Storage ring with longitudinal magnetic field LEPTA (Stellatron)

The project of the Low Energy Particle Toroidal Accumulator (LEPTA) is dedicated to the construction of a positron storage ring with electron cooling of positrons circulating in the ring. Such a specific feature of LEPTA automatically enables it to be a generator of positronium (Ps) atoms, which appear in the recombination of positrons with cooling electrons inside the cooling section of the ring. The project has the following goals: particle dynamics in the modified betatron, electron cooling with a circulating beam, positronium generation in flight, positronium physics, and feasibility of antihydrogen generation in flight. All key elements of the ring—the kicker, electron beam injection system, helical quadrupole, septum magnet—have been tested, and the expected design parameters have been achieved for these elements. The construction of LEPTA has been completed, and the circulating electron beam has been achieved. This paper discusses the issues of particle dynamics in such an accelerator, the results of numerical simulation and experimental findings of the research into beam dynamics, measurement of betatron number and beam lifetime.     

Development of the Low Energy Particle Toroidal Accumulator project

The Low Energy Particle Toroidal Accumulator (LEPTA), a positron storage ring with electron cooling, was constructed and put in operation at the Joint Institute for Nuclear Research (Dubna). The storage ring is a generator of directed beams of ortho-positronium (o-Ps) produced upon the recombination of the beam of positrons circulating in the storage ring with a single-pass electron beam. In 2004 the storage ring was put in operation with the circulating electron beam. The source of positrons of the positron injector was tested with a new radioactive source delivered from South Africa. The positron trap was put in operation for electrons. The electron cooling system was tested with a pulsed electron beam. The progress in commissioning LEPTA is described in this paper.     

Precision supply system of the group of magnetic elements of the Low-Energy Particle Toroidal Accumulator

An individual power supply source is usually used for each group of identical magnetic elements in accelerators of charge particles. We discuss the power supply and control system on the basis of additional current shunts applied for the simultaneous supply of several groups of magnets in the positron storage ring of the Low-Energy Particle Toroidal Accumulator (LEPTA). Data on the use of the shunt of the linear and key converter are given. The option of the device of a power supply system with the transformation of the recuperated energy in the storage battery and supply from it of the precision power supply sources of the LEPTA correcting magnets is considered. A channel of the individual digital transformation of power supply system elements is given which allows one to build, together with a reverse precision converter, effective intellectual balanced power supply systems.     

Intellectual system for power supply and control of magnetic component groups of particle accelerators from several MW-power sources

It is necessary for the power-consuming magnetic components of channels for beam transport in accelerators of charged particles be supplied with direct current. An individual power source is typically applied for each group of identical components. A variant of the simultaneous supply of several groups of magnets from a single medium-power source using auxiliary current shunts of different types is given by the example of a LEPTA positron storage ring. One version of using this technology with MW-power sources for a phasotron accelerator is developed. The efficiency of putting this technology into practice with the application of start-stop regimes for the phasotron is estimated.     

Low emittance lattice for the storage ring of the Turkish Light Source Facility TURKAY

The TAC(Turkish Accelerator Center) project aims to build an accelerator center in Turkey. The first stage of the project is to construct an Infra-Red Free Electron Laser(IR-FEL) facility. The second stage is to build a synchrotron radiation facility named TURKAY, which is a third generation synchrotron radiation light source that aims to achieve a high brilliance photon beam from a low emittance electron beam at 3 Ge V. The electron beam parameters are highly dependent on the magnetic lattice of the storage ring. In this paper a low emittance storage ring for TURKAY is proposed and the beam dynamic properties of the magnetic lattice are investigated.     

BEPCⅡ Positron Source

BEPCⅡ— an upgrade project of the Beijing Electron Positron Collider (BEPC) is a factory type of e^＋e^－ collider. The fundamental requirements for its injector linac are the beam energy of 1.89GeV for on-energy injection and a 40mA positron beam current at the linac end with a low beam emittance of 1.6μm and a low energy spread of ±0.5% so as to guarantee a higher injection rate (≥50mA/min) to the storage ring. Since the positron flux is proportional to the primary electron beam power on the target, we will increase the electron gun current from 4A to 10A by using a new electron gun system and increase the primary electron energy from 120MeV to 240MeV. The positron source itself is an extremely important system for producing more positrons, including a positron converter target chamber, a 12kA flux modulator, the 7m focusing module with DC power supplies and the support. The new positron production linac from the electron gun to the positron source has been installed into the tunnel. In what follows, we will emphasize the positron source design, manufacture and tests.     

