A. A. Glazov

The development of enabling technologies for producing active interrogation beams

A U.S./Russian collaboration of accelerator scientists was directed to the development of high averaged-current (∼1u2002mA) and high-quality (emittance ∼15u2002πmmu2009mrad; energy spread ∼0.1%) 1.75 MeV proton beams to produce active interrogation beams that could be applied to counterterrorism. Several accelerator technologies were investigated. These included an electrostatic tandem accelerator of novel design, a compact cyclotron, and a storage ring with energy compensation and electron cooling. Production targets capable of withstanding the beam power levels were designed, fabricated, and tested. The cyclotron/storage-ring system was theoretically studied and computationally designed, and the electrostatic vacuum tandem accelerator at BINP was demonstrated for its potential in active interrogation of explosives and special nuclear materials.

RF CAVITY SIMULATIONS FOR SUPERCONDUCTING CYCLOTRON C400

Compact superconducting isochronous cyclotron C400 [1] has been designed at IBA (Belgium) in collaboration with the JINR (Dubna). This cyclotron will be the first cyclotron in the world capable of delivering protons, carbon and helium ions for therapeutic use. 12C6+ and 4He2+ ions will be accelerated to 400 MeV/u energy and extracted by electrostatic deflector, H2+ ions will be accelerated to the energy of 265 MeV/u and extracted by stripping. It is planned to use two normal conducting RF cavities for ion beam acceleration in the cyclotron C400. Computer model of the double gap delta RF cavity with 4 stems was developed in the general-purpose simulation software CST STUDIO SUITE. Necessary resonant frequency and increase of the voltage along the gaps were achieved. Optimization of the RF cavity parameters leads us to the cavity with quality factor about 14000, RF power dissipation is equal to about 50 kW per cavity.

A Cyclotron Complex for Accelerating Multicharged Ions up to Relativistic Energies

The accelerating complex for the production of the multicharged ion beams up to uranium with a final energy of 300 MeV/amu is described. It is supposed to use a Wideroe type accelerator at the first stage of acceleration (up to 0.59 MeV/amu), a conventional isochronous cyclotron at the second stage (up to 10 MeV/amu), and an isochronous cyclotron with superconducting magnet coils at the final stage. Such a structure of the accelerating complex provides high beam intensity at the full energy of 300 MeV/amu (about 1013 particles per second for uranium), and the intermediate energy of 10 MeV/amu (about 1014 particles per second for uranium). Some preliminary parameters of the accelerator are presented.

Positron emission isotope production cyclotron in DLNP JINR (Status Report)

A C10-cyclotron for radioisotope production is under construction at the Dzhelepov Laboratory of Nuclear Problem, Joint Institute for Nuclear Research (DLNP JINR). It is a compact isochronous cyclotron for accelerating H− ions to the energy of about 10 MeV. The magnetic system, vacuum chamber and accelerating system is being built now. Results of the calculation and forming of the cyclotron magnetic field and the study of the beam dynamics from an ion source to an extraction system in calculated magnetic field are presented.

Detection of Explosives Using Nuclear Resonance Absorption of Gamma Rays in Nitrogen: A Russian/US Collaboration

A summary of the work performed to date is presented. The project brings together accelerator scientists in the US and Russia to develop high-current charged-particle accelerators for applications to explosives detection. These include an electrostatic tandem accelerator of novel design and a compact cyclotron and storage ring with energy compensation and electron cooling.

Experimental Research of the Closed Orbit Expansion Effect in the Strong Focusing Cyclotron

The theoretical and experimental study of beam extraction method using the closed orbit expansion effect is described. The steep slope of the magnetic field variation magnitude is used to change the momentum compaction factor for the limit radial area. The orbit separation is found by computing the dynamical equations, since the behaviour of the betatron oscillation frequencies and the beam phase are investigated in this radial region. The experimental study of the effect is carried out with the ring cyclotron electron model, which is a strong focusing eight sector isochronous cyclotron. Calculated orbit separation in the extraction area is about 2+4 cm. The magnet system which is to obtain the proper gradient of the magnetic field variation and the magnet measurements results are described. The measured value of the orbit separation equals 4 cm. At the same time the space between two orbits without current (free of particles) is about 2 cm and the full current on the separated orbit is equal to that before separation. The theoretically predicted beam phase shift is found to be equal to 30+40°. The obtained results confirm the possibility of the 100% beam extraction from the accelerator with space magnetic field variation.

Free particle oscillation frequency in an isochronous cyclotron as affected by space charge

Theoretical and experimental results are presented from a study of the effect of ionic space charge on the frequency of the free axial oscillations in an isochronous synchrotron. The axial oscillation frequency was determined by resonance excitation of free oscillations with an external electric field. It is shown that the change in frequency of the axial oscillations as a function of space charge density agrees with the results of the theoretical treatment. An experimental determination was made of the azimuthal dimension of the accelerated particle burst at different radii. The studies were made in the Nuclear Problems Laboratory of the United Institute of Nuclear Studies, on a cyclotron with spatial variation of the magnetic field.

A CYCLOTRON WITH A SPATIALLY VARYING MAGNETIC FIELD

This article is devoted to the design of a cyclotron with a spatially varying magnetic field. The basic conclusions of the linear theory of motion of charged particles in a magnetic field of periodic radial and azimuthal structure are given. The theoretical and experimental results of the study of nonlinear resonance close to the center of the accelerator are presented. Formulas are obtained for the calculation of required magnetic field configurations. Methods of shimming, measurement, and stabilization of the magnetic field are suggested. An accelerator designed with pole faces of diameter 120 cm was used for modeling the ion phase motion and for investigating spatial stability. Deuterons were accelerated to an energy of 13 Mev at an accelerating voltage of 5 kv.

Starting up of the cyclotron with space variation of the magnetic field

The mean magnetic field increase along the radius in accordance with relativistic mass increase of the accelerating ions is discussed. The magnetic field increase is necessary for the elimination of non-linear resonance effects at the center of the accelerator. Measurements of the magnetic field were made with an accuracy of plus or minus 1.5 gauss by a nuclear magnetometer. Deuterons were accelerated to an energy of 12 Mev and alpha particles of 24 Mev when the minimum amplitude of the accelerating voltage on the dee was 8 kv. All measurements were carried out with the intensity of the internal beam close to 1 mu a. (B.O.G.)