R. A. Jameson

Nd-YAG laser ion source for direct injection scheme

The feasibility of a “direct injection scheme” using Nd–yttritium–aluminum–garnet laser has been studied experimentally. The relationship between charge distribution and laser power density was measured. The obtained yield rate of C6+ was 46.8% at the peak current pulse with 1.6×1011u200aW/cm2 laser intensity. The current dependence of the distance from the target at this intensity was measured. The peak current of C6+ will be 60 mA with φ4.8 mm extraction aperture. It was found from the input beam condition simulation by the code PTEQ–HI that high current (from 12 to 28.6 mA) can be accelerated by the TIT–RFQ.

Simulation of direct injection scheme for RFQ linac

A new efficient injection method from a laser ion source to a RFQ was proposed and is being tested in RIKEN (The Institute of Physical and Chemical Research, Japan). Laser plasma is induced just before the entrance of the RFQ and is injected directly into the RFQ channel. In order to understand this new scheme, a particle tracking simulation study, which focused on the entrance of the RFQ, has been started with three-dimensional (3D) space charge effect in a realistic 3D electric field map. According to the beam tracking calculation, the predicted currents are smaller than experimentally obtained values. To obtain better accuracy of the simulation, motion of electrons should be described adequately.

Acceleration of high current fully stripped carbon ion beam by direct injection scheme

Acceleration of a 17mA, 100keV∕u C6+ ion beam has been successfully achieved with an radio frequency quadrupole (RFQ) linac by means of “direct injection scheme.” The C6+ beam produced by a laser ion source with a Nd:YAG laser was injected to the high current RFQ linac. It has been experimentally proved that the fully stripped carbon ion beam with a current more than 10mA was accelerated by the RFQ linac.

High current carbon beam production with direct plasma injection scheme

We have been studying a new heavy-ion production technique called “direct plasma injection scheme,” DPIS, since 2000. A new radio frequency quadrupole (RFQ) designed especially for the DPIS was commissioned in 2004 and very intense carbon beam was successfully obtained, reaching more than 60mA accelerated current from the RFQ. Most of the contents of the accelerated beam was carbon 4+ as verified by beam analysis.

Acceleration of heavy ion beams by means of direct injection into RFQ Linac

A heavy ion source based on a new principle of direct plasma injection system was developed at Tokyo Institute of Technology. This heavy ion source combines directly a laser ion source and a radio frequency quadrupole (RFQ) LINAC. We carried out an acceleration test of carbon ions on this source and proved this principle. An observed total carbon beam current of 8 mA at 214 keV/u was observed. Beam analysis using a bending magnet downstream of the RFQ LINAC showed that accelerated beam includes 4.0 and 0.8 mA C4+ and C3+, respectively.

Carbon beam acceleration using a simple injection method into an RFQ

Abstract For medium-heavy ions, a new injection method into a RFQ linac is proposed. Laser plasma is created by an intense pulsed laser system and directly injected into the RFQ without any focusing devices. This method may eliminate complex difficulties due to space-charge effects in the low-energy transport system. Using the TITech RFQ, a verification test has been performed. From the laser ablated carbon plasma, C 4+ and C 3+ beams were captured successfully and were accelerated to the designed energy of the RFQ. The observed total current of carbon beam reached 8 mA, which exceeded the designed current of the RFQ. This method can be easily applied to existing RFQs which are used in medical and industrial accelerator systems.

Time structure of an accelerated beam using a radio-frequency quadrupole linac with direct plasma injection scheme

In direct plasma injection scheme, the relation between the ion current from a laser ion source and the accelerated beam current by a radio-frequency quadrupole (RFQ) linac was studied by a series of the following analyses. First, ion current at beam extraction was calculated from measured plasma parameters using a scaling law. Second, the beam emittance at the entrance of acceleration electrode region was evaluated by the simulation of the ion extraction out of the ion source plasma using the result of the first calculation. Last, the accelerated beam current could be reproduced by the simulation of beam acceleration using the results of the second. The second calculation revealed the time variation in the injected beam parameter to the RFQ linac. Then it was proved that the time structure of the accelerated beam was different from that of the injection beam because the degree of the matching between the injected beam emittance and the RFQ acceptance varied with time.

Direct plasma injection scheme in accelerators.

The idea of direct plasma injection scheme (DPIS) was proposed in 2000. This new technique has been studied and proven to accelerate intense ion beams. To provide medium mass ions with highly charged states, small tabletop solid lasers were used for plasma production. Based on the measured plasma properties, aluminum and carbon ions were accelerated with more than 60 mA of current. The next experiments will use an radio frequency quadrupole designed for q/m=1/6 and explore beam productions using targets up to silver, and future work will explore production up to uranium. The DPIS has been established and is ready to be used with various accelerators which require pulsed high current, high charge state ion beams.

60 mA Carbon Beam Acceleration with DPIS

We have studied direct plasma injection scheme (DPIS) since 2000. This new scheme is for producing very intense heavy ions using a combination of an RFQ and a laser ion source. An induced laser plasma goes directly into the RFQ without an extraction electrode nor any focusing devices. Obtained maximum peak current of Carbon beam reached 60 mA with this extremely simple configuration.

A direct plasma injection system into an RFQ for clean and safe ion implantation

A new injection system, direct plasma injection system, was tested and its principle was proved successfully. We found that one of advantages of this injection system was efficient consumption of source materials. Large portions of induced ions can be injected into a first stage accelerator. This feature is quite useful for ion implantation applications, because toxic exhaust gas can be eliminated. In order to utilize this system for industrial application, the feasibility of a boron injection scheme using a Nd:YAG laser system was investigated.