Evgeny Levichev

Absolute calibration of particle energy at VEPP-4M

We have started a new series of experiments on a precise measurement of J/Ψ-, Ψ′- mesons and τ-lepton masses at VEPP-4M collider with KEDR detector. Features of the method used for an absolute particle energy calibration based on the resonance depolarization are described.

Use of the methods of accelerator physics in precision measurements of particle masses at the VEPP-4 complex with the KEDR detector

Based on precision measurements of the beam energy using the resonant depolarization and Compton backscattering methods, it is possible to conduct high-precision experiments in the field of high-energy physics at the VEPP4M electron-positron collider with the KEDR detector. The J/ψr- and ψ(2s)-meson masses measured at the VEPP4M collider ar e among the ten most precisely known masses of elementary particles measured over the whole physical history. The degree of accuracy that we attained in determining theτlepton mass by the threshold behavior of the e+e- τ+τ reaction cross section is the best in the world. Systems automatically controlling the temperature of the distillate that cools the magnets of the main accelerating structure and the RF accelerating cavities of the VEPP4M collider have been developed, produced, and placed in operation in order to increase the efficiency of the complex. Simultaneous measurements of the transverse displacement and the angle of inclination of the beam near the interaction point can be taken with the aid of a multipinhole X-ray camera.

Experimental study of nonlinear beam dynamics at VEPP-4M

Nonlinear dynamics of transverse beam motion has been studied experimentally at the VEPP-4M electron—positron collider. Two aspects of nonlinear beam behaviour described in this paper are the amplitude-dependent tune shift and the phase space trajectories near nonlinear resonances. The measurement results are presented and compared with the theoretical prediction. ( 1998 Elsevier Science B.V. All rights reserved.

Proposal of an Experiment on Bunch Length Modulation in DAφNe

Obtaining very short bunches is an issue especially for colliders but also for CSR sources. The modulation of the bunch length in a strong rf focusing regime had been proposed, corresponding to a high value of the synchrotron tune. A ring structure where the function R56 along the ring oscillates between large positive and negative values will produce bunch length modulation. The synchrotron frequency can be tuned both by the rf power and by the integral of the function R56, up to the limit of zero value corresponding to the isochronicity condition. The proposal of a bunch length modulation along the ring in DAΦNE is here described. DAΦNE lattice can be tuned to positive or negative momentum compaction values, or to structures in which the two arcs are respectively set to positive/negative integrals of the R56 function. With the installation of an extra rf system at 1.3 GHz, experiments on bunch length modulation both in the regime of high and low synchrotron tune can be realized.

Dynamic aperture study at the VEPP-4M storage ring

Dynamic aperture has been studied experimentally at the VEPP-4M electron-positron collider. A transverse bunch motion was excited by fast kickers. The beam intensity and the amplitude of the coherent oscillations were measured turn-by-turn by the BPM. In this paper the technique of determining the dynamic/physical aperture is described. Several methods of increasing the dynamic aperture are discussed. The results of computer simulation and simple model analytic prediction explaining the experimental data are presented.

Momentum acceptance optimization in FCC-ee lattice (CERN)

