RU2012169C1 - Method of injecting particles beam into accumulation ring - Google Patents

Abstract

FIELD: particle acceleration engineering. SUBSTANCE: typed E₂₁₀ electromagnetic field synchronized with particle revolution frequency is excited within acceleration ring section. Particles to be injected having pulse which differs from the central one, are directed into the area where longitudinal electrical component of electromagnetic field is maximum. EFFECT: increased intensity of particles beam. 1 dwg

Description

 The invention relates to accelerator technology, and in particular to the problem of injection of ions into a synchrotron or storage ring.

The usual method of injecting a particle beam into the closed orbit of a synchrotron is carried out using fast-cycling magnets or pulsed deflectors. The pulse duration of the magnetic field (voltage) should be of the order of microseconds with fronts of 10-20 ns. In order to increase the number of accumulated revolutions of the beam, the betatron phase space of the accelerator is filled by manipulating the shift of the central orbit using dipole magnets and the frequencies of betatron vibrations by quadrupole lenses, using, for example, spiral injection of particles, or using coupling resonances of axial and radial vibrations. Thus, the main requirement for the condition for obtaining an intense beam in the central orbit of the storage ring is the presence of a bright source — an ion injector, for example, a linear accelerator, which allows one to accumulate an intense particle beam over several revolutions. When using a cyclotron having a high average beam intensity (up to 10 ¹⁴ g / s) as an injector, the capture efficiency (conventional single-turn injection) is 10 ^-6 , i.e., the disadvantage is that there is a problem of obtaining an intense beam in ring.

 The aim of the invention is to increase the launch intensity of the accumulated particles.

The goal is achieved by the fact that in the known injection method, based on the action of the electrostatic field of the deflector on particles, a high-frequency electromagnetic field of type E ₂₁₀ , synchronized with the particle revolution frequency, is excited in the ring section, and injected particles with a pulse different by ΔP from the central one are sent to the maximum region of the longitudinal electric component of the electromagnetic field.

 The method is illustrated in the drawing.

 The essence of the method is as follows.

E_zoSinK_xX*SinK_yY*sin (ωt+φ),
B_y=

E_zocosK_xX*cosK_yY*cos (ωt+φ), где E_zo - амплитудное значение продольной составляющей электрического поля; K_x, K_y, K - волновые векторы; K_x = 2 π /a, K_y = 2π /b, K₂ = K_x ²+ K_y ² (изложенным выше требованиям удовлетворяет и волна Е₁₁₀ в круглом волноводе).Particles are injected into the storage device — a synchrotron in the median plane, using a high-frequency (including) resonator, the electromagnetic field of which has a longitudinal component of the electric field E _z with a sinusoidal radius distribution, where zero voltage falls on the central closed orbit of the storage device, and the maximum voltage - about half the radial aperture (track) of the drive. This can be a rectangular resonator with axbxd dimensions, in which oscillations of an electromagnetic field of the E ₂₁₀ type are excited. The field components in the middle plane of the resonator are written as:
E _z = -E _zo SinK _x X * cosK _y Y * cos (ωt + φ),
B _x =

E _zo SinK _x X * SinK _y Y * sin (ωt + φ),
B _y =

E _zo cosK _x X * cosK _y Y * cos (ωt + φ), where E _zo is the amplitude value of the longitudinal component of the electric field; K _x , K _y , K are wave vectors; K _x = 2 π / a, K _y = 2π / b, K ₂ = K _x ² + K _y ² (the above requirements are also satisfied by the wave E ₁₁₀ in a circular waveguide).

