TOF Counters Research Articles

Measurement of structure dependent radiative K+ → e+νγ decay at J-PARC

The J-PARC E36 experiment is aiming at searching for lepton universality violation by accurately measuring the ratio of branching ratio of the K + → e + ν(γ) (K e2(γ)) to K + → μ + ν(γ) (K μ2(γ)) decays. The experiment was performed at J-PARC employing a stopped K + method in conjunction with a 12-sector iron-core superconducting toroidal spectrometer. Charged particle momenta were determined by reconstructing charged particle trajectories in the spectrometer. Particle identification for e + and μ + was carried out using an aerogel Cherenkov counter and a lead-glass Cherenkov counter, as well as by measuring the time-of-flight between TOF counters. The peak structure due to K e2(γ) decay was successfully observed in the e + momentum spectrum after the e + requirement in the PID analysis. The structure dependentradiative K + → e + νγ () events were selected by imposing photon hits in the CsI(Tl) calorimeter or the GSC counter. The experimental spectra were accurately reproduced by the Monte Carlo simulation, indicating a correct understanding of the experimental conditions. The Br() value relative to Br(K e2(γ)) was determined from the and K e2(γ) yields corrected for the detector acceptances. The Br()/Br(K e2(γ)) ratio was derived to be 1.19 ± 0.07 stat ± 0.04 syst in the CsI(Tl) analysis and 1.25 ± 0.14 stat ± 0.04 syst in the GSC analysis.

Measuring time with high precision in particle physics

Time measurements with sub-nanosecond time resolution (aiming at values of few picoseconds) are of paramount importance for a wide variety of applications. In the field of particle physics, measuring with increasing precision the time taken by a particle to travel between two points (Time-of-Flight, ToF) gives information on the particle’ (relativistic) velocity, contributing to identifying the type of particle (Particle Identification Detectors, PID). Among this category of detectors are also Cherenkov counters, based on the emission of light when a charged particle travels in a transparent medium with a velocity exceeding the light velocity in that medium. Here we discuss a special category of ToF counters using the properties of Cherenkov light to determine the passage of the particles through the detectors with unprecedented precision. Results obtained with test beams are described and analysed, demonstrating the excellent timing resolution that can be obtained. Such detectors may be used to provide a ‘precision time reference’ for calibrating other types of timing detectors. Other applications are, for instance, time-tagging of ‘pile-up’ events in high-luminosity Large Hadron Collider (LHC), and identification of events with anomalous timing properties (for instance, long-lived particles, LLP).

A [formula omitted] bend curved light-guide for TOF scintillating detectors

We report here a bench study of TOF resolution using a 90° bend curved solid light-guide (LG) used to transport the light from a plastic scintillator counter to a photomultiplier (PMT). The 90° LG allows the rotation of the PMT axis to be vertical to the detector axis, in an environment featured by a strong magnetic field along the detector surface, or other geometrical constrains. We show that with a TOF counter of 2000×100×60 mm3 and light read-out by PMTs at its two 100 × 60 mm2 sides, when 90° LG benders are used between the scintillating bar and the PMTs on both sides, the TOF resolution is worsen, by 5–10%.

R&D of particle identification devices with high-precision timing

We have studied micro-channel-plate photo-multiplier tubes (MCP-PMT), which realize timing measurements of the single photons with high precision of about 30ps. We investigated the timing properties of 4 different types with a magnetic field, and measured the lifetime of the gain, quantum efficiency and transit time spread.As an application, we studied the timing resolution of TOF counters by means of Cherenkov-light detection with a MCP-PMT, and attained a 6.2ps resolution using 3GeV/c pion-beams with readout electronics of 4.1ps resolution. As another application, we have developed a novel particle identification device, named TOP counter, which is a Cherenkov ring imaging counter with precise timing determination, especially for upgrading B-factory experiments. We performed beam tests with the prototype, and obtained the expected results.

Studies of timing properties for a TOF counter at an external target facility

Timing and amplitude properties of a prototype scintillator TOF counter at an external target facility are studied with a cosmic rays test. The dependence of signal pulse height and time resolution on the coordinate along the scintillator TOF counter is investigated with two different discriminators. A time resolution of 165 ps can be achieved at the center of the counter with a constant fraction discriminator. Time resolution better than 150 ps is obtained at the center with a leading edge discriminator after time walk correction is applied for off-line analysis.

A 5 ps TOF-counter with an MCP–PMT

We measured the timing resolution of TOF counters by means of Cherenkov-light detection with a Micro-Channel Plate Photo-Multiplier Tube, and attained σ TOF = 6.2 ps using 3 GeV / c pion-beams with a readout electronics of 4.1 ps resolution. The optimum radiator thickness was examined and the detectable number of photo-electrons was analyzed.

The TOF counters of the AMS-02 experiment: space qualification tests and beam test results

The scintillator counters of the TOF system of AMS-02 is beeing constructed to match the needs of the AMS-02 experiment that is armed by a high aperture superconducting dipole magnet. The goals of the TOF-02 hodoscopes actually are: to give the fast trigger to the all sub-detectors of AMS-02; to measure the particle velocity ensuring a 1×109 albedo rejection; to measure the absolute charge by particle energy loss, up to at least Z=20. In spring of 2005 all the TOF counter planes will be assembled and the space qualification tests will be performed. A description of the first test results and of the TOF performances will be given.

Cross-talk of a multi-anode PMT and attainment of a [formula omitted] TOF counter

We extensively studied a cross-talk phenomenon that seriously deteriorates the high time-resolution of a multi-anode 16-channel linear array photo-multiplier tube (PMT); the dynode structures were modified to eliminate the cross-talk effect and to recover a time resolution of σ = 70 – 80 ps for single photons. The use of 16 anode signals of the modified PMT enabled us to attain σ = 12 ps for a small TOF counter of Cherenkov radiation.

