Lionel Prost

Scheme for a low Energy Beam Transport with a Non-Neutralized Section

A typical Low Energy Beam Transport (LEBT) design relies on dynamics with nearly complete beam space charge neutralization over the entire length of the LEBT. This paper argues that, for a beam with modest perveance and uniform current density distribution when generated at the source, a downstream portion of the LEBT can be un-neutralized without significant emittance growth.

Fermilab 4.3 MeV electron cooler

The Recycler Electron Cooler (REC) was the first cooler working at a relativistic energy ( γ = 9.5). It was successfully developed in 1995-2004 and was in operation at Fermilab in 2005–2011, providing cooling of antiprotons in the Recycler ring. After introducing the physics of electron cooling and the REC system, this paper describes measurements carried out to tune the electron beam and optimize its cooling properties. In particular, we discuss the cooling strategy adopted for maximizing the collider integrated luminosity.

PIP-II Injector Test’s Low Energy Beam Transport: Commissioning and Selected Measurements

The PIP2IT test accelerator is under construction at Fermilab. Its ion source and Low Energy Beam Transport (LEBT) in its initial (straight) configuration have been commissioned to full specification parameters. This paper introduces the LEBT design and summarizes the outcome of the commissioning activities.

Selected List of Low Energy Beam Transport Facilities for Light-Ion, High-Intensity Accelerators

This paper presents a list of Low Energy Beam Transport (LEBT) facilities for light-ion, high-intensity accelerators. It was put together to facilitate comparisons with the PXIE LEBT design choices. A short discussion regarding the importance of the beam perveance in the choice of the transport scheme follows.

The PXIE LEBT Design Choices

Typical front-ends of modern light-ion high-intensity accelerators typically consist of an ion source, a Low Energy Beam Transport (LEBT), a Radiofrequency Quadrupole (RFQ) and a Medium Energy Beam Transport (MEBT), which is followed by the main linac accelerating structures. Over the years, many LEBTs have been designed, constructed and operated very successfully. In this paper, we present the guiding principles and compromises that lead to the design choices of the PXIE LEBT, including the rationale for a beam line that allows un-neutralized transport over a significant portion of the LEBT whether the beam is pulsed or DC.

Antiproton Production and Cooling

The progress in the antiproton production and cooling has been absolutely essential for the success of the Collider Run II. Improvements of the Tevatron optics and operation resulted in a gradual increase in the fraction of antiprotons lost in the proton–antiproton collisions in the interaction points. However, by the middle of 2004, it achieved its maximum of about 30–40 % (see Fig. 7.1) determined mainly by the intra-beam scattering (IBS) and the beam–beam effects (see Chap. 8). Since that time, it stayed basically unchanged through the end of the Run II. Further progress in the luminosity could not be achieved without an increase in the antiproton production. Figure 7.2 presents the weekly antiproton production in the course of Run II. One can see that starting from the beginning of 2005, the rate of antiproton production grew significantly reflecting an increased priority for antiproton production.

Collective Instabilities in the Tevatron Collider Run II Accelerators

High luminosity operation of the Tevatron during Collider Run II required high beam intensities all over the accelerator complex, and as a result, five out of six rings (except the Debuncher) had notable problems with beam stability. The instabilities of almost every type are present there: single and multibunch, transverse and longitudinal, due to electromagnetic interaction with vacuum chamber and due to interaction with ions stored in the beam, in proton and antiproton beams. In many cases, various methods to suppress the instabilities have been implemented, including various damping systems—see Table 5.1. The most severe issues with serious impact on operations were related to transverse head-tail instability in the Tevatron, transverse beam instability in the Booster, instabilities in the Recycler antiproton beams, and longitudinal instabilities in the Tevatron.

Low-energy run of Fermilab Electron cooler's beam generation system

In the context of the evaluation of possibly using the Fermilab Electron Cooler for the proposed low-energy RHIC run at BNL, operating the cooler at 1.6 MeV electron beam energy was tested in a short beam line configuration. The main conclusion of this feasibility study is that the coolers beam generation system is suitable for BNL needs. The beam recirculation was stable for all tested parameters. In particular, a beam current of 0.38 A was achieved with the cathode magnetic field up to the maximum value presently available of 250 G. The energy ripple was measured to be 40 eV. A striking difference with running the 4.3 MeV beam (nominal for operation at FNAL) is that no unprovoked beam recirculation interruptions were observed. Electron cooling proposed to increase the luminosity of the RHIC collider for heavy ion beam energies below 10 GeV/nucleon [1] needs a good quality, 0.9-5 MeV electron beam. Preliminary design studies indicate that the scheme of the Recyclers electron cooler at FNAL is suitable for low-energy RHIC cooling and most parts of the cooler can be re-used after the end of the Tevatron Run II. To analyze issues related to the generation of the electron beam in the energy recovery mode and to gain experience with the beam transport at lower beam energy, a dedicated study was performed at FNAL with a beam run through a short beam line (so called U-bend). This report summarizes our findings and observations in the course of the measurements.