Budker INP Research Articles

Overview of neutral beam injectors for plasma heating and diagnostics developed at Budker INP

An overview of the neutral beam injectors developed at the Budker Institute of Nuclear Physics in Novosibirsk during the last 10 years is presented. These neutral injectors are used for plasma diagnostics, heating and current drive in modern fusion devices with magnetic confinement. An arc or a radio-frequency (RF) discharge generates a plasma in the ion sources of the injectors, and a positive hydrogen or deuterium ion beam is extracted and accelerated by a multiaperture ion-optical system (IOS). The accelerated ion beam is converted into a neutral one in a gas target. The precision multiaperture IOS with spherically concave electrodes provides ballistic focusing of the neutral beam. The high-energy, high-power beam injector based on negative ions, which is currently under development, is described as well. It comprises a RF negative ion source and a wide-aperture electrostatic accelerator separated from the source by a low-energy beam transport line, thereby improving the injector reliability.

Superconducting undulator with period of 15.6 mm and magnetic field of 1.2 T

A superconducting undulator with a period of 15.6 mm and a field of 1.2 T created at Budker INP SB RAS was tested in its own cryostat based on indirect cooling with zero helium consumption. The report presents the main characteristics and design features of the magnetic and cryogenic systems of this insertion device. The results of measurements of the magnetic field are presented and the features of the operation of the cryogenic system in various modes are shown.

Software framework for the Super Charm-Tau factory detector project

The project of Super Charm-Tau (SCT) factory — a high-luminosity electron-positron collider for studying charmed hadrons and tau lepton — is proposed by Budker INP. The project implies single collision point equipped with a universal particle detector. The Aurora software framework has been developed for the SCT detector. It is based on trusted and widely used in high energy physics software packages, such as Gaudi, Geant4, and ROOT. At the same time, new ideas and developments are employed, in particular the Aurora project benefits a lot from the turnkey software for future colliders (Key4HEP) initiative. This paper describes the first release of the Aurora framework, summarizes its core technologies, structure and roadmap for the near future.

Time Projection Chamber as Inner Tracker for Super Charm-Tau factory at BINP

At present time Budker INP is developing a Super Charm-Tau factory project, which consists of a high-luminosity collider with the luminosity of 1035 cm−2s−1 and a universal magnetic detector. The tracking system of the detector will comprise of an Inner Tracker (IT) and a Drift Chamber (DC). One of the options for IT is Time Projection Chamber (TPC). The advantages of the TPC are high spatial resolution and particle identification capabilities by registration of dE/dx losses. However, using a Time Projection Chamber implies serious challenges. For example, the TPC have to simultaneously deal with tracks from several thousands events and maintain the enormous data rate. This work describes the results of the Monte-Carlo studies of the transport characteristics in various gas mixtures proposed for TPC. Besides of this, the simulation of the ion back flow and its effect on spatial resolution will be reported.

Development of the micro-resistive WELL discs for the CMD-3 tracking system

Micro-pattern gas technology is planned for the upgrade of the tracking system of the CMD-3 detector at the VEPP-2000 electron-positron collider in Budker INP. The upgrade includes a new thin tracking cylinder that consists of two tracking layers at a radius of 32 to 33 cm with coordinate resolution close to 0.5 mm in z-direction (along the beam axis) and trigger segments of about 1 cm in the transverse plane. The other part of new coordinate subsystem includes two end-cap discs with active area between radius of 5 cm and 25 cm, that should provide spatial resolution close to 1 mm in both directions as well as the first level trigger signal. For these two subsystems we plan to use micro-RWELL technology because it allows much simpler assembling of large cylindrical detector and large discs due to more rigid glass-fiber support as compared to the triple GEM technology.