The Turkish accelerator complex IR FEL project

Turkish accelerator complex (TAC) project was approved by State Planning Organization (DPT) of Turkey in 2006. The complex will contain a linac-ring type electron–positron collider as a particle factory and different accelerator based light sources. As a first step to the national center, the construction of an IR FEL facility is planned until 2011. It is also planned that the technical design report for TAC will be completed in 2010. The TAC IR FEL facility will consist of an electron linac in the range of 15–40 MeV energy to obtain FEL in 2–185 microns range. In this study, the preliminary parameters of TAC IR FEL facility were presented. The possible using of the obtained FEL in material science, nonlinear optics, semiconductors, biotechnology, medicine and photochemical processes were discussed.     

Experiments on the physics of charged particle beams at the VEPP-4M electron-positron collider

The VEPP-4M accelerator facility with a universal KEDR detector is designed to conduct experiments with colliding electron-positron beams. High-energy physics, nuclear physics, and studies using synchrotron radiation are the main directions of research with this facility. In addition, experiments on poorly explored issues in the physics of beams in the electron-positron storage ring and methodological studies to prepare an experiment aimed at testing corollaries of the CPT theorem for an electron and a positron are regularly conducted at the VEPP-4 facility. A number of works performed in recent years are described: studies to increase the accuracy of comparing the electron and positron spin precession frequencies by the resonant depolarization method; measurements of the count rate of Touschek electrons as a function of the beam energy in a wide range; comparison of the methods for measuring the beam energy spread; a study of the electron beam dynamics when a nonlinear betatron resonance is crossed.     

Experiments at the Giessen source TEPOS with low energy positrons

The TEPOS facility at the Giessen LINAC delivers intense positron beams in the energy range between some eV and 6 keV; with postacceleration up to 80 keV. Results for remoderation and positron storage will be discussed. Further the energy-loss of positrons in thin aluminium foils at incident energies of 6–20 keV was measured. Cross sections for K- and L-shell ionization of thin silver and gold targets by positron and electron impact were determined at projectile energies of 30–70 keV. The experimental results are presented in detail; they are confirmed by calculations in plane wave Born approximation (PWBA) which include an electron exchange term and take into account the deceleration or acceleration of the incident projectile in the nuclear field of the target atom.     

Electrostatic ultra-low-energy antiproton recycling ring

There is a strong need to push forward developments in the storage and control of ultra-low-energy antiproton beams to enable important scientific research. To this end, a small electrostatic ring, and associated electrostatic acceleration section, is being designed and developed by the QUASAR group. The ring will be placed on the MUSASHI beamline at the CERN-AD. It will serve as a prototype for the future ultra-low energy storage ring (USR), to be integrated at the facility for low-energy antiproton and ion research (FLAIR) and will enable various components of the USR to be tested and optimised. A reaction microscope will be integrated in the ring to enable partial ionisation cross section measurements to be made. This small recycler ring will be unique due to its combination of size, electrostatic nature and energy and type of circulating particles (ca 3?C30 keV antiprotons). A short electrostatic accelerating section is also being developed, which will be placed between the beamline and the ring to accelerate the antiprotons from the trap extraction energy (typically 250 eV) to the final required (re-circulating) energy. The AD recycler project will be described, including ring design, accelerating injection section and the inclusion of a reaction microscope and the experiments it will enable.     

Positron injector for LEPTA

The low energy positron injector for the Low Energy Particle Toroidal Accumulator (LEPTA) accumulator was assembled at the Joint Institute for Nuclear Research (JINR). Key elements of the injector have been tested. The cryogenic source of slow positrons was tested with a test isotope ²²Na of the initial activity of 0.8 MBk. A continuous slow positron beam intensity of 5.8 × 10³ particle per second with an average energy of 1.2 eV and a spectrum width of 1 eV has been obtained. The achieved moderator efficiency is about 1%. The accumulation process in the positron trap was investigated with electron flux. The lifetime of the electrons in the trap, τ_life ≥ 80 s and capture efficiency ɛ ∼ 0.4, were obtained. The maximum number of accumulated particles was N _exper = 2 × 10⁸ at the initial flux of 5 × 10⁶ electrons s⁻¹. The text was submitted by the authors in English.     

