Search results for "Time of flight"

Electron-TOF-analyser for complete momentum analysis in photoemission from surfaces

2001

Abstract We present a new method for momentum-selective imaging by means of a time-of-flight (TOF) technique. The instrument employs a time- and space-resolving delayline detector in combination with a parabolic electrostatic field and a drift space. We use this kind of spectrometer, to raise the efficiency of experiments, which are total momentum resolved. The main difference to conventional photoemission experiments using a rotatable spectrometer is the simultaneous detection of all emitted photoelectrons. In addition to this feature, the angular distribution should be directly visible, to observe solid state symmetries. In order to facilitate these requirements, we use a delayline detect…

A high resolution electrostatic time-of-flight spectrometer with adiabatic magnetic collimation

1999

Abstract A new type of spectrometer for low energy charged particles is presented. It consists of an adiabatic magnetic collimation and two filters: an electrostatic retarding potential to set a lower limit (high pass) and a time-of-flight analysis to reject high energy charged particles (low pass). Both filters are only limited in their resolution by the efficiency of the adiabatic magnetic collimation. The proof of this principle is demonstrated by a pilot measurement on the K conversion line of 83mKr. Possible applications to pulsed and continuous electron sources are discussed with the emphasis on the investigation of the β spectrum of T2 to deduce information on the mass of the electro…

WITHDRAWN: A scintillator based time-of-flight hodoscope with a new type of emitter follower divider

2004

High resolution Time of Flight determination based on reconfigurable logic devices for future PET/MR systems

2013

Abstract This contribution shows how to perform Time of Flight (TOF) measurements in PET systems using low-cost Field Programmable Gate Array (FPGA) devices with a resolution better of 100 ps. This is achieved with a proper management of the FPGA internal resources and with an extremely careful device calibration process including both temperature and voltage compensation. Preliminary results are reported.

A direct determination of the proton electron mass ratio

1980

The cyclotron frequencies of free protons and electrons in a magnetic field of 5.81 Tesla with superimposed electrostatic quadrupole field have been measured. The increase of energy connected with a transition at cyclotron frequency is detected by the measurement of the time of flight through an inhomogeneous magnetic field. From the ratio of the measured cyclotron frequencies of both particles the proton electron mass ratio is deduced. The resultm p /m e =1,836.1527(11) agrees within the limits of error (0.6 ppm) with the value of the indirect determination.

Time of flight measurements based on FPGA and SiPMs for PET–MR

2014

Coincidence time measurements with SiPMs have shown to be suitable for PET/MR systems. The present study is based on 3 x 3 mm(2) SiPMs, LSO crystals and a conditioning signal electronic circuit. A Constant Fraction Discriminator (CFD) is used to digitalize the signals and a TDC FPGA-implemented is employed for fine time measurements. TDC capability allows processing the arrival of multiple events simultaneously, measuring times under 100 ps. The complete set-up for time measurements results on a resolution of 892 +/- 41 ps for a pair of detectors. The details of such implementation are exposed and the trade-offs of each configuration are discussed. (C) 2013 Elsevier By, All rights reserved,

The3He neutron spin filter at ILL

1997

Abstract Neutron Spin-Filters (NSF) using gaseous polarized 3He have long been recognized as having enormous potential value in many polarized neutron scattering applications and, accordingly, ILL started a development program some years ago. This report gives an account of the present status of the project. Let us first briefly recall the reasons why the 3He-NSF is desirable as a generic polarization tool: Being a pure transmission device, NSF naturally decouples the neutron spin selection from other optical functions. Designing polarized instruments will be simplified having no geometrical constraints due to Bragg optics or beam deviation in the polarizer. Angular acceptance and energy ba…

Calibration of a neutron time-of-flight multidetector system for an intensity interferometry experiment

2004

We present the details of an experiment on light particle interferometry. In particular, we focus on a time-of-flight technique which uses a cyclotron RF signal as a start and a liquid scintillator time signal as a stop, to measure neutron energy in the range of En approximate to 1.8-150 MeV. This dynamic range (up to 300 ns) is much larger than the beam bunch separation (54 ns) of the AGOR cyclotron (KVI). However, the problem of a short burst period is overcome by using the time information obtained from a fast projectile fragment phoswich detector. The complete analysis procedure to extract the final neutron kinetic energy spectra, is discussed. (C) 2003 Elsevier B.V. All rights reserved.

Time- and energy resolved photoemission electron microscopy-imaging of photoelectron time-of-flight analysis by means of pulsed excitations

2010

Abstract The present work enlightens the developments in time- and energy resolved photoemission electron microscopy over the past few years. We describe basic principles of the technique and demonstrate different applications. An energy- and time-filtering photoemission electron microscopy (PEEM) for real-time spectroscopic imaging can be realized either by a retarding field or hemispherical energy analyzer or by using time-of-flight optics with a delay line detector. The latter method has the advantage of no data loss at all as all randomly incoming particles are measured not only by position but also by time. This is of particular interest for pump–probe experiments in the femtosecond an…

Measurement of the4He-D2 mass difference

1990

A Penning ion trap spectrometer has been used to measure the modified cyclotron frequencies of trapped4He+ and D 2 + ions. The resonances were detected by a time of flight method after ejection of the ions from the trap. We obtain a mass differenceΔm (D2-4He) = 25600331(5)·10−9 amu in acordance with published values but with a reduced uncertainty.