Alexey Burov

Nested head-tail Vlasov solver

Nested Head-Tail (NHT) is a Mathematica-based Vlasov solver for transverse oscillations in multi-bunch beams. It takes into account azimuthal, radial, coupled-bunch and beam-beam degrees of freedom, single- and inter-bunch dipole wakes, an arbitrary damper, beam-beam effects and Landau damping.

Transverse Instabilities of Coasting Beams with Space Charge

Transverse beam stability is strongly affected by the beam space charge. Usually it is analyzed with the rigid-beam model. However this model is only valid when a bare (not affected by the space charge) tune spread is small compared to the space charge tune shift. This condition specifies a relatively small area of parameters which, however, is the most interesting for practical applications. The Landau damping rate and the beam Schottky spectra are computed assuming that validity condition is satisfied. The results are applied to a round Gaussian beam. The stability thresholds are described by simple fits for the cases of chromatic and octupole tune spreads.

Collective Instabilities in the Tevatron Complex

Although the luminosity growth for Tevatron Run II was slower than expected, steady growth of luminosity has been demonstrated during the last three years with the peak luminosity of 1.02×1032 cm−2s−1 achieved in July 2004. Suppression of instabilities has been a valuable contributor to the luminosity growth. This report discusses the transverse instabilities in the Tevatron and Recycler.

Optimization of electron cooling for a medium energy accumulator ring

Abstract The binary collision model of electron cooling is used to discuss the principal issues in the use of electron cooling for accumulating ions at medium energies, where “medium energy” is defined by a beam velocity >0.8 c . Some new general results are developed which are important in this context. Longitudinal and transverse cooling rates are calculated analytically for a particle executing betatron oscillations in a storage ring. The formulas obtained are compared with numerical results. Particular attention is paid to the case in which the transverse components of the relative velocities substantially exceed the longitudinal components. The exact analytical results for finite electron temperatures are presented. The time for longitudinal cooling of a Gaussian beam is calculated as a function of the acceptable fraction of uncooled particles; the optimum electron beam size is calculated and an optimum electron density distribution is found. The results obtained are applied to an electron cooling system for the Fermilab Recycler (Jackson, FERMILAB-TM-1991, Unpublished Internal Note, November 1999); the cooling time, optimum parameters and tolerances are calculated.

Scenario for electron cooling of antiprotons in the Recycler

Abstract A system of electron cooling of antiprotons in the Recycler must satisfy certain conditions. Analytic and numeric calculations of the cooling process allow to specify these requirements.

Optics of electron beam in the Recycler

Electron cooling of 8.9 GeV/c antiprotons in the Recycler ring (Fermilab) requires high current and good quality of the DC electron beam. Electron trajectories of ∼0.2 A or higher DC electron beam have to be parallel in the cooling section, within ∼ 0.2 mrad, making the beam envelope cylindrical. These requirements yielded a specific scheme of the electron transport from a gun to the cooling section, with electrostatic acceleration and deceleration in the Pelletron. Recuperation of the DC beam limits beam losses at as tiny level as ∼0.001%, setting strict requirements on the return electron line to the Pelletron and a collector. To smooth the beam envelope in the cooling section, it has to be linear and known at the transport start. Also, strength of the relevant optic elements has to be measured with good accuracy. Beam‐based optic measurements are being carried out and analysed to get this information. They include beam simulations in the Pelletron, differential optic (beam response) measurements and si...

Instability of a witness bunch in a plasma bubble

The stability of a trailing witness bunch, accelerated by a plasma wake accelerator (PWA) in a blow-out regime, is discussed. The instability growth rate as well as the energy spread, required for BNS damping, are obtained. A relationship between the PWA power efficiency and the BNS energy spread is derived.

Recycler Electron Cooling Project: Mechanical vibrations in the Pelletron and their effect on the beam

The Fermilabs Recycler ring will employ an electron cooler to cool stored 8.9 GeV antiprotons [1]. The cooler is based on an electrostatic accelerator, Pelletron [2], working in an energy-recovery regime. A full-scale prototype of the cooler has been assembled and commissioned in a separate building [3]. The main goal of the experiments with the prototype was to demonstrate stable operation with a 3.5 MeV, 0.5 A DC electron beam while preserving a high beam quality in the cooling section. The quality is characterized, first of all, by a spread of electron velocities in the cooling section, which may be significantly affected by mechanical vibration of the Pelletron elements. This paper describes the results of vibration measurements in the Pelletron terminal and correlates them with the beam motion in the cooling section.

Pepper-pot scraper parameters and data processing

Parameters required for the pepperpot scraper are described, and its data processing is proposed.

Envelope instability as a source of diffusion

Abstract Electron cooling increases the phase space density of the cooled particles up to a certain limit. This limit is normally characterized by a strong space charge tune shift, about 0.2–0.3. This tune shift is high enough to bring the cooled beam to the threshold of the envelope instability. The envelope instability can be in a kind of dynamic equilibrium with the cooling, keeping the cooled beam at a threshold with a high level of the coherent noise. This noise acts as a diffusion for the halo particles which puts a limit on the stored current.