skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Proton ring formation studies on the Cornell field-reversed ion ring experiment FIREX

Abstract

The goal of FIREX is to produce a field-reversed ring of greater than 500 keV protons. The ring is formed by axial cusp injection into a solenoid of an annular beam from a magnetically-insulated ion diode driven by a 1 MV, 800 kA, 150 ns pulser. The first phase of experiments using a passive flashover proton source is now complete. At 90% charge of the FIREX pulse power, the diode produces 12 mC of protons over 120 ns, while the voltage decreases from 850 to 550 kV. These protons are injected through the cusp into a 6 kG solenoid to form a ring. Diagnosis of ring formation with arrays of magnetically-insulated Faraday cups show that 6 mC are in the ring at 100 cm axial location in the solenoid, in agreement with simulations using the quasineutral FIRE code. However, the radial distribution of the ring protons differs significantly from the simulations, and is dependent on the pressure of the neutral hydrogen gas fill that is used in the solenoid to provide beamformed plasma for charge neutralization of the ring. The radial distribution is shifted strongly to smaller radius in the solenoid with fill pressures below 100 mTorr, indicating residual space-chargemore » effects in the cusp. Above 200 mTorr, no significant change in radial distribution is seen. The self-magnetic field of these rings is only about 10% of the solenoid field. To increase this to field reversal, the ring must be shortened from its present {approximately}100 cm axial length to <20 cm, and the proton charge must be increased to 20 mC. Presently the experiment is moving into a second phase using an active proton source to increase the proton output of the diode. This source uses a thin (<1 micron) titanium foil on the anode, loaded with hydrogen gas, to produce a nearly pure proton plasma on the anode at the start of the diode voltage pulse. The aim of this change is to increase the initial rate of rise of proton current, which would both increase the total proton charge output and also load down the early diode voltage to produce less spread in the proton energy, allowing an axially shortened ring in the solenoid. Both these effects would increase the ring self-field toward reversal. Initial results will be reported.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Cornell Univ., Ithaca, NY (US)
Sponsoring Org.:
USDOE
OSTI Identifier:
20050655
DOE Contract Number:  
FG02-93ER54221
Resource Type:
Conference
Resource Relation:
Conference: 1999 IEEE International Conference on Plasma Science, Monterey, CA (US), 06/20/1999--06/24/1999; Other Information: PBD: 1999; Related Information: In: The 26th IEEE international conference on plasma science, 342 pages.
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ION RINGS; PROTONS; REVERSE-FIELD PINCH; ION SOURCES; PLASMA DIAGNOSTICS; PLASMA PRODUCTION; RESEARCH PROGRAMS

Citation Formats

Podulka, W J, Greenly, J B, Gretchikha, A, and Yang, Y. Proton ring formation studies on the Cornell field-reversed ion ring experiment FIREX. United States: N. p., 1999. Web.
Podulka, W J, Greenly, J B, Gretchikha, A, & Yang, Y. Proton ring formation studies on the Cornell field-reversed ion ring experiment FIREX. United States.
Podulka, W J, Greenly, J B, Gretchikha, A, and Yang, Y. Thu . "Proton ring formation studies on the Cornell field-reversed ion ring experiment FIREX". United States.
@article{osti_20050655,
title = {Proton ring formation studies on the Cornell field-reversed ion ring experiment FIREX},
author = {Podulka, W J and Greenly, J B and Gretchikha, A and Yang, Y},
abstractNote = {The goal of FIREX is to produce a field-reversed ring of greater than 500 keV protons. The ring is formed by axial cusp injection into a solenoid of an annular beam from a magnetically-insulated ion diode driven by a 1 MV, 800 kA, 150 ns pulser. The first phase of experiments using a passive flashover proton source is now complete. At 90% charge of the FIREX pulse power, the diode produces 12 mC of protons over 120 ns, while the voltage decreases from 850 to 550 kV. These protons are injected through the cusp into a 6 kG solenoid to form a ring. Diagnosis of ring formation with arrays of magnetically-insulated Faraday cups show that 6 mC are in the ring at 100 cm axial location in the solenoid, in agreement with simulations using the quasineutral FIRE code. However, the radial distribution of the ring protons differs significantly from the simulations, and is dependent on the pressure of the neutral hydrogen gas fill that is used in the solenoid to provide beamformed plasma for charge neutralization of the ring. The radial distribution is shifted strongly to smaller radius in the solenoid with fill pressures below 100 mTorr, indicating residual space-charge effects in the cusp. Above 200 mTorr, no significant change in radial distribution is seen. The self-magnetic field of these rings is only about 10% of the solenoid field. To increase this to field reversal, the ring must be shortened from its present {approximately}100 cm axial length to <20 cm, and the proton charge must be increased to 20 mC. Presently the experiment is moving into a second phase using an active proton source to increase the proton output of the diode. This source uses a thin (<1 micron) titanium foil on the anode, loaded with hydrogen gas, to produce a nearly pure proton plasma on the anode at the start of the diode voltage pulse. The aim of this change is to increase the initial rate of rise of proton current, which would both increase the total proton charge output and also load down the early diode voltage to produce less spread in the proton energy, allowing an axially shortened ring in the solenoid. Both these effects would increase the ring self-field toward reversal. Initial results will be reported.},
doi = {},
url = {https://www.osti.gov/biblio/20050655}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {7}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share: