VEPP-2M Storage Ring Research Articles

Microstrip Silicon Detector for Study of Ultra-Fast Processes at the Synchrotron Radiation Beam

Present status of the development of the prototype of the Detector for imaging of explosions (DIMEX) based on silicon microtrip sensor is discussed. The prototype includes silicon p-in-n sensor with metal strips in direct contact with p-implants. Strips are 30 mm long and have 50 um pitch. Signals from the strips are read out with specially developed ASICs DMXS6A, that include 6 channels with DC compensation circuit at the input, four integrators, 32 analogue memory cells and output analogue shift register. The prototype detector has 96 registration channels provided with 16 DMXS6A ASICs. Each strip of the sensor is connected to the guard-ring through a 400 Ohm resistor and through 100 kOhm resistor to the input of the front-end ASIC. This resistive divider allows to adapt the dynamic range of the integrator of the ASIC to the full flux range of the beam line 8 at the VEPP-4M storage ring that includes 9-pole wiggler with 1.9 T B-field as SR source. The measurements of the dynamic range of the DIMEX-Si prototype demonstrate that maximum photon flux from one bunch that can be measured by this detector exceeds 100 000 photons per channel. For these measurements the sensor was inclined at an angle of 1.7 degrees with respect to the beam plane in order to increase quantum efficiency. The possibility to work in multi-bunch mode with bunches following in 55 ns is demonstrated, that proves that this detector can be successfully exploited at new SR-source SKIF that is under construction in Novosibirsk region.

Development of a silicon microstrip detector prototype for ultra-fast imaging at a synchrotron radiation beam

A method of imaging of ultra-fast processes, like explosion or fast combustion, at a synchrotron radiation beam is being developed at the Siberian Synchrotron and Teraherz Radiation Center (SSTRC) . Two stations are operating at beam line 0 at the VEPP-3 storage ring and at beam line 8 at the VEPP-4M storage ring. Both stations are equipped with the detector for imaging of explosions DIMEX, based on high pressure ionization chamber, and allowing to record up to 100 one dimensional images with the frame rate of 8 MHz. However the maximum flux that DIMEX can detect is limited as well as spatial resolution and frame rate because of gas technology used. In view of significant increase of SR flux at the VEPP-4M beam line due to the new 9-pole 2 T wiggler, a new detector is being developed for this beam line, based on Si microstrip sensor. The first Si microstrip detector prototype has been mounted with new specially developed front-end ASIC that allows to record data with the rate of 50 MFrames/s. The first measurements with this prototype demonstrated significant improvement of all critical parameters of the detector compared to the gaseous version.

Development of an Application Specific Integrated Circuit for Signal Detection in Experimental Studies of Fast Processes

This paper presents a new integrated circuit designed for signal readout in a silicon microstrip detector in experimental observations of fast processes at a synchrotron radiation beam. The first variants of this circuit were used in a prototype detector based on a microstrip silicon sensor and were tested at an intense synchrotron radiation beam at the VEPP-4M storage ring in the Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. The results of the first measurements showed that the main objectives of this development were achieved: the time resolution and frame rate satisfy the initial specifications and the maximum detected signal in a linear mode of operation provides a significant increase in the detected photon flux compared to the previous version of the detector based on gas technology. The main problem detected during testing of the prototype is the relatively high noise level, which will be reduced in the next version of the integrated circuit by optimizing some circuit solutions.

The SRXFA Station on the VEPP-4M Storage Ring

A description is given of the SRXFA synchrotron radiation station on the VEPP-4M storage ring at the Siberian Synchrotron and Terahertz Radiation Center. The station is intended to develop and implement SRXFA technology in the hard X-ray photon (40–120 keV) range. The main parameters of the station are given, along with its layout, its monochromatic system, and its detector. The X-ray fluorescence spectrum obtained at the SRXFA station on the VEPP-4M storage ring at an excitation energy of 112 keV is presented. Results obtained at the station on the minimum detection limits for rare-earth elements are presented.

Designing a Technological Station for Synchrotron Radiation on the VEPP-4M

A technological station for synchrotron radiation (referred to below as the TSSR) is created on Channel 1 of synchrotron radiation (SR) output on the VEPP-4M storage ring. The new station is designed for practical study of the basics of synchrotron research conducted by university students. The modular construction of the station allows us to change its equipment, test different research techniques and new equipment, and perform some auxiliary experiments. The design of the station, the radiation characteristics relative to other active SR stations, and the main training programs are described.

