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Invited Review Article: Contemporary instrumentation and application of charge exchange neutral particle diagnostics in magnetic fusion energy experiments
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Image of FIG. 1.
FIG. 1.

The upper panel shows a schematic of the fast ion diagnostic experiment (FIDE) cylindrical plate electrostatic energy analyzer used on the poloidal divertor experiment (PDX) depicting the relative positions of the stripping cell, the deflection plates, the MCP array, and the Johnston electron multiplier. Deflection plate 1 (plate 2) is at negative (positive) potential. The lower panel shows a schematic of the FIDE stripping cell and collimation mechanism. The geometry of internal baffles and the locations of the “comblike” collimator are shown in Ref. 22.

Image of FIG. 2.
FIG. 2.

The upper panel shows FIDE charge-exchange spectra from PDX for a no-fishbone discharge (two neutral beams) compared with a severe-fishbone discharge (four neutral beams). The depletion of beam ions in the region is evident . Note that these spectra were obtained by sweeping the energy analyzer in time, so that fishbone spikes appear to be localized in energy but, in fact, they are localized in time. The lower panel shows simulations of the spectra using a bounce-averaged Fokker-Planck code (Ref. 32).

Image of FIG. 3.
FIG. 3.

Illustration of orbit shifts for counterinjection of the diagnostic neutral beam on PDX experiments to measure the -profile using neutral particle diagnostics (Ref. 33).

Image of FIG. 4.
FIG. 4.

Time evolution of and measured near the plasma core, , for PDX start-up obtained using neutral particle diagnostics. The open and solid triangles are from code modeling under different assumptions for the plasma resistivity profile that were made to account for redistribution of the electrons due to the presence of sawtooth activity (Ref. 23).

Image of FIG. 5.
FIG. 5.

The concept is illustrated in the upper panel. A schematic of the spectrometer design with plan and elevation crosssections of the analyzer is shown in the lower panel. The inset (not to scale) shows the geometry of the MCP detector (Ref. 36).

Image of FIG. 6.
FIG. 6.

The upper panel shows a Fokker-Planck calculation of the tangential deuterium NPA spectrum for a typical TFTR energetic ion mode discharge. The lower panel shows a deuterium charge exchange spectrum measured using the tangential NPA. A linear least-squares fit to the data in the energy range of (open circles) yields (Ref. 43).

Image of FIG. 7.
FIG. 7.

Central ion temperature measured on TFTR using the tangential suprabeam charge exchange technique (solid circles) in comparison with measurements from the horizontal x-ray crystal diagnostic using the Doppler broadening of the Ni impurity line emission (open circles) for a discharge with low toroidal rotation velocity . The toroidal rotation correction to the charge exchange data is small and has not been applied to these data (Ref. 43).

Image of FIG. 8.
FIG. 8.

Passive and active measurements of the deuterium ion temperature in an Ohmic discharge in NSTX using the neutral particle analyzer are shown. During the NB “blips” good agreement is observed between the NPA and CHarge Exchange Recombination Spectroscopy (CHERS) measurements. A typical deuterium thermal spectrum is shown in the inset (Ref. 46).

Image of FIG. 9.
FIG. 9.

Shown is the NPA measurement of the neutral beam ion distribution vs energy and tangency radius for source injection on NSTX. The spectrum peaks around the beam injection tangency radius, , and is highly anisotropic (Ref. 46).

Image of FIG. 10.
FIG. 10.

The typical plan layout for a tandem -type neutral particle analyzer is shown (Ref. 54). Charge exchange neutrals reionized in the stripping cell undergo momentum analysis in the magnetic sector (A) followed by energy analysis in the tandem electrostatic plate sector (B). The channeltron detector plane (C) exhibits linear rows of mass and energy resolved ions (Ref. 57).

Image of FIG. 11.
FIG. 11.

ISEP NPA layout showing the elements of the instrument. 1: input diaphragm, 2: collimator slit mechanism, 3: auxiliary movable calibration aid, 4: stripping foil, 5: output diaphragm, 6: light emission diode, 7: alignment laser, 8: Hall probe, 9: analyzing magnet, 10: analyzing electrostatic condenser, 11: detector array with 32 scintillator/PMT assemblies. is the atomic flux emitted by the plasma and is the reionized atomic flux (Ref. 65).

Image of FIG. 12.
FIG. 12.

Results of laboratory tests of the neutron and gamma sensitivity of the ISEP detector using a radioactive neutron source are shown. Curve 1: bare PMT (without scintillator), curve 2: scintillator (used in the lowest energy channels), curve 3: , curve 4: , curve 5: (used in the highest energy channel) (Ref. 65).