Application of micro-pattern gas detectors in the present and future experiments in Budker INP

Micro-pattern gas technology is planned for the upgrade of the tracking system of the CMD-3 detector at the VEPP-2000 electron-positron collider in Budker INP. The upgrade includes a new cylinder tracking and trigger detector that consists of two tracking layers at a radius of 32 to 33 cm with coordinate resolution close to 0.1 mm in Z (along the beam axis) and trigger segments of about 1 cm in phi. Another new coordinate subsystem includes two end-cap discs with active area between radius of 50 mm and 250 mm, that provides spatial resolution in R and in phi close to 1 mm as well as trigger signal from the phi segments. For these two subsystems we plan to use micro-RWELL technology because it allows much simpler assembling of large cylindrical detector and large discs due to more rigid glass-fiber support as compared to the triple GEM technology. The new cylindrical detector and end-cap discs of the CMD-3 are considered as a prototypes of the Inner Tracker of the detector for the future Super C-Tau Factory (SCTF) at Budker INP. The SCTF is an electron-positron collider for the energy range of 3-7 GeV in the center of mass system that will provide luminosity of 1035 cm−2s−1. Coordinate system of the detector for the SCTF will include among other systems, the Inner Tracker and the end-cap discs. The Inner Tracker will be 60 cm long and occupy radius up to 20 cm, while the end-cap discs will have radius up to 180 cm and will have to provide trigger signal. For the end-cap discs the MPGD option is considered based either on the triple-GEM or on the micro-RWELL, while for the Inner Tracker three main options are competing: compact Time Projection Chamber, silicon micro-strip tracker and cylindrical MPGD tracker. The first results of simulations with all these options are presented with preliminary discussion about the choice of the option.

Upgrade of the KEDR detector DAQ system

The KEDR experiment is ongoing at the VEPP-4M e+e− collider at Budker INP in Novosibirsk. The collider center of mass energy range covers a wide spectrum from 2 to 11 GeV. Most of the up-to-date statistics were taken at the lower end of the energy range around the charmonia region. Planned activities at greater energies up to the bottomonia would lead to a significant increase of event recording rates and accelerator backgrounds, thus stressing the existing DAQ and trigger systems beyond their limits. The described DAQ upgrade plan includes: the redesign of the trigger electronics using modern components to improve the trigger decision time; the development of new readout processors using ethernet connections; new software for collecting events and electronics management; high level of parallelization of data transfers and events processing; improved reliability based on readout computing cluster with redundancy. The upgraded DAQ system is going to be very flexible and could be considered as a concept prototype of the projected BINP Super Charm-Tau Factory.

Particle detection efficiency of the KEDR detector ASHIPH system

The particle identification system ASHIPH (Aerogel, SHifter, PHotomultiplier) has been working in the KEDR experiment at VEPP-4M collider (Budker INP, Novosibirsk) since 2014. The system consists of 160 counters arranged in two layers and covers the 96% of the solid angle. Two layer system permits to use different approaches for π/K separation. Three such approaches are described. The status of the system is presented. Main system parameters such as BhaBha suppression factor, π/K separation power, relativistic particle detection efficiency were measured with help of cosmic particles and experimental data collected at the peak of J/ψ-meson. π/K separation in the momentum range from 0.95 to 1.45GeV/c is better than 4σ. Monte-Carlo simulation procedures are described and results are presented as well.

Геодезическое сопровождение на этапах сборки и эксплуатации модернизируемого источника синхронтронного излучения ESRF

This article reviews key activities of the ESRF Alignment and Geodesy Group and the Budker INP SB RAS survey support team in the assembly and high precision alignment of the magnets on the girders constituting the new synchrotron radiation source – the Extremely Brilliant Source (EBS) under construction in Grenoble France. The different activities considered in detail here are

Electron guns at the Budker Institute of Nuclear Physics SB RAS: prospects for the use of photocathodes with nanosecond and subpicosecond laser drivers

The problem of producing high-current electron beams with relatively small lateral sizes and small velocity spread is more than a hundred years old. The continuous improvement of near-ultraviolet electromagnetic radiation sources (lasers with harmonics generators) allows significantly improving the parameters of existing electron guns. This paper discusses some problems in the development of electron guns with photocathodes and considers possible ways of using laser photocathodes in the electron guns designed at the Budker INP SB RAS.