Upgrading a Detector for Studying Fast Processes on a Beam of Synchrotron Radiation

The current stage of the upgrade of the DIMEX detector for studying fast processes on a synchrotron radiation (SR) beam is described. The current version of the DIMEX is a one-dimensional high-pressure ionization chamber with a fast electron component readout. The detector can record photon fluxes from each bunch separately without mixing photons from different bunches. The maximum flux the DIMEX can detect is limited by the space charge of positive ions in a high-pressure gas. To substantially improve this and other parameters of the detector, it was decided to switch to microstrip silicon technology. A prototype based on a silicon-microstrip sensor was developed along with a special integrated circuit (ASIC) for reading out the signals from this prototype. The first tests of the new DIMEX-Si prototype on an SR beam show that it is superior to the gaseous version in all respects. Results are presented from the first tests of the silicon-microstrip detector prototype on the SR beam of the VEPP-4M storage ring.

A beam-position monitor system at the VEPP-4M electron−positron collider

The VEPP-4M storage ring has been designed for experiments with colliding electron−positron beams, a synchrotron radiation beam, and extracted γ-ray beams at energies of 1−5 GeV. A correct equilibrium beam orbit must be kept in the storage ring to maintain the required experimental conditions. A beam position monitor system is used for this purpose. It includes 54 beam position monitors, monitor signal-processing modules, and synch signals distributors. In 2013–2016, new signal processing modules with a high time resolution were developed and installed at the VEPP-4M storage ring. These have two main advantages over the old modules. First, the new modules allow separate position measurements of electron and positron bunches at an interval between the bunch signals as long as 18 ns. Second, they are able to perform fullfledged turn-by-turn beam position measurements, which is very important for adjustment of the storagering parameters. Turn-by-turn beam position measurements can be performed during injection of a new beam, beam kicking, beam loss, or at an arbitrary instant of time. The structures and main features of the new modules are described, the measurement accuracy is analyzed, and some results of their operation at the storage ring are presented.

Laser Polarimeter at VEPP-4M

A laser polarimeter at the VEPP-4M storage ring is being developed for the beam energy calibration by the resonant depolarization method in the future high-precision measurements of the Υ meson masses with the KEDR detector. The status of the laser polarimeter and first energy measurements at 4.1 GeV with an accuracy of 50 keV is described.

Development of a silicon microstrip detector with single photon sensitivity for fast dynamic diffraction experiments at a synchrotron radiation beam

Time-resolved experiments on the diffraction of synchrotron radiation (SR) from crystalline materials provide information on the evolution of a material structure after a heat, electron beam or plasma interaction with a sample under study. Changes in the material structure happen within a microsecond scale and a detector with corresponding parameters is needed. The SR channel 8 of the VEPP-4M storage ring provides radiation from the 7-pole wiggler that allows to reach several tens photons within one μs from a tungsten crystal for the most intensive diffraction peak. In order to perform experiments that allow to measure the evolution of tungsten crystalline structure under the impact of powerful laser beam, a new detector is developed, that can provide information about the distribution of a scattered SR flux in space and its evolution in time at a microsecond scale. The detector is based on the silicon p-in-n microstrip sensor with DC-coupled metal strips. The sensor contains 1024 30 mm long strips with a 50 μm pitch. 64 strips are bonded to the front-end electronics based on APC128 ASICs. The APC128 ASIC contains 128 channels that consist of a low noise integrator with 32 analogue memory cells each. The integrator equivalent noise charge is about 2000 electrons and thus the signal from individual photons with energy above 40 keV can be observed. The signal can be stored at the analogue memory with 10 MHz rate. The first measurements with the beam scattered from a tungsten crystal with energy near 60 keV demonstrated the capability of this prototype to observe the spatial distribution of the photon flux with the intensity from below one photon per channel up to 0∼10 photons per channel with a frame rate from 10 kHz up to 1 MHz.

Positron injector of the VEPP-4M collider

The positron injector for the VEPP-4M storage ring and its successful 40-year operation are described. The injector performance has been substantially enhanced in a number of successive upgrades, enabling precision measurements of particle masses at VEPP-4M.

