Low-energy Injection Research Articles

Ion effects in a compact electron storage ring

Ion-trapping and dc clearing effects on a stored beam in the beam energy range of 90–210 MeV were studied with a compact electron storage ring. The applied voltage and the number of electrodes used to clear trapped ions are discussed and compared with experimental data. It was demonstrated that the ion effects were noticeably reduced by the beam size growth and the decrease of gas desorption by synchrotron radiation with a decrease in beam energy. It was also found that the ion trapping became harmless with ion management near 150 MeV where the Touschek lifetime in this ring was shortest. This indicates that high beam current storage is possible using low-energy injection.

Low-energy injection rings

Low-energy injection into small electron storage rings is discussed. The most dominating effects like intrabeam scattering, ion trapping during injection and ramping are described. Examples of different low-energy injectors and their performance are given, and some features of the fast injection method are explained. Some numerical examples from the MAX storage ring are given, as well as some methods to increase the stored and ramped current.

Vacuum system design for a superconducting X-ray lithography light source

A superconducting electron storage ring for X-ray lithography (SXLS) is to be built at Brookhaven National Laboratory (BNL). The goal is to design and construct a light source specifically dedicated to X-ray lithography production and which would be used as a prototype in a technology transfer to American industry. The machine will be built in two phases: phase I, a low energy ring (200 MeV, 500 mA) using all room temperature magnets which will be used primarily for low energy injection studies. Phase II will be a full energy machine (690 MeV, 500 mA) where the room temperature 180° dipole magnets of phase I will be replaced with superconducting magnets. The machine, with a racetrack shape and a circumference of 8.5 m, is designed to be portable and replaceable as a single unit. This paper will discuss the vacuum system design for both phases; i.e. gas desorption, warm bore vs cold bore, ion trapping, clearing electrodes, and diagnostic instrumentation.

The superconducting x-ray lithography source program at Brookhaven (invited)

A compact electron storage ring with superconducting dipole magnets, is being developed at the National Synchrotron Light Source at Brookhaven. The parameters of the source have been optimized for its future use as an x-ray source for lithography. This first ring is a prototype which will be used to study the operating characteristics of machines of this type with particular attention being paid to low-energy injection and long beam lifetime.

Development of compact synchrotron light source for x-ray lithography (abstract)

Ishikawajima-Harima Heavy Industries Co., Ltd., (IHI) has developed a prototype compact synchrotron light source for x-ray lithography of semiconductors. It consists of 45-MeV linear accelerator as an electron injector and an 800-MeV synchrotron. Peak wavelength of synchrotron radiation is around 10 Å. The basic parameter of the synchrotron is as follows: (1) Beam current: more than 50 mA; (2) Beam life: more than 1 hr; (3) Circumference: 23.5 m; (4) Bending magnet: 1.33 T, 90° sector laminated core; (5) rf system: 178.5 MHz tetrode power supply. Our synchrotron is a so-called low-energy injection accelerator and various difficult problems such as ion trapping, vacuum, Touscheck effect will occur. So, we provide ion cleaning electrodes inside the vacuum chamber to avoid ion trapping. Also, we have adopted a trapezoidal magnet excitation method as an injection scheme to stimulate gas desorption of the vacuum chamber. The beamline extracted from the bending magnet will be used for various research subjects which include x-ray lithography, photoelectron spectroscopy, EXAFS, fluorescence analysis, and so on. This machine will be completed by the end of 1988 and is scheduled to use synchrotron radiation in the spring of 1989.

High power heating results on JT-60

From June to October 1987, JT-60 achieved fusion product (ne(0). tau E*.Ti(0)) of 6*1019 m-3.keV.s with hydrogen plasma at plasma current of 2.8 to 3.1 MA with neutral beam power of approximately 20 MW. The central electron density of 1.3*1020 m-3 was obtained at plasma current of 3 MA with 13 approximately 20 MW neutral beam power and the confinement time reached 0.14-0.18 s. An offset linear scaling law like the Shimomura-Odajima scaling on confinement time will be able to reproduce experimental data better than that of the Goldston type scaling. With low beam energy injection approximately 40 keV, confinement degradation was found. Many short periods (0.05 approximately 0.1 s) of H-mode phase were found in outside X-point divertor discharges with NB or NB+RF(LH or IC) heating power above 16 MW. However, improvement in energy confinement time was limited to 10 %. The ballooning/interchange stability analyses were also made for the outside X-point divertor equilibrium in connection with H0-phase capability. Heating powers of 9.5 MW and 1.9 MW were obtained by LHRF, ICRF injection, respectively. In combined LHRF and NB heating, the incremental energy confinement time of 0.064 s was obtained, which is the same level of that of NB heating only. In combined NB and on-axis ICRF heating of low ne discharge, an incremental energy confinement time of 0.21 s was obtained, which is three times as long as those of NB or ICRF heating only. High energy beam ions were accelerated by ICRF in the central region of the plasma.

Development Of A Compact Synchrotron Radiation System For X-Ray Lithography

In the work reported here, we estimate the design parameters of a superconductive synchrotron radiation (SR) ring employing the electron undulating method, which is capable of large-area exposure of SR. The optimum electron energy is found to lie in the range 0.6 to 0.7 GeV with a magnetic field B of 4.0 T to 4.5 T and a beam current in the range 200 to 300 mA. Research into the miniaturization of the SR ring and its injector to complete a practical SR system has continued. In particular, low energy injection improves the cost effectiveness of the SR system, but this requires further study. Therefore, the Electrotechnical Laboratory (ETL) of the Japanese Ministry of International Trade and Industry and Sumitomo Electric Industries, Ltd., jointly completed "NIJI-1," the first compact normal-conductive SR ring in the world designed for low energy injection studies. We succeeded in making the first beam storage in February 1986 and since then have achieved the storage of a beam current of more than 200 mA of 163-MeV electrons; its 1 /e lifetime was about 50 min. Research on topics such as high efficiency injection at low energy and miniaturization of the injector is continuing.

