K. Bishofberger

The Neptune photoinjector

Abstract The RF photoinjector in the Neptune advanced accelerator laboratory, along with associated beam diagnostics, transport and phase-space manipulation techniques are described. This versatile injector has been designed to produce short-pulse electron beams for a variety of uses: ultra-short bunches for injection into a next-generation plasma beatwave acceleration experiment, 2 space-charge dominated beam physics studies, plasma wake-field acceleration driver, plasma lensing, and free-electron laser microbunching techniques. The component parts of the photoinjector, the RF gun, photocathode drive laser systems, booster linac, RF system, chicane compressor, beam diagnostic systems, and control system, are discussed. The present status of photoinjector commissioning at Neptune is reviewed, and proposed experiments are detailed.

The special applications of Tevatron electron lens in collider operation

Besides the Tevatron Electron Lens (TEL) runs as a R&D project for Tevatron Beam-Beam Compensation, it is used daily as a Beam Abort Gap Cleaner for collider operations. It can also serve as beam exciter for beam dynamics measurements and as a slow proton or antiproton bunch remover. This report describes all these applications and related observations.

Commissioning of the Neptune photoinjector

The status of the RF photoinjector in the Neptune advanced accelerator laboratory is discussed. The components of the photoinjector: the RF gun and booster linac, chicane compressor, and beam diagnostic systems are described. Measurement techniques used to diagnose the short pulse length, high brightness beam are detailed and measurements of emittance and pulse compression are given. The effect of the pulse compressor on transverse emittance is explored.

Tevatron Beam-Beam Compensation Project Progress

In this paper, we report the progress of the Tevatron Beam-Beam Compensation (BBC) project [1]. Proton and antiproton tuneshifts of the order of 0.009 induced by electron beam have been reported in [2], suppression of an antiproton emittance growth in the Tevatron High Energy Physics (HEP) store has been observed, too [1]. Currently, the first electron lens (TEL1) is in operational use as the Tevatron DC beam cleaner. Over the last two years, we have greatly improved its reliability. The 2nd Tevatron electron lens (TEL2) is under the final phase of development and is being prepared for installation in the Tevatron in 2005.

Upgrades of the Tevatron electron lens

This paper will describe the main upgrades of the Tevatron Electron Lens (TEL) during the year 2003. The bending angle of the electron beam entrance and exit to the main solenoid will be decreased from 90 degrees to 53 degrees and three more solenoids will be added to each of the two bends, which will allow us to control the electron beam size more freely. A new gun will also be installed which will give us a Gaussian transverse beam distribution in addition to the flat beam with much smoother edge to minimize the nonlinear effect of the beam-beam force. In addition, a new BPM system will be installed to let us have more precise beam position measurements for proton, antiproton and electron beams. A knife-edge beam profile measurement system will replace the space-consuming scanning wires. We expect that these upgrades will improve the ability to increase the lifetime of the (anti)proton beam during beam-beam compensation operation.

PROGRESS REPORT ON BEAM-BEAM COMPENSATION WITH ELECTRON LENSES IN TEVATRON

We discuss the original idea of beam-beam compensation (BBC) in Section I, sequence of events in 2001-2002 and use of the Tevatron Electron Beam (TEL) for DC beam removal in Section II, (anti)proton lifetime improvement in Section III, experimental data on the BBC attempts in Section IV and, conclusively, Section V is devoted to discussion on important phenomena, needed improvements and future plans.

Operation of the Beam Diagnostics System for Tevatron Electron Lens

The first Tevatron Electron Lens (TEL) has been installed and commissioned successfully as part of the Beam‐Beam Compensation project at Fermilab[1]. Currently it is operated routinely for DC beam cleaning during Tevatron luminosity stores and for advanced beam‐beam studies. This paper reviews the electron and proton (antiproton) beam diagnostics, which allow us to measure beam intensity, waveform, losses, position, timing and profile. In addition, other proton (antiproton) diagnostics, available from the Tevatron control system, which are used for tuning beam parameters in the TEL (tune‐shift, orbit, emittances, lifetime measurements, etc) are also described. We also present the results of measurements of the beam parameters and discussions for future upgrades.

Initial Results from the Tevatron Electron Lens

A novel focusing experiment is being conducted on the Tevatron at Fermilab to compensate the beam‐beam tune shift. A 10‐keV electron beam is generated, sent along the Tevatron beam pipe, and collected; the antiproton bunches pass through the electron beam and are defocused through electrical and magnetic interaction with the electron beam. The focusing force as a function of radius is adjustable, and the passage of the electron beam quickens the settling of plasma waves caused by the interaction. The charge density is fully adjustable, allowing easy bunch‐to‐bunch adjustments on a fast, reliable basis. These aspects of the electron lens concept break through many limitations of other beam control options for future machines.

Measurements of high gain and noise fluctuations in a SASE free electron laser

Abstract We report measurements of large gain for a single pass Free-Electron Laser operating in Self-Amplified Spontaneous Emission (SASE) at 16xa0μm starting from noise. We also report the first observation and analysis of intensity fluctuations of the SASE radiation intensity in the high-gain regime. The results are compared with theoretical predictions and simulations.

Tune-shift compensation using the Tevatron electron lens

The Tevatron Electron Lens was originally designed to alleviate the tune shift and spread induced in Tevatron antiproton bunches from interactions with the proton bunches. We report recent developments and successful results of such tune-shift compensation. Lifetime measurements are central to our data and the basis of our analysis. Future goals and possible uses for the lens are also discussed.