UMD, College Park, Maryland
Beam based alignment and control has been a critical issue for many accelerators. In this paper, we've developed a new approach that can correct the beam orbit using a systematic quad-scan method, where there is an insufficient number of beam position monitors. In this approach, we've proposed a calibrated response matrix. This matrix takes consideration of the different sensitivities of different quadrupoles in the lattice. With the calibrated response matrix, we can greatly enhance our ability to control the beam centroid motion and reduce the control effort.
UMD, College Park, Maryland
The University of Maryland Electron Ring (UMER) is a scaled storage ring using low-energy electrons to inexpensively model beams with high-space-charge. With the ability to inject such beams comes the problem of longitudinal end erosion of both the head and tail. It is important therefore to apply suitably designed longitudinal focusing forces to confine the beam and prevent it from its normal expansion. This paper presents the design and prototyping of an induction cell for this purpose. Successful operation of the induction cell would push the achievable number of turns and also enable us to perform studies of the longitudinal physics of such highly space-charge dominated beams. The pulsed voltage requirements for such a system on UMER would require ear-fields that switch 3kV in about 8ns or so for the most intense flat-top rectangular beam injected into the ring. This places a considerable challenge on the electronics used to deliver ideal waveforms with a compact module. Alternate waveforms are also being explored for other various injected beam shapes into UMER.
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.
UMD, College Park, Maryland
The University of Maryland Electron Ring (UMER) is a low energy, high current recirculator for beam physics research. The electron beam current is adjustable from 0.7 mA, an emittance dominated beam, to 100 mA, a strongly space charge dominated beam. UMER is addressing issues in beam physics relevant to many applications that require intense beams of high quality such as advanced concept accelerators, free electron lasers, spallation neutron sources, and future heavy-ion drivers for inertial fusion. The primary focus of this presentation is experimental results and improvements in multi-turn operation of the electron ring. Transport of a low current beam over 100 turns (3600 full lattice periods) has been achieved. Results of high current, space charge dominated multi-turn transport will also be presented.
UMD, College Park, Maryland
The University of Maryland Electron Ring (UMER) is a low energy, high current recirculator for beam physics research. The electron storage ring has been closed and recent operations have been focused on achieving multi-turn transport. An entire suite of terminal diagnostics is available for time-resolved phase space measurements of the beam. These diagnostics have been mounted and tested at several points on the ring before it was closed. UMER utilizes a unique injection scheme which uses the fringe fields of an offset quadrupole to assist a pulsed dipole in bending the beam into the ring. Similar concepts, along with more traditional electrostatic methods, are being considered for beam extraction. This presentation will focus on the recent efforts to design and deploy these major subsystems required for beam extraction.
UMD, College Park, Maryland
Longitudinal perturbations can be generated in the space-charge dominated regimes in which most beams of interest are born. To study the modification of transverse beam distributions by longitudinal beam dynamics, we have conducted experimental studies using low energy electron beams by taking time resolved images of a beam with longitudinal density perturbations. Two different diagnostics are used: optical transition radiation (OTR) produced from an intercepting silicon based aluminum screen and a fast (<5ns decay time) phosphor screen. It is found that the beam is significantly affected by the perturbation. However the OTR signal is very weak and requires over 45 minutes of frame integration. The fast phosphor screen has much better sensitivity (~1'000 times enhancement). In this paper, we also report on the time resolved measurement of a parabolic beam, showing interesting correlations between transverse and longitudinal distributions of the beam.