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Title: SNS INJECTION AND EXTRACTION DEVICES.

Abstract

The Spallation Neutron Source (SNS) project is designed to reach an average beam power above 1.4 MW for pulsed neutron production [1,2]. The accelerator system operates at a repetition rate of 60 Hz and average current of 1.4 mA. It consists of an H{sup -} 1 GeV superconducting linac; a high energy beam transport(HEBT)[3] for diagnostics, transverse and longitudinal, collimations, matching, energy correction and painting; and an accumulator ring compressing the 1GeV, 1 ms pulse to 650 ns for delivery onto target through a ring-target beam transport (RTBT)[4]. At such intensity and power, beam loss is critical issue mainly for two reasons: (1) to guarantee hands-on maintenance of the accelerator; and (2) to protect components of the accelerator. The injection loss and subsequent beam loss due to all injection mechanisms has to be kept manageable. There are several injection loss mechanisms. These are: (1) the linac beam missing the stripping foil, (2) H{sup 0}'s emerging from the foil, which is a function of the thickness of the foil, (3) H{sup 0}'s emerging from the foil, which is calculated to be negligible, and (4) circulating beam loss due to Coulomb and nuclear scattering on the foil. Loss mechanism (1) is relatedmore » to the stripping foil size and this loss should be kept to less than a few percent. This beam loss along with loss due to mechanism (3) is well known and a controlled dumping of the waste beam is planned [5]. Loss mechanism (4) is directly related to the thickness of the foil and the amount of circulating beam hitting it, which is proportional to the foil size [6]. The foil size is chosen such that it provides a compromise between mechanisms (1) and (4). The thickness of the foil is determined by mechanisms (2), (4) and the foil heating problem [7]. Present plans call for a carbon foil of size of 8 mm x 4 mm and a thickness of 300 mg/cm{sup 2}. The size of the stripping foil is chosen such that a distribution tail of about 2% of the incoming linac beam misses the foil. This is a compromise between this loss and the loss due to Coulomb and nuclear scattering of the stored protons. For a 400-{micro}g/cm{sup 2} thick foil, about 0.82% and for a 300-{micro}g/cm{sup 2} foil about 2% of the incoming H{sup -} ions will emerge as H{sup 0}. The population of their quantum of H{sup 0} states is measured to be n{sup -2.8}, where n is the principal quantum number. The H{sup 0}'s that emerge from the foil are converted to protons by a thick foil placed in their path. The downstream magnets will separate those protons from the circulating protons. The septum magnet downstream is to be combined function magnet and together with the quadrupole placed downstream shapes the image of the dumped proton beam onto the 200 kW beam dump. For 1 GeV injection, the stripped electrons from the incoming H{sup -} beam have about one thousandth of the proton power and is 1 kW at 1 MW SNS, which is formidable electron power. It is essential to dump these electrons proper way to avoid electron cloud instability [16] and overheating of components.« less

Authors:
Publication Date:
Research Org.:
BROOKHAVEN NATIONAL LABORATORY (US)
Sponsoring Org.:
DOE/SC (US)
OSTI Identifier:
15016170
Report Number(s):
BNL-73938-2005-CP
R&D Project: 86485; ISBN KB-02-02-01-1; TRN: US0502028
DOE Contract Number:  
AC02-98CH10886
Resource Type:
Conference
Resource Relation:
Conference: PAC 05 PARTICLE ACCELERATOR CONFERENCE, KNOXVILLE, TN (US), 05/16/2005--05/20/2005; Other Information: PBD: 16 May 2005
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; BEAM DUMPS; BEAM TRANSPORT; LINEAR ACCELERATORS; NEUTRON SOURCES; PROTON BEAMS; QUADRUPOLES; QUANTUM NUMBERS; SEPTUM MAGNETS; SPALLATION; TANKS

Citation Formats

RAPARIA, D. SNS INJECTION AND EXTRACTION DEVICES.. United States: N. p., 2005. Web.
RAPARIA, D. SNS INJECTION AND EXTRACTION DEVICES.. United States.
RAPARIA, D. 2005. "SNS INJECTION AND EXTRACTION DEVICES.". United States. https://www.osti.gov/servlets/purl/15016170.
@article{osti_15016170,
title = {SNS INJECTION AND EXTRACTION DEVICES.},
author = {RAPARIA, D},
abstractNote = {The Spallation Neutron Source (SNS) project is designed to reach an average beam power above 1.4 MW for pulsed neutron production [1,2]. The accelerator system operates at a repetition rate of 60 Hz and average current of 1.4 mA. It consists of an H{sup -} 1 GeV superconducting linac; a high energy beam transport(HEBT)[3] for diagnostics, transverse and longitudinal, collimations, matching, energy correction and painting; and an accumulator ring compressing the 1GeV, 1 ms pulse to 650 ns for delivery onto target through a ring-target beam transport (RTBT)[4]. At such intensity and power, beam loss is critical issue mainly for two reasons: (1) to guarantee hands-on maintenance of the accelerator; and (2) to protect components of the accelerator. The injection loss and subsequent beam loss due to all injection mechanisms has to be kept manageable. There are several injection loss mechanisms. These are: (1) the linac beam missing the stripping foil, (2) H{sup 0}'s emerging from the foil, which is a function of the thickness of the foil, (3) H{sup 0}'s emerging from the foil, which is calculated to be negligible, and (4) circulating beam loss due to Coulomb and nuclear scattering on the foil. Loss mechanism (1) is related to the stripping foil size and this loss should be kept to less than a few percent. This beam loss along with loss due to mechanism (3) is well known and a controlled dumping of the waste beam is planned [5]. Loss mechanism (4) is directly related to the thickness of the foil and the amount of circulating beam hitting it, which is proportional to the foil size [6]. The foil size is chosen such that it provides a compromise between mechanisms (1) and (4). The thickness of the foil is determined by mechanisms (2), (4) and the foil heating problem [7]. Present plans call for a carbon foil of size of 8 mm x 4 mm and a thickness of 300 mg/cm{sup 2}. The size of the stripping foil is chosen such that a distribution tail of about 2% of the incoming linac beam misses the foil. This is a compromise between this loss and the loss due to Coulomb and nuclear scattering of the stored protons. For a 400-{micro}g/cm{sup 2} thick foil, about 0.82% and for a 300-{micro}g/cm{sup 2} foil about 2% of the incoming H{sup -} ions will emerge as H{sup 0}. The population of their quantum of H{sup 0} states is measured to be n{sup -2.8}, where n is the principal quantum number. The H{sup 0}'s that emerge from the foil are converted to protons by a thick foil placed in their path. The downstream magnets will separate those protons from the circulating protons. The septum magnet downstream is to be combined function magnet and together with the quadrupole placed downstream shapes the image of the dumped proton beam onto the 200 kW beam dump. For 1 GeV injection, the stripped electrons from the incoming H{sup -} beam have about one thousandth of the proton power and is 1 kW at 1 MW SNS, which is formidable electron power. It is essential to dump these electrons proper way to avoid electron cloud instability [16] and overheating of components.},
doi = {},
url = {https://www.osti.gov/biblio/15016170}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 16 00:00:00 EDT 2005},
month = {Mon May 16 00:00:00 EDT 2005}
}

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