Time Of Flight System Research Articles

Formation of Carbonic Cluster Ions at the Ionization of Fullerenes and Multiatomic Molecules of Hydrocarbons

Formation probability of carbonic ionized clusters arising from the collisions between multiply charged ions and fullerene – C60, toluene – C7H8, benzene – C6H6 and butane – C4H10 molecules has been measured. He2+ and Ar6+ projectile ions have been used for the ionization and following fragmentation of polyatomic molecules. The charge state analysis of projectile ions after collisions made it possible to control the minimal number of electrons removed from the target molecule and, as a result, the qualitative control of its excitation energy. The recoil fragment ions formed at target molecule dissociation have been analyzed on mass and charge by time of flight system (TOF).

The scintillator detector for the fast trigger and time-of-flight (TOF) measurement of the space experiment AMS-02

The “Time-Of-Flight” (TOF) system of the AMS-02 superconducting spectrometer, to be installed in the ISS International Space Station, consists of four layers of plastic scintillation counters. During the precursor mission AMS-01 (June 1998), a similar system successfully operated in space for 10 days. However, the AMS-02 TOF had to be redesigned taking into account the more stringent mass and power constraints of the AMS-02 detector. The main characteristics of the new TOF system are (a) capability to stand the high fringing field of AMS-02 superconducting magnet; (b) high redundancy of electronic components for unmanned operation of at least three years in the space station; (c) capability to operate in the space environment on the ISS. Counters and electronics have been extensively tested before the installation in the spectrometer.

The ToF system for the PAMELA experiment: In flight performances

A Time of Flight (ToF) scintillator system has been developed for the PAMELA satellite-borne cosmic ray experiment. The main scientific goal of the experiment is the measurement of the antiproton and positron fluxes in the cosmic radiation over large energy ranges. The ToF system provides the fast trigger to the experiment, the rejection of albedo particles and the possibility to distinguish electrons from antiprotons up to about 1.5 GeV. In this paper we describe the performances of the ToF system measured on flight data.

The non-gated charge-to-time converter for TOF detector in BES III

The TOF (Time-Of-Flight) detector in BES (Beijing Spectrometer) III experiment requires a total time resolution of better than 90ps (for the barrel part) and 110ps (for the endcap part). With the requirement of such a high precision time measurement, it is essential to measure the amplitude or charge of the PMT (photomultiplier tube) signals, in order to correct the amplitude dependent time-walk. A method of using non-gated QTC (Charge-to-Time Converter) to measure the input signal charge was developed for BES III TOF readout electronics. The non-gated QTC with differential inputs was designed to measure the input charge covering a dynamic range of about 30–927pC. Test results showed that the rms resolution is better than 10 bit and the relative error is less than 0.5% after quadratic fitting. The designed converter is simple, stable and suitable for multi-channel systems. A total of 448 channels of QTCs have been developed for BES III TOF readout electronics, which help the TOF system achieve the expected time resolution after the time-walk correction.

A multichannel time-of-flight system for observation of energetic ions of multispecies generated from relativistic laser plasma

A multichannel time-of-flight (TOF) system was constructed to observe the ions generated from relativistic laser plasma, where the ions have polychromatic energies and multiple species. The TOF system is composed of a ten-channel scintillation detector array and an electromagnet that generates a magnetic field of 0-1.24 T. The magnet field enables us to analyze protons, deuterons, and full-stripped carbon ions to 50, 25, and 150 MeV, respectively. The system experimentally identified protons of 0.27-1.6 MeV energy and ions of a half specific charge (deuterons of 0.3-0.8 MeV and full-stripped carbons of 1.8-4.8 MeV). The measured TOF values agree well with the calculated values within the designed accuracy; +/-2.5 ns for protons and +/-5 ns for the others (d or C(6+)) on each detector channel. Comparison of ion numbers detected by a track detector (CR-39) and the TOF system enabled us to obtain the number of ions detected on each scintillation counter with less than 16% error.

High-resolution reflecting time-of-flight momentum and energy mapping system

A new system to map electron momentum and energy is proposed. A reflecting electrode is introduced into a time-of-flight (TOF) system whose decelerating electric field sends all the electrons back to a position-sensitive detector close to but behind the source of the electrons. The longer flying distance that results makes it possible to significantly improve the energy-resolved performance, especially in the higher energy region. The dependence of the new TOF system on its characteristic parameters is analyzed, along with its application to attosecond streak cameras. Experimental results verified a relative energy resolution better than 0.2 eV for 22 eV electrons and also revealed the availability of the improved relative energy resolution smaller than 1.0% for electron energy ranging from 30 to 40 eV.

