Compact RF ion source for industrial electrostatic ion accelerator.

Korea Multi-purpose Accelerator Complex is developing a single-ended electrostatic ion accelerator to irradiate gaseous ions, such as hydrogen and nitrogen, on materials for industrial applications. ELV type high voltage power supply has been selected. Because of the limited space, electrical power, and robust operation, a 200 MHz RF ion source has been developed. In this paper, the accelerator system, test stand of the ion source, and its test results are described.

Compact microwave ion source for industrial applications.

A 2.45 GHz microwave ion source for ion implanters has many good properties for industrial application, such as easy maintenance and long lifetime, and it should be compact for budget and space. But, it has a dc current supply for the solenoid and a rf generator for plasma generation. Usually, they are located on high voltage platform because they are electrically connected with beam extraction power supply. Using permanent magnet solenoid and multi-layer dc break, high voltage deck and high voltage isolation transformer can be eliminated, and the dose rate on targets can be controlled by pulse duty control with semiconductor high voltage switch. Because the beam optics does not change, beam transfer components, such as focusing elements and beam shutter, can be eliminated. It has shown the good performances in budget and space for industrial applications of ion beams.

A method to measure the frequencies of individual half cells in a dumbbell cavity.

Dumbbell fabrication is a midprocess for manufacturing an elliptical superconducting rf cavity. In order to understand how a welding shrinkage affects a dumbbell's frequencies and length, we need to measure the exact frequencies of each individual half cell of a dumbbell. To improve such a calculation precision and to simplify the calculation formulae, based on a two-coupled oscillator model and a cavity perturbation theory, a new formula to calculate the individual half-cell frequencies of a dumbbell or the individual cavity frequencies of a two-cavity coupling system has been developed, and its performance has been confirmed by using a dumbbell simulation. This formula can be applied to any kind of rf cavities with electric, magnetic, or electromagnetic coupling, if a coupling hole between two coupling cavities is small compared to the wavelength. Compared to other calculation formulae, this formula simplifies the calculation process of the individual resonator frequencies of a coupling system considerably, and it can also improve the calculation precision than that of a normal calculation method. Another advantage of this new method is that we do not need to consider a coupling factor between two resonators during a testing for an individual resonator frequency of an oscillator. The developed formula has been successfully used to tune the PEFP dumbbells.

Compact magnetic quadrupole triplet for a low-energy high-current ion beam transport.

It is a difficult task to design a conventional quadrupole triplet as compact and simple as solenoids for high-current ion beam transport. In the design of a quadrupole triplet presented here, we installed three poles with the same orientation on a yoke and these were excited using two coils located between poles. This new design allows the easier fabrication of a compact quadrupole triplet compared to the conventional design. Simple equations for the preliminary design were obtained. A prototype with an aperture radius of 55 mm and a focusing power of 3.3 m(-1) for 50 keV proton beams was designed, fabricated, and tested. The measured field profile agreed well with the calculated profile. The length of the compact magnetic quadrupole triplet was comparable with a solenoid, and its electrical power consumption was about 40% that of a solenoid.

Fast triggers for a proton injector at PEFP.

A fast timing system has been developed to control transistor transistor logic (TTL) trigger signals which are used to extract the pulsed proton beam from an ion source with the precision of less than submicro seconds. The system has been designed to set a delay and duty of the pulses, respectively, and prohibit the beam pulse by an external interlock signal. The system is based on VME which is composed of VME CPU and fast I/O boards with fan-out modules. The software of the system has been developed by the record/device supports and channel access in the core of the EPICS environments. In the paper, we describe software configurations and hardware drivers.

A control system of a negative hydrogen ion sources by using an EPICS-based proportional-integral-derivative.

We have developed an EPICS-based control system for a multicusp negative ion source based on a VME IOC software, a sequencer controlling a closed proportional integral (PI) loop, and an interlock. The PI loop was tuned by a step input voltage, and tuning gains of the proportion and integral have been determined. The PI logics, developed by using standard proportional-integral-derivative records, can control the arc current within +/-1% of a given set value.

Test results of the proton injector of the Proton Engineering Frontier Project accelerator.

One of the goals of the Proton Engineering Frontier Project (PEFP) is to develop a 100 MeV proton accelerator. As a low energy part, a 20 MeV proton linac has been developed and tested. The 20 MeV accelerator consists of a 50 keV proton injector, a 3 MeV radio frequency quadrupole, and a 20 MeV drift tube linac. The proton injector includes a duoplasmatron type ion source and a low energy beam transport. After a preliminary test with 1 mA peak current of the 20 MeV accelerator, the proton injector was modified with the goal of increasing the 20 MeV beam current up to 20 mA peak value. The modifications include the reduction of the proton injector length, installation of a beam current monitor, and electron trap and supplement of the solenoid and steering magnets. In this paper, the modifications of the PEFP proton injector are described and initial test results are presented.

Development of a MeV proton beam irradiation system.

A proton beam irradiation system for the application of the MeV class proton beam, such as an implantation for a power semiconductor device and a smart-cut technology for a semiconductor production process, has been developed. This system consists of a negative ion source, an Einzel lens for a low energy beam transport, accelerating tubes, a gas stripper, a Cockroft-Walton high voltage power supply with 1 MV, a vacuum pumping system, and a high pressure insulating gas system. The negative hydrogen ion source is based on TRIUMF's design. Following the tandem accelerator, a pair of magnets is installed for raster scanning of the MeV proton beam to obtain a uniform irradiation pattern on the target. The system is 7 m long from the ion source to the target and is optimized for the proton beam irradiation. The details of the system development will be described.