Allegria: a new interface to the ERD program

As a new PC-based acquisition system has been installed to replace the VAX-based system of the elastic recoil detection by time-of-flight (ERD-TOF) and gas-counter ERD setups at University of Montréal, a new analysis software has been developed. It includes a calculation of the energy calibration involving pulse height defects corrections for each element. It has been further improved to process a number of different ERD or Rutherford backscattering spectrometry (RBS) spectra in a single run and now incorporates stopping power calculations based on SRIM-2003 parameters. The application comes with a graphical interface that is used to extract mass separated spectra from event-list files. A second application allows the user to input the experimental parameters and prepares a command file that is passed to the ERD program. The latter iteratively converts the energy spectra into depth profiles for each mass. Resulting atomic fractions are normalized to one of the elements, typically the substrate or one of its components. Some examples of analysis for both TOF and gas counter ERD measurements are presented and discussed. The program and source code will be made available to the ion beam analysis community under GNU licensing conditions.

Characteristics of the TOF counters for GlueX experiment

Timing characteristics of two time-of-flight scintillation counters were studied using particle beams at the IHEP (Protvino) accelerator. The bars were 2m long and had a cross-section of 2.5×6.0cm2. Each bar was viewed from both ends by XP2020 photomultipliers. A time resolution better than 40ps was achieved.

Universal I/O board for the laser-electron photons experiments at SPring-8

Abstract A data acquisition system on the basis of network technologies has been developed for experiments using high-energy photons from backward-Compton scattering between laser lights and 8 GeV electrons at SPring-8. A universal I/O VME-board (UIO) is designed as a buffer-sequencer module with a reconfigurable logic circuit and a 1 Mbyte memory. The UIO is applied as a high-speed module for flexible data readout and buffering. Data from the various detectors are transferred from the UIO to a VME CPU-board in the common format. Altera Hardware Description Language is used to read data from a fast encoding and readout ADC (FERA) system for TOF counters and Cherenkov counters.

Response of silicon multistrip detectors and a cesium iodide scintillator to a calcium ion beam of 0.5 GeV/u

We have constructed and operated charge preamplifiers for silicon strip detectors with a dynamic range extending from fractions of minimum ionising particle (MIP) up to 16 124 MIPs. These silicon detectors combined with time-of-flight counters and cesium iodide scintillator form a segment of the VENUS detector that has been exposed to a calcium beam of 0.5 GeV/u at the GSI accelerator. The aim of the instrument is the identification of all nuclides of the periodic table of the elements. Measurements of electronic noise, cross-talk among channels and energy deposit resolutions in various experimental conditions for silicon detectors are given. The measured light output of the CsI(Tl) crystal induced by calcium is compared with that extrapolated from lower-energy data of various nuclide species determined in other experiments. The charge resolution for calcium ions, determined by the dE dχ detectors and TOF counters of time resolution of 55 ± 7 ps, amounts to 0.42 charge units (rms). Improvements in ion discrimination with respect to the present detector configuration are considered.

High resolution TOF detector for hypernuclei lifetime measurement

Abstract We have tested several types of TOF counters based on scintillators and photomultiplier tubes in order to measure the lifetime of hypernuclei. With the advantage of small counter size, we obtained less than 30 ps timing resolution, and about 50 ps overall TOF resolution. The various factors in this resolution have been studied. The timing resolution dependence on the beam intensity is also studied.

Test of 2 mm-thick TOF scintillation counters

The performance of 2 mm-thick TOF counters was examined under various combinations of different scintillator sizes, light-guides, and photo-multipliers (PMs) with the use of a 2-GeV/c beam. The obtained time resolution (σ) was 90 ps for a 50mm w× 150mm l counter with directly coupled 2 in. diameter PMs, and 140 ps for a 150mm w× 250mm l counter coupled through twisted light-guides to the PMs. A 40 mm-thick 150mm w× 12 000mm l counter was also tested, and 60 ps was obtained.

A method for calibration and test of the time-of-flight detectors for delphi

We describe a method for calibration and test of large-area TOF counters using cosmic radiation. We applied the method to the time-of-flight system of the DELPHI detector at the LEP e +e − storage ring, made of scintillation (NE110) counters (20 × 350 cm 2). The photomultipliers used (EMI 9902KB) reach an average gain of 5×10 8 at 1700 V and the time resolution achieved is 1.2 ns. Using this method we measured the counter efficiencies as a function of the position; we obtained 135 cm for the effective attenuation length and 40 photoelectrons for a minimum-ionizing particle crossing the center of the counter.

A laser calibration system for the KEK TOPAZ barrel TOF counters: Its performance and the characteristics of its major components

A compact and nearly maintenance-free timing calibration system using a dye laser has been constructed for the KEK TRISTAN TOPAZ barrel TOF counter system. Its timing resolution has been measured to be about 50 ps. The characteristics of its major components have been obtained so as to thoroughly understand their functions and performances.

The detection of corpuscles with the aid of the third Soviet artificial earth satellite: ∗V. I. Krasovskii, Iu. M. Kushnir, G. A. Bordovskh, G. F. Zakharov and E. M. Svemlitskii: (pp. 59–60)

We extensively studied a cross-talk phenomenon that seriously deteriorates the high time-resolution of a multi-anode 16-channel linear array photo-multiplier tube (PMT); the dynode structures were modified to eliminate the cross-talk effect and to recover a time resolution of σ=70–80ps for single photons. The use of 16 anode signals of the modified PMT enabled us to attain σ=12ps for a small TOF counter of Cherenkov radiation.