Fourth order resonance of a high intensity linear accelerator

Jeon, D.; Groening, L.; Franchetti, G.

doi:10.1103/physrevstab.12.054204

Cited by 29 publications

(23 citation statements)

References 8 publications

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“…Many halo generation mechanisms have been studied such as space charge coupling resonances [2], mismatch [3], envelope instability [4], etc. Recently it is discovered that a fourth order space charge resonance 4 ¼ 360 is excited in high intensity linear accelerators, practically replacing the envelope instability when depressed phase advance per cell is close to 90 [5] and experimentally confirmed [6].…”

Section: Introductionmentioning

confidence: 97%

Evidence of a halo formation mechanism in the Spallation Neutron Source linac

Jeon

2013

Phys. Rev. ST Accel. Beams

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Phys. Rev. ST Accel. Beams 5, 094201 (2002)] are verified experimentally through a series of emittance measurements performed during the drift tube linac tank 1 commissioning of the Spallation Neutron Source. This is a rare experiment evidence of a halo formation mechanism. As the simulation predicts, the emittance measurements clearly show a visible halo reduction as well as a significant rms emittance reduction when the proposed round beam optics is employed. The emittance measurement results are consistent with multiparticle simulations and also consistent with wire scanner results. These measurements serve as a valuable code benchmarking for a beam under an intense space charge effect.

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Section: Introductionmentioning

confidence: 97%

Evidence of a halo formation mechanism in the Spallation Neutron Source linac

Jeon

2013

Phys. Rev. ST Accel. Beams

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“…It has been studied theoretically [1][2][3][4][5][6][7][8] and experimentally [9][10][11] since the 1980s. In recent years, there was growing interest in further understanding this instability and other structural resonances [12][13][14][15][16][17][18][19][20][21][22]. Some of those studies were summarized in a recently published monograph [23].…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional envelope instability in periodic focusing channels

Qiang

2018

Phys. Rev. Accel. Beams

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The space-charge driven envelope instability can be of great danger in high intensity accelerators and was studied using a two-dimensional (2D) envelope model and three-dimensional (3D) macroparticle simulations before. In this paper, we study the instability for a bunched beam using a three-dimensional envelope model in a periodic solenoid and radio-frequency (rf) focusing channel and a periodic quadrupole and rf focusing channel. This study shows that when the transverse zero current phase advance is below 90°, the beam envelope can still become unstable if the longitudinal zero current phase advance is beyond 90°. For the transverse zero current phase advance beyond 90°, the instability stopband width becomes larger with the increase of the longitudinal focusing strength and even shows different structure from the 2D case when the longitudinal zero current phase advance is beyond 90°. Breaking the symmetry of two longitudinal focusing rf cavities and the symmetry between the horizontal focusing and the vertical focusing in the transverse plane in the periodic quadrupole and rf channel makes the instability stopband broader. This suggests that a more symmetric accelerator lattice design might help reduce the range of the envelope instability in parameter space.

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“…Around 90 phase advance, there are three mechanisms: the 4 = 360 fourth order resonance [20], the second envelope instability (2 o   2,coh = 180) and the fourth order envelope instability (4 o   4,coh = 360) [11]. For realistic beams, the fourth order resonance dominates over the fourth order instability and the envelope instability is either suppressed or manifested, depending on  o of the lattice [23].…”

Section: Fourth Order Envelope Instabilitymentioning

confidence: 99%

“…[19]. The space-charge 4= 360° fourth order resonance in linear accelerators was found and reported to dominate over the envelope instability [20]. Here  is the depressed phase advance per cell.…”

Section: Introductionmentioning

confidence: 99%

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Characteristics of the fourth order resonance in high intensity linear accelerators

Jeon

Hwang

2017

Physics of Plasmas

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For the 4= 360° space-charge resonance in high intensity linear accelerators, the emittance growth is surveyed for input Gaussian beams, as a function of the depressed phase advance per cell  and the initial tune depression ( o  ). For each data point, the linac lattice is designed such that the fourth order resonance dominates over the envelope instability. The data show that the maximum emittance growth takes place at   87° over a wide range of the tune depression (or beam current), which confirms that the relevant parameter for the emittance growth is  and that for the bandwidth is. An interesting four-fold phase space structure is observed that cannot be explained with the fourth order resonance terms alone. Analysis attributes this effect to a small negative sixth order detuning term as the beam is redistributed by the resonance. Analytical studies show that the tune increases monotonically for the Gaussian beam which prevents the resonance for  > 90. Frequency analysis indicates that the four-fold structure observed for input KV beams when  < 90 is not the fourth order resonance but a fourth order envelope instability because the 1/4 = 90/360 component is missing in the frequency spectrum.

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Fourth order resonance of a high intensity linear accelerator

Cited by 29 publications

References 8 publications

Evidence of a halo formation mechanism in the Spallation Neutron Source linac

Evidence of a halo formation mechanism in the Spallation Neutron Source linac

Three-dimensional envelope instability in periodic focusing channels

Characteristics of the fourth order resonance in high intensity linear accelerators

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