This paper describes the hardware and operations of the Neutrinos at the Main Injector (NuMI) beam at Fermilab. It elaborates on the design considerations for the beam as a whole and for individual elements. The most important design details of individual components are described. Beam monitoring systems and procedures, including the tuning and alignment of the beam and NuMI longterm performance, are also discussed.

A novel modulator has been designed, built and tested for the TESLA test facility.This e+ eaccelerator concept uses superconducting RF cavities and requires 2 ms of RF power at 10 pps. As the final accelerator will require several hundred modulators, a cost effective, space saving and high efficiency design IS desired. This modulator uses a modest size switched capacitor bank that droops approximately 20% during the pulse. This large droop is compcns;~ted for by the use of a resonant LC circuit. The capacitor bank is connected to the high side of a pulse transformer primary using a series CT0 switch. The resonant circuit is connected to the low side of the pulse transformer primary. The output pulse is flat to within I% for 1.9 ms during a 2.3 ms base pulse width. Measured efficiency, from breaker to klystron and including energy lost in the rise time, is approximately 85%.

A new underground beamline is being constructed at Fermilab to generate and focus a beam of neutrinos on a detector 450 miles away in Soudan, Minnesota. A compact modulator utilizing capacitive energy storage and SCRs as the switching element has been built and tested at Fermilab. The 0.9 F capacitor bank operates at less than 1 kV. It delivers its output of up to 240 kA directly to the two series connected focusing horns via a multi-layer radiation hard stripline [1]. Dual pulse width capability allows for ready selection of 5.2 ms, for slow beam spills, or 2.6 ms operation for reduced thermal stresses on the focusing horns during fast spill. Intended for installation in an underground equipment room, the design incorporates several novel features to facilitate transport, installation, and maintenance.Various designs were examined to arrive at the most economical approach for providing the high pulse currents to the horns located in the very high radiation field, up to 3x10^7 kRads/yr absorbed dose of the beamline. These included charge recovery and electronic polarity reversal systems. The direct coupling approach was selected for its overall economy and compactness. The system has been operational for several months and results of those tests will be discussed. Controls and safety issues will also be discussed.

There are two different horn systems under construction at Fermilab for neutrino beamlines. The NuMI project requires a power supply that operates at 970 V, 205 kA, 2.6 ms, and 0.53 pps. The MiniBooNE project requires a power supply that operates at 5.5 kV, 170 kA, 140 V DQG 5 pps. Both require long low inductance connections between the power supply and horn; 60 feet for MiniBooNE and 230 feet for NuMI. This paper discusses several electrical and mechanical design requirements that have been overcome. These include low impedance, radiation hardness, voltage holdoff, clamping for electrical and mechanical connections and humidity and dust control. Measurements of the inductance of the striplines and voltage holdoff will be compared to calculations. The results of some tests will be discussed.

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