Abstract
A destructive monitor to measure the longitudinal bunch width of a low-energy and low-intensity muon beam was developed. This bunch-width monitor (BWM) employed microchannel plates to detect a single muon with high time resolution. In addition, constant-fraction discriminators were adopted to suppress the time-walk effect. The time resolution was measured to be 65 ps in rms using a picosecond-pulsed laser. This resolution satisfied the requirements of the muon linac of the J-PARC E34 experiment. We measured the bunch width of negative-muonium ions (${\ensuremath{\mu}}^{+}{e}^{\ensuremath{-}}{e}^{\ensuremath{-}}$) accelerated with a radio-frequency quadrupole using the BWM. The bunch width was successfully measured to be $\ensuremath{\sigma}=0.54\ifmmode\pm\else\textpm\fi{}0.11\text{ }\text{ }\mathrm{ns}$, which is consistent with the simulation.
Highlights
The feasibility of muon accelerators is increasing considering the recent advances in high-intensity muon beams and efficient muon cooling
H-line, a high-intensity muon beamline at the muon science facility (MUSE) [1] of Japan Proton Accelerator Research Complex (J-PARC), will provide a hundred million surface muons per second [2]
We previously demonstrated the first stage of muon acceleration using a prototype radiofrequency quadrupole linac (RFQ), which is the first rf structure with an operation frequency of 324 MHz [13]
Summary
The feasibility of muon accelerators is increasing considering the recent advances in high-intensity muon beams and efficient muon cooling. A muon beam cooling by the ionization of an absorber was recently demonstrated at the Muon Ionization Cooling Experiment in Rutherford Appleton Laboratory [3,4] As another cooling method, the use of laser ionization to create atoms of muonium (μþe−) enables the muons to be efficiently cooled to the kinetic energy of the thermal level of 25 meV [5,6]. In the case of the proposed muon linac, ten muons per second are expected Even with this rate, the measurement time is only several minutes; the intensity limit of this method itself does not prevent effective beam tuning. The measurement time is only several minutes; the intensity limit of this method itself does not prevent effective beam tuning This bunch-width monitor (BWM) employed multianode microchannel plate (MCP) and constant-fraction discriminators (CFDs) [19].
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