Degradation of brightness by resonant particle effects

Chen, Y.-J.; Caporaso, G.J.; Cole, Andrew G.; Paul, A.C.; Turner, W.C.

doi:10.1109/pac.1991.165200

Cited by 5 publications

(5 citation statements)

References 3 publications

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“…Here, V(t) is the baseline subtracted raw DML signal and τ 1 , τ 2 , and 1/ω 2 are fitting parameters which can be identified with the loop and foil L/R times respectively and the LC of the loop inductance and parasitic capacity. When τ 1 , τ 2 , and 1/ω 2 During the loop calibration we use Equation (14) to generate…”

Section: B Proceduresmentioning

confidence: 99%

“…They are principally used for the generation of flash X-rays and are an important tool of the Safeguard program [1]. Mismatching of the electron beam to its axially symmetric magnetic guide field leads to radial envelope oscillations that can cause emittance growth [2], increase the time averaged spot size and reduce the brightness of the X-ray pulse. The determination of the value of the beam radius at various positions along the accelerator is important when tuning and matching the beam.…”

Section: Introductionmentioning

confidence: 99%

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A Non-Interfering Beam Radius Diagnostic Suitable For Induction Linacs

Nexsen¹

2005

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High current electron induction linacs operate in a parameter regime that allows the use of a diamagnetic loop (DML) to measure the beam magnetic moment. Under certain easily met conditions the beam radius can be derived from the moment measurement. The DML has the advantage over the present methods of measuring beam radius in that it is an electrical measurement with good time resolution that does not interfere with the beam transport. I describe experiments on the LLNL accelerators, ETA-II and FXR that give confidence in the use of a DML as a beam diagnostic.

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Section: B Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Non-Interfering Beam Radius Diagnostic Suitable For Induction Linacs

Nexsen¹

2005

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“…These ions produce a defocusing of the electron beam and thus an increase in the beam spot size at the target by the space charge effect. Different methods were particularly studied to reduce the ion effect: self-biased target [11][12][13][14][15][16][17], barrier foil [6,7,18], target surface laser cleaning [6], time varying final focusing solenoidal lens and beam energy variation [19]. Various analytical models or numerical simulations using particle-incell (PIC) codes were carried out, with various ion species emitted with a space charge limited current (in the Child-Langmuir regime) [12][13][14][17][18][19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

“…Different methods were particularly studied to reduce the ion effect: self-biased target [11][12][13][14][15][16][17], barrier foil [6,7,18], target surface laser cleaning [6], time varying final focusing solenoidal lens and beam energy variation [19]. Various analytical models or numerical simulations using particle-incell (PIC) codes were carried out, with various ion species emitted with a space charge limited current (in the Child-Langmuir regime) [12][13][14][17][18][19][20][21][22][23][24][25]. Thus, the ion effect was attributed to the species giving the best agreement with the spot size measurement [11][12][13][14][20][21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Ion emission at the target of the radiographic devices PIVAIR and AIRIX

Fontaine¹

2007

J. Phys. D: Appl. Phys.

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On an AIRIX facility, a high-intensity electron beam is used to generate an x-ray pulse for radiographic purposes. The measured electron beam spot size is found to be much larger than its computed value. It is shown that this discrepancy is removed considering ion emission at the target, under electron beam interaction. A model has been developed to simulate the plasma produced during the interaction of the electron beam with the target. The predictions have been compared with ion identification results developed on the PIVAIR prototype accelerator as well as with the x-ray spot size and dose measurements obtained on AIRIX. The simulations show that the ion effect can be reduced by placing a thin foil (100 µm thickness) at an appropriate distance from the target to catch the ions emitted and to stabilize the electron beam spot size. The X-spot size is then reduced, as found experimentally on AIRIX. Moreover, for a smaller thickness barrier foil (5 µm), the ion effect can even be suppressed, producing an X-spot size close to that obtained without ion emission.

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“…Generally, the beam halo generation are considered as consequence of nonlinear effect from external field and self-induced space charge [5][6][7]. In this paper, heam halo due to space charge will be discussed in detail since it * lichao@ihep.ac.cn requires self-consistent treatment.…”

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confidence: 99%

A new description of space charge induced beam halo

Li,

Jameson

2018

Preprint

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In particle accelerators, particle losses to surrounding components must be minimized. These particles usually have been driven into an undesired "halo" outside the desired distribution before being lost. The processes involved and physical identification of such halo is an intense research topic especially when the nonlinear space charge effect is taken into account. In order to present a method, firmly based on the physics of the transient beam state, for determining when a particle may be defined as being in a halo, the particular example of an initially rms matched beam injected into a resonance of an alternating-gradient (AG) focusing lattice is studied, in which the resonance between the collective mode and single particle motion pushes some particles into a halo defined by extending the halo description to the action-angle frame. In this new frame of description, the halo particles can be physically defined as those with larger actions affected by the outer quasi hyperbolic tori, which contains the halo particles observed in the traditional approaches on projected 2D phase space, as well as some particles still hidden in the core.

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Degradation of brightness by resonant particle effects

Cited by 5 publications

References 3 publications

A Non-Interfering Beam Radius Diagnostic Suitable For Induction Linacs

A Non-Interfering Beam Radius Diagnostic Suitable For Induction Linacs

Ion emission at the target of the radiographic devices PIVAIR and AIRIX

A new description of space charge induced beam halo

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