A. Shemyakin

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.

Electron cooling rates characterization at Fermilab's Recycler

A 0.1 A, 4.3 MeV DC electron beam is routinely used to cool 8 GeV antiprotons in Fermilabs Recycler storage ring [1]. The primary function of the electron cooler is to increase the longitudinal phase-space density of the antiprotons for storing and preparing high-density bunches for injection into the Tevatron. The longitudinal cooling rate is found to significantly depend on the transverse emittance of the antiproton beam. The paper presents the measured rates and compares them with calculations based on drag force data.

Optics of electron beam in the Recycler

Electron cooling of 8.9 GeV/c antiprotons in the Recycler ring (Fermilab) requires high current and good quality of the DC electron beam. Electron trajectories of ∼0.2 A or higher DC electron beam have to be parallel in the cooling section, within ∼ 0.2 mrad, making the beam envelope cylindrical. These requirements yielded a specific scheme of the electron transport from a gun to the cooling section, with electrostatic acceleration and deceleration in the Pelletron. Recuperation of the DC beam limits beam losses at as tiny level as ∼0.001%, setting strict requirements on the return electron line to the Pelletron and a collector. To smooth the beam envelope in the cooling section, it has to be linear and known at the transport start. Also, strength of the relevant optic elements has to be measured with good accuracy. Beam‐based optic measurements are being carried out and analysed to get this information. They include beam simulations in the Pelletron, differential optic (beam response) measurements and si...

Efficiency of the Fermilab Electron Cooler’s Collector

The newly installed Recycler Electron Cooling system (REC) at Fermilab [1] will work at an electron energy of 4.34 MeV and a DC beam current of 0.5 A in an energy recovery scheme. As a part of the Electron cooling project, the efficiency of the collector for the REC was optimized at a dedicated test bench to the level of relative current losses of 5·10-6. The paper discusses the test bench measurements for several distributions of a transverse magnetic field in the collector cavity.

Recycler Electron Cooling Project: Mechanical vibrations in the Pelletron and their effect on the beam

The Fermilabs Recycler ring will employ an electron cooler to cool stored 8.9 GeV antiprotons [1]. The cooler is based on an electrostatic accelerator, Pelletron [2], working in an energy-recovery regime. A full-scale prototype of the cooler has been assembled and commissioned in a separate building [3]. The main goal of the experiments with the prototype was to demonstrate stable operation with a 3.5 MeV, 0.5 A DC electron beam while preserving a high beam quality in the cooling section. The quality is characterized, first of all, by a spread of electron velocities in the cooling section, which may be significantly affected by mechanical vibration of the Pelletron elements. This paper describes the results of vibration measurements in the Pelletron terminal and correlates them with the beam motion in the cooling section.

Pepper-pot scraper parameters and data processing

Parameters required for the pepperpot scraper are described, and its data processing is proposed.

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.

Transverse Instabilities in the Fermilab Recycler

Transverse instabilities of the antiproton beam have been observed in the Recycler ring soon after its commissioning. After installation of transverse dampers, the threshold for the instability limit increased significantly but the instability is still found to limit the brightness of the antiprotons extracted from the Recycler for Tevatron shots. In this paper, we describe observations of the instabilities during the extraction process as well as during dedicated studies. The measured instability threshold phase density agrees with the prediction of the rigid beam model within a factor of 2. Also, we conclude that the instability threshold can be significantly lowered for a bunch contained in a narrow and shallow potential well due to effective exclusion of the longitudinal tails from Landau damping.

IBS in a CAM-Dominated Electron Beam

Electron cooling of the 8.9 GeV/c antiprotons in the Recycler ring requires high‐quality dc electron beam with the current of several hundred mA and the kinetic energy of 4.3 MeV. That high electron current is attained through beam recirculation (charge recovery). The primary current path is from the magnetized cathode at high voltage terminal to the ground, where the electron beam interacts with the antiproton beam and cooling takes place, and then to the collector in the terminal. The energy distribution function of the electron beam at the collector determines the required collector energy acceptance. Multiple and single intra‐beam scattering as well as the dissipation of density micro‐fluctuations during the beam transport are studied as factors forming a core and tails of the electron energy distribution. For parameters of the Fermilab electron cooler, the single intra‐beam scattering (Touschek effect) is found to be of the most importance.

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.