Accelerator vacuum systems, which are adequate for the acceleration of intense beams of light elements, may not be suitable for heavy ions which have large charge changing cross sections. Charge ...charging collisions with residual gases in the accelerator tubes produce a continuous distribution of ion energies as well as the desired discrete energy output of the accelerator. An MP tandem with a carbon foil terminal stripper was used to accelerate Iodine ions. The attenuation of the unique energy beam components due to unwanted charge changing collisions was measured by energy and magnetic analysis of the accelerator output. The effects of terminal pumping, vacuum deterioration due to added gas, and reduction of the accelerator tube conductance were studied with particular attention to high charge states. Under typical conditions with a 6 MV terminal and pressure ~ 4 × 10-6 Torr in the terminal region, the total beam attenuation was ~20%.
An 800 l/s electrostatic ion pump and a 500 l/s magnetic triode ion pump have been tested to determine which would be most suitable for pumping the hydrogen gas emanating from a duoplasmatron ion ...source. The ion source and pump will be located in the terminal of a High Voltage Engineering Corporation (HVEC) type MP tandem accelerator. The two pumps were mounted on a pump test stand with a manometer, two needle valves, and two ion gauge controllers. The hydrogen flow to each pump was increased slowly until the pump was near the point of pressure instability. Flow rates and pressure were recorded for approximately 1000 hours. The performance of the magnetic triode ion pump was superior to that of the electrostatic pump. The magnetic triode ion pump has undergone another test pumping the hydrogen gas from a duoplasmatron. Pumping speed measurements, modes of failure, and other details of these continuing tests will be presented.
Bunching and chopping for tandem accelerators. Part II: Chopping Lobanov, Nikolai R.; Linardakis, Peter; Tempra, Daniel
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
07/2021, Letnik:
499
Journal Article
Recenzirano
Odprti dostop
•Beams of 1H1+, 7Li3+, 16O6+ and 58Ni12+ ions were chopped successfully in a wide range beam energy.•The measurements carried out to test the performance of the chopping system confirm the validity ...of the expressions used in the design.•The analytical expression should be used for interpretation of BPM profile of the beam modified by chopper action to reconstruct the correct maximum beam displacement.•If a parallel plate sine wave chopper is used, there is an evidence of significant loss of transmission through the 90° non-achromatic analyzing magnet, due to the increase of beam emittance, especially for heavy ions.
A chopping system of a tandem accelerator based on two pairs of parallel plates is investigated. The first chopper operating at 37.5 MHz cuts off the tails of the bunched beam and the second, at a lower frequency of 4.6875 MHz, eliminates the satellite low intensity pulses. The experimental procedures for measurement of the performance of a chopping system including a Beam Profile Monitor (BPM) technique and a pulsed beam diagnostic monitor are described. The results of simulations and experimental observations are presented. An analytical technique to reconstruct the real profile of deflected beams from the profile measured with a BPM is discussed in detail. Theoretical and experimental data on the chopper scanning window are presented. An analyses of the factors limiting the chopping system performance is conducted and technical solutions to overcome it are discussed.
Bunching and chopping for tandem accelerators. Part I: Bunching Lobanov, Nikolai R.; Linardakis, Peter; Tempra, Daniel
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
07/2021, Letnik:
499
Journal Article
Recenzirano
Odprti dostop
•Ion beams were pulsed successfully in a wide range of parameters.•The measurements confirm the validity of the expressions used in the design.•Good correlation obtained between observed and ...theoretical bunched pulsed waveforms.•For the heavy ions, the performance is restricted by transit time variation.
A pulsed system capable of delivering up to a few microamps with a mass range 1–100 u, and with pulse width of bursts of ions approximately 1–2 ns is described. Critical design limitations are discussed to show the overall approach to meet a number of experimental requirements. The system consists of a SNICS negative ion source, a low energy buncher which uses the entire tandem electrostatic accelerator as a drift path to produce bunched ion bursts at the targets or linac entry, and high energy choppers. The buncher consists of a single acceleration gap with aligned removable grids. A detailed analysis is presented of the factors limiting the system performance, with the aim to lessen their effect on the ultimate minimum longitudinal phase space of the ion burst.
CologneAMS is a new centre for accelerator mass spectrometry (AMS) at the University of Cologne. It has been funded by the German Research Foundation (DFG) to improve the experimental conditions ...especially for those German scientists that apply the AMS technique for their geologic, environmental, nuclear chemical, and nuclear astrophysical research. The new AMS-device has been built by High Voltage Engineering Europe (HVEE) and has been installed in the existing accelerator area of the Institute of Nuclear Physics. The AMS-facility is designed for the spectrometry of 10Be, 14C, 26Al, 36Cl, 41Ca, 129I in and heavy ions up to 236U and 244Pu. The central part of the AMS-facility is a 6MV Tandetron™ accelerator. Downstream of the high energy mass spectrometer an additional switching magnet is used as a further filter element which supplies also additional ports for future extensions of the detector systems. The current status of CologneAMS and the results of the first test measurements will be presented.
Epithermal neutron source based on a tandem accelerator with vacuum insulation and lithium target has been proposed, developed and operated in Budker Institute of Nuclear Physics. The source is ...regarded as a prototype of a future compact device suitable for carrying out BNCT in oncology centers. In this work the measurements of gamma-ray and neutron radiation are presented for the interaction of a 2MeV proton beam with various materials (Li, C, F, Al, V, Ti, Cu, Mo, stainless steel, and Ta). The obtained results enabled the optimization of the neutron-generating target and the high energy beam transportation path.
•Radiation is measured for interaction of 2 MeV protons with various materials.•Absorption of protons in molybdenum and tantalum leads to minimal radiation.•Neutron generating target with thin lithium layer for BNCT must be made of tantalum.
The new 6MV multi-nuclide AMS facility at the University of Tsukuba Sasa, Kimikazu; Takahashi, Tsutomu; Matsumura, Masumi ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
10/2015, Letnik:
361
Journal Article
Recenzirano
The former accelerator mass spectrometry (AMS) system installed on the 12UD Pelletron tandem accelerator at the University of Tsukuba was completely destroyed by the Great East Japan Earthquake on 11 ...March 2011. A replacement has been designed and constructed at the university as part of the post-quake reconstruction project. It consists of a 6MV Pelletron tandem accelerator, two multiple cathode AMS ion sources (MC-SNICSs), and a rare-particle detection system. The 6MV Pelletron tandem accelerator will be applied not only to AMS, but also to areas such as nanotechnology, ion beam analysis, heavy ion irradiation, and nuclear physics. The rare-particle detection system will be capable of measuring environmental levels of long-lived radioisotopes of 10Be, 14C, 26Al, 36Cl, 41Ca, and 129I. It is also expected to measure other radioisotopes such as 32Si and 90Sr. The 6MV Pelletron tandem accelerator was installed in the spring of 2014 at the University of Tsukuba. Routine beam delivery and AMS experiments will start in 2015.