High resolution micro-pattern gas detectors for particle physics

Micro-pattern gaseous detectors (MPGDs) allow operation at very high background particle flux with high efficiency and spatial resolution. This combination of parameters determines the main application of these detectors in particle physics experiments: precise tracking in the areas close to the beam and in the end-cap regions of general-purpose detectors. MPGDs of different configurations have been developed and are under development for several experiments in the Budker INP. The system of eight two-coordinate detectors based on a cascade of Gas Electron Multipliers (GEM) is working in the KEDR experiment at the VEPP-4M collider in the tagging system that detects electrons and positrons that lost their energy in two-photon interactions and left the equilibrium orbit due to a dedicated magnetic system. Another set of cascaded GEM detectors is developed for the almost-real Photon Tagging System (PTS) of the DEUTRON facility at the VEPP-3 storage ring. The PTS contains three very light detectors with very high spatial resolution (below 50 μm). Dedicated detectors based on cascaded GEMs are developed for the extracted electron beam facility at the VEPP-4M collider. These devices will allow precise particle tracking with minimal multiple scattering due to very low material content. An upgrade of the coordinate system of the CMD-3 detector at the VEPP-2000 collider is proposed on the basis of the resistive micro-WELL (μ-rWELL). A research activity on this subject has just started.

Development of two-photon event generators for the KEDR experiment

The KEDR experiment, which started in 2002, is dedicated to a study of c- and b-quarks and the two-photon physics at the e+e− collider VEPP-4M in the Budker INP. To analyze the 2γ data and estimate contribution of two-photon background events in the 1 data samples, the event generators e+e− → e+e− + hadrons, e+e− → e+e− + π+π−, and e+e− → e+e− + PS (PS – pseudoscalar meson) have been developed.

The prototype of new variable period undulator for Novosibirsk free electron laser

To improve the parameters of the second stage Novosibirsk free electron laser we plan to replace the existing electromagnetic undulator by permanent-magnet variable-period undulator (VPU). The VPUs have several advantages compared to conventional undulators, which include wider radiation wavelength tuning range and an option to increase the number of poles. Both these advantages will be realized in the new undulator under development in Budker INP. There are some technical problems, which have to be solved before this idea can be implemented in practice. To check the solution of these problems we designed and manufactured a small undulator prototype, which has just several periods. In this paper, the results of mechanical and magnetic measurements of this undulator prototype are presented and compared with simulations.

Magnetic System of the High-Field Superconducting Multipole Wiggler for LSU CAMD

Center for Advanced Microstructures and Devices of Louisiana State University (LSU CAMD) is a research center for optimization of synchrotron radiation (SR) for production of soft X-rays. New research projects have necessitated expansion of the SR spectral range to harder X-rays. This task was solved via installation of a superconducting insertion device. This paper presents a description of the superconducting wiggler with a field of 7.5 T made by Budker INP and installed on the storage ring of LSU CAMD. The wiggler consists of 11 main bending magnets with magnetic field with alternating sign and an amplitude of 7.5 T and four side poles (two on each end of the magnet array), which are to make the first and second field integrals in the longitudinal direction equal to zero at any field level of the main poles. The main attention at the designing and production of the magnetic system of the wiggler was paid to the magnetic field quality at all field levels. Presented are results of field magnetic measurements using Hall probes. The dynamic behavior of the first and second field integrals during field ramping up and down, as measured by the method of stretched wire with current, is discussed. The wiggler was installed and successfully commissioned on the CAMD LSU storage ring in 2013.

Electron Beam Stability in the Energy Recovery Linac for the Lithographic free Electron Laser

According to microelectronic production leaders the lithography based on the free electron laser (FEL) could become the main technology for the elements mass production with scale to 5nm in the nearest future. One of the main problem is the absence of the working FEL with required parameters. The feasibility study of those FEL based on superconducting energy-recovery linac (ERL) was made in Budker INP. The ERL average current is limited by longitudinal and transverse instabilities, caused by interaction between electron beam and its induced fields in the superconducting cavities. The estimations of the threshold currents and ERL parameters were made.

