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Title: Recent Operation of the FNAL Magnetron H- Ion Source

Abstract

This paper will detail changes in the operational paradigm of the Fermi National Accelerator Laboratory (FNAL) magnetron H- ion source due to upgrades in the accelerator system. Prior to November of 2012 the H- ions for High Energy Physics (HEP) experiments were extracted at ~18 keV vertically downward into a 90 degree bending magnet and accelerated through a Cockcroft-Walton accelerating column to 750 keV. Following the upgrade in the fall of 2012 the H- ions are now directly extracted from a magnetron at 35 keV and accelerated to 750 keV by a Radio Frequency Quadrupole (RFQ). This change in extraction energy as well as the orientation of the ion source required not only a redesign of the ion source, but an updated understanding of its operation at these new values. Discussed in detail are the changes to the ion source timing, arc discharge current, hydrogen gas pressure, and cesium delivery system that were needed to maintain consistent operation at >99% uptime for HEP, with an increased ion source lifetime of over 9 months.

Authors:
 [1];  [1];  [1]
  1. Fermilab
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:
1339121
Report Number(s):
FERMILAB-CONF-16-351-AD
1507632
DOE Contract Number:
AC02-07CH11359
Resource Type:
Conference
Resource Relation:
Conference: 5th International Symposium on Negative Ions, Beams and Sources, Oxford, UK, 09/12-09/16/2016
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Karns, Patrick R., Bollinger, D. S., and Sosa, A. Recent Operation of the FNAL Magnetron H- Ion Source. United States: N. p., 2016. Web.
Karns, Patrick R., Bollinger, D. S., & Sosa, A. Recent Operation of the FNAL Magnetron H- Ion Source. United States.
Karns, Patrick R., Bollinger, D. S., and Sosa, A. 2016. "Recent Operation of the FNAL Magnetron H- Ion Source". United States. doi:. https://www.osti.gov/servlets/purl/1339121.
@article{osti_1339121,
title = {Recent Operation of the FNAL Magnetron H- Ion Source},
author = {Karns, Patrick R. and Bollinger, D. S. and Sosa, A.},
abstractNote = {This paper will detail changes in the operational paradigm of the Fermi National Accelerator Laboratory (FNAL) magnetron H- ion source due to upgrades in the accelerator system. Prior to November of 2012 the H- ions for High Energy Physics (HEP) experiments were extracted at ~18 keV vertically downward into a 90 degree bending magnet and accelerated through a Cockcroft-Walton accelerating column to 750 keV. Following the upgrade in the fall of 2012 the H- ions are now directly extracted from a magnetron at 35 keV and accelerated to 750 keV by a Radio Frequency Quadrupole (RFQ). This change in extraction energy as well as the orientation of the ion source required not only a redesign of the ion source, but an updated understanding of its operation at these new values. Discussed in detail are the changes to the ion source timing, arc discharge current, hydrogen gas pressure, and cesium delivery system that were needed to maintain consistent operation at >99% uptime for HEP, with an increased ion source lifetime of over 9 months.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 9
}

Conference:
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  • This paper will cover several studies and design changes that will eventually be implemented to the Fermi National Accelerator Laboratory (FNAL) magnetron ion source. The topics include tungsten cathode insert, solenoid gas valves, current controlled arc pulser, cesium boiler redesign, gas mixtures of hydrogen and nitrogen, and duty factor reduction. The studies were performed on the FNAL test stand described in [1], with the aim to improve source lifetime, stability, and reducing the amount of tuning needed.
  • A new solid state extractor pulser has been installed on the Fermi National Accelerator Laboratory (FNAL) magnetron ion source, replacing a vacuum tube style pulser that was used for over 40 years. The required ion source extraction voltage is 35 kV for injection into the radio frequency quadrupole. At this voltage, the old pulser had a rise time of over 150 μs due to the current limit of the vacuum tube. The new solid state pulsers are capable of 50 kV, 100 A peak current pulses and have a rise time of 9 μs when installed in the operational system.more » This paper will discuss the pulser design and operational experience to date.« less
  • The new FNAL Injector Line with a circular dimple magnetron ion source has been operational since December of 2013. Since the new injector came on line there have been variations in the H- beam current flattop observed near the downstream end of the linac. Several different cathode geometries including a hollow cathode suggested by Dudnikov [1] were tried. We expanded on those studies by trying mixtures ranging from 0.25%N, 99.75%H to 3%N, 97%H. The results of these studies in our test stand will be presented in this paper.
  • The magnetron-style H- ion sources currently in operation at Fermilab use piezoelectric gas valves to function. This kind of gas valve is sensitive to small changes in ambient temperature, which affect the stability and performance of the ion source. This motivates the need to find an alternative way of feeding H2 gas into the source. A solenoid-type gas valve has been characterized in a dedicated off-line test stand to assess the feasibility of its use in the operational ion sources. H- ion beams have been extracted at 35 keV using this valve. In this study, the performance of the solenoidmore » gas valve has been characterized measuring the beam current output of the magnetron source with respect to the voltage and pulse width of the signal applied to the gas valve.« less
  • Installation of a grooved cathode and addition of a resistive heater around the source body have greatly improved the performance of the magnetron source. Lifetimes of nine months with stable pulsed beams of 50 mA have been achieved. Improvements and operation of the magnetron source at Fermilab will be presented. Recent tests with Lanthanum hexaboride as the cathode will be discussed.