Beam Intensity Measurement in ELENA Using Ring Pick-Ups

A bunched beam intensity measurement system for the CERN Extra Low ENergy Antiproton (ELENA) ring, using a cylindrical shoe-box electrostatic pick-up from the existing orbit system [1], is presented. The system has been developed to measure very challenging beam cur-rents, as low as 200nA corresponding to intensities of the order of 10$^7$ antiprotons circulating with a relativistic beta of the order of 10$^{-2}$. In this work we derive and show that the turn-by-turn beam intensity is proportional to the baseline of the sum signal and that, despite the AC-coupling of the system, the installed front-end electronics, based on a charge amplifier, not only guarantees the preservation of the bunch shape (up to a few tens of MHz), but also allows for an absolute calibration of the system. In addition, the linearity of the intensity measurements and their inde-pendence with respect to average beam position is evalu-ated using a standard electromagnetic simulation tool. Finally, experimental measurements throughout typical antiproton deceleration cycles are presented and their accuracy and precision are discussed

Schottky Signal From Distributed Orbit Pick-Ups

In the CERN Extra Low ENergy Anti-proton (ELENA) ring, intended for the deceleration of antiprotons, the longitudinal Schottky signal is obtained by summing the multiple electrostatic pick-up (PU) signals that are also used to measure the closed orbit. The signals from the individual PUs are phase-compensated to a single, common longitudinal location in the machine and added in the time domain. In this contribution, the related theoretical phase compensation is calculated and compared to measurements. We show how the cross correlation between the Schottky noise from the individual PUs can be used to find the correct phase-compensation for an optimal signal-to-noise ratio (SNR). This improvement in terms of SNR is, as expected, proportional to the square root of the number of PUs. The capability of the system to measure both, the bunched and the un-bunched low intensity (~3·10⁷ H⁻ @ 100keV / 144kHz) beams is confirmed by the experimental results presented. Furthermore, the inter-bunch phase correlation is briefly addressed and, for the case of bunched beams, the Schottky signal levels once down converted to different harmonics of the revolution frequency (f_{r}ev) are presented. In applications where the coherent beam signal dominates the spectrum and limits the dynamic range of the signal processing system, a down-conversation to a non-integer multiple of the RF harmonic is proposed as a way to reduce the coherent signal level

Commissioning the ELENA Beam Diagnostics Systems at CERN

The Extra Low ENergy Antiproton ring (ELENA) at CERN entered the commissioning phase in November 2016 using H⁻ ions and antiprotons to setup the machine at the different energy plateaus. The low intensities and energy of the ELENA beam generate very weak signals making beam diagnostics very challenging. With a circulating beam current of less than 1 μA and an energy where the beam annihilates in less than a few microns of matter, special care was taken during the design phase to ensure an optimal performance of these measurement devices once installed on the ring and transfer lines. A year on we present the performance of the various devices that have been deployed to measure the beam parameters from the extraction point of the Antiproton Decelerator (AD), through the ELENA ring and in the experimental lines

Towards optics measurements with a new LEIR BPM system

The LHC Injector Upgrade (LIU) programme forms a cornerstone of the High-Luminosity LHC project. Among its targets, a new Beam Position Monitor (BPM) system has been deployed in the Low Energy Ion Ring (LEIR) to facilitate optics measurements. This paper reports on the commissioning and analysis of turn-by-turn data from the new BPM system. Furthermore, the specific challenges and current limitations in LEIR for achieving long-term coherent excitations with sufficient amplitude for optics measurements are discussed, as well as some of the optics measurements performed so far

The Orbit Measurement System for the CERN Extra Low Energy Antiproton Ring

The CERN Extra Low ENergy Antiproton ring (ELENA) intended to decelerate anti-protons from the CERN Antiproton Decelerator from 100Mev/c to 13.7MeV/c, has been equipped with an orbit measurement system consisting of 10 horizontal and 10 vertical electrostatic pick-ups. Using charge amplifiers the signals are converted into sum and difference signals that, once digitalized, are down converted to baseband and used to calculate intensity independent beam positions. The system is implemented on seven VME switched serial based FPGA / DSP boards carrying direct digital synthesisers and analogue to digital converters on standard FPGA mezzanine cards. The switched serial high-speed bus allows intercommunication between DSPs and thus averaging of the signals from all pick-ups in real-time to be used either in the RF radial feedback system or for longitudinal Schottky diagnostics. The system implementation and initial orbit measurements with the H⁻ beam used for ELENA commissioning will be presented, as well as future upgrades for trajectory and longitudinal Schottky measurements