Magnetic Measurements of Superconducting Insertion Devices by Stretched Wire with Direct Current

The main characteristics of multipole insertion devices (ID) are the first and second field integrals along an orbit trajectory in an accelerator. Such integrals of permanent magnets or traditional electromagnets insertion devices can be obtained by means of longitudinal scanning by Hall probes. Measurements of the magnetic field by Hall probes in superconducting IDs have obvious difficulties because of limited space, temperature deviation along the path, etc. Measurements of the integrals by Hall probes, especially when the integrals has to be equal to zero, it is very difficult to make with a necessary accuracy. At Budker INP along with Hall probes the system of magnetic measurements on the basis of the tense wire with a direct current is used. The method is based on similarity of interaction of a direct current in a stretched wire and an electron beam in an accelerator with magnetic field. The stretched wire with current is a good model to describe behavior of an electron beam when passing through a magnet. Especially the method is useful at measurement of superconducting IDs where it isn’t enough space for other probes. The method provides a dynamic control of the field integrals in different modes of a magnet operation (field ramp up or down), allows to measure the integrals quickly and rather precisely.

The Novosibirsk Free Electron Laser – Unique Source of Terahertz and Infrared Coherent Radiation

The high-power free electron laser (FEL) facility NovoFEL has been created at Budker INP. Its wavelength can be tuned over a wide range in terahertz and infrared spectrum regions. This FEL uses a multi-turn energy recovery linac with five straight sections as a source of electron beam. Three sections are used for three FELs which operate in different wavelength ranges (the first at 90-240 μm; the second at 37 – 80 μm; the third at 5 – 20 μm).The first and second FELs were commissioned in 2003 and 2009, respectively. They operate for users now. The third FEL is installed on the fourth accelerator track, which is the last one; the electron energy is maximal here. This FEL comprises three undulator sections and a 40-m optical cavity. The first lasing of this FEL was obtained in the summer of 2015. The radiation wavelength was 9 μm and the average power was about 100 W. Radiation of the third FEL was delivered to the user stations, and the first user shifts were performed recently. The results of the commissioning of the third FEL, the current status of the first and second FELs and future development prospects are presented.

New RF gun for Novosibirsk ERL FEL

The new radiofrequency (RF) gun making an intensive high-quality electron beam for injecting in Novosibirsk microtron recuperator (ERL) and driving Free Electron Laser (FEL) is made in Budker INP SB RAS. Bench tests of RF gun demonstrated good results in strict accordance with the calculations predicting average current of a bunch of 100 мА, energy of particles of 400 keV and normalized emittance less than 15 microns. The RF gun stand testing showed reliable work, unpretentious for vacuum conditions and stable in long-term operation. The additional injection beamline built-in to the existing system of the NovoFEL injector with the static gun is developed and designed.

Development of the specialized integrated circuit for signal readout from micro-strip structures of a coordinate detectors

The paper presents current status of development of a specialized 64-channel integrated circuit (IC, ASIC) for front-end electronics of coordinate detectors in the Budker INP. The ASIC is produced using 180 nm process. During the recording phase the IC allows integration of short current pulses from strips of a coordinate sensor, and storing of up to 100 corresponding charge values in the analogue memory with minimum time interval of 100 ns. Maximum input charge is equal to 2×106 electrons, equivalent noise charge is ~2.7×103 electrons. Conversion of the data, stored in the analogue memory, to digital form is performed by an external ADC during the readout through an analogue multiplexer.

Development of the specialized integrated circuit for signal readout from micro-strip structures of a coordinate detectors

The paper presents current status of development of a specialized 64-channel integrated circuit (IC, ASIC) for front-end electronics of coordinate detectors in the Budker INP. The ASIC is produced using 180 nm process. During the recording phase the IC allows integration of short current pulses from strips of a coordinate sensor, and storing of up to 100 corresponding charge values in the analogue memory with minimum time interval of 100 ns. Maximum input charge is equal to 2×106 electrons, equivalent noise charge is ∼2.7×103 electrons.Conversion of the data, stored in the analogue memory, to digital form is performed by an external ADC during the readout through an analogue multiplexer.