Electron optics development for photo-electron spectrometers

The demand for simultaneous observation of photo-electron distributions in several dimensions has made the hemispherical deflection analyzer (HDA) and the time-of-flight (TOF) analyzer the dominating spectrometer types. Some common limiting factors for resolution and sensitivity are considered. Recent developments of the HDA and its lens system which increase the energy range and angular acceptance are described. The properties of a recently developed angle-resolving TOF system (AR-TOF) are also described. The possibility to avoid integration losses in energy or angular resolution by applying non-linear mappings of the primary data is discussed.

A study of oleic acid and 2,4-DHB acid aerosols using an IR-VUV-ITMS: insights into the strengths and weaknesses of the technique

An investigation of oleic acid and 2,4-dihydroxybenzoic (DHB) acid aerosols was carried out using an aerosol mass spectrometer with pulsed lasers for vaporization and ionization and an ion trap for mass analysis. The extent of ion fragmentation was studied as a function of both vaporization energy and ionization wavelength. Low CO2 laser energies in the vaporization stage and near-threshold single photon ionization resulted in the least fragmented mass spectra. For DHB, only the molecular ion was observed, but for oleic acid fragmentation could not be eliminated. Tandem MS of the main fragment peak from oleic acid was carried out and provided a tool for compound identification. Photoionization efficiency curves were also collected for both DHB and oleic acid and the appearance energies of both parent and fragment ions were measured. Evidence for fragmentation occurring post-ionization is given by the similar appearance energies for both the parent and fragment ions. The results from this study were compared with those from similar experiments undertaken with time-of-flight (TOF) mass analyzers. The degree of fragmentation in the ion trap was considerably higher than that seen with TOF systems, particularly for oleic acid. This was attributed to the long storage interval in the ion trap which allows time for metastable ions to decay. Differences in the degree of fragmentation between the ion trap and TOF studies also provided further evidence for fragmentation occurring post-ionization. For 2,4-dihydroxybenzoic acid, the long delay prior to mass analysis also allowed time for reactions with background gases, in this case water, to occur.

Dimension measurement of hot large forgings with a novel time-of-flight system

The dimension measurement of hot large forgings is necessary for process control and product quality. However, the conventional technique in forging plants leads to a high scrap rate of raw materials. In order to reduce the waste and increase the productivity, this paper presents a novel measurement technique based on the pulsed time-of-flight (TOF) laser radar to measure the dimensions of hot large forgings. The system consists of a TOF, a scanning device of the two-degree-of-freedom (2-dof) spherical parallel mechanism (SPM), and two motors. Then, its measuring principle and the SPM are described. A special data-processing method is developed to extract the dimensions and the shape of a large forging by scanning for a few times. The laboratory experiments indicate that the shape and dimensions such as the diameter and length can be achieved by virtue of the TOF system. The dimension measurement in a forging plant is also conducted to verify the effectiveness of the presented system.

Multi-scattering time-of-flight neutron spectrometer for deuterium to tritium fuel ratio measurement in fusion experimental reactors

A time-of-flight (TOF) neutron spectrometer has potential as a fuel ratio ( n D/ n T) measurement system in the International Thermonuclear Experimental Reactor (ITER). A new neutron spectrometer is proposed to monitor the fuel ratio in the core of the ITER plasma. This system is based on a conventional TOF method and is composed of a water cell and a few tens of scintillator pairs. The water cell is inserted before the first scintillator of the TOF system and serves as a neutron scattering material. A trial experiment demonstrates the feasibility of this system for detecting trace-DD neutrons within a DT neutron beam. The system responses to DT and DD neutrons are also presented.

Current status of the CMD-3 time-of-flight system

CMD-3 is a detector for experiments with the e + e - collider VEPP-2000. Maximum center-of-mass energy of the collider equal to 2 GeV allows to study the cross-section of the process ee → n n ¯ near the threshold. Due to the low momentum of the produced neutron–antineutron pairs it is possible to select them using time-of-flight (TOF) system. This article describes the current status of the CMD-3 TOF system development.