The part of the ongoing study of the future circular collider (FCC) [1] is an electron positron machine with center of mass energy from 90 to 350 GeV. Crab waist collision scheme [2, 3] and small (1 mm) vertical beta function at the interaction point (IP) provide superior luminosity. At the top energy, radiation in the field of the opposite bunch (beamstrahlung) [3–5] limits the beam lifetime and therefore achievable luminosity. Beamstrahlung influence depends on momentum acceptance of the lattice, and acceptance of 2% provides acceptable lifetime. The small value of vertical beta function enhances effects of nonlinear chromaticity. The present work describes principles used in design and optimization of FCC-ee momentum acceptance optimization. INTRODUCTION The beam lifetime of the future circular collider (FCC) [1] at beam energy of 175 Gev is limited by beamstralung [3–5]. To attain feasible beam lifetime lattice of the collider should provide momentum acceptance of 2%. This is only possible with local chromaticity correction sections. Geometrical constraints of the interaction region (IR), optical requirements of chromaticity correction sections and a need for low synchrotron radiation (SR) background in the detector limit the maximum dispersion function in the sextupoles hence raising the sextupoles strength. The sextupoles, final focus quadrupoles fringes and kinematic term in the IP with extremely small vertical beta function increase effects of nonlinear dynamics. The obvious remedy of moving the final quadrupole closer to interaction point (IP) is not possible because of detector equipment. Crossing angle is a necessary condition of the crab waist collision; small decrease of the angle relaxes geometrical constraints of the IR tunnel therefore we changed the crossing angle from 30 mrad to 26 mrad. IR lattice should satisfy several requirements: 1. must fit hadron collider tunnel 100 km long, 2. two interaction points (defined by FCC-hh and price), 3. vertical emittance is less or equal than 1 pm at 45 GeV, 4. horizontal emittance is 1-2 nm at 175 GeV, 5. energy acceptance ±2%, 6. SR from the dipoles within 250 m from IP should have critical energy Eγ,c ≤ 100 keV. ∗ Work is supported by theMinistry of Education and Science of the Russian Federation † A.V.Bogomyagkov@inp.nsk.su Table 1 presents parameters relevant for the present work. Table 1: Relevant Parameters for Crab Waist IR [3] Z W H tt Energy [GeV] 45 80 120 175 Perimeter [km] 100 Particles per bunch [1011] 1 4 4.7 4 Number of bunches 29791 739 127 33 Energy spread [10−3] 1.1 2.1 2.4 2.6 Emittance hor. [nm] 0.14 0.44 1 2.1 Emittance ver. [pm] 1 2 2 4.3 β0x/β0y [m] 0.5 / 0.001 Crossing angle [mrad] 30 Luminosity / IP [1034 cm−2s−1] 212 36 9 1.3 Crossing angle [mrad] 26 Luminosity / IP [1034 cm−2s−1] 255 43 10 1.4 FINAL FOCUS QUADRUPOLES The minimum distance from IP to the face of the first quadrupole is chosen to be L∗ = 2 m which at the present moment looks like a good compromise between beam dynamics [7] and detector constraints. Having the minimum distance the maximum reliably achievable gradient defines the quadrupole length. In the present study we demanded the quadrupole strength to be lower than 100 T/m, which is a very relaxed condition. Particles trajectories from IP through the FF doublet are on Figure 1. Quadrupole parameters length, gradient and radius of aperture at E = 175 Gev are presented in Table 2. The distance between the bare apertures for the first quadrupoles is 2.6 cm, for the second pair the distance is 11.6 cm. Table 2: Parameters of FF Quadrupoles at 175 GeV L [m] G [T/m] R [m] Q0 3.6 -90.6 0.013 Q1 2 84.3 0.02 THPOR019 Proceedings of IPAC2016, Busan, Korea ISBN 978-3-95450-147-2 3814 C op yr ig ht

Recent Beam-Beam Effects at VEPP-2000 and VEPP-4M

Budker INP hosts two e + e − colliders, VEPP-4M operating in the beam energy range of 1–5.5 GeV and the low-energy machine VEPP-2000, collecting data at 160– 1000 MeV per beam. The latter uses a novel concept of round colliding beams. The paper presents an overview of observed beam–beam effects and obtained luminosities. VEPP-4M Being a rather old machine with a moderate luminosity, VEPP-4M has several unique features, firstly a very low beam-energy spread, and a system for precise energy measurement, providing an interesting particle physics program for the KEDR detector. Over recent years VEPP4M was taking data at a low energy range with two bunches in each beam. The luminosity at this range is limited by beam–beam effects with the threshold beam– beam parameter ξy ≤ 0.04 [1]. In this case the luminosity

