Section of Atomic Collisions

Facilities

Used accelerators:



  ESA 21 electrostatic spectrometer at 5 MeV VDG
ESA-21 electrostatic spectrometer
and universal measuring chamber labortory for atomic collisions

Type combination of a spherical mirror and a two stage cylindrical mirror
Electron energy range 50 eV - 16 keV
Energy resolution 5 x 10-4 - 6 x 10-3
Angular range of electron detection 0o - 180o
(at 13 angles, by 15o, simultaneously)


Contact: sulik at atomki.hu

      ESA21ESA 21

      ESA-22 Multiparameter electronspectrometer at Electronspectroscopy Laboratory


        Type combination of a spherical and a cylindrical mirror
        Electron energy range 20 eV - 10 keV
        Energy resolution 2 x 10-4 - 4 x 10-3
        Angular range 0o - 360o (continuously)
        Energy- and angular measurements Simultaneously
        Coincidence measurements between two independent energy electrons
        Solid and gas phase samples applicable
        Equipped with Electron gun (up to 5 kV)
        Ion gun for surface cleaning

        The low energy electron spectroscopy is widely used in different fields of physics. In the last 30 years different type of electrostatic analyzers were developed and applied to determine the energy distribution of electrons. The traditional way to measure the angular distributions of the emitted photo- and Auger electrons is to rotate the analyzer around the interaction region. It is very time consuming and causes serious calibration problems. In order to overcome these problems and to perform electron – electron coincidence measurements, a new electron spectrometer (ESA-22) was developed in ATOMKI, Debrecen.

        The ESA-22 is a modified version of ESA-21 analyzer [1]. It consists of a spherical and a cylindrical part. Comparing with ESA-21, the main differences is that the focal ring can be set to different diameters, thus either a series of channel detectors can be used to detect the electrons at different angles, or a position sensitive channel plate can be applied for simultaneous angular recording the electrons. Furthermore, the outer sphere and cylinder are cut into two parts, so the spectrometer is capable to analyze two independent angularly resolved electron spectra (in the 0o – 180o region) at different energy regions, simultaneously. A special electronic control and data handling electronics and software was worked out to control the analyzer.

         The performance of the analyzer: Relative energy resolution is DE/E= 4*10-3 (for slit size of 1.4 mm) which can be improved by using a retardation lens. The position sensitive detector records not only  the angular distribution of electrons simultaneously, but it simultaneously detects the energy distribution, too, in an energy region which is about ± 1% of the nominal energy value.

         These advanced properties of the spectrometer offer a new way to investigate the angular distributions of the electrons with high efficiency and to perform completely new coincidence measurements, e.g. the detection of coincidences between photo- and Auger electrons, etc.


        Contact: ricz at atomki.hu

          ESA 22







          Electron spectroscopy laborarory











          Versions:

          • ESA-22L - Built in 1998 in Debrecen in corporation with the University of Oulu, Finland. Recently mounted to the I-411 beamline of the MAX-II synchrotron. Further information

          • ESA-22D - Built in 2003 in Debrecen to investigate the angular distribution of  photo and Auger electrons originated from solid surfaces. Further information

          • ESA-22G - Built in 2003 in University of Giessen, Germany to investigate the angular distribution of electrons originated from electron - ion collisions. Further information

           

          Reference:

          [1] Varga D., Kádár I., Ricz S., Végh J., Kövér Á., Sulik B., Berényi D. Nucl. Instrum. Meth.  A 313 (1992) 163.


          Time-of-flight (TOF) electron spectrometer for study of forward-electron emission in ion-atom collisions
           

          Type

          Time-of-flight

          Electron energy range

          5 eV - 20  eV  (~ 5 eV –  ~200 eV)*

          Energy resolution

          6%  - 10.5%  (~ 2%  -  ~10% )*

          Detection angle

          0o

          Acceptance (half) angle

          0.5o  and 1o  in the horizontal and vertical plane, respectively

          (~ 0.17o  and ~ 0.33o  in the horizontal and vertical plane, respectively)*

          Coincidence measurements

          Electron - electron - ion

          * In a new version of the TOF spectrometer (under construction).

          The spectrometer is suitable for measurement of the energy spectrum of the electrons emitted in ion-atom collisions into a small solid angle around the direction of the incoming ion beam (0o) [1]. The principle of operation is the following. The electrons ejected from the target by the ion beam are reflected by the electric field of an electrostatic mirror into backward angles, while the ion beam passes through the mirror. Following the refection, the electrons fly in a field-free space until reaching the detector. The time-of-flight is measured by detecting the electrons in coincidence with the outgoing scattered ions.


          The spectrometer is equipped with further units that make it possible to identify the different reaction channels leading to electron emission in a given atomic collision system. An electrostatic charge-state selector (“beam cleaner”) mounted in front of the beam collimator defines the charge state of the incoming ion. The charge state of the outgoing ions can be selected by an electrostatic charge-state analyser. The ions are detected with a fast particle detector [2].


          The advantage of our TOF spectrometer is that it is suitable  for study of simultaneous multiple (up to quadruple) electron emission (see, e.g., ref. [3]) . This is achieved by using a detector array consisting of four channel electron multipliers for detection of the electrons.

           The set-up of the TOF electron spectrometer on the ion beam channel of the 1 MV Van de Graaff accelerator



           The principle of operation of the TOF  electron spectrometer


           The TOF electron spectrometer




           References:


          [1] L. Sarkadi and A. Orbán, Meas. Sci. Technol. 17 (2006) 84

          [2]  A. Báder, L. Sarkadi, Gy. Hegyesi, L. Víkor and J. Pálinkás, Meas. Sci. Technol. 6 (1995) 959

          [3] L. Sarkadi and A. Orbán, Phys. Rev. Lett. 100 (2008) 133201
          Contact: sarkadil at atomki.hu

          Measuring chamber for capillary-guiding experiments at ECR laboratory

           

          Diameter

          30 cm

          Vacuum level

          5x10-7 mbar

          Equipped with

          • Sample holder (3 axial, 1 rotational adjusment)
          • MCP detector ~40 mm (rotatable)
          • 45parallel-plate ion spectrometer (rotatable)
          • Differential faraday  cups

           

           

          Contact: zjuhasz at atomki.hu
          Measuring chambre for capillaries

          Measuring chamber for ion-molecule collosion  experiments at 5 MeV VDG accelerator

          Under consruction

          Features:
          • Diameter: ~ 100 cm


          Contact: sulik at atomki.hu