• R. A. Kishek, G. Bai, B. L. Beaudoin, S. Bernal, D. W. Feldman, R. Feldman, R. B. Fiorito, T. F. Godlove, I. Haber, T. Langford, P. G. O'Shea, C. Papadopoulos, B. Quinn, M. Reiser, D. Stratakis, D. F. Sutter, J. C.T. Thangaraj, K. Tian, M. Walter, C. Wu
  UMD, College Park, Maryland

Circular accelerators and storage rings have traditionally been designed with limited intensity in order to avoid resonances and instabilities. The possibility of operating a ring beyond the Laslett tune shift limit has been suggested but little tested, apart from a pioneering experiment by Maschke at the BNL AGS in the early 1980s. We have recently circulated the highest-space-charge beam in a ring to date in the University of Maryland Electron Ring (UMER), achieving a breakthrough both in the number of turns and in the amount of current propagated. At undepressed tunes of up to 7.6, the space charge in UMER is sufficient to depress the tune by nearly a factor of 2, resulting in tune shifts up to 3.6. This makes the UMER beam the most intense beam that has been propagated to date in a circular lattice. This is an exciting and promising result for future circular accelerators, and the UMER beam can now be used as a platform to study intense space charge dynamics in rings.

• R. B. Fiorito, B. L. Beaudoin, S. J. Casey, D. W. Feldman, P. G. O'Shea, B. Quinn, A. G. Shkvarunets
  UMD, College Park, Maryland

We present strong evidence of the observation of optical transition radiation (OTR) from aluminized silicon targets intercepting the UMER 10 keV, 100 ns pulsed electron beam, using fast (300ps and 1ns rise time) photomultiplier tubes. An intensified gated (3ns-1ms) CCD camera is used to image the beam using OTR and to study its time evolution throughout the beam pulse. A comparison of wave forms and time resolved OTR images is presented along with time integrated images obtained with phosphor screens for different initial conditions, i.e. beam currents and gun bias voltages.

correspondance email: rfiorito@umd.edu