Conference Proceeding

Uniform beam intensity redistribution in the LENS nonlinear transport line

IUCF, Bloomington
07/2007; DOI:10.1109/PAC.2007.4440885 In proceeding of: Particle Accelerator Conference, 2007. PAC. IEEE
Source: IEEE Xplore

ABSTRACT The Low Energy Neutron Source (LENS) at Indiana University is producing neutrons by using a 7 MeV proton beam incident on a Beryllium target. The Proton Delivery System is currently being upgraded [1], [2]. A new AccSys Technology,Inc. DTL section [3] will be added to increase proton beam energy from 7 to 13 MeV. A 3 MeV RFQ and 10 MeV DTL will be powered by two 1.25 MW klystrons. The goal of this upgrade is a 13 MeV,25 mA proton beam with duty factor greater than 3%. At this power level it becomes increasingly important to make a proton beam that is uniformly distributed to prevent excessive thermal stress at the surface of the Be- target. To achieve this goal two octupole magnets are being implemented in each LENS beam transport line. In this paper we discuss the experimental results of the beam intensity redistribution as well as some features inherent in tuning of the nonlinear beamline and our operational experience.

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    ABSTRACT: The Indiana University Cyclotron Facility is operating a low energy neutron source which provides cold neutrons for material research and neutron physics as well as neutrons in the MeV energy range for the neutron radiation effects studies. Neutrons are being produced by a 7 MeV proton beam incident on a beryllium target. Since the first commissioning of the LENS Proton Delivery System (PDS) in December 2004 its performance has been significantly improved. The RF system of the accelerator has been upgraded by replacing 350 kW 425 MHz 12 tube amplifiers with two Litton 5773 klystron RF tubes capable of running at 425 MHz and 1.25 MW. Since the commissioning of the klystrons, a proton current of 25 mA at 7 MeV and 0.6% duty factor has been successfully delivered to the beryllium target. A future part of this upgrade will introduce a new 6 MeV DTL section to increase proton beam energy from 7 to 13 MeV. The 3 MeV RFQ and 4 MeV DTL will be powered by one klystron and the 6 MeV DTL will be powered by the second klystron. The expected output is 25 mA and 13 MeV of proton current at 0.6% duty factor. A second target station has been added to allow separate source optimization for the two primary research programs (cold neutrons and radiation effects). Other upgrades include increasing the RF duty factor to 3% through the installation of a new power supply for the klystrons. In this contribution we discuss the results of the commissioning of the new RF system, second beamline and second target station, as well as improvement in the beam parameters after these upgrades. The future plans will also be outlined.
    Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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    ABSTRACT: It has been known that uniformization of a beam with a Gaussian profile is possible utilizing odd-order nonlinear focusing in the beam transport system, and this has recently been employed for uniform beam irradiation. Here, we have theoretically studied uniformization of the transverse beam profile using nonlinear-focusing forces produced by multipole magnets in detail. In the case where the nonlinear field of the multipole magnet is given by an infinite power series, all the odd-order multipole strengths required for uniformization of a Gaussian beam and the extent of the resultant uniform region have been expressed using the Twiss parameters. We have shown the principle of uniformization using even-order nonlinear fields. We have also actually demonstrated the transformation of a beam with an asymmetric distribution into one with a uniform distribution by utilizing nonlinear focusing, especially with the sextupole and octupole fields. The validity of the formulas presented here was confirmed through particle-tracking simulations. A practical method to realize a uniform profile using beam collimation and octupole focusing is also presented.
    Review of Modern Physics 01/2007; 10(10). · 44.98 Impact Factor

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