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

Jeon, D.

doi:10.1103/physrevstab.16.040103

Cited by 6 publications

(3 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We suppress the beam tails and improve the quality of the beam going into the CCL by adopting the "round beam MEBT optics" in the MEBT (Medium Energy Beam Transport) which suppresses the halo formation induced by the optics of the SNS MEBT [24,25]. Both the simulation [24] and the experiment [25] show that the "round beam MEBT optics" reduces the X rms emittance and beam halo significantly. The quality of the beam going into the CCL can be measured with the four upstream CCL wire-scanners installed in series (WS104, 106, 108, 110 in Fig.…”

Section: B Beam Matching and Incoming Beam Qualitymentioning

confidence: 99%

Experimental evidence of space charge driven resonances in high intensity linear accelerators

Jeon

2016

Phys. Rev. Accel. Beams

Self Cite

View full text Add to dashboard Cite

In the construction of high intensity accelerators, it is the utmost goal to minimize the beam loss by avoiding or minimizing contributions of various halo formation mechanisms. As a halo formation mechanism, space charge driven resonances are well known for circular accelerators. However, the recent finding showed that even in linear accelerators the space charge potential can excite the 4σ ¼ 360°fourth order resonance [D. Jeon et al., Phys. Rev. ST Accel. Beams 12, 054204 (2009)]. This study increased the interests in space charge driven resonances of linear accelerators. Experimental studies of the space charge driven resonances of high intensity linear accelerators are rare as opposed to the multitude of simulation studies. This paper presents an experimental evidence of the space charge driven 4σ ¼ 360°r esonance and the 2σ xðyÞ − 2σ z ¼ 0 resonance of a high intensity linear accelerator through beam profile measurements from multiple wire-scanners. Measured beam profiles agree well with the characteristics of the space charge driven 4σ ¼ 360°resonance and the 2σ xðyÞ − 2σ z ¼ 0 resonance that are predicted by the simulation.

show abstract

Section: B Beam Matching and Incoming Beam Qualitymentioning

confidence: 99%

Experimental evidence of space charge driven resonances in high intensity linear accelerators

Jeon

2016

Phys. Rev. Accel. Beams

Self Cite

View full text Add to dashboard Cite

show abstract

“…Some attempts aim to directly mitigate the halo, as for example using a round input beam (Jeon, 2013) or using the transverse-longitudinal coupling resonance to get rid of the longitudinal halo (Hofmann, 2013). We propose to use a radical method called "halo matching" aiming to smooth the extension of the external border of the beam, thus directly minimizing the halo (Chauvin et al, 2009).…”

Section: Beam Optimizationmentioning

confidence: 99%

Advanced concepts and methods for very high intensity accelerators

et al. 2014

View full text Add to dashboard Cite

For very high intensity accelerators, not only beam power but also space charge is a concern. Both aspects should be taken into consideration for any analysis of accelerators aiming at comparing their performances and pointing out the challenging sections. As high beam power is an issue from the lowest energy, careful and exhaustive beam loss predictions have to be done. High space charge implies lattice compactness making the implementation of beam diagnostics very problematic, so a clear strategy for beam diagnostic has to be defined. Beam halo is no longer negligible. Its dynamics is different from that of the core and plays a significant role in the particle loss process. Therefore, beam optimization must take the halo into account and beam characterization must be able to describe the halo part in addition to the core one. This paper presents the advanced concepts and methods for beam analysis, beam loss prediction, beam optimization, beam diagnostic, and beam characterization especially dedicated to very high intensity accelerators. Examples of application of these concepts are given in the case of the IFMIF accelerators.

show abstract

“…Beam halos have been studied with a variety of theoretical [7][8][9][10][11][12], computational [13,14] and experimental [15][16][17][18] tools. Theoretical studies have used a core-particle model [19,20] to study the dynamics of halo particles in the presence of initial beam mismatch, but assume a uniform beam core, which implies a linear space-charge force.…”

Section: Introductionmentioning

confidence: 99%

Higher order mode beams mitigate halos in high intensity proton linacs

Pathak

Krishnagopal

2017

Phys. Rev. Accel. Beams

View full text Add to dashboard Cite

High intensity proton linacs (HIPLs) for applications such as Accelerator Driven Reactor Systems (ADRS) have serious beam dynamics issues related to beam halo formation. This can lead to particle loss and radioactivation of the surroundings which consequently limit the beam current. Beam halos are largely driven by the nonlinear space-charge force of the beam, which depends strongly on the beam distribution and also on the initial beam mismatch. We propose here the use of a higher order mode beam (HOMB), that has a weaker nonlinear force, to mitigate beam halos. We first show how the nonlinear space-charge force can itself be exploited in the presence of nonlinear solenoid fields, to produce a HOMB in the low energy beam transport (LEBT) line. We then study the transport of such a beam through a radio frequency quadrupole (RFQ), and show that the HOMB has a significant advantage in terms of emittance blow-up, halo formation and beam loss, over a Gaussian beam, even with a finite initial mismatch. For example, for the transport of a 30 mA beam through the RFQ, with an initial beam mismatch of 45%, the Gaussian beam sees an emittance blow-up of 125%, while the HOMB sees a blow-up of only 35% (relative to the initial emittance of 0.2π mm-mrad). Similarly, the beam halo parameter and beam loss are 0.95 and 25% respectively for a Gaussian beam, but only 0.35 and 15% for a HOMB. The beam dynamics of the HOMB agrees quite well with the particle-core model, because of the more linear space-charge force, while for the Gaussian beam there are additional particle loss mechanisms arising from nonlinear resonances. Therefore, the HOMB suppresses emittance blow-up and halo formation, and can make high current ADRS systems more viable.

show abstract

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

Cited by 6 publications

References 8 publications

Experimental evidence of space charge driven resonances in high intensity linear accelerators

Experimental evidence of space charge driven resonances in high intensity linear accelerators

Advanced concepts and methods for very high intensity accelerators

Higher order mode beams mitigate halos in high intensity proton linacs

Contact Info

Product

Resources

About