Synchrotron Stories from Stanford—From a Parking Lot to First Beam

Our journey in synchrotron radiation started in July 1972 when we joined a group at Stanford led by Seb Doniach and Bill Spicer to build a “Pilot Project” to test the feasibility of performing X-ray photoemission experiments on the newly commissioned SPEAR storage ring at SLAC. The SPEAR ring was expressly built for high-energy physics using colliding electron and positron beams (ultimately discovering the existence of quarks and garnering two Nobel prizes). As a result, anything we did could not interfere with the high-energy physics experiments.     

Infrared Applications at ANKA

ANKA is a relatively new synchrotron radiation facility at the Forschungszentrum Karlsruhe, a large government research center in the southwest of Germany. The acronym stands for Angstrom Source Karlsruhe. The electron storage ring is 110.4 m in circumference and stores a 2.5 GeV electron beam at a typical current of 200 mA. The facility has been open for users since March 2003.     

ON THE AVERAGE LUMINOSITY OF ELECTRON POSITRON COLLIDER AND POSITRON-PRODUING ENERGY

In this paper, the average luminosity of linac injected electron positron collider is investigated from the positron-producing energy point of view. When the energy of the linac injector is fixed to be less than the operating energy of the storage ring, it has been found that there exists a positron-producing energy to give optimum average luminosity. Two cases have been studied, one for an ideal storage ring with no single-beam instability and the other for practical storage ring with fast head-tail instability. The result indicates that there is a positron-producing energy corresponding to the minimum injection time, but this does not correspond to the optimum average luminosity for the practical storage rings. For Beijing Electron Positron Collider (BEPC), the positron-producing energy corresponding to the optimum average luminosity is about one tenth of the total injector energy.     

BEPC中电子云导致的束团横向尺寸增长研究

多束团正电子储存环中可能发生电子云不稳定性. 由于电子云导致的束团横向尺寸增长已经成为提高对撞机对撞亮度的主要限制因素之一. 介绍了在BEPC储存环中, 利用条纹相机直接测量由于电子云导致的束团横向尺寸增长结果, 并与模拟计算进行了比较.     

Current Status and Planned Upgrades of the VEPP-5 Injection Complex

Physics of Particles and Nuclei Letters - The VEPP-5 injection complex, consisting of two linacs and a damping storage ring, delivers electron and positron beams to the VEPP-4M and VEPP-2000...     

Toward therapeutics for clostridium botulinum neurotoxins

Construction work on the new MAX IV synchrotron light facility in northeastern Lund, Sweden, began on May 18, 2011. The MAX IV accelerator system will consist of three parts: one 3 GeV injector linac (also used for the production of short X-ray pulses) and two storage rings operated at 1.5 GeV and 3 GeV, respectively. The two-ring concept will allow the production of synchrotron radiation from optimized undulators within a broad spectral region. The 3 GeV ring has an emittance between 0.2 and 0.4 nm rad, depending on the ID configuration, and the emittance of the 1.5 GeV ring is 5 nm rad.     

High accuracy comparison of the electron and positron magnetic moments

A comparison of the electron and positron anomalous magnetic moments has been performed using the resonance depolarization method for the VEPP-2M storage ring beams. It has been shown, that the difference between anomalous magnetic moments of electron and positron doesn't exceed 1.0 × 10^?5 with 95% confidence level in agreement with CPT-theorem prediction on equality of the particle and antiparticle magnetic moments. The achieved accuracy is two orders better than that available up to now.     

Progress of the Injector Linac Upgrade for the BEPCⅡ Project

BEPCⅡ—an upgrade project of Beijing Electron Positron Collider (BEPC) is a factory type of e+e- collider. It requires its injector linac to have a higher beam energy (1.89 GeV) for on-energy injection and a higher beam current (40 mA e+ beam) for a higher injection rate ( 50 mA/min). The low beam emittance (1.6π mm·mrad for e+ beam, and 0.2πmm·mrad for 300 mA e- beam) and the low beam energy spread (±0.5%) are also required to meet the storage ring acceptance. Thus the original BEPC injector linac must be upgraded to have a new electron gun with its complete tuning system, a new positron source with a flux concentrator, a new RF power system with its phasing loops and a new beam tuning system with orbit correction and optics tuning devices. These new components have been designed, fabricated, tested and will be installed in their final positions in this spring and summer, which are described in this paper.