양전자 소멸 Auger 전자 에너지 측정을 위한 Time of Flight의 분해도 향상에 관한 이론적 연구

저에너지(수 eV) 양전자 빔을 이용하여 도체나 반도체의 표면/계면의 물리화학적 특성 분석에 독특한 유용성이 보고 되고 있다. 기존의 표면 분석법에 비해 표면의 선택도가 향상되어 반도체 소자의 박막 두께가 얇아지는 최신기술에 적합한 분석법으로 주목을 받고 있다. 물질표면에 조사된 저에너지 양전자는 표면 근처의 image potential에 포획이 되어 표면에 있는 전자들과 쌍소멸하며 Auger 전자를 방출한다. 표면으로부터 방출된 Auger 전자의 에너지를 측정함으로 원자의 화학적 구별이 가능하므로 검출기의 에너지 분해도가 중요하다. 기존의 ExB 형태의 에너지 측정기는 분해도가 <TEX>$6{\sim}10\;eV$</TEX> 정도이고 특정한 에너지 영역만을 일정시간 스캔하여 스펙트럼을 측정하므로 측정시간이 길어진다는 단점이 있다. 반면에 Time-Of-Flight(TOF) 시스템은 방출되는 전자들의 에너지를 동시에 검출하므로 측정시간이 단축되어 측정 효율이 향상된다. 에너지 분해도를 높이기 위해서는 측정하고자 하는 전자의 진행거리를 길게 할수록 좋으나, 공간적 제약을 고려한 reflected TOF 시스템과 retarding tube을 이용한 linear TOF 시스템의 에너지 분해도를 이론적으로 시뮬레이션하였다. Since the presence of the chemical impurities and defect at surfaces and interfaces greatly influence the properties of various semiconductor devices, an unambiguous chemical characterization of the metal and semiconductor surfaces become more important in the view of the miniaturization of the devices toward nano scale. Among the various conventional surface characterization tools, Electron-induced Auger Electron Spectroscopy (EAES), X-ray Photoelectron Spectroscopy (XPS) and Secondary Electron Ion Mass Spectroscopy (SIMS) are being used for the identification of the surface chemical impurities. Recently, a novel surface characterizaion technique, Positron-annihilation induced Auger Electron Spectroscopy (PAES) is introduced to provide a unique method for the analysis of the elemental composition of the top-most atomic layer. In PAES, monoenergetic positron of a few eV are implanted to the surface under study and these positrons become thermalized near the surface. A fraction of the thermalized positron trapped at the surface state annihilate with the neighboring core-level electrons, creating core-hole excitations, which initiate the Auger process with the emission of Auger electrons almost simultaneously with the emission of annihilating gamma-rays. The energy of electrons is generally determined by employing ExB energy selector, which shows a poor resolution of <TEX>$6{\sim}10eV$</TEX>. In this paper, time-of-flight system is employed to measure the electrons energy with an enhanced energy resolution. The experimental result is compared with simulation results in the case of both linear (with retarding tube) and reflected TOF systems.

Magnetospheric and solar physics observations with the PAMELA experiment

PAMELA is a satellite-borne experiment designed to make long duration measurements of the cosmic radiation in Low Earth Orbit. It is devoted to the detection of the cosmic-ray spectra in the 100MeV–300GeV range with primary scientific goal the measurement of antiproton and positron spectra over the largest energy range ever achieved. Other tasks include the search for antinuclei with unprecedented sensitivity and the measurement of the light nuclear component of cosmic rays. In addition, PAMELA can investigate phenomena connected with solar and Earth physics. The apparatus consists of: a Time of Flight system, a magnetic spectrometer, an electromagnetic imaging calorimeter, a shower tail catcher scintillator, a neutron detector and an anticoincidence system. In this work we present some measurements of galactic, secondary and trapped particles performed in the first months of operation.

The time-of-flight system of the PAMELA experiment: In-flight performances

The time-of-flight (ToF) system is one of the key elements of the PAMELA apparatus, since it must generate the trigger for all the subdetectors and provide, alongside with the magnetic spectrometer, particle identification in the lower part of the explored energy spectrum. The ToF system will be described, with particular attention to its in-flight performances.

The Time-of-Flight system for the PAMELA experiment in space

The Time-of-Flight (ToF) system is one of the key elements of the a Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) apparatus, since it must generate the trigger for all the subdetectors and provide, alongside with the magnetic spectrometer, particle identification in the lower part of the explored energy spectrum. The ToF system will be described from the point of view of its geometrical design, its mechanics and its performances. In addition, since the extremely hostile space environment, several tests have been carried out in order to qualify the entire ToF system. The measured features and performance will be also described.

PAMELA observational capabilities of Jovian electrons

PAMELA is a satellite-borne experiment that has been launched on June 15th, 2006. It is designed to make long duration measurements of cosmic radiation over an extended energy range. Specifically, PAMELA is able to measure the cosmic ray antiproton and positron spectra over the largest energy range ever achieved and will search for antinuclei with unprecedented sensitivity. Furthermore, it will measure the light nuclear component of cosmic rays and investigate phenomena connected with solar and earth physics. The apparatus consists of: a time of flight system, a magnetic spectrometer, an electromagnetic imaging calorimeter, a shower tail catcher scintillator, a neutron detector and an anticoincidence system. In this work a study of the PAMELA capabilities to detect electrons is presented. The Jovian magnetosphere is a powerful accelerator of electrons up to several tens of MeV as observed at first by Pioneer 10 spacecraft (1973). The propagation of Jovian electrons to Earth is affected by modulation due to Corotating Interaction Regions (CIR). Their flux at Earth is, moreover, modulated because every ∼13 months Earth and Jupiter are aligned along the average direction of the Parker spiral of the Interplanetary Magnetic Field. PAMELA will be able to measure the high energy tail of the Jovian electrons in the energy range from 50 up to 130 MeV. Moreover, it will be possible to extract the Jovian component reaccelerated at the solar wind termination shock (above 130 MeV up to 2 GeV) from the galactic flux.

