Beam-Halo Measurements in High-Current Proton Beams

Allen, C.K.; Chan, K.C.D.; Colestock, P.L.; Crandall, K.R.; Garnett, R.W.; Gilpatrick, J.D.; Lysenko, W. P.; Qiang, Ji; Schneider, J.D.; Schulze, Martin; Sheffield, R.L.; Smith, H. Vernon; Wangler, T.P.

doi:10.1103/physrevlett.89.214802

Cited by 72 publications

(35 citation statements)

References 6 publications

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“…To test the two models, we installed a 52-quadrupole periodic-focusing beam-transport channel at the end of the Los Alamos low-energy demonstration accelerator (LEDA) [6]. LEDA 3 delivers a 6.7-MeV proton beam from a 350-MHz radiofrequency-quadrupole (RFQ) linac.…”

Section: Beam-halo Experimentsmentioning

confidence: 99%

“…The rms-size measurements were used to calculate the rms emittances at scanners 20 and 45 [6]. Assuming zero emittance growth in the channel for the matched beam, the tune depression from space-charge was 0.82 immediately after the matching quadrupoles at scanner 4, and was constant at 0.95 after the beam had debunched at approximately quadrupole 16, about 3.5 m from the beginning of the channel.…”

Section: Beam-halo Experimentsmentioning

confidence: 99%

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Beam-halo in mismatched proton beams

Wangler

Allen

Chan

et al. 2004

Nuclear Instruments and Methods in Physics Research Section A:

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Progress was made during the past decade towards a better understanding of halo formation caused by beam mismatch in high-intensity beams. To test these ideas an experiment was carried out at Los Alamos with proton beams in a 52-quadrupole focusing channel. Rms emittances and beam widths were obtained from measured beam profiles for comparison with the maximum emittance growth predictions of a free-energy model and the maximum haloamplitude predictions of a particle-core model. The experimental results are also compared with multiparticle simulations. In this paper we will present the experimental results and discuss the implications with respect to the validity of both the models and the simulations.

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Section: Beam-halo Experimentsmentioning

confidence: 99%

Section: Beam-halo Experimentsmentioning

confidence: 99%

Beam-halo in mismatched proton beams

Wangler

Allen

Chan

et al. 2004

Nuclear Instruments and Methods in Physics Research Section A:

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Section: Introductionmentioning

confidence: 89%

“…Several mechanisms can lead to the formation of a beam halo including machine mismatch, beam dispersion and scattering effects [1]. Measurements done in proton machines [2,3] confirm, to a large extent, the validity of the particle core model [4,5,6].On the other hand, limited experience on halo formation in intense electron beams is available on the international scene, and besides the clear need for corresponding models, beam diagnostic techniques need to be developed that allow experimental verification.One possible approach towards high dynamic range measurements is the exploitation of OTR created by the electron beam when passing through a thin screen introduced into the beam line. This kind of radiation guarantees a fast time response and very good linearity with the beam signal over a wide intensity range.…”

mentioning

confidence: 99%

Alternative techniques for beam halo measurements

Welsch¹,

Bravin²,

Burel³

et al. 2006

Meas. Sci. Technol.

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In future high intensity, high energy accelerators it must be ensured that particle losses are minimized, as activation of the vacuum chambers or other components makes maintenance and upgrade work time consuming and costly. It is imperative to have a clear understanding of the mechanisms that can lead to halo formation and to have the possibility to test available theoretical models with an adequate experimental setup.Measurements based on optical transition radiation (OTR) are a well-established technique for measurements of the transverse beam profile. However, in order to be suitable for halo measurements as well, the dynamic range of the final image acquisition system needs to be high, being able to cover at least five orders of magnitude in intensity changes.Here, the performance of a standard acquisition system as it is used in the CLIC test facility (CTF3) is compared to a step-by-step measurement with a small movable photo multiplier tube and an innovative camera system based on charge injection device (CID) technology. Special emphasis is given on a description of the characteristics of the latter system. In future high intensity, high energy accelerators it must be ensured that particle losses are minimized, as activation of the vacuum chambers or other components makes maintenance and upgrade work time consuming and costly. It is imperative to have a clear understanding of the mechanisms that can lead to halo formation and to have the possibility to test available theoretical models with an adequate experimental setup. Published in MEASUREMENT SCIENCEMeasurements based on optical transition radiation (OTR) are a well-established technique for measurements of the transverse beam profile. However, in order to be suitable for halo measurements as well, the dynamic range of the final image acquisition system needs to be high, being able to cover at least five orders of magnitude in intensity changes.Here, the performance of a standard acquisition system as it is used in the CLIC test facility (CTF3) is compared to a step-by-step measurement with a small movable photo multiplier tube and an innovative camera system based on charge injection device (CID) technology. Special emphasis is given on a description of the characteristics of the latter system. INTRODUCTIONFor a future linear collider, it will be of central importance to have a detailed understanding of beam halo formation, since beam losses in high intensity machines will cause severe activation of the surrounding vacuum chambers and thus complicate maintenance and increase costs. Several mechanisms can lead to the formation of a beam halo including machine mismatch, beam dispersion and scattering effects [1]. Measurements done in proton machines [2,3] confirm, to a large extent, the validity of the particle core model [4,5,6].On the other hand, limited experience on halo formation in intense electron beams is available on the international scene, and besides the clear need for corresponding models, beam diagnostic techniques need to be de...

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“…In fact the trajectories of our Lévy-Student process show the typical jumps of the non-Gaussian Lévy processes: a feature that we propose to use as a model for the halo formation. It is worth remarking that, albeit the more recent empirical data about halos [19] are still not accurate enough to distinguish between the suggested distributions and the usual Gaussian ones, our conjecture on the role of Student laws in the transverse beam dynamics has recently found a first confirmation [20] in numerical simulations showing how these laws are well suited to describe the statistics of the random features of the particle paths.…”

Section: Introductionmentioning

confidence: 98%

Lévy-Student distributions for halos in accelerator beams

et al. 2005

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We describe the transverse beam distribution in particle accelerators within the controlled, stochastic dynamical scheme of the Stochastic Mechanics (SM) which produces time reversal invariant diffusion processes. This leads to a linearized theory summarized in a Shchrödinger-like (S-ℓ) equation. The space charge effects have been introduced in a recent paper [1] by coupling this S-ℓ equation with the Maxwell equations. We analyze the space charge effects to understand how the dynamics produces the actual beam distributions, and in particular we show how the stationary, self-consistent solutions are related to the (external, and space-charge) potentials both when we suppose that the external field is harmonic (constant focusing), and when we a priori prescribe the shape of the stationary solution. We then proceed to discuss a few new ideas [2] by introducing the generalized Student distributions, namely non-Gaussian, Lévy infinitely divisible (but not stable) distributions. We will discuss this idea from two different standpoints: (a) first by supposing that the stationary distribution of our (Wiener powered) SM model is a Student distribution; (b) by supposing that our model is based on a (non-Gaussian) Lévy process whose increments are Student distributed. We show that in the case (a) the longer tails of the power decay of the Student laws, and in the case (b) the discontinuities of the Lévy-Student process can well account for the rare escape of particles from the beam core, and hence for the formation of a halo in intense beams.

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Beam-Halo Measurements in High-Current Proton Beams

Cited by 72 publications

References 6 publications

Beam-halo in mismatched proton beams

Beam-halo in mismatched proton beams

Alternative techniques for beam halo measurements

Lévy-Student distributions for halos in accelerator beams

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