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Experimental Progress in 2003 of the UW IEC Facility
6th U.S.-Japan IEC WorkshopTokyo, Japan
October 20-21, 2003
R. P. Ashley and the UW IEC Team
University of Wisconsin-Madison, Fusion Technology Institute1500 Engineering Drive
Madison WI 53706(608) 265-3098
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Overview of Activities
• Operation to 180 kV• Produced 180 million neutrons per second steady state• Fabricated internal and external activation systems• Studied 3He ion damage of tungsten grid wire• Upgraded diagnostics with the addition of a pyrometer,
spectrometer, and off axis proton detector• Designed a standardized cathode grid fabrication system• Conducted thermionic electron emission studies• Developed and constructed a helicon source ion gun
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We Have Produced a UW IEC Record of 1.8 x 108 D-D Neutrons /s
1.E+06
1.E+07
1.E+08
1.E+09
Jan-98
Jan-99
Jan-00
Jan-01
Jan-02
Jan-03
Jan-04
Date Experiments Conducted in Wisconsin IEC Device
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We Have Operated at a Maximumof 180 kV D-D
Maximum Voltage vs. Time
0
20
40
60
80
100
120
140
160
180
200
Sep-99
Dec-99
Mar-00
Jun-00
Sep-00
Dec-00
Mar-01
Jun-01
Sep-01
Dec-01
Mar-02
Jun-02
Sep-02
Dec-02
Date
D-3HeD-D
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University of Wisconsin IEC Facility
High Voltage Feedthru
Typical operating conditionsCathode voltage:40-150 kVCathode current: 30-60 mAPressure:1.5-2.5 mTorr
450 l/s Turbo Pump
91cm
65cmOuter grid anode:50cm diameter SS
Inner grid cathode:10cm diameter SS
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Primary Diagnostics
Silicon charged particleon axis proton detector
1200 mm2
3He Neutron Detector
Video camera
Grid Temperature
Pyrometer
VoltageCurrent
PressureChamber Temp
LabView Data Loggercomputer
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Off Axis Detector Confirms SignificantVolume Source of D-D Protons
Silicon charged particle detector 450 mm2
There are three main regions of fusion reactionsin the UW IEC reactor
1. converged core region2. 3He embedded fusion3. volume source region
• Off axis detector shows similar D-D proton rates per unit volume as the on axis detector, confirming a volume source of D-D protons
• Off axis detector shows negligible D-3He proton rates per unit volume confirming embedded D-3He fusion
12
3
3
3
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Gamma Detector
Ion ExchangeResin
13N Production Has Been Accomplished with Water Cooled Cathode Target
Heat Exchanger
1. Embedded 3He fusion occurs in the stainless steel tube cathode2. 13N is produced in the cathode tube cooling water
Stainless steel tube cathode
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13N Production Also Accomplished with Internal Water Circulator
Gamma Detector
Ion ExchangeResin
Heat ExchangerWater pump
1. Stainless steel tube assembly is exposed to D-3He fusion proton flux2. 14 MeV protons penetrate the tubes and activate the oxygen in H2O3. 13N is captured in the ion exchange resin
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• Thermionic emission reduces the overall fusion rate at fixed meter current
Diagwire experiments help determine ion flow characteristics *
• Wire power balance helps diagnose ion flux patterns
*details will be reported at next workshop
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Fast He Ions Can Produce Significant Damage in Tungsten
Wire grid cathode was replaced by a1 cm square tungsten sample target
5 µm
SEM picture of sample before
operation
sample after 6 x 1018
helium ions /cm2
5 µm
sample after2 x 1019
deuterium ions /cm2
25 µm
D+, 20 kV, 5 mA2 mtorr, 1100 °C
1 CM
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Fabrication System for Standardized Grid
2. Wax poured into mold
4. Wires spot welded at junctions 5. Wax form melted away@100C
6. Finished grid cathode
1. Mold produced fromrapid prototype model
10 cm
3. Wires wound around wax form
10 cm
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Ion Gun on New Chamber(see talk by Piefer)
IEC Chamber
Ion source
Source Turbo pump
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Future Plans
• Improve proton rates for medical isotope production• Study converged core formation with new ion source• Understand grid wire damage caused by helium ions• Characterize ion and impurity population densities
with spectroscopy studies• Simulate ion flow to better understand the source
regions and reaction rates
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At 100 kV, We Have Seen Lower Rates of D-D Neutrons at Lower Pressures
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Gamma detector is all-in-one instrument for ease of use
Scintillation headPhoto multiplierTube
Powered by USB cable
Preamp, multi-channel analyzer and HV power supply contained in base
ORTEC model 950-4 Gamma detector with MicrobaseTM
Specs:
Laptop displays data in real time