(

+a/4)= P_у+ΔP, где

,

- среднее магнитное поле и радиус центральной замкнутой орбиты кольца; Z_e- заряд иона. Проходя резонатор, установленный в месте максимального отклонения пучка по радиусу наружу (для определенного диапазона фаз в. ч. напряжения), импульс частицы уменьшается. С учетом времени пролета энергия, теряемая ионом в резонаторе, составит:
δw= ZE

Sin

sin

cos

β = φ / c ; λ- длина волны резонатора (при a= βλ/2, t_o= 0, x=

=

- δW_макс= ZE_zoβλ/Π ). Приближенно радиус частицы уменьшится на ΔR=

, W - энергия иона. Например, для ионов Xe⁺³⁰ ₁₃₂ , W = 50 МэВ/н,

= 8 м, E_zo = 20 кВ/см, λ = 60 см значение Δ R составит 2 мм, что позволит значительной части пучка на последующем обороте миновать тонкий (0,2 мм) септум дефлектора или малопротяженную по радиуса (2 мм) перезарядную мишень, сдвигаясь в дальнейшем к центральной орбите накопителя.A beam of charged particles using an electrostatic deflector or a recharge target is introduced into the storage ring into an orbit corresponding to the momentum _Pinj = Z

(

+ a / 4) = P _y + ΔP, where

,

- the average magnetic field and the radius of the central closed orbit of the ring; Z _e is the ion charge. Passing a resonator installed in the place of the maximum deviation of the beam along the radius outward (for a certain range of phases including the voltage), the particle momentum decreases. Given the time of flight, the energy lost by the ion in the resonator will be:
δw = ZE

Sin

sin

cos

β = φ / c; λ is the cavity wavelength (for a = βλ / 2, t _o = 0, x =

=

- δW _max = ZE _zo βλ / Π). Approximately, the particle radius decreases by ΔR =

, W is the ion energy. For example, for Xe ions ⁺³⁰ ₁₃₂ , W = 50 MeV / n,

= 8 m, E _zo = 20 kV / cm, λ = 60 cm, the value of Δ R will be 2 mm, which will allow a significant part of the beam to pass a thin (0.2 mm) septum of the deflector or a rechargeable one short in radius (2 mm) target, shifting further to the central orbit of the drive.

) = 3 Т. м, инжектируемым ионам - с P = P (

+ 5 см) и промежуточным - P = P (

+ 3 см).For example, the drawing shows the period of the magnetic structure of the storage ring (N = 6; ν ₂ = 2.7; ν _z = 1.64) with the characteristic functions of the twiss matrix and radial bending particle beam with ε _r = 5 x 5 mm mrad, ΔP / P = ± 0.5%, with a particle momentum corresponding to the central orbit P = P (

) = 3 T. m, injected ions - with P = P (

+ 5 cm) and intermediate - P = P (

+ 3 cm).

For efficient particle accumulation work in. h. Injector and drive systems must be synchronized. So, for example, for f the resonator = 500 MHz (T = 2 ns), f _cycle = 20 MHz (T = 50 ns) - τ bunch ≠ 1 ns (Δ φ = ± 3 ^° C). The resonator frequency must also be a multiple of the particle revolution frequency in the storage ring. To reduce the shift in the field revolution frequency per revolution (or dω -> 0), it is necessary to exclude the dependence of the closed orbit length on the spread of momenta, which is exactly true under the condition α = γ ^-2 [5], where γ is the relative energy of the particles; α is the coefficient of orbit expansion, which reduces to the formation in a certain way of the magnetic structure of the ring. It seems that the proposed method will allow multi-turn beam injection without the use of pulsed magnets and deflectors.

Claims (1)

METHOD OF BEAM INJECTION INTO THE ACCUMULATION RING, based on the action of the electrostatic field of the deflector on particles, characterized in that, in order to increase the intensity of the beam of accumulated particles, a high-frequency electromagnetic field is excited using a rectangular resonator in the portion of the ring located after the deflector in the direction of particle movement type E ₂₁₀ or with the help of a round resonator a high-frequency electromagnetic field of type E ₁₁₀ synchronized with the particle revolution frequency, and the injected particles with a pulse differing by Δ P from the equilibrium is directed to the region of the maximum longitudinal electric component of the electromagnetic field, where Δ P is the maximum deviation of the particle momentum from the equilibrium.

Images