The Orbit Measurement System for the CERN Extra Low Energy Antiproton Ring

The CERN Extra Low ENergy Antiproton ring (ELENA) intended to decelerate anti-protons from the CERN Antiproton Decelerator from 100Mev/c to 13.7MeV/c, has been equipped with an orbit measurement system consisting of 10 horizontal and 10 vertical electrostatic pick-ups. Using charge amplifiers the signals are converted into sum and difference signals that, once digitalized, are down converted to baseband and used to calculate intensity independent beam positions. The system is implemented on seven VME switched serial based FPGA / DSP boards carrying direct digital synthesisers and analogue to digital converters on standard FPGA mezzanine cards. The switched serial high-speed bus allows intercommunication between DSPs and thus averaging of the signals from all pick-ups in real-time to be used either in the RF radial feedback system or for longitudinal Schottky diagnostics. The system implementation and initial orbit measurements with the H⁻ beam used for ELENA commissioning will be presented, as well as future upgrades for trajectory and longitudinal Schottky measurements

ELENA Commissioning and Status

The Extra Low ENergy Antiproton ring ELENA is a small synchrotron recently constructed and commissioned to decelerate antiprotons injected from the Antiproton Decelerator AD with a kinetic energy of 5.3 MeV down to 100 keV. Controlled deceleration in the synchrotron, equipped with an electron cooler to reduce losses and generate dense bunches, allows the experiments, typically capturing the antiprotons in traps and manipulating them further, to improve the trapping efficiency by one to two orders of magnitude. During 2018, bunches with an energy of 100 keV with parameters close to nominal have been demonstrated, and first beams have been provided to an experiment in a new experimental zone. The magnetic transfer lines from the AD to the experiments have been replaced by electrostatic lines from ELENA. Commissioning of the new transfer lines and, in parallel, studies to better understand the ring with H⁻ beams from a dedicated source, have started in autumn 2020. The first 100 keV antiproton physics run using ELENA will start in late summer 2021

Performance of the Low Energy Ion Ring at CERN with lead ions in 2022

2022 has been a performance consolidation year for the Low Energy Ion Ring (LEIR) at CERN that demonstrated its capability of delivering the target beam parameters required for high luminosity production in the LHC in a reproducible and reliable way. The main steps that have led to the high performance reach of this beam, together with the machine stability improvements deployed, are detailed in this paper

Performance of the Low Energy Ion Ring at CERN with Lead Ions in 2022

2022 was a performance consolidation year for the Low Energy Ion Ring (LEIR) at CERN that demonstrated its capability of delivering the target beam parameters required for high luminosity production in the LHC in a reproducible and reliable way. The main steps that have led to the high performance reach of this beam, together with the machine stability improvements deployed, are detailed in this paper

Performance of the CERN Low Energy Ion Ring (LEIR) with Xenon beams

In 2017 the CERN Low Energy Ion Ring demonstrated once more the feasibility of injecting, accumulating, cooling and accelerating a new nuclei, $^{129}$Xe${39+}$. The operation of this new ion species started at the beginning of March with the start up of the xenon ion source and the Linac3. Ten weeks later the beam arrived to the Low Energy Ion Ring (LEIR) triggering the start of several weeks of beam commissioning in view of providing the injector complex with Xenon beams for different experiments and a series of machine development experiments in LEIR. Two types of beams were setup, the so called EARLY beam, with a single injection into LEIR from Linac3, and the NOMINAL beam with up to seven injections. 2017 was as well an interesting year for LEIR because several improvements in the control system of the accelerator and in the beam instrumentation were done in view of increasing the machine reliability. This paper summarises the beam commissioning phase and all the improvements carried out during 2017