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Title: Low emittance growth in a low energy beam transport line with un-neutralized section

Abstract

In a Low Energy Beam Transport line (LEBT), the emittance growth due to the beam's space charge is typically suppressed by way of neutralization from either electrons or ions, which originate from ionization of the background gas. In cases where the beam is chopped, the neutralization pattern usually changes throughout the beginning of the pulse, causing the Twiss parameters to differ significantly from their steady state values, which, in turn, may result in beam losses downstream. For a modest beam perveance, there is an alternative solution, in which the beam is kept un-neutralized in the portion of the LEBT that contains the chopper. The emittance can be nearly preserved if the transition to the un-neutralized section occurs where the beam exhibits low transverse tails. This report introduces the rationale for the proposed scheme and formulates the physical arguments for it as well as its limitations. In conclusion, an experimental realization of the scheme was carried out at Fermilab's PIP2IT where low beam emittance dilution was demonstrated for a 5 mA, 30 keV $$H^{-}$$ beam.

Authors:
; ;
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1419706
Alternate Identifier(s):
OSTI ID: 1415629
Report Number(s):
Fermilab-Pub-17-599-AD; arXiv:1805.01920; FERMILAB-PUB-17-599-AD
Journal ID: ISSN 2469-9888; PRABCJ; 020101
Grant/Contract Number:  
AC02-07CH11359
Resource Type:
Published Article
Journal Name:
Physical Review Accelerators and Beams
Additional Journal Information:
Journal Name: Physical Review Accelerators and Beams Journal Volume: 21 Journal Issue: 2; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Prost, L., Carneiro, J. -P., and Shemyakin, A. Low emittance growth in a low energy beam transport line with un-neutralized section. United States: N. p., 2018. Web. doi:10.1103/PhysRevAccelBeams.21.020101.
Prost, L., Carneiro, J. -P., & Shemyakin, A. Low emittance growth in a low energy beam transport line with un-neutralized section. United States. doi:10.1103/PhysRevAccelBeams.21.020101.
Prost, L., Carneiro, J. -P., and Shemyakin, A. Tue . "Low emittance growth in a low energy beam transport line with un-neutralized section". United States. doi:10.1103/PhysRevAccelBeams.21.020101.
@article{osti_1419706,
title = {Low emittance growth in a low energy beam transport line with un-neutralized section},
author = {Prost, L. and Carneiro, J. -P. and Shemyakin, A.},
abstractNote = {In a Low Energy Beam Transport line (LEBT), the emittance growth due to the beam's space charge is typically suppressed by way of neutralization from either electrons or ions, which originate from ionization of the background gas. In cases where the beam is chopped, the neutralization pattern usually changes throughout the beginning of the pulse, causing the Twiss parameters to differ significantly from their steady state values, which, in turn, may result in beam losses downstream. For a modest beam perveance, there is an alternative solution, in which the beam is kept un-neutralized in the portion of the LEBT that contains the chopper. The emittance can be nearly preserved if the transition to the un-neutralized section occurs where the beam exhibits low transverse tails. This report introduces the rationale for the proposed scheme and formulates the physical arguments for it as well as its limitations. In conclusion, an experimental realization of the scheme was carried out at Fermilab's PIP2IT where low beam emittance dilution was demonstrated for a 5 mA, 30 keV $H^{-}$ beam.},
doi = {10.1103/PhysRevAccelBeams.21.020101},
journal = {Physical Review Accelerators and Beams},
number = 2,
volume = 21,
place = {United States},
year = {2018},
month = {2}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1103/PhysRevAccelBeams.21.020101

Figures / Tables:

Figure 1 Figure 1: Emittance growth as a function of the H- beam current simulated with TraceWin [8]. The beam energy is 30 keV. Blue - Double-Gaussian initial distribution; Red - UG initial distribution. The drift length is 251 mm, the initial rms beam size is 7.5 mm, and the initial anglemore » is adjusted for each current to provide the final rms size equal to the initial’s. Initial beam emittance is 25 µm (rms, unnormalized) for both distributions. There is no beam loss.« less

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Works referenced in this record:

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