Injection and stability of high-intensity ion beams in synchrotrons with electron cooling
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jection and Stability of HighIntensity Ion Beams in Synchrotrons with Electron Cooling E. M. Syresin Joint Institute for Nuclear Research, ul. JoliotCurie 6, Dubna, Moscow oblast, 141980 Russia email: [email protected] Abstract—The electron coolingstacking injection is one of the most widely used injection methods applied in forming highintensity cooled ion beams in the synchrotrons. The maximum available ion intensity in the synchrotron is determined by the lifetime of ions and the coolingstacking efficiency. The formation of cooled highintensity beams is constrained by instability, leading to a strong reduction in the ion lifetime. The results of experimental investigations and simulations of the coolingstacking injection and stability of highintensity cooled ion beams in synchrotrons with electron cooling are discussed. DOI: 10.1134/S1063779615060052
INTRODUCTION The electron cooling method [1, 2] was first pro posed and implemented at the Institute for Nuclear Physics (Novosibirsk). It enabled the use of the stack ing method for particle storage in electron synchro trons when forming intense ion beams. The injection with electron cooling and stacking is used in ion syn chrotrons to increase a current by 5 to 20 times as compared to the injection current. It is used effectively in the storage rings and synchrotrons, in particular, at LEIR [3], SIS [4], COSY [5], HIMAC [6, 7], and SLSR [8]. In the course of multiturn injection, a new portion of ions is injected into the ring with high horizontal emittance. As a result of electron cooling, the ampli tude of betatron oscillations of injected ions decreases and the next portion of ions enters into the free space.
As an example, Fig. 1 shows the scheme of multiturn injection in the horizontal plane in the HIMAC med ical synchrotron [6, 7]. The electron cooling enables an automatic stacking of ions, and as a result, the ion current rises with time (Fig. 2). In the course of injection, the orbit of accumulated ions is displaced in the horizontal direction at a certain distance relative to the septum and newly injected ions perform betatron oscillations near an equilibrium orbit. The minimum clearance between the septum and the equilibrium ion orbit determines the accep tance of stacked ions. The distance between the equi librium ion orbit of stacked ions and the septum varies upon multiturn injection and causes filling the phase space in the horizontal direction. If in the course of cooling the amplitude of betatron oscillation of ions is smaller than the width of the horizontal gap between the septum and the equilibrium orbit, they are cap
Circulation orbit Septum electrode (injection orbit) Vacuum chamber
Projection of electron beam Iom beam after cooling Iom beam after multitum injection
65 mm 81 mm
Fig. 1. Schematic view of the vacuum chamber of the HIMAC synchrotron in the region of electrostatic inflector for multiturn injection.
919
920
SYRESIN (a)
(b)
Intensity, 109 ppp
Intensity, 109 ppp
3.0
1.5
I = 120 mA, R = 2, Tinj = 1.
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