STAR TIME OF FLIGHT READOUT ELECTRONICS, DAQ, AND COSMIC RAY TEST STAND

The new Time-of-Flight (TOF) subsystem for STAR at RHIC will have 3840 6-pad Multigap Resistive Plate Chambers (MRPC) distributed over 120 trays. Each tray contains 192 channels and three types of electronics cards: “TINO”, “TDIG” and “TCPU”. Every 30 trays send data to a “THUB” card that interfaces to STAR trigger and transmits data over fiber to a STAR DAQ fiber receiver. TINO contains analog front end electronics based on the CERN/LAA NINO custom IC. TDIG digitizes the data using the CERN HPTDC ASIC. TCPU formats and buffers the digital information. A cosmic ray test system comprised of three plastic scintillators, 4 MRPC modules, and TOF prototype electronics is used to determine the timing resolution to be achieved for the entire TOF system. Overall timing resolution of 80 – 110 ps has been achieved.

Novel concept of time-of-flight neutron spectrometer for measurement of the D/T burning ratio in the ITER

A time-of-flight (TOF) neutron spectrometer is a candidate for the measurement of the D/T burning ratio in the International Thermonuclear Experimental Reactor (ITER). In ITER high-power experiments, the TOF system suffers from a high event rate or accidental counts due to high radiation intensities, which is one of several background sources in DD neutron measurement. We herein propose a new neutron spectrometer to apply to the measurement of the D/T burning ratio in the ITER high-power operation region. This system is based on the conventional double-crystal TOF method and consists of a water cell and several pairs of scintillators. A water cell is inserted before the first scintillator of the TOF system and acts as a radiator or neutron scattering material. Because DD neutrons have a larger cross section of elastic scattering with hydrogen than DT neutrons, the elastic scattering in the radiator enhances the relative ratio of DD/DT intensity by approximately three times before entering the TOF system. The enhancement of the relative intensity of DD neutrons makes the detection of DD neutrons easier. The feasibility of this method as a neutron spectrometer has been verified through a preliminary experiment using a DT neutron beam (20mm ϕ) at the Fusion Neutronics Source, Japan Atomic Energy Agency. The present article describes the basic performance of the prototype system.

The MRPC detector for the ALICE Time Of Flight System: Final Design and Performances

The ALICE Time Of Flight (TOF) system will perform charged particle identification in the intermediate momentum range (from 0.5 to a few GeV/c) and in the central pseudorapidity region ( | η | 0.9 ). In particular the TOF has to cover an area of ∼ 160m2 and has to be highly segmented (∼ 160000 readout pads of 2.5 × 3.7 cm2 active area) in order to keep the occupancy in Pb-Pb collisions below the 15 % level. In order to satisfy these requirements, the double-stack MRPC detector has been chosen for the TOF system. The most relevant results on the performances of the final version of the MRPC and of the front-end/readout electronics will be presented. The device has a very good uniformity, a long streamer-free plateau, an efficiency higher than 99 % and an intrinsic time resolution below 50 ps.

A spectrometer for low energy heavy ion ERDA

An ERDA detector telescope consisting of a time-of-flight (ToF) system combined with a gas ionization chamber (GIC) has been developed which is specialized for the identification of very low energy ions. Equipped with a large area patterned silicon nitride entrance window of 130 nm thickness, the GIC allows heavy ion detection well below 1 MeV with sufficient resolution for particle identification. The ToF system has a start detector with a diamond-like carbon (DLC) foil of only 0.5 μg/cm 2, which warrants excellent energy resolution for depth profiling. The system has been tested with 127I, 197Au and 48Ti projectiles of energies between 1.5 and 12 MeV. In the low mass range (up to 30 amu) the mass resolution is better than 1 in 35 at a recoil energy of approximately 3 MeV. A depth resolution of 1.5 nm (FWHM) has been obtained at a TiO 2 surface using 1.5 MeV 127I projectiles. The spectrometer is well suited for high resolution near-surface ERDA analysis even at accelerators with very low beam energies.