Development of a high-precision low-latency position feedback system for single-pass beamlines using stripline and cavity beam position monitors

Thesis

The FONT beam-based, intra-train feedback system has been designed to provide beam stability at single-pass accelerators, such as at the interaction point (IP) of the International Linear Collider. Two FONT feedback systems have been commissioned at the Accelerator Test Facility (ATF) at KEK, Japan, and the operation, optimisation and performance of these systems is the subject of this thesis. For each system, the accelerator is operated with two-bunch trains with a bunch separation of around 200 ns, allowing the first bunch to be measured and the second bunch to be subsequently corrected.

The first system consists of a coupled-loop system in which two stripline beam position monitors (BPMs) are used to characterise the incoming beam position and angle, and two kickers are used to stabilise the beam. A BPM resolution of about 300 nm has been measured. On operating the feedback system, a factor ~ 3 reduction in position jitter has been demonstrated at the feedback BPMs and the successful propagation of this correction to a witness BPM located 30 m downstream has been confirmed.

The second system makes use of a beam position measurement at the ATF IP that is used to drive a kicker to provide a local correction. The measurement is performed using a high-resolution cavity BPM with a fast decay time of around 20 ns designed to allow multiple bunches to be resolved. The linearity of the cavity BPM system and the noise floor of the electronics are discussed in detail. The performance of the BPM system under standard ATF operation and with the beam waist at the BPM is described. A BPM resolution of about 50 nm has been measured. This IP feedback system has been used to stabilise the beam position to the 75 nm level.

Authors: Kraljevic, N

• DOI: 10.5287/ora-ozyw5qrpx
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Subjects: Particle accelerators; Beam-based feedback; Linear colliders; Particle physics