S. Konstantinov

Multiaperture negative ion source

The long-pulse multiaperture surface-plasma source with negative ion production on a cesiated grid is under construction at Budker Institute. The ion source includes RF plasma driver, an expansion chamber with multicusp magnetic filed, an external magnetic filter and a four-electrode ion-optical system for beam extraction and acceleration. The projected parameters of the ion source are: beam current 1.5 A, beam energy 120 keV, pulse duration 100 s, RF power in plasma 40 kW, hydrogen filling pressure < 0.5 Pa, e/H− ratio 1:1, H− ions emission current density 30 mA/cm2.

First neutron generation in the BINP accelerator based neutron source.

Pilot innovative facility for neutron capture therapy was built at Budker Institute of Nuclear Physics, Novosibirsk. This facility is based on a compact vacuum insulation tandem accelerator designed to produce proton current up to 10 mA. Epithermal neutrons are proposed to be generated by 1.915 MeV protons bombarding a lithium target using (7)Li(p,n)(7)Be threshold reaction. The results of the first experiments on neutron generation are reported and discussed.

COMMISSION OF ELECTRON COOLER EC-300 FOR HIRFL-CSR

HIRFL-CSR, a new ion accelerator complex, is under construction at IMP, Lanzhou, China. It is equipped with two electron cooling devices. This article describes the commissioning of cooler at electron energy 300 keV. The cooler is one of the new coolers with some unique manufactured in BINP, Russia. It has a new electron gun producing a hollow electron beam, electrostatic bending and a new structure of solenoid coils at the cooling section. The test results of cooler obtained in Novosibirsk and Lanzhou are reported.

Efficient cesiation in RF driven surface plasma negative ion source

Experiments on hydrogen negative ions production in the large radio-frequency negative ion source with cesium seed are described. The system of directed cesium deposition to the plasma grid periphery was used. The small cesium seed (∼0.5 G) provides an enhanced H(-) production during a 2 month long experimental cycle. The gradual increase of negative ion yield during the long-term source runs was observed after cesium addition to the source. The degraded H(-) production was recorded after air filling to the source or after the cesium washing away from the driver and plasma chamber walls. The following source conditioning by beam shots produces the gradual recovery of H(-) yield to the high value. The effect of H(-) yield recovery after cesium coverage passivation by air fill was studied. The concept of cesium coverage replenishment and of H(-) yield recovery due to sputtering of cesium from the deteriorated layers is discussed.

Negative ion production in the RF multiaperture surface-plasma source

The experiments on negative hydrogen ion beam production in a multi-aperture long-pulse surface-plasma source are described. H- ions are produced on the surface of a plasma grid covered by cesium and illuminated by fast plasma particles. The source uses a radio-frequency driver to generate plasma. A composite magnet system made of external permanent magnets confines and filters electrons in the plasma region, and deflects them in the extraction area. A multiaperture, multi-electrode ion optical system is used for beam formation. The electrode heating and cooling during long pulses is accomplished by circulating a heat transfer fluid through channels drilled in the electrodes bodies. H- ions extraction through a single aperture and 21 apertures was performed and studied. A stable H- beam with the current up to 0.7 A, energy up to 74 kV, and pulse duration up to 7 s was routinely obtained

Precise Measurements of a Magnetic Field at the Solenoids for Low Energy Coolers

Description of equipment developed at BINP SB RAS for precision solenoid magnetic field measurement is presented in the paper. Transversal field components are measured by small compass‐based sensor during its motion along the field line. The sensor sensitivity is a few tenth parts of mG and is limited in this range by external noise sources only. Scope of the device application is illustrated by results obtained at BINP during tests of cooling solenoids for electron coolers built at the Institute recently.

Space charge oscillation in electron cooling devices

Electron cooling is used for improving the parameters of ion beams. The cooling efficiency depends drastically on the space charge fluctuation intensity in the beam. The fluctuations present in the cooling region cause the stochastic heating of the ions, which adversely affects the cooling efficiency and may even annihilate the ion beam. The space charge fluctuation intensity as a function of various operating parameters of a cooler is studied experimentally. A mechanism of fluctuation generation is suggested, and the effect of fluctuations on the ion beam parameters is estimated.

Emission properties of inductively driven negative ion source for NBI

H− beam with current ∽1A and energy up to 90 kV was routinely produced by the negative ion source, developed at Budker Institute of Nuclear Physics for N-NBI use. The essential source features are: the surface-plasma negative ion production on the plasma grid surface, the active temperature control of the ion-optical system electrodes, the convex magnetic field in the ion optics for the high-voltage holding enhancement, and the directed cesium deposition to the plasma grid electrode. The emission properties of the source have been studied for two RF driver configurations: with and without Faraday screen. Negative ion beam with current of 1.1 A, energy 93 keV and duration 1.6 s was produced in the cases of driver without Faraday screen. Beams with current of 0.6 A, energy 74 keV were obtained in pulses with duration of 25 s for driver with Faraday screen. Long-term stability of the beam current during 25 s pulse confirms the dynamic stability of cesium coverage on emission area of plasma grid electrode.