Electron-beam diagnostic for space-charge measurement of an ion beam

Roy, P.K.; Yu, S.S.; Henestroza, E.; Eylon, S.; Shuman, D.; Ludvig, J.; Bieniosek, F.M.; Waldron, W.L.; Greenway, W.; Vanecek, D.; Hannink, Ryan; Amezcua, Monserrat

doi:10.1063/1.1847392

Cited by 11 publications

(4 citation statements)

References 16 publications

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“…This technique offers a non-perturbing, line-integrated measurement of the electric field in the beam plasma, and can map the beam cross-section by sweeping the electron beam. The diagnostic is straightforwardly applied to smalldiameter beams with cylindrical symmetry, however a more general use is suggested by recent improvements [163,164]. A synergic study on space charge compensation of small multi-beamlet negative ion beams (such as NIO1) will profit from this diagnostic in combination with other indirect or perturbing techniques, such as those for single-beamlet positive ions, e.g.…”

Section: Measurement Of Beam Space Charge Compensation or Beam Plasmamentioning

confidence: 99%

Neutralisation and transport of negative ion beams: physics and diagnostics

Serianni¹,

Agostinetti²,

Agostini³

et al. 2017

New J. Phys.

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Neutral beam injection is one of the most important methods of plasma heating in thermonuclear fusion experiments, allowing the attainment of fusion conditions as well as driving the plasma current. Neutral beams are generally produced by electrostatically accelerating ions, which are neutralised before injection into the magnetised plasma. At the particle energy required for the most advanced thermonuclear devices and particularly for ITER, neutralisation of positive ions is very inefficient so that negative ions are used. The present paper is devoted to the description of the phenomena occurring when a high-power multi-ampere negative ion beam travels from the beam source towards the plasma. Simulation of the trajectory of the beam and of its features requires various numerical codes, which must take into account all relevant phenomena. The leitmotiv is represented by the interaction of the beam with the background gas. The main outcome is the partial neutralisation of the beam particles, but ionisation of the background gas also occurs, with several physical and technological consequences. Diagnostic methods capable of investigating the beam properties and of assessing the relevance of the various phenomena will be discussed. Examples will be given regarding the measurements collected in the small flexible NIO1 source and regarding the expected results of the prototype of the neutral beam injectors for ITER. The tight connection between measurements and simulations in view of the operation of the beam is highlighted. operating in the existing tokamaks. Consequently, PRIMA, the ITER Neutral Beam Test Facility [2], was set up to constitute a test-bed, where the solutions to all the issues related to the achievement of full performances in the heating NBI system for ITER are going to be addressed and optimised, particularly regarding critical aspects like density and uniformity of the extracted negative ion current, high voltage holding and heat loads on the components [3]. Megavolt ITER Injector Concept Advancement (MITICA) is the full-scale prototype of the ITER NBIs [4]; it includes an RF-driven plasma source for the production of negative ions and should operate at a pressure as low as 0.3 Pa in hydrogen or deuterium gasses. The negative ions are produced on the surface of the grid (Plasma Grid, PG) that closes the plasma region; their production is enhanced thanks to a thin caesium layer continuously deposited over the PG by evaporation. Negative ions are extracted through the 1280 apertures in the PG by application of a suitable positive voltage to the extraction grid (EG), located just downstream of the PG. The RF plasma source operates at an applied electric potential of about −1 MV. Five additional acceleration grids (AG1, AG2, AG3, AG4, GG), at intermediate electric potential increasing by 200 kV steps, are located downstream with respect to the EG, thus constituting a 5-stage electrostatic accelerator. The resulting negative ion beam at 1 MeV, after passing through a gas cell neutraliser and an electro...

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Section: Measurement Of Beam Space Charge Compensation or Beam Plasmamentioning

confidence: 99%

Neutralisation and transport of negative ion beams: physics and diagnostics

Serianni¹,

Agostinetti²,

Agostini³

et al. 2017

New J. Phys.

View full text Add to dashboard Cite

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“…In general, there are two ways of producing parallel electron beams. Lawrence Berkeley National Laboratory use four dipole magnets of equal strengths to form a chicane system [7],…”

Section: Producing Parallel Elec-tron Beammentioning

confidence: 99%

“…In general, there are two ways of producing parallel electron beams. Lawrence Berkeley National Laboratory use four dipole magnets of equal strengths to form a chicane system [7], which is similar to a bump system. By virtue of this arrangement, the electron beam can be swept in the y axis while remaining parallel to the x axis in the gap between the middle two magnets.…”

Section: Producing Parallel Elec-tron Beammentioning

confidence: 99%

Beam distribution reconstruction simulation for electron beam probe

et al. 2017

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An electron beam probe (EBP) is a detector which makes use of a low-intensity and low-energy electron beam to measure the transverse profile, bunch shape, beam neutralization and beam wake field of an intense beam with small dimensions. While it can be applied to many aspects, we limit our analysis to beam distribution reconstruction. This kind of detector is almost non-interceptive for all of the beam and does not disturb the machine environment. In this paper, we present the theoretical aspects behind this technique for beam distribution measurement and some simulation results of the detector involved. First, a method to obtain a parallel electron beam is introduced and a simulation code is developed. An EBP as a profile monitor for dense beams is then simulated using the fast scan method for various target beam profiles, including KV distribution, waterbag distribution, parabolic distribution, Gaussian distribution and halo distribution. Profile reconstruction from the deflected electron beam trajectory is implemented and compared with the actual profile, and the expected agreement is achieved. Furthermore, as well as fast scan, a slow scan, i.e. step-by-step scan, is considered, which lowers the requirement for hardware, i.e. Radio Frequency deflector. We calculate the three-dimensional electric field of a Gaussian distribution and simulate the electron motion in this field. In addition, a fast scan along the target beam direction and slow scan across the beam are also presented, and can provide a measurement of longitudinal distribution as well as transverse profile simultaneously. As an example, simulation results for the China Accelerator Driven Sub-critical System (CADS) and High Intensity Heavy Ion Accelerator Facility (HIAF) are given. Finally, a potential system design for an EBP is described.

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“…The test experiment demonstrated a continuous-wave proton beam whose energy is about 20.18 MeV and the current intensity is about 10 mA. Moreover, using magnetic field to guide and focus ion beam [20][21][22][23][24] has become an important part in the development of ion beam application technology, which lets the ion beam move in magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the confinement of high energy non-neutral proton beam in a bent magnetic mirror

Wang¹,

Zhang²,

Zhang³

et al. 2022

Plasma Sci. Technol.

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By using the Particle-In-Cell(PIC) simulation method, we study how the proton beam is confined in a bent magnetic mirror. It is found that the loss rate of the charged particles in a bent mirror is less than that in the axi-symmetric mirror. For a special bent mirror with the deflection angle of the coils $\alpha=45^{\circ}$, it is found that the loss rate reaches maximum value at certain ion number density where the ion electrostatic oscillation frequency is equal to the ion cyclotron frequency. In addition, the loss rate is irrelevant to the direction of the proton beam. Our results may be helpful to devise a mirror. In order to obtain the least loss rate, we may choose a appropriate deflection angle, and have to avoid a certain ion number density at which the ion electrostatic oscillation frequency is equal to the ion cyclotron frequency.

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Electron-beam diagnostic for space-charge measurement of an ion beam

Cited by 11 publications

References 16 publications

Neutralisation and transport of negative ion beams: physics and diagnostics

Neutralisation and transport of negative ion beams: physics and diagnostics

Beam distribution reconstruction simulation for electron beam probe

Investigation of the confinement of high energy non-neutral proton beam in a bent magnetic mirror

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