity collider, is presented. Some new approaches to obtain ultimate efficiency of muon production, including polarized ones, as well as some practical limits, are considered briefly.

The Novosibirsk FEL (NovoFEL) generates tunable monochromatic coherent radiation as a continuous stream of 100-ps pulses with a repetition rate of up to 11.2 MHz and average power of up to 500 W. After commissioning of the second laser resonator in 2010, the spectral ranges of 120–240 μm and 40–80 μm are available to users. A review of experimental results for the past year is given.