Abstract
A high-resolution, low-latency beam position monitor (BPM) system has been developed for use in particle accelerators and beam lines that operate with trains of particle bunches with bunch separations as low as several tens of nanoseconds, such as future linear electron-positron colliders and free-electron lasers. The system was tested with electron beams in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. It consists of three stripline BPMs instrumented with analogue signal-processing electronics and a custom digitizer for logging the data. The design of the analogue processor units is presented in detail, along with measurements of the system performance. The processor latency is $15.6\ifmmode\pm\else\textpm\fi{}0.1\text{ }\mathrm{ns}$. A single-pass beam position resolution of $291\ifmmode\pm\else\textpm\fi{}10\text{ }\mathrm{nm}$ has been achieved, using a beam with a bunch charge of approximately 1 nC.
Highlights
A number of in-construction and proposed future particle accelerator designs feature trains of particle bunches with bunch-separation intervals in the ranges of nanoseconds to tens or hundreds of nanoseconds
The International Linear Collider (ILC) design [1] calls for bunch trains comprising thousands of bunches separated in time by around 500 ns with a train repetition frequency of 5 Hz; the Compact Linear Collider (CLIC) design [2] specifies bunch trains comprising several hundred bunches separated in time by around 0.5 ns, with a train repetition frequency of 50 Hz
In the stripline beam position monitor (BPM) design, as used in the FONT5 system, four 12 cm strips are arranged as two orthogonal diametrically opposed pairs separated by 23.9 mm, as shown in Fig. 4 [11]
Summary
A number of in-construction and proposed future particle accelerator designs feature trains of particle bunches with bunch-separation intervals in the ranges of nanoseconds to tens or hundreds of nanoseconds. Time scale, with submicron position resolution in singlepass mode The design of such a BPM system is presented here. The goals of the ATF2 collaboration [9] are to produce an electron beam spot with a 37 nm vertical size, and eventually to stabilize the vertical beam position at the focal point at the nanometer level. The design goal for the FONT5 system is to stabilize the vertical beam position to the 1 μm level at the entrance to the finalfocus system This requires BPMs capable of resolving bunches separated in time by around 100 ns, and with a position resolution at the submicron level.
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