Development of the microstrip silicon detector for imaging of fast processes at a synchrotron radiation beam

In situ imaging of explosions allows to study material properties under very high pressures and temperatures. Synchrotron radiation (SR) is a powerful tool for such studies because of its unique time structure. Flashes of X-rays from individual bunches in a storage ring are so short that an object under study does not move more than 1–10μm during exposure. If a detector is able to store images synchronously with bunches of an SR source the time resolution of such method will be determined by the duration of SR flash from individual bunch. New beam line at the VEPP-4M storage ring will allow to get X-Ray flux from each bunch close to 106 photons/channel where channel area is 0.05×0.5mm2 and average beam energy is about 30keV. Bunches in the machine can be grouped into trains with 20ns time gap. In order to meet these requirements a new detector development was started based on Si microstrip technology. The detector with a new dedicated front-end chip will be able to record images with maximum signal equivalent to 106 photons/channel, with signal to noise ratio of ∼103, spatial resolution of 50 μm and maximum frame rate of 50MHz. The detector has to drive very high peak and average currents without affecting the front-end chip, therefore a specific design of Si sensor should be developed. The front-end chip has to provide signal measurements with the dynamic range of about 104 or more and recording of the signal to an analogue memory with the rate of 50MHz. The concept of such detector is discussed in the paper. The results of the simulations of the main detector parameters and the results of the first measurements with the prototype sensors are presented.

Upgrade of the Detector for Imaging of Explosions

Methods of dynamic imaging of explosions at a synchrotron radiation (SR) beam and small-angle X-ray scattering experiments with exploding samples are being developed in the Siberian Synchrotron Radiation Center (SSRC) at the Budker Institute of Nuclear Physics for more than fifteen years. The detector for imaging of explosions (DIMEX) was developed for these purposes and successfully operating at the beam line 0 at the VEPP-3 storage ring and at the beam line 8 at the VEPP-4M storage ring. The DIMEX is based on gas technology and allow to measure SR flux as a function of position and time with spatial resolution of ∼200 μm (FWHM), maximum frame rate of 2MHz and time resolution of ∼80ns. Maximum value of the SR flux that can be measured by the present detector corresponds to ∼5000 photons/(channel*bunch) (20 keV average energy, channel area 0.1x0.5 mm2, bunch revolution frequency 4MHz). Maximum number of frames that can be stored in the present detector is 32 and the number of channels with 0.1mm width is 512. In order to significantly improve the precision of data obtained by the DIMEX an upgrade of the detector has been started. The electronics of the gaseous version of the detector has been changed such that the new detector is able to operate with frame rate of 8MHz and store data in up to 100 frames. A new ASIC was developed for this purpose called DMXG64A that includes 64 channels with low noise integrator and 100 analogue memory cells in each channel. Input charge can be stored to and read out from analogue cells with maximum frequency 10MHz. This new version of the detector is called the DIMEX-G and is planned to be used at the VEPP-3 storage ring and for SAXS studies at the VEPP-4M storage ring. For imaging of explosions at the beam line 8 at the VEPP-4M storage ring, where SR flux is expected to be about 10-100 times higher than at the VEPP-3, a new detector based on Si micro-strip technology is being developed. Si micro-strip sensors with special design have been manufactured by Hamamatsu Photonics company. Each sensor contains 1024 30mm long strips with 50μm pitch. The sensor thickness is 320μm and it will be positioned at an angle of 1.7 degrees with respect to the SR beam plane in order to get effective Si thickness along the beam close to 10mm. The new detector called DIMEX-Si will have spatial resolution of 50μm (FWHM) and time resolution close to 10ns. The new ASIC is under development for this project that will allow to operate with the frame rate of 50MHz and record maximum charge that corresponds to the flux close to 106 photons/(chan*bunch), i.e. about 100 times higher than with present detector.

Development of high resolution tracking detectors with Gas Electron Multipliers

Cascaded Gas Electron Multipliers (GEM) allow to construct detectors for charge particles tracking with high spatial resolution and rate capability. Such detectors can withstand high background fluxes up to 105 particles/mm2/s and determine track coordinates with precision of 50 – 70 micron. These remarkable features of GEM govern the use of this technology in a number of experiments at the Budker Institute of Nuclear Physics. In this paper the current status and progress in the performance studies and the development of the detectors for the tagging system of the KEDR experiment at the VEPP-4M collider and for the DEUTERON facility at the VEPP-3 storage ring will be covered. The new proposals for the upgrade of tracking and trigger system of the CMD-3 detector, the tracking detectors for the extracted beam from the VEPP-4M storage ring and the tracking detectors for the polarimeter at the VEPP-4M with the use of GEM technology will be discussed.

