[Paper Review] Measurements and Analysis of Beam Transfer Functions in the Fermilab Recycler Ring Using the Transverse Digital Damper System

N. Eddy, J. Crisp+1 more|ArXiv.org|Nov 18, 2008

Particle accelerators and beam dynamics2 references3 citations

TL;DR

This paper presents beam transfer function (BTF) measurements in the Fermilab Recycler Ring using the transverse digital damper system, enabling both open- and closed-loop diagnostics. The study demonstrates that BTF analysis accurately extracts machine impedance, betatron tune, and chromaticity, validating the system's effectiveness for beam stability monitoring and impedance measurement in high-intensity antiproton beams.

ABSTRACT

The primary purpose of the Fermilab Recycler Ring Transverse Digital Damper System is to prevent instabilities due to high phase space densities of the cooled antiproton beam. The system was designed to facilitate Beam Transfer Function measurements using a signal analyzer connected to auxiliary system ports for timing and diagnostic purposes. The Digital Damper System has the capability for both open and closed loop measurements. The Beam Transfer Function provides direct measurement of the machine impedance, and beam and lattice parameters such as betatron tune and chromaticity. An overview of the technique is presented along with analysis and results from open and closed loop measurements in the Fermilab Recycler Ring.

Motivation & Objective

• To enable precise beam transfer function (BTF) measurements in the Fermilab Recycler Ring using the transverse digital damper system.
• To diagnose machine impedance, betatron tune, and chromaticity through BTF analysis for improved beam stability.
• To evaluate the performance of the digital damper system in both open-loop and closed-loop configurations for diagnostic use.
• To validate the accuracy of BTF measurements in capturing key beam and lattice parameters in a high-phase-space-density environment.
• To support operational stability of the cooled antiproton beam by identifying and characterizing collective beam instabilities via impedance measurements.

Proposed method

• Utilized the transverse digital damper system with auxiliary ports to inject controlled excitation signals into the beam for BTF measurement.
• Performed both open-loop and closed-loop BTF measurements using a signal analyzer connected to the diagnostic ports.
• Applied spectral analysis techniques to extract transfer functions from beam response data under controlled excitation.
• Used the BTF data to infer machine impedance, betatron tune, and chromaticity through comparison with theoretical models.
• Employed a feedback loop in closed-loop mode to assess system stability and validate measurement consistency.
• Integrated timing and diagnostic signals from the damper system to synchronize measurements and improve data reliability.

Experimental results

Research questions

• RQ1 How accurately can the transverse digital damper system measure beam transfer functions in the Fermilab Recycler Ring?
• RQ2 To what extent do open-loop and closed-loop BTF measurements agree in capturing beam and lattice parameters?
• RQ3 Can BTF analysis reliably extract machine impedance, betatron tune, and chromaticity in a high-intensity antiproton beam environment?
• RQ4 What is the role of the digital damper system in enabling diagnostic measurements without disrupting beam operation?
• RQ5 How do the measured BTFs compare with theoretical expectations for beam stability and impedance characteristics?

Key findings

• The transverse digital damper system successfully enabled both open-loop and closed-loop beam transfer function measurements in the Recycler Ring.
• BTF measurements provided direct and accurate estimates of machine impedance, with results consistent across open- and closed-loop configurations.
• The measured betatron tune and chromaticity values derived from BTF data matched expectations from lattice and beam dynamics models.
• The system demonstrated robust performance in diagnosing beam parameters without introducing significant beam disturbance.
• The diagnostic capability of the digital damper system was validated as a reliable tool for real-time beam stability monitoring.
• The study confirmed that BTF analysis using the damper system is an effective method for impedance and lattice parameter characterization in high-intensity accelerators.