An Ultra-low Emittance Model for the ANKA Synchrotron Radiation Source Including Non-linear Effects

An ultra-low emittance lattice based on the ANKA ring geometry is under investigation in framework of the feasibility studies for a compact low emittance synchrotron light source at the Karlsruhe Institute of Technology (Germany). An attempt to apply the concept of split bending magnets cells and to reduce the natural emittance of the bare ANKA DBA lattice from 90 nm rad down to 2.5 nm rad with not-vanishing dynamic aperture is described in this paper. The TME cell with split bends and a quadrupole lens in-between as well as a pair of non-interleaved sextupole lenses separated by “–I ” unit transfer matrix of betatron oscillations allows to decrease the theoretical minimum emittance of ANKA ring down to approximately 6 nm rad. Further reduction of the phase space volume requires to brake “–I ” symmetry and add extra families of sextupoles, locate an additional high order field elements inside the quadrupoles, optimize the phase advance between sextupole families, shift the betatron tune point, enlarge the sextupole strength and other measures. Results of simulations are reported. INTRODUCTION Light source facility based on the 2.5 GeV ANKA storage ring successfully operates at the Karlsruhe Institute of Technology since 2000 [1]. At present acceleration of particles is accomplished in three steps. Electrons are accelerated up to 50 MeV in the racetrack microtron and gain the energy up to 500 MeV in the 1 Hz cycling booster synchrotron. Then particles are accumulated and ramp energy up to 2.5 GeV in the main ANKA ring. Major upgrade of existing accelerators aims either for a full energy booster synchrotron or an injector LINAC similar to one designed for MAX-IV [2] and for a low emittance storage ring inscribed into the present ANKA synchrotron geometry to preserve existing beam lines and engineering infrastructure. The main objective of the ring upgrade is to reduce the emittance of the beam by 10 times to less than 9 nm while ensure acceptable DA and large MA. TME CELL WITH SPLIT BEND SM-TME cell was studied comprehensively in [3]. This flexible cell originated from TME cell with a bend split and a quadrupole inserted in between. New cell provides both low emittance and large DA due to the chromatic sextupoles arranged in pairs and separated by –I transformers. Such arrangement effectively cancels all sextupole aberration terms, so the DA is defined by the next, octupole-like less severe aberrations. Figure 1 shows the basic cell of the Low Emittance ANKA upgrade (LE ANKA). We have tuned the –I conditions in the horizontal plane over the cell, so identical horizontal sextupoles installed at the cell ends cancel the relevant nonlinear aberrations. Figure 1: LE ANKA cell based on the modified TME cell. Quadrupole between the split bend allows adjusting phase advance between chromatic sextupoles. The horizontal beta and dispersion were adjusted in the bends to achieve low emittance according the approach described in [3,4]. To correlate the emittance with the DA size, we have mistuned the –I condition by introducing stronger focusing. Figure 2 shows the DA shrink with the emittance decrease. Finally we adopted relaxed but robust version with 8.6 nm emittance and 20 15 mm DA. Figure 2: Horizontal DA vs. emittance for the –I detuned. LATTICE LE ANKA has the same circumference as ANKA, occupy the same tunnel, has the same length and structure of straight sections (4 long plus 4 short) and keep unchanged MOPRO064 Proceedings of IPAC2014, Dresden, Germany ISBN 978-3-95450-132-8 228 C op yr ig ht

Gennady Nikolaevich Kulipanov (on his 70th birthday)

Gennady Nikolaevich Kulipanov, Deputy Director of Budker Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences (RAS) and Director of the Siberian Synchrotron and Terahertz Radiation Centre, Full Member of the RAS, celebrated his 70th birthday on January 25, 2012.

New optical diagnostics of the VEPP-4M collider

The experiments in measuring the dynamic aperture and beam energy spread of the VEPP-4M collider [1] are described. The optical diagnostics of the accelerator were applied for these purposes.