Equipment for soft X-Ray lithography on the VEPP-4M

An X-ray scanner for X-ray mask lithography is described. It is mounted onto the synchrotron radiation (SR) beamline of the VEPP-4M storage ring. The main advantage of this scanner is the possibility of varying the SR spectral range within wide limits and its fine tuning for solving specific technical tasks by changing the working energy of the VEPP-4M and using corresponding filters, which is illustrated by tables and plots of the calculated spectra. Calculated estimates of the lithographic resolution of lithographic complex, exposure times for various types of X-ray masks, and thicknesses of their masking layers providing the required level of X-ray mask contrast are given.

Experimental research on the spatial positions of SI beams in beamlines Nos. 13 and 7 of the VEPP-4M ring

Dynamics of the positions of SI beams was experimentally investigated over time in beamlines No. 13 and No. 7 in the VEPP-4M storage ring. An ion chamber with cutting electrodes was used in our research. The operability of the scheme of beam line No.13 is demonstrated. The ion chamber is tested in a regime in which the energy of the electrons in the storage ring is 3.5 GeV.

Calculation of the intensity of Touschek electrons in the VEPP-4M storage ring

Formulas for calculating the intensity of intrabeam scattering of electrons in the Born approximation for the one- and two-dimensional collision models have been obtained for the nonrelativistic and relativistic cases. The Baier-Katkov-Strakhovenko two-dimensional relativistic model with Coulomb corrections has been analyzed. Formulas in the ultrarelativistic limit have been obtained using this model. Different models have been compared. The intensities of Touschek electrons and the polarization contribution have been calculated under the conditions of the detection of scattered particles at the VEPP-4M storage ring. The calculations have been compared to experimental data.

Comparative certification of secondary-electron multipliers within the ultrasoft X-ray range

The results of studying the band characteristics and the efficiency of recording the secondary-electron multipliers VEU-6 and VEU-GOI (manufactured by the Vavilov State Optical Institute (GOI), St. Petersburg) within the ultrasoft X-ray range are given. The measurements were carried out at the metrological station Kosmos with the use of synchrotron radiation from the storage ring VEPP-4M (Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk) in monochromatic radiation at a photon energy of 268 eV. A strong irregularity in the band characteristics of both VEU-6 and VEU-GOI has been found. Their quantum efficiencies are estimated. The measurements are a continuation of the works on calibration of the equipment of the Space Solar Patrol (developed by GOI) using synchrotron radiation from the VEPP-4M storage ring (project MNTTs no. 2500).

Kosmos station: Application of synchrotron radiation from the VEPP-4M storage ring for metrological measurements in the VUV and soft X-ray ranges

This paper describes the development and implementation of metrological methods in the soft X-ray (80–2000 eV) and vacuum ultraviolet (10–100 eV) ranges at the Kosmos synchrotron radiation metrological station, functioning at the Siberian International Centre for Synchrotron Radiation. The station’s basic parameters are presented and a short description of its configuration and systems of monochromatization and reference detectors are given. A list of basic metrological methods used at the station for the calibration of various types of detectors is also provided.

High vacuum ionization chamber with high spatial resolution for monitoring synchrotron radiation beams

The possibility of using an ionization chamber with a cutting collectorin vacuum (10−4–10−5 Pa) for online monitoring of the position of a synchrotron radiation (SR) beam is studied experimentally The possibility of measuring the vertical position of the SR beam with a precision of up to several micrometers is demonstrated in the high vacuum conditions of an open channel in the VEPP-4M storage ring (in the absence of a beryllium window). Two such ionization chambers operating synchronously and situated one after another can serve as a basis for the SR beam stabilization system in neighboring channels.

VEPP collider facilities in Novosibirsk: status and plan

In this report the overview of activity at existing and future electron-positron high energy colliders at BINP is presented. The operating machine is the VEPP-4M storage ring being run at the moment at its low energy (Tau and Charmonia region). The new collider VEPP-2000, based on round beams approach, for energy range from pion threshold up to 2 GeV was constructed and now is in commissioning stage. First luminosity 1 ⋅ 10 31 c m −2 s −1 in 1 + 1 bunch mode at phi-meson energy was successfully achieved. At the moment, two detectors are in final preparation for data taking. The new e + e − injector complex VEPP-5 with production rate 10 10 positrons per second was constructed to guarantee ultimate parameters of VEPP-2000 and VEPP-4M, and open prospects for future high luminosity e + e − collider(s). The VEPP-5 injector complex is in commissioning phase now. First electrons accelerated up to 300 MeV are stored in the damping ring. The active R&D and civil construction efforts are aimed to the Tau/Charm Factory with luminosity 10 35 c m −2 s −1 and longitudinal polarization.