Preparations for proof-of- principle D-T IEC experiments

Transcription

1 14 th US-Japan Workshop on IEC October 15-16, 2012 University of Maryland Preparations for proof-of- principle D-T IEC experiments Yasushi YAMAMOTO 1, Masami Ohnishi 1, Hodaka, Osawa 1, Yuji Hatano 2 and Kai Masuda 3 1 Faculty of Engineering Science, Kansai University, 2 Hydrogen Isotope Research Center, Toyama University 3 Institute of Advanced Energy, Kyoto University, 1

2 What need for D-T experiments As an proof-of-principle D-T IEC experiment, we have been considering to make experiments with tritium ratio of 1~10 %, and measure increase of neutron productions vs. tritium ratio. We consider to use only small amount of tritium for this experiment, but still there are several things we need to think about as a facility, which has both tritium handing license and neutron shielding tritium collection after experiment, oxidation and collecting device (water bubbler) how to keep IEC discharge without vacuum pumping? how to identify D-T neutron from D-D neutron. 2

3 Facility? The IEC facility at IAE dose not have a license to use isotope. Isotope laboratory in main building has a license to use tritium but does not have neutron shield.? what we can do (1) As tritium less than 1GBq is not considered isotope, it is possible to make experiment with keeping total inventory in the facility less than 1GBq for proof-of-principle D-T IEC experiment. kyoto university code does not allow (2) find out some place which has both license. OKTAVIAN facility at Osaka University. restriction no license for gaseous tritium tritium gas must not be detected entrance size 1m x 1.8m 3

4 Preparation? New IEC device (under construction) can be divided to less than entrance size Preliminary experiments using IAE device last year IEC discharge without vacuum pumping? Hydrogen discharge How long does it take to remove deuterium on the surface Isotope effects on discharge parameter Tritium collection device purge gas line, oxidation catalyst and water bubbler how to identify D-T neutron from D-D neutron RRI, Osaka university prepares 4

5 Schematics of experimental device Ion pump Display Vacuum gage 温調器 Right angle valve Vacuum gage Stabilizing Resistor High Voltage feed through Web camera Valve MFC1 MFC2 High voltage power supply High voltage power supply Purge gas MFC TMP QMS Valve VCR Valve MFC Neutron measurment diaphragm Pump D2/T2 Gas cylinder Regulator Heater Heater chiller CuO Catalyst Water bubbler 3He Neutron Detector D2 Gas Cylinder 5

6 Current status Faculty of Engineering Science, Kansai Univ. High voltage line Power Supply 125kV-60mA D2/T 2 supply Vacuum chamber Bubbler unit Main Unit Pumping & Gas feed unit 6

7 Current status Pumping line Gage Faculty of Engineering Science, Kansai Univ. Initial evacuation test 250 Pa by diaphragm pump only 1x10-4 Pa with 70-l/s TMP Withstand high voltage test ~ 20 kv Extension (temp) Cathode 65Φ High Voltage Feed Through Diaphragm Pump TMP 7

8 Initial discharge for cleaning on Oct.12 TMP 17Pa, 1kV, 20mA 4Pa, 7kV, 20mA 8

9 Experiment with sealed vessel Current experiments balance between gas feed and evacuation determine pressure gas feed : a few SCCM deuterium gas 6SCCM = 10 Pa L/sec, volume of chamber = ~8.5 L gas inside the chamber exchanged every second Seal operation using SASE getter pump hydrogen partial pressure is function of temperature but this operation requires to about 1.5 L at standard condition ( 1.5x10 5 Pa L) As tritium 1GBq = mol = 1.12 Pa L both methods look like not applicable Can we make IEC discharge with sealed chamber? 9

10 Pressure [x10-2 Pa] Faculty of Engineering Science, Kansai Univ. Amount of leak & effective pumping speed Pressure increase of vacuum chamber during 60 minutes without pumping Time [sec] Pressure before close pumping line 8.8 x 10-5 Pa Pressure 60-minites after close pumping line 3.92 x 10-2 Pa Leak speed 0.9x10-4 [Pa l/s] ( about 1/60 smaller than estimated from achieved vacuum level ) IEC discharge at 1 Pa, 1 hour impurity level will be about 4 % at maximum, thus we consider that there is not detectable change in neutron production level. 10

11 Voltage [kv] Faculty of Engineering Science, Kansai Univ. Current[mA] / Pressure[Pa] Discharge without pumping Pressure Current Voltage Time [sec] Successfully made 1.19 Pa, 42kV, 1.0 ma, 90-minites discharge without pumping Key issue : keep surface clean, do not overfill gas as it increase trapped gas on the surface 11

12 Neutron Production [x100/sec] Faculty of Engineering Science, Kansai Univ. Neutron production Discharge without pumping Time [sec] Some fluctuations were observed in the beginning, but after then neutron production was stable during 90-minites discharge. At this time, we stopped experiments at 90-minites, but a few hours discharge could be made as discharge itself was quite stable. 12

13 Examine Neutron Production by remaining deuterium Objective Tritium is expected to captured on the chamber surface, and it must be removed as possible as we can after experiments. For simulation, we measure neutron production by the remaining deuterium in hydrogen discharge after deuterium experiments. Procedure 1 Deuterium discharge at 1Pa 2 Evacuate until 10-4 Pa 3 Exchange gas cylinder, evacuate piping line 4 Hydrogen discharge at 1-Pa for 10- minites (flow rate is 2-SCCM) 5 Measure neutron production (49.5-kV, 1-mA, 1.1-Pa ) Hydrogen 13

14 Neutron Production [x100/sec] Faculty of Engineering Science, Kansai Univ. Results Time [sec] Neutron production was reduced to about 1/4 after 30-minites discharge. We need to find out more quick removal of deuterium from surface. baking or glow discharge at lower voltage? 14

15 Summary To make proof-of-principle D-T burning experiments, 1. we have been developing a new IEC device, which can be bring into the OKTAVIAN facility at Osaka University. It should be able to divide to less than 1-m width x 1.8-m height operate without vacuum pumping collect tritium from exhaust Device is now almost ready to start testing 2. Experiments using current IAE device shows it is possible to operate an IEC device without pumping for a few hour it may require several hours to evacuate tritium captured on surface of chamber We continue to exam these problems using new device, and develop gas feed system. 15

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17 Discharge voltage [kv] Faculty of Engineering Science, Kansai Univ. P-V characteristics Deuterium Hydrogen Tritium? Pressure [Pa] P-V characteristics with tritium gas is expected to shift to upper-right region. It is expect that discharge occurs at gas pressure of 1.5-Pa and voltage of 80-kV. 17