Ballistic transport in II–VI semiconductor compounds and alloys

Realistic band structures are used in calculating the group velocity and scattering rates for electrons with injection energies up to 1 eV in ZnTe, CdTe, and the low-effective-mass alloy Hg0.7Cd0.3Te. Scattering from longitudinal optical phonos, ionized impurities, and alloy disorder have been included in our full band-structure calculation, which automatically includes both intra- and intervalley scattering. Of the II–VI materials considered, at 77 K HgCdTe is superior for low injection energies (up to 0.25 eV) while CdTe is superior at higher injection energies (1 eV) at room temperature. The attainable mean free paths ( ≥ 1000 Å) and group velocities ( ≥108 cm/s) for both systems are comparable to values found in III–V systems.

Storage Ring Filling via Direct Production of Electron and Positrons by High Energy Protons

In the context of the proposals to build an electron proton colliding facility at Fermilab, the authors present a new scheme for the electron ring injector, based on the production of high energy electrons or positrons by a suitably prepared 100 GeV high intensity proton beam. With this scheme one can achieve electron ring filling times of a few minutes, while avoiding the instabilities associated with low energy injection.

The Radio-Frequency Quadrupole - A New Linear Accelerator

In many Laboratories, great emphasis now is placed on the development of linear accelerators with very large ion currents. To achieve this goal, a primary concern must be the low-velocity part of the accelerator, where the current limit is determined and where most of the emittance growth occurs. The use of magnetic focusing, the conflicting requirements in the choice of linac frequency, and the limitations of high-voltage dc injectors, have tended to produce lowvelocity designs that limit overall performance. The radio-frequency quadrupole (RFQ) linear accelerator, invented in the Soviet Union and developed at Los Alamos, offers an attractive solution to many of these low-velocity problems. In the RFQ, the use of RF electric fields for radial focusing, combined with special programming of the bunching, allows high-current dc beams to be captured and accelerated with only small beam loss and low radial emittance growth. Advantages of the RFQ linac include a low injection energy (20-50 keV for protons) and a final energy high enough so the beam can be further accelerated with high efficiency in a Wideroe or Alvarez linac. These properties have been confirmed at Los Alamos in a highly successful experimental test performed during the past year. The success of this test and the advances in RFQ design procedures have led to the adoption of this linac for a wide range of applications. The beam-dynamics parameters of three RFQ systems are described.

New Developments in Accelerator Technology at LASL

The objective of the PIGMI (Pion Generator for Medical Irradiations) program at LASL is to develop the technology to allow the construction of smaller, less expensive and more reliable proton linacs for medical applications. Now in the final year of a three year program, a prototype accelerator is being prepared for beam tests. The high electric field gradients required have already been achieved in PIGLET, an accelerator test cavity. The injector for the prototype features a compact ion source and accelerating column assembly, a double frequency buncher, a tape wound edge cooled solenoid magnet and a series of versatile beam diagnostic boxes. The control system makes use of distributed microprocessor control with a powerful operators console. This system is currently being used to tune the injector and to develop diagnostic tools for evaluation of the performance of the prototype. The accelerating cavity itself is a copperplated 450-MHz structure featuring an alternating phase focused section followed by a transition to a conventional drift tube structure employing permanent magnet focusing. An exciting new rf quadrupole structure (RFQ) which provides an alternate technique for achieving low energy injection will be tested with beam using the PIGMI prototype as a test stand. The design features and current status of the PIGMI program are discussed.

Low-Energy Linac Structure for Pigmi

The higher radio frequency (450 MHz) and lower injection energy (250 keV) of the PIGMI (Pion Generator for Medical Irradiations) linac design seriously compound the problem of beam containment in the first few meters of the structure. The conventional quadrupole-focused, drift-tube linac represents the best solution for beam energies above 8 MeV, but because of the small space available for quadrupoles in the PIGMI designs, cannot provide the required focusing at lower energies. A satisfactory solution to this focusing problem has been found based on pure alternating phase focusing for the first few MeV, followed by a smooth transition to a pure permanent magnet quadrupole-focused structure at 8 MeV. The structure and its calculated performance are described.

Reactor aspects of counterstreaming-ion tokamak plasmas

Toroidal DT plasmas in which the D and T ions make up two distinct, quasi-thermal velocity distributions, oppositely displaced in velocity along the magnetic axis, can be set up by introducing all ions by tangential injection of neutral beams, and by removing ions from the plasma shortly after they have decelerated to an energy <̃2Te by Coulomb drag on the plasma electrons. A simple physical model for this counterstreaming-ion operation allows one to deduce the ion velocity distributions and required energy and particle confinement times that are in good agreement with the results of previous Fokker-Planck calculations. These distributions are used to calculate fusion reactivities, from which the variation of fusion power gain and power density with injection energy and Te are determined. The practical problems of implementing counterstreaming operation in a tokamak include charge-exchange losses, impurities, and the need to minimize plasma re-cycling.Several properties of the counterstreaming system that make it advantageous for near-term reactor applications are (1) optimal performance at relatively low injection energy (40–60 keV), because of head-on nuclear collisions, (2) small electron energy confinement time for Q ∼ 1 (e. g. neτE ≈ 2 × 1012 cm−3·s at Te ≈ 3.5 keV), (3) fuelling solely by the injected beams, and (4) possible maintenance of the plasma current by the beams. For realistic tokamak parameters, neutron wall loading is limited to 0.5 MW/m2 or less. Plasma parameters appropriate to radiation test reactors and fusion-fission hybrid reactors are discussed.