The design and commissioning of the MICE upstream time-of-flight system

Abstract

In the MICE experiment at RAL the upstream time-of-flight detectors are used for particle identification in the incoming muon beam, for the experiment trigger and for a precise timing (σ t ∼ 50 ps) with respect to the accelerating RF cavities working at 201 MHz. The construction of the upstream section of the MICE time-of-flight system and the tests done to characterize its individual components are shown. Detector timing resolutions ∼ 50 − 60 ps were achieved. Test beam performance and preliminary results obtained with beam at RAL are reported.(submitted to Nuclear Instruments and Methods A) * Corresponding author: M. Bonesini, E-mail address: maurizio.bonesini@mib.infn.it + permanent address: Department of Physics, Oxford University, UK, Published by SIS-Pubblicazioni Laboratori Nazionali di FrascatiThe MICE experiment [1] at RAL (see figure 1 for a schematic layout) aims at a systematic study of a section of a cooling channel of a neutrino factory (νF ) [2]. The 5.5 m long cooling section consists of three liquid Hydrogen absorbers and eight 201 MHz RF cavities encircled by lattice solenoids.Different neutrino factory designs require a muon cooling factor from 2 to 16, over a ∼ 100 m distance. For a cooling section prototype of affordable size, a cooling factor ∼ 10% at most may be expected. A precision of ∼ 10% on the design of the whole cooling channel implies emittance measurements at a level of 0.1% on the cooling cell prototype, thus excluding conventional emittance measurement methods, that have errors around 10%.A method based on single particle measurements has been envisaged, to obtain such a level of precision. Particles are measured before and after the cooling section by two magnetic spectrometers complemented by time-of-flight (TOF) detectors. For each particle x, y, t, p x , p y , E coordinates are measured. In this way, for an ensemble of N particles, the input and output emittances may be determined accurately. The upstream MICE time-of-flight systemIn the MICE experiment, precision timing measurements are required to relate the time of the incoming beam muons to the phase of the accelerating field in each RF cavity and simultaneously for particle identification (PID) by a TOF method. Three time-of-flight detectors (TOF0, TOF1, TOF2) are foreseen. The last two (TOF1 and TOF2) are at the entrance and the exit of the MICE cooling channel; the first one (TOF0) instead is placed about 10 m upstream of its entrance. Figure 1 shows a layout of the full MICE cooling channel with the foreseen positions of the TOF detectors. The upstream TOF detectors (TOF0, TOF1) must separate the pion contamination of the muon beam at low momenta (below ∼ 210 MeV/c) and are used for the experiment trigger. All TOF detectors are used to determine the time coordinate (t) in the measurement of the emittance.The TOF stations share a common design based on two planes of fast one-inch scintillator counters along X/Y directions (to increase measurement redundancy) read at both edges by R4998 Hamamatsu fast photomult...

The liquid-hydrogen absorber for MICE

“…The individual coils in the spectrometer modules are labelled thus: E2, C, E1, M2, M1 in the upstream module, and M1, M2, E1, C, E2 in the downstream module. The various detectors (time-of-flight hodoscopes [23,24], Cerenkov counters [25], scintillating-fibre trackers [26], KLOE Light (KL) calorimeter [21,27], and electron muon ranger [28]) used to characterise the beam are also represented.…”

Pion contamination in the MICE muon beam

“…The PID system consists of scintillator time-of-flight x/y hodoscopes TOF0, TOF1 and TOF2 [17] read at both ends of each scintillator slab by fast Hamamatsu R4998 photomultiplier (PMT) tubes [24], and two threshold Cherenkov counters Ckova and Ckovb [20]. The TOF system -2 -is required to tag electrons and pions in the muon beam with a rejection factor exceeding 99%.…”

“…Any unidentified contamination in the muon beam from pions and electrons can affect the accuracy of the measurement of the muon-beam emittance. Electrons are identified using a time-of-flight (TOF) system [17] and an Electron-Muon Range (EMR) detector [18,19] after the cooling channel. Pions in the beam are also identified by the TOF system, two aerogel Cherenkov detectors [20], a preshower calorimeter (Kloe-Light or KL) [21] and the EMR.…”

Status of MICE, the international Muon Ionisation Cooling Experiment

“…Target operation and the effect of varying the current in the beam line magnets have been studied in order to optimize the beam performance. The particle content of the muon beam has been measured by using time-of-flight detectors (TOF0, TOF1, TOF2) [4], Cherenkov detectors and KL (KLOE Light) calorimeter that provide precise muon, pion and electron identification [5]. Time-of-flight detector timing resolutions of 52 ps for TOF0, 60 ps for TOF1 and 54 ps for TOF2 were achieved.…”