The klystron RF systems for the indiana university lens accelerator
This paper describes the Klystron RF systems for the Indiana University Low Energy Neutron Source (LENS) accelerator 425 MHz radiofrequency quadrupole (RFQ) and drift tube linac (DTL) systems. Of interest in the power conditioning system is the design of the totem-pole grid-catch modulator for the mod-anode klystrons. This topology provides a fast rise and fall and closed loop regulation for the klystron mod-anode to cathode voltage, which minimizes RF amplitude and phase droop while maximizing efficiency. Another advantage is that short pulse high rep-rate operation is viable within the average power capabilities of the klystron. The 425 MHz, 1.25 MW klystron amplifier chain will also be detailed. Of final interest, is the digital low level RF system. This provides vector control of the cavity field using direct conversion, non-I/Q sampling architecture, at a sampling rate of 132 MHz with a 12-bit analog-to-digital converter (ADC). Four input and two output channels are integrated into a 6 unit (6U) VME module, with all DSP functions performed in Xilinx Spartan-3 field-programmable gate arrays. The design and implementation of these systems, coupled with LENS operational results, will be presented.
Uniform beam intensity redistribution in the LENS nonlinear transport line
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.
The effect of continuous exposure to low frequency electric fields on three generations of mice: A pilot study
Mice were allowed to mate, gestate, deliver and rear their offspring for 3 successive generations while being continuously exposed to 60 Hz electric fields. Mice exposed to vertical electric fields exhibited decreased body weights at 35 days postpartum and increased mortality, rates for 3 successive generations. Mice exposed to horizontal electric fields exhibited decreased body weights for 2 successive generations.