Trubnikov, G. V.

Paper	Title	Page
THAP02	Implementation of Synchrotron Motion in Barrier Buckets in the BETACOOL Program	163
	A. V. Smirnov, A. O. Sidorin, G. V. Trubnikov JINR, Dubna, Moscow Region O. Boine-Frankenheim GSI, Darmstadt
	In the case of the internal pellet target the electron cooling and the stochastic cooling systems cannot compensate the mean energy losses of the ion beam. In bunched ion beams the space charge limit is reduced and the influence of intrabeam scattering is enhanced, which causes a decrease of the luminosity in comparison with a coasting beam. To resolve these problems barrier buckets are proposed for experiments with the pellet target. In the barrier bucket the long ion bunch fills nearly the whole circumference of the storage ring and a rf pulse is applied at the head and at the tail of the bunch. The general goal of the BETACOOL program is to simulate long term processes (in comparison with the ion revolution period) leading to the variation of the ion distribution function in six dimensional phase space. The investigation of the beam dynamics for arbitrary distribution functions is performed using multi particle simulation in the frame of the Model Beam algorithm. In this algorithm the ion beam is represented by an array of macro particles. The heating and cooling processes involved in the simulations lead to a change of the particle momentum components and particle number, which are calculated each time step. The barrier bucket model was developed in the Model Beam algorithm of the BETACOOL program. The trajectory of each model particle is solved analytically for a given barrier bucket voltage amplitude. An invariant of motion is calculated from the current position of the model particle and from the barrier bucket voltage amplitude. Then the phase of the invariant is calculated in accordance with the integration step and the particle gets a new coordinates. The heating and cooling effects are applied in usual procedure of the Model Beam algorithm. First simulation results for the FAIR storage rings are presented.
WEM1C01	Status of the LEPTA Project	113
	A. G. Kobets, E. V. Ahmanova, V. Bykovsky, I. I. Korotaev, V. I. Lokhmatov, V. N. Malakhov, I. N. Meshkov, V. Pavlov, R. Pivin, A. Yu. Rudakov, A. O. Sidorin, A. V. Smirnov, G. V. Trubnikov, S. Yakovenko JINR, Dubna, Moscow Region
	The Low Energy Positron Toroidal Accumulator (LEPTA) is under commissioning at JINR. The LEPTA facility is a small positron storage ring equipped with the electron cooling system. The project positron energy is of 4-10 keV. The main goal of the facility is to generate an intense flow of positronium atoms–the bound state of electron and positron. The focusing system of the LEPTA ring after solenoidal magnetic field remeasurement and correction has been tested with pulsed electron beam by elements. Some resonant effects of beam focusing have been observed. The experiments aiming to increase the life time of the circulating electron beam and test the electron cooling elector beam are in progress. Construction of the pulsed injector of the low energy positrons is close to the completion (CPS). The injector is based on 22Na radioactive isotope and consists of the cryogenic positron source, the positron trap and the acceleration section. In the CPS positrons from the 22Na tablet are moderated in the solid neon and transported into the trap, where they are accumulated during about 80 seconds. Then accumulated positrons are extracted by the pulsed electric field and accelerated in electrostatic field up to required energy (the injector as a whole is suspended at a positive potential that corresponds to required positron energy in the range of 4-10 keV). In injection pulse duration is about 300 nsec. The CPS has been tested at the low activity of isotope 22Na tablet (100 MBq). The continuous positron beam with average energy of 1.2 eV and spectrum width of 1 eV has been obtained. The achieved moderation efficiency is about 1 %, that exceeds the level known from literature. The accumulation process in the positron trap was studied with electron flux. The life time of the electrons in the trap is 80 s and capture efficiency is about 0.4. The maximum number of the accumulated particles is 2·10+8 at the initial flux of 5·10+6 electrons per second.
	Slides