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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 |
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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.
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Contact: ricz at atomki.hu
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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.
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Time-of-flight (TOF) electron spectrometer for study of forward-electron emission in ion-atom collisions
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Type
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Time-of-flight
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Electron energy range
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5 eV - 20 eV
(~ 5 eV – ~200 eV)*
|
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Energy resolution
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6% - 10.5%
(~ 2% - ~10% )*
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Detection angle
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0o
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Acceptance (half) angle
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0.5o and 1o in the horizontal and vertical plane,
respectively
(~
0.17o and ~ 0.33o in the horizontal and vertical plane, respectively)*
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Coincidence
measurements
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Electron - electron - ion
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* 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.
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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
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Measuring chamber for capillary-guiding experiments at ECR laboratory
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Diameter
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30 cm
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Vacuum level
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5x10-7 mbar
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Equipped with
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- Sample holder (3 axial, 1 rotational adjusment)
- MCP detector ~40 mm (rotatable)
- 45o parallel-plate ion spectrometer (rotatable)
- Differential faraday cups
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Contact: zjuhasz at atomki.hu
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Measuring chamber for ion-molecule collosion experiments at 5 MeV VDG accelerator
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