Direkt zum Inhalt
  • Paul Scherrer Institut PSI
  • PSI Research, Labs & User Services

Digital User Office

  • Digital User Office
  • DE
  • EN
  • FR
Paul Scherrer Institut (PSI)
Suche
Paul Scherrer Institut (PSI)

Hauptnavigation

  • Research at PSIÖffnen dieses Hauptmenu Punktes
    • Research Initiatives
    • Ethics and Research integrity
    • Scientific Highlights
    • Scientific Events
    • Scientific Career
    • PSI-FELLOW
    • PSI Data Policy
  • Research Divisions and LabsÖffnen dieses Hauptmenu Punktes
    • Overview
    • Research with Neutrons and Muons
    • Photon Science
    • Energy and Environment
    • Nuclear Energy and Safety
    • Biology and Chemistry
    • Scientific Computing, Theory and Data
    • Large Research Facilities
  • Facilities and InstrumentsÖffnen dieses Hauptmenu Punktes
    • Overview
    • Large Research Facilities
    • Facilities
    • PSI Facility Newsletter
  • PSI User ServicesÖffnen dieses Hauptmenu Punktes
    • User Office
    • Methods at the PSI User Facilities
    • Proposals for beam time
    • Proposal Deadlines
    • Data Analysis Service (PSD)
    • EU support programmes
  • New ProjectsÖffnen dieses Hauptmenu Punktes
    • SLS 2.0
    • IMPACT
  • DE
  • EN
  • FR

Digital User Office (mobile)

  • Digital User Office

Sie befinden sich hier:

  1. PSI Home
  2. Labs & User Services
  3. NUM
  4. SINQ
  5. POLDI
  6. Description
  7. Basic principle

Sekundäre Navigation

POLDI

  • Description Ausgeklappter Submenü Punkt
    • Basic principle
    • Components
    • Parameters
    • Sample Environments
      • Sample table
      • Uniaxial load frame
      • Multiaxial load frame
      • Furnace
      • Cryostat
  • User Information
    • Schedule
    • Data Analysis
  • Publications
  • People
  • Safety

Info message

Dieser Inhalt ist nicht auf Deutsch verfügbar.

Time-of-flight principle

POLDI is a so-called neutron Time-Of-Flight (TOF) diffractometer. Thermal and cold neutrons have such a low velocity that their energy can be determined by the accurate measurement of the time needed to travel a given distance. This allows using the full neutron energy spectrum combined with a neutron detector at a fixed diffraction angle.

For strain scanning experiments TOF diffractometers have important advantages compared to constant wave length diffractometers. However, SINQ is a continuous neutron source so therefore a chopper is needed to create a pulsed neutron beam. Conventional TOF-diffractometers usually have choppers with a low duty cycle because of the restriction that fast neutrons from a given neutron pulse may not catch up with slow neutrons from previous pulses (pulse overlap). In this case a constant wavelength diffractometers would provide better performance.

POLDI concept

Intensity vs. arrival time and scattering angle
Intensity vs. arrival time and scattering angle

The principal idea of the POLDI concept is that the restriction that fast neutrons may not catch up slower neutrons of previous pulses is dropped and that the angular dependence of the TOF is used as additional parameter for data analysis. The arrival time of the neutrons are measured in dependence of the scattering angle. In a plot of intensity vs. arrival time and scattering angle each Bragg reflection is represented by a Bragg line (see figure 1).

The slopes of these Bragg lines are given by:

$\frac{\mathrm{d}t}{\mathrm{d}\theta} = t_{flight} \cdot \left(\cot\theta + \frac{1}{s_{tot}}\frac{\mathrm{d}s_{tot}}{\mathrm{d}\theta}\right)$

Therefore, the slope of the Bragg lines alone give information about the flight time of the neutrons. This information allows to trace the slit of the chopper the neutron came from. Since the exact time when this slit opened the neutron beam and the arrival time of the neutron at the detector is known it is now possible to determine the exact time-of-flight of the neutrons, and therefore also the lattice spacing, with the same accuracy as with a conventional time-of-flight diffractometer.

Main advantages of the POLDI concept

The quantities intensity and resolution are decoupled:

  • The intensity is given by the duty cycle of the chopper but the resolution by the chopper speed.
  • High intensity and good resolution can be achieved simultaneous.

Mit Sidebar

Organization

  • LNS Groups
  • LNS Home
  • NUM Division
SINQ Quicklinks
  • Instruments Overview
  • Experiment Proposals

User Contact Points at PSI

PSI User Office
DUO Login


Call for Proposals

Next submission deadline:
May 15, 2023

More Information


SINQ Sample Environment

Get full information on the SINQ sample environment
top

Fussbereich

Paul Scherrer Institut

Forschungsstrasse 111
5232 Villigen PSI
Schweiz

Telefon: +41 56 310 21 11
Telefax: +41 56 310 21 99

Der Weg zu uns
Kontakt

Besucherzentrum psi forum
Schülerlabor iLab
Zentrum für Protonentherapie
PSI Bildungszentrum
PSI Guest House (in english)
PSI Gastronomie
psi forum-Shop

 

Service & Support

  • Telefonbuch
  • User Office
  • Accelerator Status
  • Publikationen des PSI
  • Lieferanten
  • E-Rechnung
  • Computing
  • Sicherheit

Karriere

  • Arbeiten am PSI
  • Stellenangebote
  • Aus- und Weiterbildung
  • Career Center
  • Berufsbildung
  • PSI Bildungszentrum

Für die Medien

  • Das PSI in Kürze
  • Zahlen und Fakten
  • Mediacorner
  • Medienmitteilungen
  • Social Media

Folgen Sie uns: Twitter (deutsch) LinkedIn Youtube Facebook Instagram Issuu RSS

Footer legal

  • Impressum
  • Nutzungsbedingungen
  • Editoren-Login