(Annual Report to the IEA)
IEA Three Large Tokamak Cooperation
(January to December 1986)
1 . Conclusion of the Agreement
The IEA Implementing Agreement on Cooperation among the Three Large Tokamak Facilities (JET, JT-60 and TFTR) was finalized on 15th January 1986 in Garching, FRG.
2. First Meeting of the Executive Committee
The first meeting of the Executive Committee was held on 12th and 13th May 1986 at the Naka Fusion Research Establishrnent of JAERI. The members were Dr. J. Poffe and Dr. A. Gibson from JET, Dr. D. Grove and Dr. J. Willis from TFTR and USDOE, and Dr. M. Yoshikawa and Dr. Y. Suzuki from JT-60. The Committee elected Dr. Yoshikawa as the chairman acting until the next meeting. JAERI acted as the Secretariat, represented by Dr. A. Kitsunezaki.
Discussions were made on the following issues.
On the relation between the IEA agreement and the bilateral agreements, it was agreed that all personnel and information exchanges including workshops among the three large tokamaks will be executed under the IEA agreement. The exchange of hardwares such as diagnostics tools will be taken care of by the bilateral agreements.
The treatment of the industry personnel and the framework of the exchange of information were also discussed and agreements were made.
The plan of personnel exchanges and workshops until the end of 1987 was agreed for 7 workshops and 25 personnel exchanges as shown in the attachment #1 and #2. The plan will be reviewed at the next meeting.
Necessary procedures (Forms A to D) in implementing cooperative activities and the Secretariat's role therein were discussed and agreed upon.
The minutes of the first meeting of the Executive Committee is attached to this report. (Attachment #3)
The members of the Executive Committee met in November 1986 at Kyoto, Japan, on the occasion of the IAEA international conference, and confirmed that the cooperation activities were being carried on satisfactorily. The second meeting of the Executive Committee will be held on 26th and 27th February 1987 at PPPL.
3. Cooperation Activities
Three workshops and ten personnel exchanges marked at the left of the attachment #1 and #2 have been completed or started before the end of 1986. The report forms of those are attached to this report. (Attachment #4)
The Personnel Assignment Agreement between JT-60 and JET is in the final stage before conclusion. The TFTR/JET agreement has been signed.
4. Status of Three Large Tokamaks
All three tokamaks showed steady progresses toward the break-even condition which is expected to be reached in next few years. Each facility produced excellent results in its own area that were found beneficial to the others.
The status and major results of the three large tokamaks are summarized below.
Discharges with the plasma current up to 5 MA and the additional heating power up to 16 MW with neutral beam injection and radio frequency (ion cyclotron frequency) heating have systematically been investigated. An energy confinement time of 0.9 sec was attained in ohmic plasmas. A discharge mode with a better confinement compatible with a high heating power (so called "H-mode") was found in November 1986 in discharges with magnetic separatrix (or X-point) inside the vacuum vessel. The highest parameters presented at the Kyoto conference were Ti(0)=Te(0)=6 keV, nd (0)=5x1019 m-3 and =0.65 s resulting in a fusion product nd(0)Ti(0)(0) of about 2x1020 m-3keVs, with Ip=3.0 MA, Padd=9.5MW.
The energy confinement times of ohmic heated plasmas were consistent with eqR2a scaling and was about 0.44s at e < 4.8x1019 m-3 in deuterium discharge. A high central density of 2.8x1020 m-3 and a line averaged density of 1.4x1020 m-3 has been achieved by pellet fuelling, with a fusion product of about 2x1020 m-3keVs.
The additional heating power by neutral beam injection reached 20 MW. In discharges called 'supershot', high values of ion temperature of more than 20 keV at the plasma center were obtained with the central plasma density about 7x1019 m-3. A plasma current driven partly by intense beam injection and partly by the "bootstrap" current has been studied with considerable evidence supporting the existence of the "bootstrap" component.
Experiments with additional heating were started in August 1986. Neutral beam injection reached its full power of 20 MW. Clean plasmas of Zeff ~ 1.5 were produced in the divertor configuration. The energy confinement time in ohmic plasma was about 0.5 sec and it degraded with increase of the heating power, down to about 0.12 sec for Padd > 10 MW.
In the current drive experiment, a plasma current of 1.7 MA was driven at a plasma density of about 3x1018 m-3 by 1.2 MW of lower hybrid frequency power. The energy confinement time with NB heating was improved by the addition of lower hybrid frequency power, although the plasma density studied so far was low (e < 1.0x1019 m-3).
5 . Summary
The cooperation under IEA among the Three Large Tokamaks is progressing smoothly and yielding productive effects.