We introduce the R&D program for electron-cooling of the Relativistic Heavy Ion Collider (RHIC). This electron cooler is designed to cool 100 GeVInucleon bunchedbeam ion collider at storage energy using 54 MeV electrons. The electron source will be an RF photocathode gun. The accelerator will be a superconducting energy recovery linac. The frequency of the accelerator is set at 703.75 MHz. The maximum bunch frequency is 28.15 MHz, with bunch charge of 10 nC. The R&D program has the following components: The photoinjector, the superconducting linac, start-to-end 'beam dynamics with magnetized electrons, electron cooling calculations and development of a large superconducting solenoid.

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R&D High Temperature Superconductor (HTS) power leads were developed and built for Fermilab by American Superconductor Corporation and Intermagnetics General Corporation. Each company provided one pair of 5kA HTS current leads, and these have been successfully tested at Fermilab. This paper summarizes the test results.

A mathematical model of the gas-cooled, resistive portion of a binary current lead has been developed. An analytical solution of the time-dependent differential equations for the resistive portion of the forced flow cooled current lead is presented which allows one to calculate the evolution of the temperature profile and voltage drop. A comparison of analytical with numerical calculations and a comparison of the calculations with experimental data are given.

We present here the design and construction of an all niobium superconducting RF injector to generate high average current, high brightness electron beam. A ?4 cell superconducting cavity has been designed, built, and tested. A cryostat has been built to cool the cavity to-2 K. The RF system can deliver up to 500 W at 1.3 GHz to the cavity. A mode-locked NdYV04 laser, operating at 266 nm with 0.15 W average power, phase locked to the RF, will irradiate a laser cleaned Nb surface at the back wall of the cavity. Description of critical components and their status are presented in the paper. Based on DC measurements, QE of up to lo4 can be expected from such cavity