Image of FIG. 13.
FIG. 13.

Shown is a computer code simulation of the ISEP detector pulse height distribution for detection of ions in the presence of DT neutron radiation. The ion energy is , acceleration voltage (total energy ), count rate is . The neutron emission rate varies from (curve B) to (curve E) (Ref. 65).

Image of FIG. 14.
FIG. 14.

The intensity of ISEP magnetic field vs distance from the entrance edge of the magnet is shown. The open circles are the experimental measurements made with the use of a Hall probe and the solid line is the calculation (Ref. 65).

Image of FIG. 15.
FIG. 15.

Deuterium and hydrogen atom spectra for the case of a beam-heated high-density JET plasma (shot 52246, , deuterium heating beams, total beam ) are shown. Solid and open symbols correspond to deuterium and hydrogen. Dashed and solid lines are the results of numerical modeling of atom energy spectra (Ref. 65).

Image of FIG. 16.
FIG. 16.

Shown are typical time evolutions of tritium neutral fluxes with different energies detected by ISEP in a JET trace tritium experiment (shot 61161) with gas puff along with the intensity of neutrons (Ref. 66).

Image of FIG. 17.
FIG. 17.

Calculated source functions for tritium neutral fluxes of different energies (Ref. 66).

Image of FIG. 18.
FIG. 18.

Diagram of the CNPA analyzer: (1) stripping and acceleration system; (2) stripping foil; (3) analyzing magnet; (4) Hall probe; (5) analyzing electrostatic condenser; (6) shielding mask at the entrance to the detectors; (7) detectors (channeltrons); atomic flux emitted by plasma; secondary ions; (H) hydrogen detector array; and (D) deuterium detector array (Ref. 67).

Image of FIG. 19.
FIG. 19.

Shown are the efficiencies for the detection of hydrogen and deuterium atomic fluxes in the CNPA. The electrostatic acceleration of ions scattered by the stripping foil provides focusing of ions before the dispersion which leads to an increase of the detection efficiency in the energy range (Ref. 67).

Image of FIG. 20.
FIG. 20.

Shown is a schematic drawing of a low energy time-of-flight analyzer (Donné).

Image of FIG. 21.
FIG. 21.

CX neutral fluxes measured at RFX with a vertical TOF, horizontal TOF, and a magnetic NPA for a low-density discharge. The line of sight of the vertical system does not pass through the plasma center and therefore the measured fluxes are somewhat lower. Those of the horizontal time of flight agree well with the values of the magnetic NPA system in the energy ranger of (Ref. 73).

Image of FIG. 22.
FIG. 22.

Layout of the time-of-flight (TOF)-type neutral particle analyzer applied at JET. The upper panel shows the mechanical assembly of the analyzer: (A) stripping cell, (B) cylindrical electrostatic plates, (C) TOF detectors, (D) light trap. The lower panel shows the TOF detecting unit: (A) CEM start detector, (B) CEM stop detector, (C) carbon stripping foil, (D) input aperture, (e) -metal enclosure (Ref. 79).

Image of FIG. 23.
FIG. 23.

Measurement of the isotope ratio in JET. The squares were measured by a quadrupole mass analyzer, the crosses by active Balmer-alpha spectroscopy, and the diamonds by the TOF NPA system (Ref. 84).

Image of FIG. 24.
FIG. 24.

Contour plot of the pitch angle distribution of neutral particles measured with the TOF analyzer in the stationary phase of a neutral beam heated LHD discharge. The measurement was done in a single discharge with a scan speed of . The color indicates the flux of the particles (, ). Trapped particles are clearly observed around a 90° pitch angle (Ref. 86).

Image of FIG. 25.
FIG. 25.

Illustration of the pellet charge exchange (PCX) concept using lithium as an example of low- pellet injection (Ref. 97).

Image of FIG. 26.
FIG. 26.

Calculated neutral equilibrium fractions for alpha particles on heliumlike lithium and boron (Ref. 98).

Image of FIG. 27.
FIG. 27.

Shown are alpha spectra measured on TFTR using the pellet charge exchange diagnostic and comparison with the evolution computed using the FPPT code (curves) for two times: (1) near the birth phase shown as full squares corresponding to and (2) during the slowing-down phase shown as full circles corresponding to (Ref. 98).


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Invited Review Article: Contemporary instrumentation and application of charge exchange neutral particle diagnostics in magnetic fusion energy experiments